Orthopaedic Knowledge Home Study by R. Alexander

Adult Spine Trauma Orthopaedic Knowledge Update 8 Figure 13 Bilateral cervical spinal facet dis- locations. A, Plain radiograph demonstrates 50% subluxation of C4 on C5. B, T2-weighted MRI scan reveals large posteriorly extruded disk fragment at the level of injury. The patient underwent an anterior decompression and an- terior open reduction and instrumented fu- sion. (Reproduced with permission from Klein GR, Vaccaro AR: Cervical spine trauma: Upper and lower, in Vaccaro AR, Betz RR, Zeidman SM (eds): Principles and Practice of Spine Surgery. Philadelphia, PA, Mosby, 2003, pp 441-462.) trauma, and patients must be evaluated thoroughly for vertebral bodies are typically 1 to 2 mm smaller in other injuries. Although they represent only a small per- height anteriorly, resulting in the kyphosis seen in the centage of thoracolumbar fractures, the narrow thoracic thoracic spine. The kyphotic alignment of the thoracic spinal canal and the precarious blood supply to the tho- spine results in the concentration of axial load transmis- racic spinal cord make these injuries potentially devas- sion in the anterior column. The apex of the kyphosis is tating. normally over T6 through T8, where maximal anterior column forces are generated and fractures within the rib Fractures of the thoracic spine from T2 through T10 cage are most likely to occur. are relatively infrequent as a result of unique anatomic features of the thoracic spine that provide enhanced sta- Diagnostic Imaging bility. Fractures of the thoracolumbar spine from T11 through L2 will be discussed separately because the Plain films of the thoracic spine should provide an ini- transition from the rigid thoracic spine to the more flex- tial assessment of any fracture as well as its impact on ible lumbar spine creates a transition zone that is sus- overall sagittal alignment. It is of paramount importance ceptible to injury. to evaluate the entire spine once a fracture is identified because concomitant spinal fractures can be present in Biomechanics up to 20% of patients. CT scans should be obtained in patients with fractures on plain films, in any multiple The thoracic spine has several unique anatomic features trauma patient with lower extremity neurologic deficits, that provide it with more stability than either the cervi- and for any patients with inadequate plain films. The ax- cal or lumbar spine. Each thoracic vertebra has articula- ial images will help evaluate the vertebral body fracture tions with and ligamentous attachments to the adjacent anatomy, pedicle anatomy, and presence of bony retro- ribs at both the transverse process and the vertebral pulsion. Coronal and sagittal reconstructions may reveal body that increase rigidity. In addition, the ribs articu- fractures missed in the axial plane, and they provide a late with the sternum, which provides another point of better appreciation of the fracture anatomy. MRI can be fixation and thereby limits thoracic motion. The facets useful in evaluating the soft tissues of the spine. The an- of the thoracic spine are oriented in the coronal plane, terior and posterior ligamentous complexes can be eval- with the lamina and spinous processes arranged in a uated for injury as well as spinal cord encroachment by shingled fashion, which reduces the amount of extension either disk or osseous material. In addition, the spinal of the thoracic spine. The intervertebral disks of the tho- cord can be evaluated for the presence of edema or racic spine are very thin, which provides increased stiff- hemorrhage. ness and more rotational stability. The vertebral bodies are asymmetric in height from anterior to posterior. The 520 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 41 Adult Spine Trauma Classification systems for spinal fractures have been decompression and stabilization of these injuries has yet difficult to standardize because of the complex loads to be demonstrated in the scientific literature. Patients that are applied to result in these injuries. A compre- who have a complete neurologic injury are typically sta- hensive classification system has been proposed for tho- bilized posteriorly in a nonemergent fashion to facilitate racic and lumbar fractures based on their radiographic earlier rehabilitation. morphology. Three basic forces—compression, distrac- tion, and rotation—were found to be responsible for the Flexion-Distraction Injuries injuries and are labeled A, B, and C, respectively. In ad- dition, each group is subdivided into three subgroups. Flexion-distraction injuries result from a flexion mo- The severity of the injury increases from group A to ment that is combined with a fulcrum located at varying group C. Because describing every variant in this system distances from the anterior portion of the vertebral col- is beyond the scope of this text, only the classic exam- umn. The resulting injury can involve bone, ligament, or ples from each group will be discussed. a combination of bone and ligament. When the fulcrum is located adjacent to the vertebral body, the anterior Compression Fractures column will fail in compression and the middle and pos- terior columns will fail in tension. As the fulcrum moves In its purest form, a compression fracture results from more anterior, the deforming forces become purely dis- an axial load applied to the spine. The anterior column tractive and all three columns will fail in tension. Pa- of the spine (vertebral body and disk) is involved with- tients with pure ligamentous and combined bony and out involvement of the middle column (posterior verte- ligamentous injuries should undergo a posterior stabili- bral cortex and posterior longitudinal ligament). Radio- zation procedure because of involvement of all three graphs will demonstrate a wedge-shaped defect in the columns and the poor healing properties of ligaments. vertebral body that results in varying degrees of kypho- Typically, these injuries can be treated with short- sis. Neurologically intact patients with less than 30° of segment posterior compression constructs. Patients with kyphosis and less than 50% loss of vertebral body a purely bony injury can undergo reduction in extension height can be treated with a hyperextension orthosis. and can be treated in a thoracolumbosacral orthosis be- Patients with more than 30° of kyphosis or more than cause of the healing properties of bone. They should be 50% loss of vertebral body height can also be treated assessed for nonunion and deformity progression. nonsurgically, but must be watched carefully for possible failure of the posterior ligamentous structures. These pa- Fracture-Dislocations tients are more likely to develop a kyphotic deformity, and close radiographic and clinical follow-up is war- Fracture-dislocations are common injuries in the tho- ranted. In patients with fractures above T6, a cervical racic spine because of the significant forces acting on a extension on the thoracolumbosacral orthosis should be rigid portion of the spine. Up to 90% of these injuries used for better control. are associated with a spinal cord injury, most commonly complete (ASIA impairment scale category A). Because Burst Fractures all three spinal columns are involved, these fractures are very unstable. In patients with complete neurologic in- Burst fractures also result from an axial load and are in- jury, a posterior stabilization procedure can be per- herently unstable because of the involvement of the an- formed once their clinical condition is optimized. This terior and middle columns of the spine. Radiographs will allow for early mobilization and help minimize the will typically demonstrate a widening of the pedicles at morbidity and mortality associated with these injuries. the affected vertebral body and a varying degree of bony retropulsion into the canal. Treatment of these in- Thoracic Pedicle Screws juries must be based on consideration of neurologic sta- tus, sagittal alignment, and the integrity of the posterior The use of thoracic pedicle screws has become more ligamentous structures. Patients who are neurologically widespread based on numerous reports of safe place- intact with less than 30° of kyphosis and less than 50% ment techniques and success in clinical practice. Pedicle loss of vertebral body height can be managed in a thora- screws offer several advantages over traditional hook columbosacral orthosis. Patients with more than 30° of and rod constructs. The pedicle is the strongest bony at- kyphosis and more than 50% loss of vertebral body tachment to the vertebra and provides excellent pur- height with failure of the posterior column should be chase, even in osteoporotic bone. Pedicle screws provide considered for a posterior stabilization procedure. fixation of all three spinal columns, which provides for better sagittal and coronal stability. This increased sta- Patients with incomplete neurologic deficits and ra- bility can decrease the number of levels included in a diographic evidence of spinal cord compression may fusion construct. benefit from an acute anterior decompression and stabi- lization. However, the benefit of early versus delayed The thoracic pedicles are the narrowest in the T4-6 region and become progressively larger toward the lum- American Academy of Orthopaedic Surgeons 521

Adult Spine Trauma Orthopaedic Knowledge Update 8 Figure 14 A, From the levels T3 through T10, the entrance point to cannulate the pedicle can be determined by using the intersection point between a line drawn from the superior border of the transverse process and a line drawn from the midpoint of the cephalad fac- et. B, At the levels of T11-12, the entrance point to cannulate the pedicle can be deter- mined by using the intersection point between a line drawn from the middle of the transverse process and a line drawn from the midpoint of the cephalad facet. bar spine. Preoperative planning with CT is critical in nation of fracture stability. A two-column model of the evaluating the diameter of the pedicles to ensure they spine was proposed in which it was hypothesized that can accommodate instrumentation. Pedicle screws can injuries with involvement of the posterior column are be placed with the assistance of fluoroscopy or by using associated with instability. Denis proposed a three- anatomic landmarks. One method that has been de- column concept that stressed the importance of the scribed for screw placement between T3 and T10 uses newly defined middle column, which comprises the pos- the intersection of a vertical line through the middle of terior 50% of the vertebral body and disk along with the cephalad articular surface and a horizontal line at the posterior longitudinal ligament (Figure 15). Based the superior border of the transverse process (Figure 14, on biomechanical data, Denis proposed that an isolated A). At the T11 and T12 levels, the horizontal line should posterior ligamentous complex injury was not sufficient be made from the middle of the transverse process (Fig- to produce instability and that concomitant involvement ure 14, B). of the middle column resulted in instability in flexion. However, the integrity of the posterior ligamentous The complications of thoracic pedicle screw place- complex (supraspinous and interspinous ligaments) is a ment can be devastating. Injuries to the spinal cord, crucial factor in determining stability because posterior nerve roots, esophagus, and major blood vessels have all column disruption in conjunction with involvement of been reported. Thorough preoperative planning with ax- the anterior and middle columns creates instability and ial CT that documents the diameter and length of the increases the risk of posttraumatic kyphosis. pedicle as well as the angle of insertion and intraopera- tive neurophysiologic monitoring are important for Treatment avoiding complications. The treatment of most patients with thoracolumbar Thoracolumbar Junction Trauma fractures is nonsurgical. Patients who are neurologically intact with less than 25° kyphosis, less than 50% loss of Biomechanics vertebral body height, and less than 50% of canal occlu- sion and an intact posterior longitudinal ligament are Injuries to the thoracolumbar junction (T11 through L2) the best candidates for nonsurgical treatment. Depend- are usually the result of significant blunt trauma. These ing on the severity of the collapse, these patients may be injuries represent approximately 50% of all thoracic and managed with hyperextension body casting and/or a lumbar fractures. This increased incidence of fractures thoracolumbosacral orthosis for 3 months. Regular clini- to the thoracolumbar junction is the result of its loca- cal and radiographic follow-up of these patients is im- tion at the transition point between the rigid thoracic portant to rule out the development of progressive ky- rib cage and the more mobile lumbar spine. In addition, phosis or neurologic deficits. the sagittal alignment of the spine changes from kypho- sis to lordosis, which more evenly distributes stress on Surgical treatment should be reserved for patients the anterior and middle columns. The facet alignment with unstable fracture patterns and/or neurologic defi- changes from a coronal orientation in the thoracic spine cits. For patients with incomplete neurologic injuries to a sagittal alignment in the lumbar spine, allowing for and spinal cord compression, anterior decompression greater flexion and extension motion. Also, the interver- and stabilization is typically required. The anterior pro- tebral disks are taller than in the thoracic spine, decreas- cedure may need to be performed in conjunction with a ing anterior column stiffness. posterior stabilization procedure in patients with poste- rior column involvement. Early stabilization of patients The indications for surgical management of thora- columbar fractures remain controversial. Central to de- fining the need for surgical management is the determi- 522 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 41 Adult Spine Trauma Figure 15 Denis’ three-column model of the spine. (Reproduced with permission from Gar- fin SR, Blair B, Eismont FJ, Abitol JJ: Thoracic and upper lumbar spine injuries, in Browner BD, Jupiter JB, Levine AM, Trafton PG, Lampert R (eds): Skeletal Trauma: Fractures, Disloca- tions, Ligamentous Injuries, ed 2. Philadel- phia, PA, WB Saunders, 1997, pp 947-1034.) with neurologic injuries will allow for early mobilization Lower Lumbar Spine Trauma and rehabilitation placement. Biomechanics Patients with unstable burst fractures that include failure of the posterior column should undergo an initial Fractures of the lower lumbar spine (L3-L5) are less posterior stabilization procedure. Posterior instrumenta- common than in the thoracolumbar region. The lower tion on a lordosing frame can help restore the normal lumbar spine is the lordotic alignment in the sagittal sagittal alignment of the thoracolumbar spine and will plane, which results in a weight-bearing axis that falls assist in the reduction via ligamentotaxis of the retro- through the middle and posterior columns, making this pulsed fragment. However, patients with excessively anatomic region more intrinsically stable. Such fractures comminuted vertebral body fractures may be candidates are unlikely to progress into a kyphotic deformity. In for a staged anterior procedure. addition, the facets of the lumbar spine are oriented in the sagittal plane, which can accommodate greater Recently, prospective studies have compared pa- flexion-extension bending moments. Finally, the lum- tients with stable burst fractures of the thoracolumbar bosacral junction can withstand large forces transmitted junction treated surgically and nonsurgically with regard across it. to pain, spinal canal compromise, and residual kyphosis. In patients with mild to moderate initial kyphosis, much Because the load-bearing axis is more posterior, of the sagittal correction gained surgically is lost over compression fractures are much less common than burst time, approaching the final segmental kyphosis seen for fractures in the lower lumbar spine. For the anterior col- these fractures in the nonsurgical treatment group. In umn to fail, a significant flexion moment must be ap- addition, residual kyphosis has not been a reliable pre- plied. However, these large flexion moments are typi- dictor of chronic pain. Similarly, the degree of spinal ca- cally neutralized by the increased ability of the lumbar nal encroachment has also not been associated with in- spine to accommodate loads in the sagittal plane. If a jury to neural structures over the long term. Canal compression fracture is detected, suspicion should be remodeling is to be expected, and up to 50% of the ca- high for a concomitant posterior ligamentous injury, es- nal can be restored. The degree of remodeling has been pecially in the setting of more than 50% loss of verte- reported to be similar in groups of patients treated sur- bral body height. gically or nonsurgically. Burst fractures are the most common fracture pat- tern seen in the lower lumbar spine. Most of these inju- ries occur with the spine in a neutral position, resulting in axial loading of both anterior and middle columns of the spine. As with burst fractures in other parts of the spine, a variable amount of bone may be retropulsed American Academy of Orthopaedic Surgeons 523

Adult Spine Trauma Orthopaedic Knowledge Update 8 Figure 16 A, An axial CT scan demonstrates the narrowest portion along the sacral pedicle. B, Sagittal view of the narrowest portion of the sacral ala with height and width dimensions. C, Drawing demonstrating the adjacent bony structures and the L5 and S1 nerve roots. (Reproduced with permission from Noojin FK, Malkani AL, Haikal L, Lundquist C: Cross-sectional geometry of the sacral ala for safe insertion of iliosacral lag screws: A computed tomography model. J Orthop Trauma 2000;14:31-35.) into the spinal canal. However, the incidence of signifi- The length of the fusion in the lower lumbar spine cant and/or permanent neurologic sequelae from these typically involves the fractured level and the cephalad injuries is much lower than elsewhere in the spinal col- and caudad levels. If the fracture involves the L5 level, umn; the spinal cord ends above this level, and the fusion to the sacrum will be necessary, and attention to nerve roots of the cauda equina are more tolerant of the maintenance of the normal lordotic sagittal align- compression than the spinal cord. ment is important. Isolated injuries of the posterior liga- mentous complex may be addressed with a single-level Flexion-distraction injuries account for less than compression construct using screws or hooks. Patients 10% of lumbar spine fractures. They are most com- with these injuries may also require a course of postop- monly seen at L2, L3, or L4 and are typically the result erative immobilization in a thoracolumbosacral orthosis, of the increased stability imparted at the level of L5 to which possibly includes leg extension. the pelvis via the iliolumbar ligaments. The large flexion moments cause flexion of the upper lumbar segments, Sacral Spine Trauma whereas the lower segments are stabilized. As a result, the posterior elements fail in tension from the distrac- Biomechanics tive forces. Sacral fractures are usually the result of high-energy Treatment trauma and occur in isolation in fewer than 5% of pa- tients. As a result, a thorough evaluation of the pelvis Most patients with lower lumbar fractures can be and spine should be undertaken for associated fractures. treated conservatively with external immobilization, a Sacral fractures are generally classified according to the short course of bed rest, and a custom-molded thora- direction of the fracture line. Fractures may be vertical, columbosacral orthosis. A single leg spica attachment transverse, or oblique, although vertical fractures are the may be necessary for fractures of L4 and L5 to allow for most common. Denis’ classification system divides the control of the pelvis and immobilization of the lum- sacrum into three zones. Zone 1 spans the sacral ala to bosacral junction. Patients should wear a brace for ap- the lateral border of the neural foramen. Zone 2 repre- proximately 8 to 12 weeks and undergo regular clinical sents the neural foramen. Zone 3 involves the central and radiographic follow-up. sacrum and canal. Patients who have a cauda equina syndrome or sig- Sacral injuries commonly are associated with sacral nificant neurologic deficit with canal compromise root deficits. Because of the relative kyphosis of the should be considered for surgical treatment. Such pa- sacrum, the sacral nerve roots are tethered and re- tients will typically have near-complete canal occlusion stricted within long bony tunnels and therefore not from bony fragments and should undergo decompres- much motion is allowed. These two anatomic factors sion and a posterior stabilizing procedure using pedicle predispose the neural structures to injury. In addition, screws. The decompression can usually be performed the direction of the fracture line and type of fracture de- posteriorly via a laminectomy. If a posterior decompres- termine the likelihood of a neurologic injury. Neurologic sion is going to be performed in a patient with a neuro- injuries of the lower sacral roots (S2-S4) are often logic deficit, evaluation for the presence of a laminar missed because only L5 and S1 can be evaluated by fracture should be sought. Case reports have described manual muscle testing. Perianal sensory changes should herniated nerve root entrapment within the laminar be sought in patients with this type of injury. In the fracture site. Denis classification system, zone 1 vertical injuries have a 5.9% incidence of neural injury. If there is a neural in- 524 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 41 Adult Spine Trauma jury, it is usually an injury to the L5 nerve root or the restoring and maintaining sagittal alignment and minimizing sciatic nerve. Zone 2 fractures have an incidence of the rate of treatment failures. 28.4% of neural injury. The nerve injuries are commonly unilateral in nature. This is important because patients Guidelines for management of acute cervical spinal in- with unilateral sacral root injuries usually have normal juries. Neurosurgery 2002;50(suppl 3):S1-S179. bowel and bladder function. Zone 3 injuries have a 50% incidence of neurologic injuries, and most of these pa- Under the sponsorship of the American Association of tients will have bilateral sacral root involvement with Neurologic Surgeons and the Congress of Neurologic Sur- bowel, bladder, and sexual dysfunction. geons, a computerized English-language literature search was performed covering the preceding 25 years. Studies involving Treatment cervical spinal trauma were reviewed and critically evaluated. Results were organized and presented in several topical sec- Indications for surgical management of sacral fractures tions designed to provide reasonable standards, guidelines, and include bowel and bladder dysfunction in the setting of options for care of patients with acute cervical spinal injuries. an unstable fracture with substantial coronal or sagittal deformity. Vertical fractures can typically be treated Peris MD, Donaldson WF, Towers J, Blanc R, Muzzoni- with posterior sacroiliac plating or percutaneously gro TS: Helmet and shoulder pad removal in suspected placed sacroiliac screws. Placement of percutaneous sac- cervical spine injury. Spine 2002;27:995-999. roiliac screws can be technically demanding, and the L5 and S1 nerve roots are at risk during the procedure This fluoroscopic study supports the efficacy of the current (Figure 16). If this technique is used to treat a zone 2 in- protocol used by the National Athletic Trainers’ Association jury, the screw should not be loaded in compression to that uses four individuals for the safe removal of the helmet avoid neural injury. Patients who have displaced trans- and shoulder pads from an injured football player with mini- verse or oblique fractures may undergo bilateral plating. mal cervical motion. Neural decompression via laminectomy may be indi- cated in patients with neurologic deficits and canal com- Vaccaro AR, Madigan L, Bauerle WB, Blescia BS, Cot- promise, and recovery of bowel and bladder function ler JM: Early halo immobilization of displaced trau- may be seen. In patients without neurologic injury who matic spondylolisthesis of the axis. Spine 2002;27:2229- have minimally displaced fractures, bracing is only nec- 2233. essary in the setting of fractures, which extend to or above the level of the sacroiliac joint. This retrospective study of 31 patients with traumatic spondylolisthesis of the axis confirms that early halo immobili- Annotated Bibliography zation after traction reduction is a safe and effective form of treatment in this patient population. Patients with type II frac- Cervical Spine Trauma tures angled greater than or equal to 12° may require more extended periods of traction. Blake WED, Stillman BC, Eizenberg N, Briggs C, Mc- Meeken JM: The position of the spine in the recovery Thoracic Spine Trauma/Thoracolumbar Junction position: An experimental comparison between the lat- Trauma/Lower Lumbar Spine Trauma eral recovery position and the modified HAINES posi- tion. Resuscitation 2002;53:289-297. Finkelstein J, Wai E, Jackson S, Ahn H, Brighton-Knight M: Single-level fixation of flexion distraction injuries. This study identifies a new patient recovery position, the J Spinal Disord Tech 2003;16:236-242. modified HAINES position, in which the patient is in the lat- eral position with the head lying on the fully abducted depen- This prospective study evaluated 17 patients with flexion- dent arm and both legs are drawn up, with hips and knees distraction injuries of the thoracic and lumbar spine. The pa- flexed. This position results in a more neutral position of the tients had an average follow-up of 17.6 months and were spine compared with the traditional lateral recovery position treated with single-level posterior fixation. The average preop- and may be preferable to the lateral recovery position during erative kyphosis was 10.1°, which was corrected to a postoper- resuscitation of trauma patients. ative lordosis of 0.9°. The mean Oswestry score was 11.5 and 88% of the patients reported having only minimal disabilities. Fisher CG, Dvorak MFS, Leith J, Wing PC: Comparison of outcomes for unstable lower cervical flexion teardrop Wood K, Butterman G, Mehbod A, Garvey T, Jhanjee fractures managed with halo thoracic vest versus ante- R, Sechriest V: Operative compared with nonoperative rior corpectomy and plating. Spine 2002;27:160-166. treatment of a thoracolumbar burst fracture without neurological deficit: A prospective, randomized study. This retrospective cohort study of 45 patients with cervical J Bone Joint Surg Am 2003;85:773-781. flexion teardrop fractures indicates that anterior cervical plat- ing is a safe and effective treatment of this patient population This prospective randomized trial evaluated 47 consecu- and may be superior to halo vest immobilization in terms of tive patients with a thoracolumbar fracture without neurologic deficit for a minimum 2-year follow-up. The group of patients that underwent surgical treatment had a mean preoperative American Academy of Orthopaedic Surgeons 525

Adult Spine Trauma Orthopaedic Knowledge Update 8 and postoperative kyphosis of 10.1° and 13°, respectively. The patients and review of the literature. J Bone Joint Surg group of patients that underwent nonsurgical treatment had a Am 1979;61:1119-1142. mean preoperative and postoperative kyphosis of 11.3° and 13.8°, respectively. No difference was found between groups Clark CR, White AA III: Fractures of the dens: A multi- with respect to return to work. The average pain scores were center study. J Bone Joint Surg Am 1985;67:1340-1348. similar for both groups. The authors concluded that surgical treatment provided no long-term advantage compared with Denis F: Instability as defined by the three-column nonsurgical treatment. spine concept in acute spinal trauma. Clin Orthop 1984; 189:65-76. Yue J, Sossan A, Selgrath C, et al: The treatment of un- stable thoracic spine fractures with transpedicular screw Denis F, Davis S, Comfort T: Sacral fractures: An impor- instrumentation: A 3-year consecutive series. Spine 2002; tant problem. Retrospective analysis of 236 cases. Clin 27:2782-2787. Orthop 1988;227:67-81. This study evaluated 32 patients in a 3-year consecutive Hoffman JR, Mower WR, Wolfson AB, Todd KH, prospective experience of using pedicle screw fixation to treat Zucker MI: Validity of a set of clinical criteria to rule unstable thoracic spine injuries. Fracture healing was noted to out injury to the cervical spine in patients with blunt take place at an average of 4.8 months. Two-hundred fifty-two trauma: National Emergency X-Radiography Utilization pedicle screws were placed without any intraoperative compli- Study Group. N Engl J Med 2000;343:94-99. cations. The Gardner segmental kyphotic deformity angle pre- operative mean was 15.9° and the mean postoperative angle Levine AM, Edwards CC: The management of trau- was 10.6° (which was significant). All neurologically intact pa- matic spondylolisthesis of the axis. J Bone Joint Surg tients reported very good to good results with regard to pain, Am 1985;67:217-226. activity, function, employment, and satisfaction. Sacral Spine Trauma Magerl F, Aebi M, Gertzbein SD, Harms J, Nazarian S: A comprehensive classification of thoracic and lumbar Noojin F, Malkani A, Haikal L, Lundquist C, Voor M: injuries. Eur Spine J 1994;3:184-201. Cross-sectional geometry of the sacral ala for safe inser- tion of iliosacral lag screws: A computed tomography Mestdagh H, Letendart J, Sensey JJ, Duquennoy A: model. J Orthop Trauma 2000;14:31-35. Treatment of fractures of the posterior axial arch: Re- sults of 41 cases. Rev Chir Orthop Reparatrice Appar This study evaluated 13 adult patients with intact pelves in Mot 1984;70:21-28. a trauma setting to determine the geometry of the sacral ala for placement of iliosacral screws. Each patient had CT scans Schiff DCM, Parke WW: The arterial supply of the od- of the pelvis with sagittal reconstructions. The narrowest por- ontoid process. J Bone Joint Surg Am 1973;55:1450. tion of the sacral ala was determined, and height, width, and slope of the geometric center were calculated. The mean width Spence KF, Decker S, Sell KW: Bursting atlantal frac- of the sacral ala was 28.05 mm, the mean height was 27.76 ture associated with rupture of the transverse ligament. mm, and the sacral slope ranged from 25° to 65°. The authors J Bone Joint Surg Am 1970;52:543-549. concluded that despite individual variability there is room for two screws to be placed in the sacral ala safely. Classic Bibliography Vaccaro AR, Rizzolo SJ, Allardyce TJ, et al: Placement of pedicle screws in the thoracic spine: Part I. Morpho- Allen BL Jr, Ferguson RL, Lehman TR, O’Brien RP: A metric analysis of thoracic vertebra. J Bone Joint Surg mechanistic classification of closed, indirect fractures Am 1995;8:1193-1199. and dislocations of the lower cervical spine. Spine 1982; 7:1-27. Vaccaro AR, Rizzolo SJ, Balderston RA, et al: Place- ment of pedicle screws in the thoracic spine: Part II. An Bohlmann HH: Acute fractures and dislocations of the anatomic and radiographic assessment. J Bone Joint cervical spine: An analysis of three hundred hospitalized Surg Am 1995;8:1200-1205. 526 American Academy of Orthopaedic Surgeons

Chapter 42 Cervical Disk Disease Jonathan N. Grauer, MD John M. Beiner, MD Todd J. Albert, MD Introduction of area available for the spinal cord. Radiculopathy de- velops as exiting nerve roots become irritated or com- Cervical disk disease is a degenerative process that is of- pressed. This radiculopathy can be caused by either a ten encountered in the aging patient. Although a patient soft disk herniation, or more commonly it is secondary can occasionally identify a single inciting traumatic to a chronic irritation from the uncovertebral or facet event, more often no specific trauma is identified. Disk joints in the patient with gradual onset of degenerative degeneration is thought to be initiated by microtrauma, changes. causing a change in the proteoglycan and collagen con- tent of the nucleus, loss of water content, and ultimately Symptoms of radiculopathy include pain, paresthe- altered biomechanics. Patients may have disk herniation sias, or weakness with or without associated neck pain. (“soft disk”) through an annular tear or loss of disk Objective signs of a radiculopathy include hyporeflexia height, causing bulging past the borders of the vertebral in the biceps (C5), brachioradialis (C6), or triceps (C7), end plates. Osteophyte (“hard disk”) formation can con- weakness or atrophy of the innervated muscle group, or tribute to narrowing of the neural foramen, central ca- pain or paresthesias in a dermatomal fashion (Figures 1 nal stenosis, and eventually compression of the neural and 2). Provocative maneuvers such as Spurling’s test elements. In most of these patients, these events are as- can exacerbate such symptoms. ymptomatic, even in the presence of advanced radio- graphic changes. The first seven cervical nerve roots originate and exit above their named vertebrae and the eighth cervi- Symptoms of such disk degeneration can be insidi- cal root originates and exits below the C7 vertebra. In ous or acute in onset. Once foraminal or central stenosis contrast to the lumbar spine, because the nerves in the has developed, minor injuries have the potential to cervical spine exit the spinal canal relatively orthogo- cause local neural irritation and reaction. This can occur nally at or below the level of the disk space, disk pathol- at the level of the root (radiculopathy) or the spinal ogy generally affects the exiting nerve at that segment. cord (myelopathy). If there is compression of the nerve For example, C6-7 disk pathology will generally affect roots and spinal cord, both radiculopathy and myelopa- the C7 nerve root (Figure 3). However, cervical nerve thy may result (know as radiculomyelopathy). roots exhibit a higher degree of overlap than seen in the thoracolumbar spine, and therefore symptom patterns Pathophysiology and Examination may fail to localize to a specific nerve root in some pa- tients. The pathophysiology of degenerative cervical disease involves the disk, zygapophyseal facet joints, uncoverte- The nerve roots most commonly affected by cervical bral joints of Luschka, posterior longitudinal ligament, disk disease are C5, C6, and C7 because the associated and the ligamentum flavum. As the disk loses water motion segments have the most flexion and extension in content and the proteoglycan content changes, it be- the subaxial spine and are thus associated with the comes less able to support load. With progressive degen- greatest incidence of spondylosis. In addition, the water- eration, there is decreased disk height, which is associ- shed area of blood supply to the cervical spinal cord and ated with loss of the normal cervical lordosis and the nerve roots makes those nerve roots most susceptible to transfer of load to the facet and uncovertebral joints. ischemic injury. Osteocartilaginous overgrowth may then occur in accor- dance with Wolff’s law to stabilize the lax segment and Cervical spondylotic myelopathy involves central increased loads. rather than foraminal stenosis. This myelopathy is most typically caused by the combination of disk bulging and With loss of segment height, the ligamentum flavum uncovertebral hypertrophy with vertebral end plate os- can become redundant, further contributing to the loss teophytes (the disk-osteophyte complex) in conjunction with ligamentum flavum hypertrophy/redundancy and American Academy of Orthopaedic Surgeons 527

Cervical Disk Disease Orthopaedic Knowledge Update 8 Figure 1 Upper extremity motor testing for the cervical spine. Note there is dual innervation of some of these muscles. Figure 2 Upper extremity sensory (A) and reflex (B) examination for the cervical facet arthrosis. These changes lead to mechanical com- spine. pression of the spinal cord that can be static or dynamic (such as with neck extension). Anterior pathology may also exert compression on the anterior spinal arteries, which can in turn contribute to ischemia of the spinal cord. Because such insults to the spinal cord occur very slowly, a large degree of central canal stenosis (down to a cross-sectional area of 17 mm2) can generally be toler- ated relatively well. Myelopathy is most commonly manifested as clumsi- ness (loss of fine motor skills), ataxia, and spasticity. Specific symptoms may include dropping of objects, changes in handwriting, and restlessness in the legs and can progress to include loss of bowel or bladder control. The physical examination for myelopathy should in- clude testing for pathologic hyperreflexia below the level of spinal cord compression, the presence of Hoff- man and Babinski reflexes, and difficulty with tandem gait. Clinicians must have a high level of suspicion for this condition and be vigilant in their evaluation for as- sociated signs and symptoms. Additionally, differential diagnoses such as multiple sclerosis, anterior horn dis- ease, and central nervous system tumors may be consid- ered. Because radiculopathy and myelopathy are both caused by some of the same underlying pathology, it is not uncommon to see patients with spondylotic radicu- lomyelopathy. There will often be a combination of the signs and symptoms described for each independent pa- thology. Hyporeflexia is common in the upper extremi- ties where nerve roots are compressed and hyperre- flexia is usually present in the lower extremities below the level of spinal cord compression. Cervical spondylosis may also be associated with neck pain. In addition to radicular pain, felt in a myoto- mal nerve root distribution, patients can feel pain or dis- comfort in a referred sclerotomal distribution corre- sponding to the embryologic origin of individual nerve roots. Pain can be referred to the occiput, interscapular region, or shoulders. The natural history of cervical disk disease helps dictate treatment guidelines. In more than 75% of patients, symptoms of radiculopathy improve with conservative treatment, including physical therapy, 528 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 42 Cervical Disk Disease anti-inflammatory medication, and activity modification. Soft disk herniations can resorb or shrink, and inflam- mation around a compressed nerve root can resolve. In contrast, cervical myelopathy has a less predictable course. Several studies have reported a gradual stepwise progression of the disease, with variable intervals during which patients’ symptoms remained quiescent. Most studies, however, demonstrated a slowly worsening clini- cal picture. Imaging Studies Figure 3 The C7 nerve root exits the thecal sac above the C7 pedicle and is most likely to be affected by pathology at the C6-7 interspace. Plain radiographs are appropriate in the evaluation of neck pain, cervical radiculopathy, and cervical myelogra- though much of this information can be obtained with phy. Such series include AP and lateral films to assess noninvasive MRI, myelography is particularly useful for overall spinal alignment and level of spondylosis, as well patients who cannot have an MRI secondary to im- as to rule out other structural lesions and deformity. planted devices such as pacemakers. In other patients, myelography can be useful if the results of MRI are in- Flexion and extension radiographs can be used to as- conclusive, such as with dynamic compression of the sess angular or translational instability and demonstrate neural elements that cannot be demonstrated with static whether a patient can achieve normal lordosis. Oblique imaging. Flexion-extension radiographs following my- radiographs better visualize the neural foramen and fac- elography can reveal this dynamic compression. ets and can facilitate visualization of the cervicothoracic junction. A swimmer’s view allows for visualization of Diskography has been used to evaluate cervical disk the cervicothoracic junction, if not otherwise possible, degeneration. The procedure is performed via an ante- by limiting the obstructions imposed by the shoulders. rior approach in a trajectory similar to that used for the Other views such as the open mouth odontoid radio- standard anterior cervical approach. Once needles are graph are generally not needed for degenerative condi- in place in the intervertebral disks, fluid can be injected tions. and the distribution and pain provocation can be stud- ied. However, the validity and usefulness of this proce- Plain radiographs are often all that is needed to ini- dure is controversial. The risks of this procedure include tiate conservative treatment. However, if concerns are esophageal puncture and potential mediastinal or disk raised, or if a patient’s symptoms persist beyond appro- space infection. priate conservative treatments, advanced imaging may be indicated. MRI is the axial imaging modality of Electrodiagnostic Studies choice for the cervical spine, allowing visualization of the soft tissues including disks, spinal cord, nerve roots, In most patients, the history and clinical examination and ligaments. Sagittal imaging provides a good over- can reliably identify the presence and level of nerve view of the levels of cord compression and central disk root or spinal cord pathology. Combined with radiogra- pathology. However, sagittal imaging can give the false phy and advanced imaging modalities, accuracy rates impression of cervical kyphosis if the head of the pa- tient if flexed during the imaging study. Parasagittal im- aging can provide information about lateral disk hernia- tions and foraminal narrowing. Axial imaging refines information about cord or root compression and allows for visualization of other surrounding structures such as the vertebral artery or muscles. CT can be used to define the bony anatomy of the cervical spine. However, as the relationship to the neu- ral elements must be inferred, the use of CT is best combined with an intrathecal injection of a contrast me- dium for imaging of degenerative conditions (myelogra- phy). The contrast medium is injected into the thecal sac via a C1-C2 puncture and allowed to diffuse caudally, or via a lumbar puncture and allowed to diffuse proximally with the patient in the Trendelenburg position. This al- lows precise visualization of the neural elements, with filling voids present at sites of neural compression. Al- American Academy of Orthopaedic Surgeons 529

Cervical Disk Disease Orthopaedic Knowledge Update 8 Figure 4 Preoperative sagittal MRI (A) and postoperative lateral radiograph (B) of a patient with persistent C6 radicular symptoms who underwent anterior cervical diskectomy and fusion with autograft and instrumentation. are even higher. In some patients, however, the radia- experienced by the spine. Traction may be useful for tion of arm pain or symptoms such as paresthesias can- radicular symptoms and should generally be done with not be localized to a specific spinal level. In other pa- some degree of flexion to open the neural foramen. Al- tients, clinical examination may not correlate with though modalities often are useful at the time of appli- imaging studies or root symptoms may not be ade- cation, they are not believed to provide lasting relief. quately differentiated from more distal nerve compres- sion. In these patients, electromyogram and/or nerve These therapeutic interventions may break the cycle conduction velocity studies may be useful to differenti- of irritation and splinting, allowing the reestablishment ate acute or chronic radiculopathy from more distal of painless range of motion. Therapy should then focus compressive neuropathies such as carpal tunnel syn- on neuromuscular control and active range-of-motion drome or cubital tunnel compression, which may mimic and stabilization exercises. Finally, general aerobic con- cervical root compression. ditioning should be added. Nonsurgical Care Medical management generally consists of nonste- roidal anti-inflammatory drugs. These drugs can help Management of neck pain and cervical radiculopathy control the inflammatory factors that are often responsi- should start with conservative, nonsurgical measures, in- ble for acute symptoms. Oral steroids can be considered cluding physical therapy, traction, activity modification, for significant exacerbations of symptoms, but potential and certain medications. adverse effects must be considered. The role of narcotics in such degenerative processes is limited. Narcotics With physical therapy, extremes of motion are gener- should be reserved for acute injuries or exacerbations, ally not an important objective. Rather, physical therapy and they should only be used for a limited period. Nar- should emphasize isometric exercises to build tone and cotics should clearly be avoided for chronic pain. control for debilitated muscles and limit the shear forces Selective nerve root blocks and epidural steroid in- jections can be beneficial both diagnostically and thera- 530 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 42 Cervical Disk Disease peutically. Relatively high concentrations of steroids can be achieved while limiting potential systemic adverse ef- fects. Nevertheless, the risks associated with injections into an already stenotic canal or neural foramen have led to questions about their usefulness. The role of conservative care in the management of cervical spondylotic myelopathy is more controversial. It appears that early myelopathy may not always follow the pattern of progressive neurologic deterioration, and therefore a close observational treatment may be indi- cated. Many surgeons believe, however, that once signs or symptoms of myelopathy develop, surgical decom- pression is indicated to optimize neurologic recovery and abate progression. Radiographic evidence of spinal cord compression is not a surgical indication unto itself because many patients will not have correlating symp- toms or examinations. Surgical Indications Figure 5 When a patient has cord compression behind the vertebral bodies as well as at the disk spaces, corpectomy should be considered as shown in this radiograph, Axial neck pain from degenerative disk disease is rarely with a C4 and C5 corpectomy, allograft strut graft, and anterior instrumentation. an indication for surgical intervention. In patients who have been resistant to conservative measures, success incisions may be necessary for longer exposures. The rates of surgical fusion for axial neck pain have gener- level of incision can be guided by anatomic landmarks. ally only been in the 60% to 70% range. This may be re- For example, the carotid tubercle, which can be palpated lated to an incomplete understanding of the associated percutaneously, is the lateral process of C6. The cricoid pain generators and potential painful foci at other cervi- cartilage is approximately at the C6 level, and the thy- cal levels, posterior facets, or nonspinal sources. roid cartilage at the C4-C5 level. The anterior approach is carried down medial to the sternocleidomastoid and In recent years, clinical trials of cervical disk replace- carotid sheath and lateral to the trachea and esophagus. ments have begun in the United States. Goals of this This provides exposure to the anterior aspect of the cer- technology are to allow decompression or removal of a vical spine. The longus coli are then elevated to allow degenerative disk while preserving motion. However, access to the entire disk space. the role and long-term outcome of such implants have not yet been defined. Once a diskectomy is carried back to the posterior disk space, the posterior osteophytes can be taken down In contrast to axial neck pain, radiculopathy re- with or without the associated posterior longitudinal lig- sponds well to a variety of surgical treatments. When an ament. This scenario may be associated with more im- appropriate course of nonsurgical management has mediate and complete relief of symptoms, more com- failed, and radiculopathy persists, the surgeon can offer plete foraminal decompression, and better identification greater than 90% success rates with surgical interven- of extruded disk fragments. Some authors have found tion. Clinically significant myelopathy is generally be- that taking down the posterior osteophytes and poste- lieved to be an indication for surgical intervention. rior longitudinal ligament is not always necessary and that disk height restoration and fusion (with its associ- Surgical Treatment Options for Radiculopathy ated elimination of motion) may be adequate and asso- and Myelopathy ciated with lesser bleeding and surgical times. The type of surgical procedure advocated for cervical arthrosis is dictated by the location and extent of the pathology. There are also situations in which similar pa- thology can be addressed in several ways, with roughly similar results. Anterior decompression can be performed, as ini- tially described in the classic study by Smith and Robin- son. When there is a central disk herniation, significant uncovertebral spurring, or central canal stenosis, ante- rior decompression is the most direct means of decom- pressing the neural elements. Transverse incisions are made for one, two, or arguably three levels, and oblique American Academy of Orthopaedic Surgeons 531

Cervical Disk Disease Orthopaedic Knowledge Update 8 Figure 6 Preoperative sagittal MRI (A) and postoperative lateral (B) and AP (C) radiographs of a patient with multilevel cervical stenosis and myelopathy who was treated with posterior decompression and fusion. Once the diskectomy and decompression have been the vertebral bodies can be addressed. It also offers achieved, interbody fusion is performed by decorticating fewer surfaces to fuse compared with multiple interbody the end plates and inserting a bone graft. This has tradi- grafts, potentially increasing fusion rates (Figure 5). tionally been iliac crest autograft. However, according Bone graft can be autograft, structural allograft (poten- to a recent study, allograft has been shown to afford al- tially filled with local corpectomy bone), or synthetic most identical fusion rates for single-level procedures cages. As constructs grow in length to corpectomies of without the donor site morbidity associated with au- two or more vertebral bodies, consideration should be tograft. This phenomenon does not appear to be as true given to supplementation with posterior stabilization. for multilevel procedures or in the presence of factors However, it is generally believed that lordosis can be re- that inhibit fusion such as smoking. Diskectomy without stored and maintained better with multiple interbody fusion has largely been abandoned because of its associ- grafts. ation with kyphotic collapse, neck pain, and potential for recurrent foraminal narrowing. Alternatively, if there is purely foraminal stenosis and radiculopathy from a soft disk or hypertrophied Plate fixation can be added to potentially increase facet or uncovertebral joint, posterior laminoforaminot- the rate of union, limit kyphotic collapse, and minimize omy may be considered. This procedure allows decom- the need for external cervical orthoses (Figure 4). Many pression without fusion, and destabilization is avoided types of plates exist. All current plate systems lock the as long as the surgeon avoids total facetectomy unilater- screw to the plate to prevent screw backout. Some sys- ally or partial facetectomy bilaterally. Because the disk, tems allow for variable angle screw insertions to facili- which is often thought to be the pain generator for axial tate implantation. Others systems allow for settling of pain, is not directly addressed, posterior laminaforami- the screws within the plate (dynamic plates) to allow the notomy is not a good treatment option if axial pain is a graft to be better loaded. Although plates are now rou- large component of a patient’s symptoms. This approach tinely used by many surgeons, the justification for this is avoids the dangers of anterior dissection, such as recur- uncertain given the high fusion rate in single-level non- rent laryngeal nerve palsy, and preserves the motion instrumented fusions. The potential benefits of plating segment. However, central pathology cannot be ad- must be contrasted with the expense and the potential, dressed because the spinal cord cannot be retracted to but limited, risks of implantation. allow access to the region. Furthermore, disadvantages lie in the muscle dissection and facet capsule disruption With larger procedures such as multilevel diskec- inherent in the procedure. tomy, corpectomy, or partial corpectomy, recent studies have indicated that strut grafting is a good surgical alter- Myelopathy can be treated from posterior as well as native. With this technique, central compression behind anterior approaches. The choice of approach depends on 532 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 42 Cervical Disk Disease Figure 7 A and B, Imaging studies of a patient with multilevel cervical stenosis and ossification of the posterior longitudi- nal ligament who presented with myelopa- thy. Treatment was laminaplasty at C3-C6 with plate fixation (C and D). Note the in- crease in canal diameter between preop- erative (B) and postoperative (C) CT re- constructions. factors including the site of compression (anterior spurs/ screws at C3-C6 and pedicle screws at C2, C7, and below. ossification of the posterior longitudinal ligament versus The disadvantages of this technique include the morbid- posterior ligamentum flavum hypertrophy/redundancy), ity of muscle dissection from a posterior cervical approach overall spinal alignment, and number of levels involved. and the associated loss of motion. The anterior approach allows removal of anterior cord compression, but this must often involve removal of the As an alternative to fusion, laminaplasty was devel- vertebral body if compression is in this region. oped in Japan for the treatment of cervical myelopathy as- sociated with ossification of the posterior longitudinal lig- Posterior decompression in the form of laminectomy ament. Laminaplasty involves hinging open the lamina at has previously been the standard procedure, but was as- multiple levels, affecting decompression. Such openings sociated with postlaminectomy kyphosis in a large per- can be held with sutures, instrumentation, and/or struc- centage of patients. Posterior cervical fusion is thus now tural bone grafts. The goal of the procedure is to decom- generally performed with a laminectomy to restore and press without adding the complications inherent to fusion. maintain cervical lordosis and allow the spinal cord to Outcome studies support these goals, but potential ad- float away from any anterior compressive pathology (Fig- verse effects include increased axial neck pain and loss of ure 6). Posterior fixation can be achieved with lateral mass motion (Figure 7). American Academy of Orthopaedic Surgeons 533

Cervical Disk Disease Orthopaedic Knowledge Update 8 Fusion procedures may be associated with acceler- disk spaces even if there is not compression behind the verte- ated degenerative changes adjacent to the fused seg- bral body. ments. This phenomenon may be alleviated with lamina- plasty as opposed to decompression and fusion. In Malloy KM, Hilibrand AS: Autograft versus allograft in addition, disk arthroplasty may help limit the incidence degenerative cervical disease. Clin Orthop 2002;394:27- of adjacent level disease in the cervical spine, but this 38. has not yet been conclusively demonstrated. Although allograft is the gold standard bone grafting ma- Annotated Bibliography terial, high fusion rates have been observed when allograft is used, especially for single-level cases in nonsmokers. This of- Bryan VE: Cervical motion segment replacement. Eur fers the potential of eliminating the morbidity associated with Spine J 2002;11:S92-S97. the harvest of autograft. Cervical disk arthroplasty is being developed as an alter- Patel CK, Fischgrund J: Complications of anterior cervi- native to fusion procedures. The possibility of limiting adjacent cal spine surgery. Instr Course Lect 2003;52:465-469. level degeneration is one of the potential benefits. This article presents a review of the potential complica- Edwards CC, Heller JG, Murakami H: Corpectomy ver- tions associated with anterior cervical spine surgery for which sus laminoplasty for multilevel cervical myelopathy: An the incidence is relatively low. independent matched-cohort analysis. Spine 2002;27: 1168-1175. Sampath P, Bendebba M, Davis JD, Ducker TB: Out- come of patients treated for cervical myelopathy: A pro- In this study, corpectomy and laminaplasty were found to spective, multicenter study with independent clinical re- arrest myelopathic progression and offer the potential for neu- view. Spine 2000;25:670-676. rologic recovery. However, this study suggested that the lami- naplasty group had less pain at follow-up than the multilevel Authors of this multicenter study of patients with cervical corpectomy group. myelopathy concluded that patients treated with surgery ap- pear to do better than those treated nonsurgically. Fouyas IP, Statham PFX, Sandercock PA: Cochrane re- view of the role of surgery in cervical spondylotic radic- Classic Bibliography ulomyelopathy. Spine 2002;27:736-747. Bohlman HH, Emery SE, Goodfellow DB, Jones PK: In this critical review of the literature, it was difficult to Robinson anterior cervical discectomy and arthrodesis draw reliable conclusions about the risk/benefit balance for for cervical radiculopathy. J Bone Joint Surg Am 1993; cervical spine surgery for spondylotic radiculopathy or my- 75:1298-1307. elopathy. Herkowitz HN: A comparison of anterior cervical fu- Hilibrand AS, Fye MA, Emery SE, Palumbo MA, Bohl- sion, cervical laminectomy, and cervical laminoplasty for man HH: Increased rate of arthrodesis with strut graft- the surgical management of multiple level spondylotic ing after multilevel anterior cervical decompression. radiculoparhy. Spine 1988;13:774-780. Spine 2002;27:146-151. Smith GW, Robinson RA: The treatment of certain A higher rate of fusion was seen after corpectomy and cervical-spine disorders by anterior removal of the inter- strut grafting than after multilevel diskectomy and interbody vertebral disc and interbody fusion. J Bone Joint Surg grafting. This therefore suggests that strut grafting should be Am 1958;40:607-624. considered in patients requiring surgical attention at multiple 534 American Academy of Orthopaedic Surgeons

Chapter 43 Thoracic Disk Disease Chetan K. Patel, MD Introduction Symptomatic thoracic disk disease is relatively uncom- mon compared with disk disease in the cervical and lumbar regions, with an estimated incidence of between 1 in 10,000 and 1 in 1 million persons. The occurrence of symptomatic thoracic disk herniation is greatest be- tween the fourth and sixth decade of life, with a peak in- cidence in the fifth decade. Diagnosis can be difficult because of a variety of clinical presentations. Wide- spread availability and use of MRI has aided in the di- agnosis of symptomatic thoracic disk herniations (Fig- ure 1). However, one MRI study documented thoracic degenerative changes in 73% of asymptomatic individu- als, with 37% showing a disk herniation. Anatomy and Biomechanics Figure 1 Axial MRI scan demonstrating a thoracic herniated nucleus pulposus. The thoracic spine, a relatively rigid structure, is stabi- Etiology lized by the rib cage. Thoracic facets are generally ori- ented vertically, which allows lateral bending and rota- Between 33% and 50% of patients report a history of tion while limiting flexion and extension. These trauma or significant physical exertion before the onset anatomic and biomechanical properties would be ex- of symptoms. However, the role of trauma as the cause pected to decrease the potential of injury to the thoracic of thoracic disk herniations is controversial. Most au- intervertebral disk. This is confirmed clinically by the thors favor degenerative processes as the major cause of observation that less than 1% of symptomatic disk her- disk herniations. This theory is supported by the com- niations occur in the thoracic spine. mon findings of disk degeneration at the level of hernia- tion and the higher incidence of herniations in the lower When a thoracic disk herniation occurs, biomechani- thoracic spine where greater degenerative changes have cal studies have shown the mechanism to be a combina- been reported. End plate changes consistent with tion of torsion and bending load. Several anatomic fac- Scheuermann’s disease are seen more often in symp- tors are suspected in the pathogenesis of neurologic tomatic patients than in those who are asymptomatic, compromise in thoracic disk herniations. Kyphosis of the suggesting an association between Scheuermann’s dis- thoracic spine places the spinal cord directly on the pos- ease and symptomatic herniated thoracic disks. terior longitudinal ligament and the posterior aspect of the vertebrae and disks. Additionally, the vascular sup- Clinical Presentation ply to the thoracic spine is much more tenuous than that of the cervical and lumbar spine, especially from T4 The clinical presentation of patients with thoracic disk through T9. Although the size of the spinal cord is disease is variable, and the differential diagnosis for tho- smaller in the thoracic spine than in the cervical spine, the cord to canal ratio is actually higher because of the smaller size of the thoracic spinal canal. These factors together explain how the thoracic spinal cord is vulnera- ble to injury. American Academy of Orthopaedic Surgeons 535

Thoracic Disk Disease Orthopaedic Knowledge Update 8 racic back pain and myelopathy is extensive. The differ- and highly sensitive. However, as mentioned previously, ential diagnosis includes thoracic herniated nucleus pul- the findings should be interpreted in the context of clin- posus, thoracic degenerative disk disease, cervical and ical findings because of the high percentage of abnormal lumbar herniated nucleus pulposus, intercostal neural- MRI findings in asymptomatic individuals. A CT myelo- gia, multiple sclerosis, amyotrophic lateral sclerosis, gram is also highly sensitive, but this modality is inva- ankylosing spondylitis, fractures, metabolic bone disor- sive and should be reserved for patients who cannot un- ders, tumors, infection, herpes zoster, and diseases of the dergo MRI. Diskography is controversial but can be thoracic and lumbar viscera including aneurysm. A thor- considered in patients with axial pain, multilevel dis- ough history and physical examination are the best tools ease, and no neurologic findings. At this time, no out- for the expeditious diagnosis and treatment of patients come studies exist that demonstrate a correlation be- with thoracic disk disease. tween diskography results and surgical outcomes. Symptoms of thoracic disk herniations occur in one Nonsurgical Treatment of three distinct patterns—axial, radicular, or myelo- pathic. Axial pain usually presents in the mid- to lower To decide on the best treatment course for thoracic disk thoracic regions, worsens with activity, and improves disease, its natural history must first be understood. with rest. Radicular symptoms typically arise from a lat- Asymptomatic patients with abnormal MRI findings eral disk herniation impinging on a nerve root and pro- were noted to remain asymptomatic at a follow-up of ducing symptoms that follow the course of that nerve more than 26 months. Children with painful calcified root. Most commonly, pain and paresthesias are re- thoracic disks improve spontaneously with resorption of ported starting in the back and radiating anteriorly in a calcification; however, these children should be closely band-like pattern in the distribution of the more caudal followed because a few instances of neurologic deficit nerve root. Thoracic dermatomes can be roughly identi- requiring surgical intervention have been reported in fied by the following landmarks: T4 at the nipple line, this population. In adults, the natural history of acute T7 at the xiphoid process, T10 at the umbilicus, and T12 thoracic disk herniations without neurologic deficit is at the inguinal crease. If any skin lesions are noted in a benign. Most patients can be treated with activity modi- dermatomal pattern, herpes zoster may be the underly- fication, anti-inflammatory medications, exercise, and ing cause. Although motor testing is difficult in this re- with bracing in rare occasions. Most patients are ex- gion, the patient can do a partial sit-up to help identify pected to return to their normal activities, including vig- an asymmetric contraction of the segmentally inner- orous sports and work. In patients with radicular symp- vated rectus abdominis. toms, corticosteroid injections of intercostal nerves should be considered when other modalities do not pro- Myelopathy may also be the presentation of a tho- vide adequate pain relief. racic disk herniation when there is significant spinal cord compression. The presentation can vary from sub- Surgical Treatment tle sensory changes to obvious paraparesis and bowel and bladder dysfunction. In addition to the motor and Indications for surgery include progressive neurologic sensory examination, attention should focus on upper deficit, myelopathy, and pain refractory to conservative motor neuron signs such as lower extremity hyperre- treatment. The herniated thoracic disk can be accessed flexia, clonus, Babinski sign, wide-based gait, and super- using the posterior, posterolateral, lateral, or anterior ficial abdominal reflexes. The Romberg sign can help approach (Figure 2). detect subtle changes in proprioception. The results of an upper extremity neurologic examination should be Laminectomy and the transpedicular approach are normal in addition to the patient exhibiting a negative posterior approaches. The surgical approach of choice Hoffmann sign. was once straight posterior laminectomy and disk exci- sion. However, because this approach was associated Diagnostic Imaging with significant risk of neurologic deterioration, it has been largely abandoned. The transpedicular approach Plain radiographs should be obtained first. In addition was developed to allow less retraction of the spinal cord to being used to assess overall alignment, the plain ra- by removing the pedicle and facet joint. Although this diographs should be scrutinized for degenerative approach is well suited for the treatment of a lateral changes, calcification in the disk space or in the canal, disk herniation, a central or paramedial disk herniation fractures, and tumors. Intradiskal calcification is noted is difficult to excise using this approach because of poor in 45% to 71% of patients with symptomatic thoracic visualization. Removal of the pedicle and facet joint herniated disks compared with 10% of asymptomatic in- complex may lead to instability and postoperative pain. dividuals. The posterolateral approach is also known as a costo- MRI is the diagnostic modality of choice in further transversectomy. In this approach, the posteromedial por- evaluation of these patients because it is noninvasive tion of the ipsilateral rib along with the transverse process, 536 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 43 Thoracic Disk Disease Figure 2 Illustration of four surgical approaches to the thoracic disk pathology: transpedicular (A), extracavitary (B), costotransversectomy (C), and transthoracic (D). (Repro- duced from Wood KB, Mehbad A: Thoracic disk herniation, in Koval KJ (ed): Orthopaedic Knowledge Update 7. Rosemont, IL, American Academy of Orthopaedic Surgeons, pp 621-625.) a portion of the pedicle, and the posterosuperior vertebral with the available exposure. Many authors have re- body are removed. This allows gentle removal of the disk ported good visualization and excellent results with this fragment without manipulating the cord. This approach technique. The drawbacks of this technique include the can be used for multiple levels and allows resection of possibility of pneumothorax, pulmonary contusion, paramedian as well as lateral disks. Visualization of cen- atelectasis, pneumonia, and the need for a postoperative tral disks is poor with this approach, and it does involve a chest tube. generous amount of bone resection and significant disrup- tion of the paraspinal musculature. VATS was first reported in 1993 as a minimally inva- sive procedure that can minimize the morbidity of an The lateral extracavitary approach, another extra- open thoracotomy and allow excellent visualization of pleural approach, is a modification of the lateral thora- the anterior approach. One of the main disadvantages cotomy approach that involves resection of the postero- of this technique is the steep learning curve to attain the medial rib in addition to the transverse process, pedicle, high level of technical skills required for the procedure. facet, and posterosuperior portion of the vertebral bod- Calcified protrusions can be adherent to or penetrate ies. Midline access is less than optimal, and a large through the dura and can be difficult to treat via VATS. amount of bone resection and disruption of paraspinal Two-year follow-up data are now available and suggest musculature can lead to postoperative pain. that VATS is effective in a select group of patients. The anterior approaches include thoracotomy and The role of fusion in thoracic disk surgery is contro- video-assisted thoracoscopic surgery (VATS). Anterior versial. Relative indications for fusion include multilevel approach via a thoracotomy was first reported in 1969 diskectomy, Scheuermann’s disease, and bony resection and since then has gained wide popularity. This ap- that removes a large portion of the vertebral body or proach allows excellent visualization of midline and lat- the pedicle facet complex. The resected rib often pro- eral pathology from T5 through T12. Multilevel access is vides sufficient autologous bone graft material without also readily available. The base of the rib articulating the need for added morbidity from harvesting a graft. A with the body and a portion of the pedicle are removed, small fibular allograft augmented with local autograft followed by a partial diskectomy. Using a burr, a trough can also be used. Instrumentation is generally not used is created into which disk material can be pulled for- because the rib cage provides a protective splinting ef- ward to decompress the canal and remove the herniated fect. If deformity correction is desired in multilevel fragment. Fusion can easily be added to the diskectomy cases, instrumentation should be considered. American Academy of Orthopaedic Surgeons 537

Thoracic Disk Disease Orthopaedic Knowledge Update 8 Most patients with thoracic disk herniation and axial Dickman CA, Rosenthal D, Regan JJ: Reoperation for pain alone can be treated successfully with nonsurgical herniated thoracic discs. J Neurosurg 1999;91(suppl 2): treatment. In patients who do not respond well to non- 157-162. surgical treatment, thoracic diskectomy and fusion can be considered; however, the role of surgical intervention Fessler RG, Sturgill M: Review: complications of surgery is controversial. for thoracic disc disease. Surg Neurol 1998;49:609-618. Annotated Bibliography Fidler MW, Goedhart ZD: Excision of prolapse of tho- racic intervertebral disc: A transthoracic technique. Anand N, Regan JJ: Video-assisted thoracoscopic sur- J Bone Joint Surg Br 1984;66:518-522. gery for thoracic disc disease: Classification and out- come study of 100 consecutive cases with a 2-year mini- Otani K, Yoshida M, Fujii E, Nakai S, Shibasaki K: Tho- mum follow-up period. Spine 2002;27:871-879. racic disc herniation: Surgical treatment in 23 patients. Spine 1988;13:1262-1267. The authors present their experience of 100 patients who underwent VATS for the treatment of thoracic disk hernia- Rogers MA, Crockard HA: Surgical treatment of the tions with at least a 2-year follow up. This prospective, nonran- symptomatic herniated thoracic disk. Clin Orthop 1994; domized study supports the conclusions that VATS is effective 300:70-78. in a select group of patients, it is a reasonably safe procedure, and satisfactory outcomes are achieved for most patients. Schellas KP, Pollei SR, Dorwart RH: Thoracic discogra- phy: A safe and reliable technique. Spine 1994;19:2103- Oskouian RJ, Johnsin JP, Regan JJ: Thoracoscopic mi- 2109. crodiscectomy. Neurosurgery 2002;50:103-109. Simpson JM, Silveri CP, Simeone FA, Balderston RA, The authors of this article present a detailed description of An HS: Thoracic disc herniation: Re-evaluation of the a technique for thoracic diskectomy via thoracoscopy. posterior approach using a modified costotransversec- tomy. Spine 1993;18:1872-1877. Classic Bibliography Vanichkachorn JS, Vaccaro AR: Thoracic disk disease: Arce CA, Dohrmann GJ: Herniated thoracic disks. Diagnosis and treatment. J Am Acad Orthop Surg 2000; Neurol Clin 1985;3:383-392. 8:159-169. Awwad EE, Martin DS, Smith KR Jr, Baker BK: As- Wood KB, Blair JM, Aepple DM, et al: The natural his- ymptomatic versus symptomatic herniated thoracic tory of asymptomatic thoracic disc herniations. Spine discs: Their frequency and characteristics as detected by 1997;22:525-530. computed tomography after myelography. Neurosurgery 1991;28:180-186. Wood KB, Garvey TA, Gundry C, Heithoff KB: Mag- netic resonance imaging of the thoracic spine: Evalua- Bohlmann HH, Zdeblick TA: Anterior excision of herni- tion of asymptomatic individuals. J Bone Joint Surg Am ated thoracic discs. J Bone Joint Surg Am 1988;70:1038- 1995;77:1631-1638. 1047. Brown CW, Deffer PA Jr, Akmakjian J, Donalson DH, Wood KB, Schellhas KP, Garvey TA, Aeppli D: Thoracic Brugman JL: The natural history of thoracic disc hernia- discography in healthy individuals: A controlled pro- tion. Spine 1992;17(suppl 6):S97-S102. spective study of magnetic resonance imaging and dis- cography in asymptomatic and symptomatic individuals. Currier BL, Eismont FJ, Green BA: Transthoracic disc Spine 1999;24:1548-1555. excision and fusion for herniated thoracic discs. Spine 1994;19:323-328. 538 American Academy of Orthopaedic Surgeons

Chapter 44 Lumbar Degenerative Disorders Raj D. Rao, MD Kenny S. David, MD Introduction portions of the ventral nerve root, dorsal root ganglion, and nerve root. Stenosis in this region is commonly the Low back pain accounts for more than 15 million pa- result of cartilaginous overgrowth or osteophytes arising tient visits to the physician’s office per year in the from the anterior-inferior aspect of a pars defect, foram- United States, second only to the number of patient vis- inal disk or end plate protrusion, or superior-inferior its for respiratory infections. Complaints of back pain compression between two pedicles as a result of loss of begin around age 35 years and increase in prevalence up disk height. Foraminal height normally ranges from 20 to age 50 years in men and age 60 years in women. The to 23 mm, and anterior-posterior depth ranges from 8 to overall point prevalence of back pain in the United 10 mm in the upper foramen. A foraminal height of less States is estimated to be 18%. The annual cost for man- than 15 mm and a posterior disk height of less than 4 aging back pain is approximately $50 billion, the bulk of mm are associated with nerve root compression in 80% which is spent on an estimated 1% of the patients. The of patients. The lumbar nerve roots lie in the upper fora- three most common lumbar degenerative disorders are men and occupy approximately 30% of the available fo- lumbar spinal stenosis, lumbar disk herniation, and dis- raminal area. Evidence of obliteration of perineural fat cogenic low back pain. on radiographic images is an early indicator of forami- nal stenosis. The extraforaminal zone is lateral to the in- Lumbar Spinal Stenosis tervertebral foramen and contains the exiting root. Lumbar spinal stenosis is a reduction in the dimensions Alteration of lumbar canal dimensions with trunk of the central or lateral lumbar spinal canal that occurs posture results in dynamic stenosis. Extension of the most frequently as a result of chronic degenerative lumbar spine leads to reduced interlaminar space and changes at the lumbar motion segment (Table 1). Pa- buckling of the ligamentum flavum, which can result in tients with lumbar spinal stenosis have back pain associ- spinal stenosis. Foraminal height and width decrease by ated with neurogenic claudication and/or radicular pain. 14% to 18% in extension. Foraminal area decreases by 20% during extension. CT studies show that the cross- Pathoanatomy sectional area of the foramen increases by 12% in flex- ion, and that nerve root compression is least in flexion Absolute stenosis is defined as a decrease in the midsag- and highest in extension. ittal lumbar canal diameter of less than 10 mm, whereas 10 to 13 mm represents relative stenosis. The normal Pathophysiology cross-sectional area of the lumbar canal is 150 to 200 mm2, and a decrease to less than 100 mm2 is a more re- The development of symptoms in a subset of these liable indicator of the combined effects of central and patients can be explained by the pathophysiologic lateral lumbar stenosis. Central stenosis results from changes that occur concurrently with the morphologic congenitally short pedicles, diffuse posterior protrusion changes of stenosis. In animals, 50% constriction of the of the degenerative disk, and infolding of the ligamen- cauda equina results in major changes in cortical evoked tum flavum. potentials and mild motor weakness. These findings gen- erally resolve by 2 months despite persistent compres- The lateral portion of the lumbar canal is divided sion. With constriction to 75%, motor and sensory defi- into three zones: the lateral recess, foraminal zone, and cits are more profound and show only slight recovery at extraforaminal zone (Figure 1). The most common pa- 2 months. Claudication and neurologic symptoms may thology in the lateral recess is bony overgrowth of the initially result from venous distension in the nerve roots superior articular process caused by degenerative facet and dorsal root ganglion. Obstruction of microcircula- joint arthrosis. The foraminal zone lies distal to the pedi- cle and ventral to the pars interarticularis and contains American Academy of Orthopaedic Surgeons 539

Lumbar Degenerative Disorders Orthopaedic Knowledge Update 8 Table 1 | Etiologic Classification of Lumbar Spinal Stenosis Congenital/Developmental Figure 1 Illustration of lateral recess stenosis in which the superior articular process Chondrodystrophy-achondroplasia impinges on the traversing lumbar nerve root. The coronal section shows the relative Congenital small spinal canal with short vertebral pedicles positions of the central canal, lateral recess, foraminal zone, and extraforaminal zone. Congenital cysts from the dura/arachnoid narrowing an otherwise normal canal damage. Compression at multiple sites may explain de- Osteoporosis velopment of symptoms in some patients. Animal stud- Acquired ies have shown that single-level compression of 10 mm Degenerative Hg had marginal effect on nerve function, whereas two- Central canal/lateral recess/foraminal zone level compression caused significant reduction in blood Degenerative spondylolisthesis flow of the cauda equina. Degenerative scoliosis Inflammatory arthritis At the cellular level, bone morphogenetic proteins Ankylosing spondylitis are related to chondrogenesis within the aging disk. The Rheumatoid arthritis migration of these factors from the region of the verte- Pseudogout bral end plates to fibrous cells within the anulus fibrosus Spondylolytic may contribute to osteophyte formation and the bone Iatrogenic overgrowth seen in the degenerative spine. Postdiskectomy/laminectomy/fusion Postchemonucleolysis Vertebral fractures Traumatic Pathologic Spinal infections with abscess bone collapse Miscellaneous Paget’s disease Fluorosis Acromegaly Diffuse idiopathic skeletal hyperostosis Pseudogout Oxalosis Combined Degenerative changes superimposed on a developmentally narrow canal tion at the site of constriction, nerve root fibrosis, and Clinical Features wallerian degeneration of the motor root and posterior spinal tracts contribute to subsequent neurologic mani- Classically, patients have back, buttock, or posterior leg festations. The same general rules appear to apply to the pain that gets worse with standing and walking. Leg human lumbar canal, with significant symptoms appear- symptoms may also be described as cramps, burning ing when the stenosis is greater than 75%. Claudication pain, or weakness. Flexion of the trunk alleviates symp- symptoms from lumbar spinal stenosis occur in 90% of toms, and extension aggravates the symptoms. Leaning patients who have a cross-sectional spinal canal area on a cart helps, primarily because of the flexed posture less than 100 mm2. of the trunk in this position. Sleeping is comfortable in the fetal position. The limitations in activity and stooped In animal studies, the rate of onset of compression forward posture are commonly attributed to age, and plays a role in the pathophysiology of stenosis. Rapid many patients learn to work within their limitations. Au- onset (0.05 to 0.10 s) compression causes more damage tonomic sphincter dysfunction manifests as recurrent than insidious onset (20 s) pressure. The compressive le- urinary tract infection associated with an atonic bladder, sion results in greater mechanical deformation at the incontinence, or retention, and occurs in up to 10% of edge of nerve root, a phenomenon referred to as the patients with advanced degrees of stenosis. edge effect. Histologic examination of edge segments has revealed significant microvascular and neural tissue Claudication manifests as diffuse buttock and/or leg pain, nonspecific paresthesias, or radicular symptoms 540 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 44 Lumbar Degenerative Disorders that commence with walking for varying distances. Un- tectomy can result in iatrogenic instability and may re- like vascular disease, the claudication distance with quire fusion. symptomatic spinal stenosis may vary considerably and is relieved by sitting and not by standing. Activities per- There are no guidelines on whether adjacent levels formed with the trunk flexed, such as cycling or walking with lesser degrees of stenosis should be included in the uphill, are performed more easily. The exertion-induced decompression. The benefits of a greater decompression symptoms of spinal stenosis can be accurately repro- of the neural elements need to be weighed against the duced using a treadmill, providing a method for preop- potential morbidity of a longer operation. In general, a erative and postoperative quantification of symptoms. level with mild stenosis may be excluded if radicular symptoms corresponding to that level are absent. De- The manifestations of central and lateral canal compressing too few levels may be a source of persis- stenosis are not easily distinguished. Unilateral radicular tent symptoms postoperatively. Somatosensory-evoked pain from foraminal stenosis is worsened by extension potential techniques may serve as a guide to the extent to the painful side (Kemp sign). Paresthetic and dyses- of decompression in the future. thetic symptoms may be an indicator of dorsal root gan- glion entrapment in the foramen. Unlike disk hernia- The anulus fibrosus is left intact when possible, re- tions, radicular pain from stenosis is typically not secting only free fragments or extruded segments of the aggravated by Valsalva maneuvers or accompanied by a disk that result in neural impingement. Diffuse bulging positive straight leg raising sign. of the disk is unlikely to result in continued neural com- pression in patients who have undergone a wide lami- Management nectomy with bilateral partial facetectomy. Nonsurgical therapy with anti-inflammatory agents, an- Based on the existing literature, a fusion should be algesics, activity modification, exercises, and soft braces considered following decompressive laminectomy in (1) may help patients with exacerbations of pain but seldom patients who have stenosis with degenerative spondy- achieve sustained improvement. Epidural steroid injec- lolisthesis; (2) when radiographic criteria for instability tions or selective nerve root injections result in substan- exist preoperatively; (3) when more than a combined tial relief of radicular pain and may obviate the need for 50% of the bilateral facet joints are resected as part of surgery over the short term in a subset of patients. Ide- the decompression; and (4) when decompression is per- ally, the injections are performed at the level of the formed in a patient with a flexible or progressive degen- symptomatic nerve root through a fluoroscopically di- erative scoliosis. rected transforaminal technique. One to three injections are typically performed, with 1-to 2-week intervals be- The precise role of instrumentation in lumbar spinal tween injections. stenosis is currently unclear. The aims of pedicle screw instrumentation in spinal stenosis surgery include defor- Patients with persistent lower extremity symptoms mity correction, immediate stabilization of an unstable from lumbar spinal stenosis are generally offered surgi- spine, improvement in fusion rates, and faster mobiliza- cal decompression. The physician should make clear tion of patients. The advantages of instrumentation need that the aim of surgery is to relieve current disability to be weighed against the potential morbidity of extend- rather than prevent future complications. There is no ing the surgical procedure. A randomized prospective conclusive evidence that disability from spinal stenosis study showed that the addition of instrumentation to worsens over time. Less frequent indications for surgery lumbar decompression and posterolateral arthrodesis include progressive neurologic deficit or cauda equina for degenerative spondylolisthesis with stenosis resulted syndrome. in improved fusion rates, but it did not improve the overall clinical outcome of patients. The optimal surgical approach combines maximal thecal sac and nerve root decompression and preserves Alternative Surgical Techniques stability. The facet joints, capsule, intervertebral disk, and interspinous ligaments are important lumbar spine Several limited approaches have been proposed as alter- stabilizers. In typical degenerative lumbar spinal steno- natives to the traditional decompressive laminectomy sis, maximal compression of the thecal sac occurs at the and partial facetectomy. The rationale for these ap- level of the disk. Decompression of a single level is proaches involves decreased patient morbidity and achieved by resection of approximately 50% of the faster rehabilitation with a more limited operation, lim- cephalad and caudad laminae and the intervening liga- iting the surgery to the pathologic area (the bony and mentum flavum. After creation of a central trough, the soft-tissue pathology in most patients with degenerative decompression is extended laterally to the medial wall stenosis is at the level of the interlaminar window and of the pedicle bilaterally to ensure that the traversing can be adequately addressed through an interlaminar nerve root is free of pressure. Greater than 50% exci- fenestration or laminotomy), decreased postoperative sion of the bilateral facets or unilateral complete face- radiographic listhesis, reduced scarring posterior to the thecal sac and root, awareness that paraspinal muscle American Academy of Orthopaedic Surgeons 541

Lumbar Degenerative Disorders Orthopaedic Knowledge Update 8 atrophy with wide exposure may be a source of postop- preoperatively may be a negative prognostic indicator. erative back pain, and limited surgical destabilization, The results in general deteriorate over a 5- to 10-year which potentially obviates the need for fusion. The ben- period, with increasing back pain, claudication, and rates efits of these approaches need to be weighed against of revision surgery. Mortality in these elderly patients is their limitations, which include a higher incidence of 0.6% to 1.0% following surgery. nerve root injury and dural tears, bone regrowth poten- tially compromising the result, the need for technically The rates of lumbar fusion vary considerably across demanding procedures and longer surgical times, the geographic regions and specialties, suggesting uncer- fact that most of these procedures do not address cen- tainty among surgeons on the indications for fusion fol- tral stenosis, and the lack of long-term clinical efficacy lowing decompressive laminectomy. In a multicenter studies. study of patient selection and outcomes following de- compressive laminectomy, instrumented and noninstru- A unilateral hemilaminectomy or laminotomy may mented fusion in patients with degenerative spinal be indicated in a patient with one-sided symptoms from stenosis, the major predictor of the decision to perform lateral stenosis and no significant central stenosis. Simul- arthrodesis was found to be the individual surgeon. taneous diskectomy should be performed if there is re- Other factors associated with this decision were the sidual bulging of the disk, especially when the patient presence of more than 5 mm of spondylolisthesis, has good disk height. Bilateral or multilevel laminotomy younger age, female patients, scoliosis greater than 15°, may be considered in patients with degenerative steno- patients with greater severity of back pain, and fewer sis at multiple levels. Myelography in these patients usu- levels decompressed. The authors reported significantly ally shows an hourglass compression of the thecal sac at greater relief of back pain after 6 and 24 months in the several levels, with spacious intervening areas. The pro- noninstrumented arthrodesis group. The decreased satis- cedure differs from the traditional multilevel laminec- faction in the instrumented arthrodesis group at these tomy by leaving the spinous processes and interspinous earlier stages cannot be well explained, but it may be re- ligaments intact. In unilateral laminotomy with bilateral lated to pain associated with the instrumentation itself. decompression, an ipsilateral laminotomy and decom- The increased likelihood of a successful arthrodesis with pression is followed by decompression of the contralat- instrumentation may result in improved results in this eral side by angling the microscope or endoscope across group over a longer period. Hospital costs were highest the top of the dural sac. Resection of the contralateral in patients who underwent instrumented arthrodesis. ligamentum flavum allows good exposure of the con- tralateral side. Lumbar Disk Herniation Prognosis and Outcomes Pathoanatomy There is little published information regarding the true A disk herniation is a localized displacement of disk natural history of lumbar spinal stenosis. Studies that in- material beyond the limits of the intervertebral space. clude nonsurgical treatment show that about 15% to The disk material can be nucleus pulposus, cartilage, an- 20% of patients improve, 15% to 20% get worse, and ulus fibrosus, fragments of apophyseal bone, or any 60% to 70% remain unchanged. Surgery appears to im- combination of these materials. A herniated disk should prove short-term outcomes in patients with severe be distinguished from a disk bulge, which is a diffuse stenosis. In one study, 52% of nonsurgically treated pa- symmetric outpouching of the anulus fibrosus associated tients showed improvement at 4-year follow-up com- with varying degrees of disk degeneration. A true herni- pared with 70% of surgically treated patients. Patients ation may either be a protrusion, extrusion, or seques- undergoing surgical treatment generally had more se- tration (Figure 2). The base of a protrusion is wider than vere degrees of stenosis and were more symptomatic any diameter of the displaced material. In an extrusion, than the nonsurgically managed group. the diameter of the displaced material in at least one plane is greater than the width at its base. If a displaced Appropriate patient selection and thorough decom- fragment loses all continuity with the parent disk, it is pression result in good long-term results following de- termed a sequestration, and is prone to migrate within compressive lumbar laminectomy with or without fu- the spinal canal. The relationship of the herniated nu- sion. A meta-analysis of the surgical treatment of spinal clear material to the surrounding anulus fibrosus and stenosis found that the average proportion of good to the overlying posterior longitudinal ligament defines its excellent results in 74 studies was 64%. There were no containment. A herniation completely enveloped by an- consistent predictors of clinical outcome, but younger ulus fibrosus, posterior longitudinal ligament, or both is age, greater severity and duration of symptoms, previous termed a contained herniation. Nuclear material that es- back surgery, multilevel involvement, coexisting medical capes through the annular periphery and rests beneath morbidity, and litigation issues were associated with the posterior longitudinal ligament has been referred to poorer outcome. The presence of bladder symptoms as subligamentous. 542 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 44 Lumbar Degenerative Disorders Figure 2 Illustration of four morphologic types of disk herniations: contained disk to induce mild local discomfort. Stimulation of a root protrusion (A), noncontained subligamentous disk extrusion (B), noncontained transli- exposed to nucleus pulposus reproduced sciatic pain in gamentous disk extrusion (C), and noncontained disk sequestration (D). the leg. Epidural application of extracts of nucleus pul- posus in animal models when combined with mild defor- The geographic relationship of the herniated nucleus mation of the nerve root and dorsal root ganglion re- to the circumference of the anulus fibrosus and the in- sulted in increased tissue edema, fibrosis in and around tervertebral foramen is used to classify herniations as nerve root, demyelination of axons, and Schwann cell central, paracentral, foraminal, or extraforaminal. Para- hypertrophy. central herniations are the most common pattern en- countered in clinical practice. They are caused by the Inflammatory cytokines such as interleukin-1β, weaker posterolateral portion of the posterior longitudi- interleukin-6, prostaglandin-E2, and phospholipase A2 nal ligament overlying this segment of the anulus fibro- are found in significant concentrations in the nerve root sus. Posterolateral herniations compress the lower exit- and dorsal root ganglion, suggesting they play a role in ing root (for example, the L5 root at L4-5 level), the inflammatory process. The presence of these agents whereas the more lateral and extraforaminal herniations incites vascular changes around the nerve root and also are more likely to compress the upper root (for exam- has a direct effect on the blood-nerve barrier, promoting ple, the L4 root at L4-5 level). Axillary and shoulder de- intraneural edema and reducing neuronal perfusion. In- scriptions refer to the position of the herniated disk teractions between nerve growth factors at the nerve with respect to the origin of the nerve root from the root and dorsal root ganglion may play a role in the thecal sac. central modulation of spinal pain. Pathophysiology Clinical Features Several pathophysiologic events occur in the nucleus Lumbar disk herniation is the most common cause of pulposus and adjacent areas that act in concert to pro- radicular pain in the adult working population, with an duce radicular symptoms. Tumor necrosis factor-α estimated 2.8 million herniations (1% of the general (TNF-α) may be a key component of this process in that population) occurring annually. Ninety-five percent of it exerts its effect by sensitizing the nerve root to pro- these herniations involve the L4-5 or L5-S1 lumbar disk duce pain in the presence of a mechanically deforming spaces, and most patients are between the ages of 20 force. Local accumulation of sodium ion channels and and 50 years. Patients typically present with back pain spontaneous axonal activity may be pathways through and sharp, stabbing leg pain accompanied by a feeling of which TNF-α acts. numbness or tingling in a specific dermatomal distribu- tion. One study reports a dermatomal sensitivity and The effects of mechanical deformation are com- specificity of 74% and 18% for paresthesias from lum- pounded by chemical sensitization of the nerve root. bar disk herniation. Referred (sclerotomal) pain in the When diskectomy is performed using local anesthetic in buttock or posterior thigh arises from stimulation of human subjects, light mechanical stimulation of nerve muscles, ligaments, periosteum, and other structures of roots not exposed to nucleus pulposus have been noted mesodermal origin and does not go beyond the knee. Symptoms are aggravated by activities and maneuvers that raise the intra-abdominal and intradiskal pressure, such as coughing, sneezing, and sitting. Motor, sensory, and reflex evaluation corresponding to the lumbar roots should be specifically evaluated (Figure 3). The straight leg raising test is a clinical ma- neuver that demonstrates limited excursion of inflamed lumbosacral nerve roots. In lumbar disk herniation, the test is sensitive (true positive in 72% to 97% of pa- tients) but not specific (false positive in 11% to 66% of patients). In contrast, the crossed straight leg raising test has a lower sensitivity (true positive in 23% to 42% of patients) but much higher specificity (false positive in 85% to 100% of patients). There is minimal movement in the sciatic nerve or roots during the first 20° to 30° of straight leg raising; most tension in the roots develops at 35° to 70° of elevation. Large lumbar disk herniations may result in a cauda equina syndrome, characterized by bilateral leg pain, American Academy of Orthopaedic Surgeons 543

Lumbar Degenerative Disorders Orthopaedic Knowledge Update 8 Figure 3 Illustration of the motor, reflex, and sensory radicular findings in various types of lumbar disk herniation. 544 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 44 Lumbar Degenerative Disorders lower limb weakness, saddle anesthesia, and bowel/ headlight and a small posterior midline incision cen- bladder changes. One percent to 10% of all patients un- tered on the disk space. Surgeons must be aware of the dergoing surgery for lumbar disk herniation have symp- anatomic peculiarities of the upper lumbar canal when toms of cauda equina syndrome. The incidence may be treating patients with high lumbar disk herniations. Ana- higher when patients with subtle urinary symptoms are tomic peculiarities include smaller interlaminar spaces, included. Pain varies substantially in patients, and it is greater coverage of the disk space by the lamina of the modified and influenced by several factors including in- superior vertebra, proximity to the conus medullaris, a dividual cultural and psychologic factors, sleep depriva- smaller spinal canal with a higher volume of nerve tis- tion, and secondary gain. Evaluation of the patient sue, and a more horizontal orientation of the upper lum- should include a skillful appraisal of these issues. bar nerve roots. An extraforaminal disk herniation is ideally accessed through the Wiltse paraspinal approach, Management which preserves motion segment stability by avoiding injury to the lamina and facet joints. Injury to the dorsal Nonsurgical measures including activity modification, root ganglion with postoperative dysesthesias is a poten- anti-inflammatory agents, physical therapy modalities, tial complication when treating patients with this form exercises, spinal manipulation, corsets, epidural injec- of disk herniation. Endoscopic and other percutaneous tions, and nerve root blocks result in good resolution of techniques for disk decompression are discussed in symptoms in most patients. It is unclear whether any of chapter 50. these treatment options actually alters the natural his- tory of disease. Prognosis and Outcome Following Intervention Foraminal epidural steroid injections accurately ad- Lumbar disk herniation is a self-limiting disease in most ministered under fluoroscopic control may help in com- patients. Eighty percent to 90% of patients obtain satis- bating the chemical mediators of pain and inflammation factory resolution of symptoms with nonsurgical treat- associated with disk herniations. A positive response is ment. Imaging studies that monitor the changes in size usually indicated by a reduction of leg pain by more of nonsurgically treated disk herniations have shown a than 50%. The steroid load generally precludes more progressive decrease in the size of herniations over than three to four injections over a 1-year period. The time. Large extrusions have a greater likelihood of total most important application of these injections may be in resorption; they are phagocytosed by cells attracted by shortening the pain-control phase of treatment, which the disk-incited inflammatory response or from desicca- allows early reconditioning to begin. tion and atrophy secondary to loss of nutrient supply. Persistent intractable pain following nonsurgical Nonsurgical treatments will likely result in favorable treatment during a minimum 6-week period is the most outcomes when the duration of sciatica is less than 6 frequent indication for surgery. There is some evidence months, the patient is younger, and there is no litigation that results of surgery deteriorate when nonsurgical care involved. The results of surgical treatment are better in exceeds 12 months. Imaging studies must correlate with patients with large anterior-posterior herniated disk the symptoms and neurologic findings. The presence of length and in patients who have a greater compromise a nerve tension sign improves the likelihood of a good of the canal area by the disk herniation. Patients who postoperative result. have an extruded or sequestered fragment with a mini- mal fissure in the anulus fibrosus or those who have a Other factors that influence the decision to proceed detached fragment lying beneath an intact anulus fibro- with surgery include disk herniation into a stenotic ca- sus are likely to do better following surgery than those nal, which may lead to recurrent or persistent symp- who have an extruded disk with a large or massive an- toms; inability of patients to comply with the dictates of nular defect or those who have an intact anulus fibrosus a conservative therapy regimen; and the number of sci- and no detached fragment beneath the anulus fibrosus. atica episodes experienced by a patient. Among patients experiencing a second episode of sciatica, 90% will im- The likelihood of recovery of neurologic deficit is in- prove but 50% will have a recurrence of symptoms. The dependent of surgical intervention, and patients with incidence of future episodes of sciatica rises to almost neurologic deficit but no pain do not require surgery. 100% in patients who have experienced three prior epi- Surgery is considered in some patients with painless mo- sodes. Absolute indications for surgery in lumbar disk tor deficits when there is functional weakness in a major herniation are bladder and bowel involvement and pro- muscle group or in those with significant motor deficits gressive neurologic deficit. and no return of function after 6 weeks. Recovery of motor deficit is the general rule, although in some pa- A laminotomy and diskectomy (microdiskectomy) is tients complete recovery may take a long time. Long- the gold standard for surgical treatment of a posterolat- term studies have shown that 30% of patients will con- eral lumbar disk herniation. This treatment is frequently tinue to have sensory deficits despite resolution of pain. performed as an outpatient or short-stay procedure us- ing an operating microscope or surgical loupes with a American Academy of Orthopaedic Surgeons 545

Lumbar Degenerative Disorders Orthopaedic Knowledge Update 8 This finding is consistent with the fact that sensory fi- herniations in patients in this age group are more fre- bers are the most vulnerable to compression (they are quent in the upper lumbar spine. Nerve root tension affected first and recover last). signs such as the straight leg raising test are commonly negative in elderly patients. This may be secondary to One prospective controlled study compared out- reduced resting tension in the nerve roots as a result of comes of surgical and nonsurgical treatment in a group reduced disk height from the degenerative process or of patients with lumbar radicular pain and concordant reduced limb length from degenerative hip and knee myelograms. Surgery was superior to nonsurgical treat- changes. Chronic fibrosis of the roots from compro- ment at 1-year follow-up and continued to be slightly mised microcirculation may contribute to the severity of better at 4-year follow-up. Outcomes were similar in the radicular pain. Histologically, the herniated disk both groups at 10-year follow-up. Approximately 60% fragment primarily contains sections of anulus fibrosus. of both groups of patients were symptom free at 10-year Spontaneous resorption and improvement is less likely follow-up, although clinical recovery occurred earlier in to occur. the surgically treated group. In another 5-year follow-up study, 56% of nonsurgically managed patients reported Disk Herniation in Young Patients symptomatic improvement compared with 70% of surgi- Pediatric disk herniations constitute 1% to 3% of all in- cally treated patients. stances of lumbar disk herniation. Previous trauma and vertebral column abnormalities such as congenital Long-term success rates following open diskectomy stenosis or transitional vertebrae may increase the like- are between 76% and 93%. In a study of 63 patients 10 lihood of herniation. The clinical presentation is similar years after interlaminar fenestration and diskectomy, to that for adults, with back pain and nerve tension signs 75% of patients reported some back pain, but only 13% being frequently reported; neurologic deficits in these reported severe back pain. Younger patients with preop- patients is typically uncommon. The herniation is fre- erative degenerative changes at the disk had a higher in- quently an avulsed fragment of the ring apophysis of the cidence of back pain. Sensory disturbances were present vertebral body. In children and adolescents who have in 81% of patients preoperatively, but in only 31% of persistent symptoms despite nonsurgical treatment, sur- patients at final follow-up. Motor deficits were present gery usually results in good relief of symptoms. A uni- in 76% of patients preoperatively, and in 14% of pa- lateral hemilaminectomy with partial diskectomy is tients at 10-year follow-up. A complete foot drop was sufficient treatment for most patients. A bilateral lami- present in four patients preoperatively and this symp- nectomy is occasionally necessary when the avulsed tom did not improve after surgery. The straight leg rais- apophysis fragment is large. ing test was negative in 97% of patients at the 10-year follow-up. Mild preoperative urinary disturbances in Discogenic Low Back Pain four patients resolved completely. Discogenic pain refers to pain originating from a degen- Special Situations erative lumbar disk, which is characterized by axial low back pain without associated radicular findings, spinal Recurrent Herniation and Reoperation deformity, or instability. The controversy surrounding Recurrent herniations at the same level occur in ap- discogenic low back pain primarily exists because de- proximately 5% of surgically treated patients at 5-year generative changes at the disks are ubiquitous, yet follow-up and can be ipsilateral or, less frequently, con- symptoms arise in only a few patients; multiple addi- tralateral. Survival analysis or rates of revision are a tional anatomic sources of low back pain exist (Table 2); better measure of surgical success. A recent large the diagnosis of discogenic low back pain is made pri- population-based study from Finland analyzed the risk marily with provocative diskography, which is controver- of reoperations after lumbar diskectomy. Fourteen per- sial in itself; it is unclear whether the treatment options cent of a total of 35,309 patients in the study group un- for discogenic low back pain are superior to the natural derwent a second procedure during the 10-year period history of the disorder over the long term. Notwith- of the study. The second procedure was diskectomy in standing these issues, the degenerative lumbar disk is 63% of patients, decompression in 23%, and fusion in being increasingly recognized as a valid source of axial 14%. Among the patients who underwent a second pro- low back pain. cedure, there was a 25% cumulative risk of needing a third spinal surgical procedure within the next 10 years. Pathoanatomy and Pathophysiology A pain-free interval of more than 1 year was associated with a lower risk of revision. As the disk ages, several chemical and mechanical changes occur within it, which result in a continuum of Disk Herniation in the Elderly changes that can be observed using radiographic imag- Disk herniation in elderly patients commonly occurs in ing. Type II collagen in the nucleus pulposus and anulus the setting of spinal stenosis or spondylolisthesis. Disk 546 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 44 Lumbar Degenerative Disorders Table 2 | Differential Diagnosis of Low Back Pain Spinal Causes Figure 4 Illustration of the axial lumbar vertebra showing the origin, course, and Trauma structures innervated by the sinuvertebral nerve. Fractures closer to each other. Laxity in the peripheral attach- Musculoligamentous injury ments of the anulus fibrosus and the facet joint capsules Fracture in pathologic bone may allow motion or displacement between the verte- Infections bral bodies. Increased load transfer at the facet joints Diskitis, osteomyelitis and vertebral end plates results in degenerative changes Epidural abscess at both these sites. Inflammatory Seronegative spondyloarthropathy Nerve fibers and nerve endings found in the periph- Rheumatoid arthritis eral portions of the disk offer a possible mechanism by Tumors which lumbar disks act as pain generators. The disk is Primary − arising from bone or marrow elements innervated by the sinuvertebral nerve, which is formed Metastatic by branches from the ventral nerve root and sympa- Degenerative conditions thetic plexus (Figure 4). Once formed, the nerve turns Spinal stenosis back into the intervertebral foramen along the posterior Spondylolisthesis aspect of the disk, supplying portions of the anulus fi- Scoliosis brosus, posterior longitudinal ligament, periosteum of Discogenic low back pain the vertebral body and pedicle, and adjacent epidural Miscellaneous veins. The free nerve endings in the peripheral anulus fi- Paget’s disease brosus are immunoreactive for several pain-related neu- Arachnoiditis ropeptides—substance P, calcitonin gene-related pep- Sickle cell disease tide, and vasoactive intestinal peptide. In degenerative Extraspinal Causes disks, nerve endings penetrate deep into the anulus fi- Visceral origin brosus and even into nucleus pulposus. The free nerve Urinary system-kidney stones, pyelonephritis endings that penetrate deep into the disk are also im- Reproductive system (endometriosis, retroverted uterus, ectopic preg- munoreactive for substance P. nancy) Gastrointestinal tract (duodenal ulcers, pancreatitis, biliary colic) Chemical factors may help explain why pain devel- Abdominal aortic aneurysm ops in a subset of patients with degenerative changes. Retroperitoneal tumors Mechanical deformation of the anulus fibrosus stimu- Musculoskeletal origin lates both mechanoreceptors as well as nociceptors by Myofascial pain lowering their firing thresholds. Inflammatory mediators Hip arthrosis eluted by the disk (phospholipase A2, interleukin-1, and Sacroiliac joint pathology matrix metalloproteinases) may play a role in the sensi- Miscellaneous causes tization of pain receptors. Phospholipase A2 also stimu- Psychogenic lates the dorsal root ganglion, which can serve as an- Central pain syndromes other pathway for axial pain generation. fibrosus is increasingly replaced by type I collagen, Mechanoreceptors and nociceptors in the facet joint chondroitin sulfate is replaced by keratan sulfate, and capsules and synovium may play an accessory role in there is increasing dissociation between the collagen the symptoms of discogenic pain. The number of these and proteoglycans within the disk. The resulting loss in receptors in the facet joints falls during the weeks fol- hydrostatic properties of the disk leads to altered load transmission, with asymmetric and abnormal stresses being transmitted from the vertebral end plate to the periphery of the anulus fibrosus. Radial tears develop within the anulus fibrosus, with subsequent fissuring and ingrowth of granulation tissue. As the process continues, the disk loses height, and the vertebral bodies come American Academy of Orthopaedic Surgeons 547

Lumbar Degenerative Disorders Orthopaedic Knowledge Update 8 Table 3 | Radiographic Criteria for Lumbar Spine Instability small degrees of instability, but intraoperative measure- ments of motion may provide more information in the Resting radiographs future. 1. Sagittal displacement > 4.5 mm or 15% 2. Relative sagittal plane angulation > 22° Diagnostic Testing or Flexion-extension radiographs Patients with discogenic low back pain typically have 1. Sagittal displacement > 4.5 mm or 15% MRI scans showing a degenerative disk without signifi- 2. Relative sagittal plane rotation cant stenosis or herniation and concordant provocative > 15° at L1-2, L2-3, L3-4 diskography. Patients who have normal MRI scans cor- > 20° at L4-5 relate highly with negative lumbar diskograms, and such > 25° at L5/S1 patients should be presumed to have a nondiscogenic cause of low back pain. Degenerative changes are inter- (Reproduced with permission from Posner I, White AA III, Edwards WT, Hayes WC: A biome- preted with caution in older patients because of the chanical analysis of the clinical stability of the lumbar and lumbosacral spine. Spine ubiquitous nature of these changes in asymptomatic 1982;7:374-389.) older patients. Patients who have obvious radiographic instability or multilevel severe degenerative disk and lowing interbody fusion in animals, suggesting that ap- facet joint changes cannot be categorized as having dis- propriate stabilization of the disk space reduces noci- kogenic back pain. It is helpful to categorize patients ception from the facets. Vertebral end plates and the into two groups: those who have radiographic evidence underlying cancellous bone have an increased density of of loss of disk height and those who do not. sensory nerves in patients with degenerative disk dis- ease, thereby providing another pathway for pain gener- Patients With Loss of Disk Height ation. In patients with loss of disk height, plain radiographs show a decrease in disk height, which is often associated Clinical Features with vertebral end plate sclerosis or mild facet joint ar- throsis. MRI will usually show a greater degree of de- Clinically, discogenic pain is characterized by axial low generative changes at the disk. There is loss of disk back pain without associated radicular pain, nerve ten- height often associated with bulging of the posterior an- sion signs, spinal deformity, or instability. The pain is ulus fibrosus into the canal, some infolding of the liga- generally deep, aching, and exacerbated by sitting, bend- mentum flavum, minor degrees of canal and foraminal ing, and axial loading. Symptoms are predominantly me- stenosis, and abnormal signals at the vertebral end plate. chanical, and rest may provide relief. There may be a history of prior injury to the spine such as a fall, lifting Provocative diskography is used to confirm the diag- with outstretched arms, or sudden twisting that resulted nosis of discogenic low back pain when surgery is being in back pain. Instead of getting better, the pain gradu- considered. The procedure is performed using fluoro- ally gets worse. Referred pain may radiate in a scleroto- scopic control with the patient awake. Several criteria mal fashion to the sacroiliac joints, buttocks, or posterior must be met for a diskogram to be considered positive. thighs, and occasionally into the inguinal region with in- There must be a concordant pain response from the pa- volvement of the L5-S1 disk. Greater degrees of back tient, evidence of abnormal disk morphology on fluoros- pain appear to be associated with a more distal pattern copy and postdiskography CT examination, and nega- of pain referral. tive control levels in the lumbar spine. Some authors report that low-pressure pain responses suggest a chem- Traditional instability of a motion segment is a rec- ical pathway for pain generation and have better out- ognized cause of low back pain. This instability is diag- comes following fusion. nosed radiographically by intervertebral translation or angulation, using criteria put forth by White and Panjabi Although complications from the procedure are un- (Table 3). Patients frequently have mechanical back common, diskography continues to be controversial. pain related to posture or motion but no apparent ra- Positive diskograms have been found in up to 25% of diographic instability. These patients may have a painful patients who were only mildly symptomatic, which arc of motion during forward bending or extension or raises the risk of overdiagnosing discogenic disease. report a sense of shifting of their trunk with certain pos- When using strict criteria, including low-pressure injec- tures. Micromotion at the intervertebral segment may tion and a normal control disk, positive results may be play a role in the pathogenesis of pain in these patients. as low as 30% in patients with chronic low back pain. There are currently no reliable methods of verifying Normal psychologic profiles have been reported in about 20% of patients with chronic low back pain who are candidates for diskography. 548 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 44 Lumbar Degenerative Disorders Patients Without Loss of Disk Height other patients may be associated with approach-related Plain radiographs in patients without evidence of loss of muscle denervation and necrosis or disruption of the ad- disk height generally do not show any significant jacent facet joints. Posterior lumbar interbody fusion or changes. Disk height is maintained, and there are no transforaminal interbody fusion can allow posterior de- facet joint nor end plate changes. MRI typically shows compression and concurrent anterior column stabiliza- mild changes such as desiccated disks with low signal on tion, while avoiding the morbidity of a separate anterior T2-weighted imaging or annular tears. operation. The drawbacks include limitations on the size of the anterior graft or implant, nerve root injury, epidu- Prognosis ral fibrosis and chronic radiculitis, and potential instabil- ity from resection of the facet joints needed for expo- The natural history of acute low back pain is generally sure. excellent. Ninety percent of patients will go on to com- plete pain relief within 2 to 6 weeks. In patients who Anterior lumbar interbody fusion (ALIF) has sev- have chronic pain, one study found that 40% of patients eral theoretic benefits in the treatment of discogenic could be diagnosed as having discogenic back pain with low back pain. It can remove pain fibers and receptors positive diskograms at L4-L5 or L5-S1. There is limited from the anulus fibrosus and nucleus pulposus, elimi- information on the natural history of confirmed disco- nate motion across disk, restore disk height and indi- genic low back pain. One study found 68% of patients rectly decompress foramen, and enable surgeons to improved, 24% worsened, and 8% remained unchanged avoid posterior muscle disruption during the approach. over a 5-year period. Fusion rates are high, varying from 80% to 96% of pa- tients. The disadvantages of the anterior approach are Management the risks of major vessel injury and, in males, retrograde ejaculation and impotence. Laparoscopic ALIF tech- Anti-inflammatory, analgesic, and antispasmolytic medi- niques require a skilled general surgeon for the ap- cations are effective in the management of acute back proach and are more likely to be successful at the L5-S1 pain, although their usefulness in managing chronic interspace. The type of anterior structural support used back pain is unclear. Gastrointestinal toxicity and renal in ALIF surgery has received much attention. Autolo- impairment are concerns with the use of these drugs, es- gous cancellous bone shows high fusion rates, but migra- pecially in the elderly population. Flexible or rigid spi- tion and collapse have been drawbacks. Threaded cages nal supports may reduce lumbar mobility and decrease or machined allografts are being increasingly used with intradiskal pressure in certain positions of lumbar flex- interbody fusion, with the aim of reducing the morbidity ion. A program of physical therapy should be directed associated with bone graft harvest. Bone morphogenetic at ergonomic instruction, stretching maneuvers, and iso- protein used within threaded interbody cages in ALIF metric stabilization exercises. Nonimpact type exercise shows high fusion rates and relief of back pain similar to such as swimming or cycling is recommended. Other autograft over the short term. measures used with varying degrees of success include acupuncture, hydrotherapy, ultrasound, biofeedback, Annotated Bibliography electrical stimulation, manipulation, massage, and psy- chotherapy. Intradiskal electrothermal therapy has been Lumbar Spinal Stenosis proposed as an option in the management of discogenic back pain (see chapter 50). Atlas SJ, Keller RB, Robson D, Deyo RA, Singer DE: Surgical and nonsurgical management of lumbar spinal Lumbar fusion is the surgical procedure of choice stenosis: 4-year outcomes from the Maine Lumbar for the treatment of discogenic low back pain in patients Spine Study. Spine 2000;25:556-562. who have intractable pain after an aggressive nonsur- gical management program, MRI findings of disk de- A cohort of 119 patients underwent either surgical or non- generation, and concordant diskography at one or two surgical treatment and were followed for 4 years. Seventy per- levels. Disk excision or other disk decompression proce- cent of surgically treated patients and 52% of nonsurgically dures are not recommended for these patients. treated patients reported improvement in symptoms. The au- thors report that the relative benefits of surgery diminished The fusion approach may be posterior, anterior, or over time but remained superior to those of nonsurgically both. Instrumentation is generally used with posterior treated patients. fusion, and implants or bone graft are used with inter- body fusion. Successful fusion is obtained in 60% to Fischgrund JS, Mackay M, Herkowitz HN, Brower R, 90% of patients who undergo a posterior procedure, but Montgomery D, Kurz LT: Degenerative lumbar spondy- clinical outcomes are satisfactory in only 40% to 70%. lolisthesis with spinal stenosis: A prospective, random- Even with posterior instrumentation, there is some mo- ized study comparing decompressive laminectomy and tion across the disk space that may account for persis- arthrodesis with and without spinal instrumentation. tent symptoms in some patients. Residual symptoms in Spine 1997;22:2807-2812. American Academy of Orthopaedic Surgeons 549

Lumbar Degenerative Disorders Orthopaedic Knowledge Update 8 This randomized study showed that fusion rates were su- Osterman H, Sund R, Seitsalo S, Keskimaki I: Risk of perior in instrumented patients undergoing single level sur- multiple reoperations after lumbar discectomy: A gery, but overall clinical improvement was identical in instru- population-based study. Spine 2003;28:621-627. mented and noninstrumented groups. This 11-year review of 35,309 patients who underwent dis- Iguchi T, Kurihara A, Nakayama J, Sato K, Kurosaka M, kectomy showed that 14% had at least one more operation, Yamasaki K: Minimum 10-year outcome of decompres- whereas 2.3% had two or more operations. Sixty-three percent sive laminectomy for degenerative lumbar spinal steno- of the second operations were diskectomies, 14% were fusions, sis. Spine 2000;25:1754-1759. and 23% were decompressions. In this study, decompressive laminectomies without fusion Yorimitsu E, Chiba K, Toyama Y, Hirabayashi K: Long- in patients older than 60 years were shown to produce long- term outcomes of standard discectomy for lumbar disc term satisfactory results in more than half of the patients. The herniation. Spine 2001;26:652-657. authors concluded that the presence of sagittal rotation of more than 10° in patients needing multiple laminectomies may In this study, 74% of patients who underwent lumbar dis- be related to deterioration of outcome. kectomy reported some back pain at 10 years, although dis- abling pain was reported in only 12.7%. Decreased disk height Katz JN, Lipson SJ, Lew RA, et al: Lumbar laminectomy was associated with more disability, whereas recurrent hernia- alone or with instrumented or noninstrumented arthro- tions were more common in those with preserved disk height. desis in degenerative lumbar spinal stenosis: Patient se- lection, costs, and surgical outcomes. Spine 1997;22:1123- Discogenic Low Back Pain 1131. Fritzell P, Hagg O, Wessberg P: Nordwall Anders, Swed- The authors of this study report that adding arthrodesis to ish Lumbar Spine Study Group: Lumbar fusion versus decompression for spinal stenosis depends primarily on sur- nonsurgical treatment for chronic low back pain. Spine geon preference and that noninstrumented fusions produce 2001;26:2521-2534. superior relief of back pain, whereas instrumentation adds substantial costs to the treatment. This randomized controlled multicenter study showed that lumbar fusion in a carefully selected group of patients with se- Rao RD, Wang M, Singhal P, McGrady LM, Rao S: In- vere chronic low back pain decreases pain and disability more tradiscal pressure and kinematic behavior of lumbar than nonsurgical treatment. spine after bilateral laminotomy and laminectomy. Spine J 2002;2:320-326. Riew KD, Yin Y, Gilula L, Bridwell KH, Lenke LG, Lau- ryssen CC, Goette K: The effect of nerve-root injections This article presents a biomechanical analysis of bilateral on the need for operative treatment of lumbar radicular laminotomy as an alternative to wide laminectomy in the de- pain: A prospective, randomized, controlled, double- compression of patients with lumbar spinal stenosis. blind study. J Bone Joint Surg Am 2000;82:1589-1593. Lumbar Disk Herniation This prospective study demonstrated the efficacy of selec- tive nerve root injections of corticosteroid in patients with Atlas SJ, Keller RB, Chang Y, Deyo RA, Singer DE: lumbar radiculopathy. Twenty of 28 patients who received in- Surgical and nonsurgical management of sciatica sec- jection of bupivacaine and betamethasone declined surgery ondary to a lumbar disc herniation: Five-year outcomes over a 13- to 28-month period after receiving one to four in- from the Maine Lumbar Spine Study. Spine 2001;26: jections, whereas the remainder of the patients eventually un- 1179-1187. derwent surgery. A 5-year follow-up of 402 patients showed that 70% of Classic Bibliography surgically treated patients and 56% of nonsurgically treated patients reported improvement in their predominant symp- Abumi K, Panjabi MM, Kramer KM, Duranceau J, Ox- toms. Patients with moderate or severe symptoms did better land T, Crisco JJ: Biomechanical evaluation of lumbar after surgery than after nonsurgical care. spinal stability after graded facetectomies. Spine 1990; 15:1142-1147. Carragee EJ, Han MY, Suen PW, Kim D: Clinical out- Bogduk N, Tynan W, Wilson AS: The nerve supply to the comes after lumbar discectomy for sciatica: The effects human lumbar intervertebral discs. J Anat 1981;132:39- of fragment type and annular competence. J Bone Joint 56. Surg Am 2003;85:102-108. Freemont AJ, Peacock TE, Goupille P, Hoyland JA, This prospective study correlated intraoperative morpho- O’Brien J, Jayson MI: Nerve ingrowth into diseased in- logic patterns of disk herniation with outcomes following sur- tervertebral disc in chronic back pain. Lancet 1997;350: gical intervention, with particular reference to reherniation, re- 178-181. operation rates, and the incidence of persistent symptoms. 550 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 44 Lumbar Degenerative Disorders Herkowitz HN, Kurz LT: Degenerative lumbar spondy- Mixter WJ, Barr JS: Rupture of the intervertebral disc lolisthesis with spinal stenosis: A prospective study com- with involvement of the spinal canal. N Engl J Med paring decompression with decompression and inter- 1934;211:210-215. transverse process arthrodesis. J Bone Joint Surg Am 1991;73:802-808. Turner JA, Ersek M: Herron L, Deyo R: Surgery for lumbar spinal stenosis: Attempted meta-analysis of the Kuslich SD, Ulstrom CL, Michael CJ: The tissue origin literature. Spine 1992;17:1-8. of low back pain and sciatica: A report of pain response to tissue stimulation during operations on the lumbar Weber H: Lumbar disc herniation: A controlled, pro- spine using local anesthesia. Orthop Clin North Am spective study with 10 years of observation. Spine 1991;22:181-187. 1983;8:131-140. American Academy of Orthopaedic Surgeons 551



Chapter 45 Spondylolysis-Spondylolisthesis Thomas J. Puschak, MD Rick C. Sasso, MD Introduction slippage is recorded. Grade 1 is 0 to 25% slippage (Fig- ure 1), grade 2 is 26% to 50%, grade 3 is 51% to 75% Spondylolysis refers to a bony defect in the pars interar- (Figure 2), and grade 4 is 76% to 100% (Figure 3). Slip- ticularis, which is the isthmus or bony bridge that con- page of 100% or more is referred to as spondyloptosis. nects the superior and inferior articular facets of the This classification system is frequently used because it is posterior neural arch. Spondylolysis can occur unilater- simple and reliable. ally or bilaterally and is an acquired condition because it has never been reported at birth. Spondylolysis is Wiltse and Associates more common in males and occurs in approximately 6% of the general population. A higher prevalence (up to The Wiltse and associates classification system is based 53%) is seen in Eskimo populations. Also, athletes who on anatomic etiology and classically consists of five participate in sports that repeatedly cause the spine to types of spondylolisthesis, although iatrogenic postoper- be hyperextended, such as gymnastics, football, and ative instability is sometimes included as a sixth type. wrestling, may have an increased predisposition to de- Type 1 slips are dysplastic or congenital. These occur at veloping spondylolysis. Spondylolysis occurs most often the lumbosacral junction as a result of incomplete or in- at L5, with decreasing incidence at the more cranial adequate development of the facet joints and superior lumbar levels. Several factors have been implicated in sacral end plate. Facets are often sagittally oriented and the etiology of spondylolysis; however, the primary le- the superior end plate of S1 is rounded or domed, which sion is believed to be a stress fracture of the pars inter- predisposes patients to slippage. The intact pars interar- articularis that remains unhealed. This theory is sup- ticularis usually limits slippage to approximately 30%. ported by the fact that there are no reported instances Spondyloptosis can occur, and patients with higher- of spondylolysis in patients who have never walked. grade slips of this type can develop significant neuro- There also seems to be a genetic predisposition for logic symptoms from severe stenosis resulting from an spondylolysis because relatives of index cases have a intact pars interarticularis. Type 2 slips are referred to as greater than fourfold increased incidence. lytic or isthmic because they are secondary to defects of the pars interarticularis. There are three subtypes in this Spondylolisthesis refers to the translation of a verte- category: a pars defect, an elongated pars (possibly bral body on the caudal vertebra. This translation can be caused by repeated fracture and healing of the pars), anterior, lateral, or posterior. The term comes from the and an acute pars fracture. Type 3 slips are degenerative Latin roots spondy, which means “the spine,” and olis- and occur as a result of the incompetence of arthritic thesis, which means “a slipping.” Spondylolisthesis most facet joints in the degenerative lumbar spine. Degenera- often occurs in the lower lumbar spine. Several different tive spondylolisthesis can occur with or without spinal forms of spondylolisthesis exist and can be classified by stenosis. Type 4 slips are caused by traumatic injuries to severity of slip, etiology, and potential for progression. the posterior neural arch in areas other than the pars in- terarticularis and lead to a destabilization of the facet Classification Systems joints. Type 5 slips are caused by pathologic destabiliza- tion of the spine from tumors, infection, and other sys- Meyerding temic diseases. The Meyerding classification system is a radiographic Marchetti and Bartolozzi system based on the severity of vertebral slippage. Slips are classified as grade 1 through grade 4 based on the The system described by Marchetti and Bartolozzi at- percentage of translation of the cranial vertebra on the tempts to classify spondylolisthesis based on anatomic caudal vertebra. The superior end plate of the caudal vertebra is divided into quarters, and the percentage of American Academy of Orthopaedic Surgeons 553

Spondylolysis-Spondylolisthesis Orthopaedic Knowledge Update 8 Figure 2 Lateral radiograph showing a Meyerding grade 3 slip. Dysplastic features such as a trapezoidal L5 body and rounded sacral dome are often seen in slips that progress beyond Meyerding grade 2. Figure 1 Lateral radiograph showing a Meyerding grade 1 slip. slips, and therefore, they have less potential for slip pro- gression. Acquired spondylolisthesis occurs as a result of ac- quired pathology, such as pars defects, trauma, degener- ative facets, pathologic instability, and iatrogenic injury. The main difference between the developmental and ac- quired categories is that the basic spinal architecture is developed normally in the acquired group and therefore has more potential stability or less potential for progres- sion of slippage. Figure 3 Lateral radiograph showing a Meyerding grade 4 slip. As in Figure 2, signifi- Diagnostic Imaging cant dysplastic features are present. Plain Radiographs etiology and prognostic factors. Slips are divided into two main categories: developmental and acquired. De- Initial assessment should at least consist of standing AP velopmental spondylolisthesis is categorized as either and lateral radiographs. The standing position may ac- high dysplastic or low dysplastic. Dysplastic features of centuate existing translational deformity. Spondylolis- the anterior and posterior elements, which lead to insta- thesis can be missed on supine lateral films up to 20% bility, characterize developmental slips. Posteriorly, the of the time because of reduction of the deformity when pars interarticularis, laminae, or facets may be incompe- the patient is in the supine position. Standing films may tent; anteriorly, the L5 body tends to be trapezoidal and also accentuate angular deformities better than those oriented toward the floor and the S1 superior end plate obtained with the patient supine. Pars interarticularis tends to be rounded. Low dysplastic slips tend to have defects and other defects of the posterior arch such as less profound dysplastic features than high dysplastic spina bifida occulta may be identified on AP views. In patients with high-grade slips with significant angulation of the cephalad vertebra, a Napoleon’s hat sign may be seen on AP views (Figure 4). A standard AP view may not be helpful for visualization of the pedicles and other surgical anatomy in patients with high-grade slips. In these patients, a Ferguson view (AP radiograph angled 30° cephalad) will yield a true AP view of the lumbosac- ral junction. Although pars interarticularis defects are usually identifiable on lateral films, right and left oblique radio- graphs may help in the diagnosis of subtle pars defects not readily seen on AP or lateral views. 554 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 45 Spondylolysis-Spondylolisthesis Dynamic flexion-extension lateral radiographs can be helpful in assessing translational stability. Patients with bilateral pars interarticularis defects as well as those with arthritic degenerative facets (especially sagit- tally oriented facets) may elicit significant translational motion on flexion-extension radiographs that is not evi- dent on standing lateral films. The difficulty in interpret- ing dynamic radiographs is that there is no clear consen- sus on the definition of normal translational motion. Traditionally, the definition of instability is greater than 3 mm of translation on flexion-extension views. Several clinical studies have reported large variations in transla- tional motion in asymptomatic individuals. Also, the re- liability of dynamic studies is questionable because the quality of the study depends on the effort of the individ- ual. Dynamic radiographs can be valuable diagnostic tools when used in conjunction with other data, but they should not be used as the sole criteria for treatment. Computed Tomography Figure 4 AP radiograph of a high-grade slip. The Napoleon’s hat sign is outlined. Severe angulation of the L5 body allows an end-on axial projection on AP views. CT scans are useful in the diagnosis of occult pars inter- articularis defects. Thin section cuts (1 to 2 mm) should end plate changes are also signs of disk degeneration. be obtained because larger axial sections may miss the Often disks adjacent to slips may be radiographically defects. Sagittal reconstruction technology is also help- normal, but they elicit significant degenerative changes ful because pars interarticularis defects may be difficult on MRI, which must be considered during surgical plan- to see on axial images. These defects often lie in a simi- ning. Although knowing the status of the adjacent disk lar plane to the axial cuts. Pars interarticularis defects is important, there are no conclusive findings that war- tend to lie more dorsal and posterior to the facet joints rant routinely incorporating the adjacent degenerative on the axial images and are often associated with signif- level in patients with spondylolisthesis. icant bony and cartilaginous overgrowth. In the degen- erative spine, axial CT images allow assessment of the Nuclear Medicine Studies orientation of facet joints (coronal or sagittal) to help determine the relative stability of a segment after de- Technetium bone scans have been historically popular compression. CT scans are also helpful in assessing sur- in the diagnosis of spondylolysis. These scans are used to gical bony anatomy, such as pedicle size and orientation. determine the acuteness of a pars injury, with positive scans suggesting a more acute injury and greater poten- Myelograms in conjunction with CT scans are help- tial for healing with bracing or conservative care. Nega- ful in assessment of the neuroanatomy. Although central tive scans indicate an old or chronic defect with little and lateral recess stenosis is easily identified, foraminal healing potential. Recently, single photon emission CT stenosis may be missed because the compression occurs has been shown to be more specific and sensitive in de- lateral to the root sleeve beyond the extent of the my- tecting radiographically occult pars defects than techne- elogram dye. tium scans. Magnetic Resonance Imaging MRI scans are not often helpful in identifying spondy- litic defects. They are most helpful in the evaluation of the neuroanatomy and disks. Central and lateral recess stenosis caused by facet hypertrophy, overgrown pars in- terarticularis defects, and translational offset is easily seen. Also, sagittal images allow accurate assessment of the nerve root in the foramina. MRI scans can evaluate the status of the interverte- bral disks at the affected and adjacent levels. Normal disks appear bright on T2-weighted images because of good hydration, and they appear dark when degenera- tion (relative dehydration) is present. Reactive bony American Academy of Orthopaedic Surgeons 555

Spondylolysis-Spondylolisthesis Orthopaedic Knowledge Update 8 Degenerative Spondylolisthesis Clinical Presentation Pathogenesis/Pathoanatomy Patients with degenerative spondylolisthesis initially re- port low back pain secondary to the degenerative Degenerative spondylolisthesis tends to occur in pa- changes in the spine. These are usually mechanical com- tients older than 60 years. It is more prevalent in women plaints worsened with activity and improved with rest. and more common in African Americans than Cauca- With time, neurogenic back pain may develop in which sians. It occurs five to six times more frequently at L4-5 pain is exacerbated with prolonged standing or walking than at L3-4 or L5-S1. The average amount of anterior and improved with sitting and flexion. The back pain slippage is 15% to 33%. Hormonal influence may con- tends to be located in the lower lumbar and buttock re- tribute to the development of degenerative spondylolis- gion and is often described as an aching, burning, or thesis. The increased incidence in women with a history pulling sensation. of pregnancy may be the result of increased ligamentous and joint laxity in conjunction with a large flexion mo- As nerve compression progresses, lower extremity ment on the lumbar spine. symptoms increase. Leg pain may be unilateral or bilat- eral and neuroclaudicatory or radicular in nature. Symp- The role of facet joint orientation has also been in- toms tend to be worsened in an upright or extended vestigated as a potential cause of degenerative spondy- posture and improved with sitting and flexion. The L5 lolisthesis. Several authors have shown a positive corre- root is most commonly affected; however, in patients lation between sagittally oriented facet joints and a with instability and foraminal stenosis, the L4 roots are predisposition for spondylolisthesis. A bilateral facet an- also involved. Reflexes are often diminished or absent, gle greater than 45° at L4-5 has been shown to result in and sensation may be anywhere from normal to se- a 25-fold increased incidence of degenerative spondy- verely impaired. Bladder dysfunction only occurs in 3% lolisthesis. The L5-S1 facet joint tends to be oriented to 4% of patients. more in the coronal plane, offering greater resistance to anterior translational forces. This orientation may ex- Peripheral neuropathy must be considered in pa- plain the greater incidence of degenerative spondylolis- tients with a history of diabetes and stocking glove pat- thesis at L4-5 than at L5-S1. tern dysesthesias. Other diagnoses that can mimic spinal stenosis symptoms are cervical myelopathy and primary Degenerative changes in the intervertebral disk com- hip disease with anterior thigh pain. bined with hormonal factors and facet orientation can lead to intersegmental instability. Disk space collapse Nonsurgical Management leads to buckling of the ligamentum flavum and altered stress loading of the facet joints. Ligamentous laxity and Most patients with degenerative spondylolisthesis will remodeling of the facet joints create a hypermobile seg- respond to nonsurgical treatment. Initial treatment is fo- ment, which leads to spondylolisthesis. The hypertrophy cused on the mechanical back pain and consists of a and buckling of ligamentum flavum combined with bony short rest period, administration of nonsteroidal anti- translational offset lead to central canal stenosis. Hyper- inflammatory drugs, a short course of oral analgesics, trophy of the facet joints creates lateral recess and foram- and passive physical therapy modalities. Once the acute inal stenosis. Facet cysts, often associated with advanced pain phase is controlled, active physical therapy can be degenerative facet arthrosis, can add to the degree of instituted for trunk stabilization and aerobic condition- nerve root compromise in the lateral recess. ing. Avoidance of hyperextension activities is recom- mended to limit recurrence of acute episodes. Natural History Similarly, leg symptoms from spinal stenosis can be Few data are available regarding the natural history of managed with rest, nonsteroidal anti-inflammatory degenerative spondylolisthesis. Severe disk space nar- drugs, and oral analgesics. Oral steroids and injectable rowing has been shown to be associated with a lower steroids in the form of epidural steroid injections or se- likelihood of progression of slippage. In a study follow- lective nerve root blocks may also be used. Despite be- ing patients with degenerative spondylolisthesis who ing somewhat controversial and lacking significant pro- were treated nonsurgically over 10 years, 76% of pa- spective data proving their efficacy, epidural steroid tients without neurologic symptoms remained symptom injections are widely used and are often effective (if free. Eighty-six percent of patients with lower extremity only in temporizing lower extremity symptoms). complaints saw an initial improvement in symptoms; however, 37% had redevelopment of symptoms. Eighty- Surgical Management three percent of patients presenting with neurologic symptoms who refused surgical treatment eventually ex- The main goals of surgery are pain reduction, restora- perienced a deterioration of symptoms. Although de- tion of function, and preservation of neurologic func- generative spondylolisthesis symptoms tend to be inter- tion. The most common indication for surgery is persis- mittent, complete resolution of symptoms is not likely. tent incapacitating claudication and radicular leg pain, which significantly compromises function, and the fail- 556 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 45 Spondylolysis-Spondylolisthesis ure of 6 to 12 weeks of nonsurgical therapy to relieve has not been shown to consistently improve outcome symptoms. Absolute indications for surgery include pro- over noninstrumented arthrodesis. No known random- gressive and evolving motor deficits and cauda equina ized prospective data have been published to date re- syndrome. Surgical intervention should address the two garding the role of interbody fusion in the treatment of components of degenerative spondylolisthesis—spinal degenerative spondylolisthesis. stenosis and instability. Acquired Isthmic Spondylolisthesis in Adults The management of spinal stenosis includes laminec- tomy or laminotomy with partial or total facetectomy. Pathogenesis/Pathoanatomy Depending on symptoms, decompression may be unilat- eral or bilateral. All regions of compression must be ad- The primary lesion responsible for isthmic or lytic dressed because incomplete decompression of the lat- spondylolisthesis is a defect of the pars interarticularis. eral recess and stenosis can lead to persistent symptoms Several etiologies for this defect have been proposed, and poor outcome. Outcomes of decompression without including acute or chronic traumatic injuries. Congenital fusion in the face of degenerative spondylolisthesis are abnormalities can contribute to instability as well. There mixed. Several studies show significant improvement in are several types of pars defects: chronic stress fractures, leg symptoms initially; however, up to 33% of patients elongated pars from healing of multiple stress fractures had severe worsening of back and leg symptoms by 5 over time, and acute pars fractures. These lesions are ac- years, with nearly 25% requiring reoperation for the quired, not congenital, and result from repeated mi- treatment of recurrence of stenosis and/or progression crotrauma of the pars as it is loaded in extension. Isth- of instability. In one study, more than half of the pa- mic spondylolisthesis occurs at L5-S1 in 82% of patients tients with decompression alone were unable to walk compared with 11% at L4-5 and 0.5% at L3-4 and L2-3. more than two blocks after 3 to 6 years, and 25% of pa- Forces in the lumbar spine are greatest at the lumbosac- tients were very dissatisfied with the treatment out- ral junction and likely are the reason for the high preva- come. lence of pars defects at L5-S1. Several studies have addressed the role of arthrode- Natural History sis in addition to decompression for the treatment of de- generative spondylolisthesis. In a prospective random- Relatively few patients with spondylolysis will acquire ized study comparing decompression alone to spondylolisthesis. Those who do typically have some as- decompression with posterolateral noninstrumented fu- sociated dysplastic features such that the true incidence sion, at 3-year follow-up 96% of the patients who under- of acquired isthmic spondylolisthesis may be much less. went decompression alone had radiographic slip pro- Many patients who eventually acquire spondylolisthesis gression compared with 28% of those in the arthrodesis are asymptomatic. True acquired slips are almost always group. Despite a pseudarthrosis rate of 36%, 96% of pa- grade I or II and rarely progress beyond grade I or II tients in the arthrodesis group had good or excellent re- severity unless there is dysplasia present. Isthmic sults compared with 44% of those who underwent de- spondylolisthesis that progresses beyond Meyerding compression alone. grade II almost always is associated with dysplasia as well. Numerous studies have also assessed the effects of using instrumentation in conjunction with arthrodesis. A Progression of isthmic spondylolisthesis is most com- randomized prospective study comparing single-level mon in the adolescent population. Significant increase laminectomy and posterolateral fusion with and without in slippage in adulthood is uncommon. In contrast to transpedicular fixation showed that the addition of in- the L5-S1 isthmic slip, lesions at L4-5 or other more cra- strumentation significantly improves fusion rates. De- nial levels may remain unstable into the third and spite the significant difference in fusion rates, in 83% of fourth decades of life, with progression of translation patients in the instrumented group versus 45% of those and increase in back and leg symptoms. An isthmic le- in the noninstrumented group, there was no significant sion at L4-5 is less stiff in sagittal rotation and shear difference in clinical outcomes, with 78% to 85% of translation than a lesion at L5-S1. Overloading a lesion those in both groups reporting good and excellent re- at L4-5 may lead to premature translational wear of the sults. Several other authors have reported an improve- disk, contribute to the inherent instability of the seg- ment in both fusion rates and clinical outcomes when ment, and may be the reason why previously asymptom- comparing instrumented and noninstrumented fusions atic isthmic slips at L4-5 progress later in adulthood. for the treatment of patients with degenerative spondy- lolisthesis. Clinical Presentation When surgical treatment is indicated, a thorough de- The most common presenting symptom is low back compression is mandatory, and the addition of arthrode- pain. Patients often have a long history of periodic self- sis improves intermediate- and long-term outcomes. The limited low back pain episodes that vary in intensity addition of instrumentation increases fusion rates, but it and/or duration. Neurologic deficits are infrequent be- American Academy of Orthopaedic Surgeons 557

Spondylolysis-Spondylolisthesis Orthopaedic Knowledge Update 8 cause slips rarely progress beyond grade II and the rela- been used. These approaches include anterior interbody tive detachment of the posterior arch prevents signifi- fusion, posterolateral fusion with and without instru- cant central canal stenosis. Patients may present with mentation, anterior-posterior procedures, and posterior unilateral or bilateral radiculopathy. Radicular symp- interbody procedures. toms may be caused by nerve root irritation from the reactive tissue around the pars defect combined with Posterolateral fusion is commonly used to treat pa- the micromotion of the unstable posterior arch. Addi- tients with isthmic spondylolisthesis. Midline dissection tionally, significant foraminal stenosis may occur as a re- is performed laterally over the facet joints and trans- sult of loss of sagittal foraminal height from the transla- verse processes and sacral alae. Abundant lateral bone tion and degeneration of the intervertebral disk. graft leads to stabilization of the segment by intertrans- Typically, the exiting nerve root (L5) is most affected for verse process fusion. A Gill laminectomy may be done an L5-S1 isthmic spondylolisthesis. in conjunction with the posterior fusion. Removal of the loose lamina and inflammatory pars defect allows de- Nonsurgical Treatment compression of the nerve roots, direct visualization of the pedicles for hardware placement, and potentially re- Most patients with acquired isthmic spondylolisthesis moves part of the inflammatory back pain generator. In will respond to nonsurgical management. Medical treat- addition, the laminectomy bone may be processed for ment should follow similar guidelines for nonspecific bone graft. Although the roles of instrumentation and low back pain. Oral anti-inflammatory drugs may re- decompression with posterolateral fusion remain con- duce acute pain and improve function. Long-term use of troversial, Gill decompression without fusion is not rec- these drugs should be avoided if possible because of po- ommended. Potential complications of the posterior ap- tential renal and gastrointestinal adverse effects. Nar- proach include infection, dural tear, nerve root injury, cotic pain medication, muscle relaxers, and other con- hematoma, and pedicle fracture. trolled substances should be used with extreme caution and definitely should be avoided in long-term treat- Anterior lumbar interbody fusion (ALIF) can be ment. successfully used to treat isthmic spondylolisthesis even when radicular symptoms are present. Although the di- There are no known studies that address the role of rect decompression of nerves is difficult, indirect de- injections in the facet joints or pars defects in patients compression can be obtained by foraminal distraction. with isthmic spondylolisthesis. Injection of local anes- A transabdominal retroperitoneal approach is usually thetic and corticosteroid into the facets or pars defects used to minimize the risk to abdominal viscera. Caudal may have therapeutic effects. However, diagnostic infor- to the iliac vessels, cautery should be used sparingly to mation from these injections is at best difficult to inter- decrease the risk of injuring the presacral nerves, which pret because the pars defects often communicate with may result in retrograde ejaculation and sexual dysfunc- the facet joints, causing an uncontrolled extravasation of tion. The anterior approach allows for an aggressive disk- steroid and local anesthetic. In patients with radicular ectomy with good removal of cartilage from the verte- symptoms, selective nerve blocks or epidural steroid in- bral end plates and increase of the fusion surface area. jections may be used for diagnostic and therapeutic pur- Additionally, anterior grafts provide excellent anterior poses. No prospective studies have yet been conducted column support and may aid in partial reduction of the that address the effectiveness of these injections in isth- slip as well as restoration of disk space height. The mic spondylolisthesis. choice of graft material is generally based on surgeon preference and includes autologous iliac crest, structural The use of external bracing in the treatment of pa- allograft, and various metallic cages packed with autog- tients with acquired isthmic spondylolisthesis has been enous cancellous graft. This method of anterior diskec- reported. In addition, patients may benefit from initial tomy and interbody fusion cannot be done in patients rest in the acute phase followed by physical therapy that with high-grade spondylolisthesis because of the pres- is focused on strengthening of the abdominal and lum- ence of significant translational and angular deformity. bosacral muscles. Physical therapy has been shown to Risks of the anterior approach include wound infection, decrease pain and functional disability. Once the acute vascular injury, deep venous thrombosis, pulmonary em- pain is resolved, the focus of physical therapy is on ham- bolism, sympathetic chain injury, retrograde ejaculation, string stretching, pelvic tilts, and abdominal and pelvic and ventral hernia. stabilizer strengthening for approximately 6 months. Stand-alone ALIF reconstruction for patients with Surgical Treatment isthmic spondylolisthesis works best for those with a Meyerding grade 1 slip. Several clinical studies have Failure of conservative management (persistence of shown adequate results with good and excellent results pain, progression of neurologic symptoms, or progres- ranging from 87% to 94% at 2 years. One study re- sion of slippage) is an indication for surgical treatment. ported that 75% of patients had excellent and 20% had Numerous approaches to surgical reconstruction have satisfactory results at 10-year follow-up. The fusion rates 558 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 45 Spondylolysis-Spondylolisthesis in these studies did not correlate with clinical outcome. Figure 5 Preoperative photograph of a pa- Some patients had good clinical improvement despite tient with a high-grade slip. Note the eventually having a pseudarthrosis. Persistent leg pain crouching posture caused by severe ham- may occur as a result of inadequate indirect foraminal string tightness. Upper lumbar hyperlordosis decompression. Patients may also have persistent low is also seen. back pain because of the pain fibers present in the in- flammatory tissue of the pars interarticularis defect, lordosis of the upper lumbar spine usually develops. which is not removed with an isolated anterior ap- This type of slip has the highest risk for malignant pro- proach. Nociceptive pain fibers are histologically gression. Patients with this type of slip and an intact present in the pars interarticularis defect. pars interarticularis must be observed closely because they may develop cauda equina syndrome as the slip Circumferential (360°) fusion can be accomplished progresses. by a combined anterior-posterior fusion or by a postero- lateral fusion combined with a posterior lumbar inter- Low dysplastic slips also tend to occur at the lum- body fusion (PLIF) or transforaminal lumbar interbody bosacral junction. This type of slip is characterized by fusion. Both techniques provide anterior column sup- dysplastic changes in the posterior elements with rela- port, foraminal distraction, posterior stabilization, ar- tively normal anatomy anteriorly. These slips are less throdesis, and the ability to perform a Gill laminectomy likely to progress given the increased stability of the rel- decompression if indicated. Three series have shown ex- atively normal anterior structures. A vertical sacrum and cellent success with circumferential procedures when hyperlordosis are not traditionally seen in patients with compared with other approaches alone. In one study, low dysplastic slips. posterolateral fusion alone was compared with postero- lateral fusion combined with posterior lumbar interbody Clinical Presentation fusion. Outcomes were comparable when good and ex- cellent results were grouped together (95% and 97%, Most developmental spondylolisthesis presents in ado- respectively). However, the circumferential group had lescence during the growth spurt. The disease course of 75% excellent results compared with 45% in the poster- patients with low dysplastic slips may progress slowly; olateral fusion group. Several other studies have shown consequently, these patients may not present until early higher fusion rates for circumferential fusions when adulthood. Traditionally, patients present with severe compared with anterior or posterior fusions alone. Spe- acute low back pain without neurologic findings. Some cific risks related to circumferential fusions include in- patients present in a listhetic crisis (severe back pain, creased surgical time, more blood loss, and potentially hamstring spasm, and various neurologic deficits). Pa- longer hospital stays. tients walk with a crouched gait because of severe ham- string tightness (Figure 5). Compensatory upper lumbar Developmental Spondylolisthesis hyperlordosis often creates a significant abdominal crease (Figure 6). Neurologic symptoms range from iso- Developmental spondylolisthesis was formerly referred lated radiculopathy resulting from the stretch of exiting to as congenital spondylolisthesis. Current thought is nerve roots to cauda equina syndrome in patients with that the defects and slip are not present at birth but de- high-grade slips and intact posterior arches. Because velop over time. Unlike acquired isthmic spondylolisthe- these slips usually occur at the lumbosacral junction, the sis, the pars fractures are thought to develop as a result of the slippage rather than causing the slip. The dysplas- tic nature of this type of spondylolisthesis often leads to the development of high-grade slips. Developmental spondylolisthesis is the most common type of slip seen in children, and as such will be covered in greater detail in chapter 66. The focus of this section will be on the treatment of high-grade spondylolisthesis in adults. Pathomechanics/Pathogenesis Developmental spondylolisthesis is categorized as either high dysplastic or low dysplastic slips based on radio- graphic findings. Radiographic findings include deficien- cies of the posterior arch, a trapezoidal L5 body, rounded sacral dome, incompetent L5-S1 disk, and poorly formed facet articulations. Severe lumbosacral kyphosis with verticalization of the sacrum and hyper- American Academy of Orthopaedic Surgeons 559

Spondylolysis-Spondylolisthesis Orthopaedic Knowledge Update 8 Figure 6 Photograph of a patient with the without decompression may be considered. combination of severe lumbosacral kyphosis The indication for instrumentation is not well de- with compensatory upper lumbar hyperlor- dosis, which typically creates a prominent fined. Good clinical results with noninstrumented in situ abdominal crease in patients with high- fusion have been reported in several studies; however, grade spondylolisthesis. postoperative slip progression has been reported even after successful arthrodesis. The addition of instrumen- L5 nerve roots are most commonly affected. Some tation may help increase fusion rates and decrease the adults with high-grade slips may have subtle bowel and risk for postoperative slip progression; however, this has bladder neurologic symptoms resulting from the slow not been definitively proven. One randomized prospec- progression of slip over time and may warrant urologic tive study comparing in situ fusions with and without in- evaluation. strumentation found that at 2-year follow-up there was no significant difference in fusion rates and that pain Treatment Algorithm and functional disability were similar in the two groups. Treatment recommendations are based on the type of The addition of interbody fusion may help increase slip (high dysplastic slips versus low dysplastic slips), pa- fusion rates and minimize progression of slippage post- tient age, neurologic status, slip severity, and the pa- operatively. The traditional ALIF and PLIF techniques tient’s symptoms. described earlier are not possible in patients with high- grade slips when in situ fusion is performed because of In Situ Fusion the presence of significant translational and angular de- formities. Interbody fusion using fibular struts placed Posterior in situ fusion has been a widely recommended across the L5-S1 disk space through the bodies of L5 surgical treatment for patients with spondylolisthesis be- and S1 has been described (Figure 7). This technique cause of the low rates of neurologic injury and high was first reported with the grafts placed from posterior rates of clinical success. Several techniques have been to anterior after a wide posterior decompression and used for in situ fusion, including posterior, posterolat- then augmented with a posterolateral fusion. Patients eral, anterior interbody, and posterior interbody fu- were followed for 2 to 12 years, and all patients sion—all of which can be done with or without instru- achieved fusion and had significant or complete resolu- mentation. In situ fusion with decompression has been tion of preoperative neurologic deficits. This technique shown to provide good results when neurologic symp- has also been described with placement of the grafts toms are present preoperatively. Other studies show from an anterior approach with similar results. No dif- that in situ fusion without decompression can be effec- ference in outcomes has been reported when comparing tive in treating back pain and radicular symptoms. In allograft and autogenous fibula. one study in which eight high-grade slips were treated with in situ fusion without decompression, all patients Reduction achieved fusion and had good resolution of their back and radicular symptoms. In the presence of progressing The indications for reduction of spondylolisthesis are neurologic deficits or cauda equina symptoms, decom- extremely controversial, and there are currently no pression should be performed in addition to fusion. In widely accepted reduction guidelines. Reduction of the the absence of these neurologic symptoms, in situ fusion translational displacement and slip angle may occur in- dependently, either partially or fully. The argument for reduction is to restore sagittal alignment, reduce lum- bosacral kyphosis and translation, and restore the nor- mal lumbosacral biomechanics. The main detraction of using reduction in the treat- ment of patients with high-grade slips is the risk of sig- nificant associated complications. Neurologic complica- tions include L5 and S1 nerve root injuries, paresis, paralysis, cauda equina syndrome, sensory deficits, bowel/bladder dysfunction, and sexual dysfunction. Other complications include nonunion, hardware fail- ure, sacral fracture, dural tear, graft resorption, loss of fixation, and prolonged immobilization or bed rest sec- ondary to unstable fixation. Reported rates of neuro- logic deficits range from 8% to 30% after reduction of high-grade slips. Although most of these deficits are transitory, permanent deficits have been reported. High 560 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 45 Spondylolysis-Spondylolisthesis Figure 7 A, Intraoperative photograph of the placement of a transsacral fibula poste- rior interbody graft. The cauda equina is protected with nerve root retractors as the graft is placed across the L5-S1 disk space through the sacrum and L5 body from a posterior approach. B, Postoperative sagittal reconstruction CT scan of a transsacral fibular graft. C, Axial CT scan of transsacral fibular grafts in which the grafts are placed bilaterally and purchase in both the S1 and L5 bodies is seen on the same CT cut because of the severity of the slip. rates of pseudarthrosis, progression of slippage, and rior translation forces are used to gradually reduce the hardware failure have also been reported after reduc- slip. In the past, repeated wake-up tests were used tion and posterolateral instrumented fusion. One study during the reduction. Electrophysiologic monitoring reported implant failure in five of six patients who had (somatosensory-evoked potentials, electromyograms, an isolated posterolateral instrumented fusion following and motor-evoked potentials) should be used with this reduction. The addition of anterior interbody fusion af- procedure. ter reduction and posterolateral instrumented fusion has been shown to decrease these complications. High rates of implant failure and loss of reduction have been reported when reduction is performed and Recent improvements in spinal instrumentation have only posterior instrumented fusion is used for stabiliza- increased the interest in the use of open reduction to tion. The reduction of the spondylolisthesis normalizes treat patients with spondylolisthesis. Several techniques the shear forces at the lumbosacral junction; however, have been described. One technique involves pedicle an anterior column defect is also created by the reduc- screw instrumentation from L4 to S1 or S2. A wide de- tion. Posterior instrumentation may fatigue and fail, re- compression is performed so that the nerve roots are di- sulting in loss of reduction. Posterior distraction forces rectly visualized during reduction. Distraction and poste- do not adequately resist shear, and compression forces American Academy of Orthopaedic Surgeons 561

Spondylolysis-Spondylolisthesis Orthopaedic Knowledge Update 8 applied through posterior instrumentation may result in bar interbody fusion improve outcome over posterolat- foraminal stenosis. The best way to biomechanically re- eral fusion? J Neurosurg 2003;99(suppl 2):143-150. sist these shear forces is by providing anterior column support in the form of interbody fusion to augment the Addition of a PLIF procedure to posterolateral instru- posterior instrumentation. If reduction is near anatomic, mented fusion in patients with isthmic spondylolisthesis im- traditional ALIF or PLIF procedures can be used for proves slip correction and maintenance of reduction over pos- anterior column support, depending on surgeon prefer- terolateral instrumented fusion alone. The authors report no ence. Several studies have reported decreased nonunion difference in fusion rates or functional and neurologic out- rates when either ALIF or PLIF procedures were com- come. bined with posterior instrumented open reduction. In the treatment of patients with high-grade spondylolis- Natarajan RN, Garretson RB III, Biyani A, Lim TH, thesis the benefits of reduction must be weighed against Andersson GBJ, An HS: Effects of slip severity and the significant potential complications and these issues loading directions on the stability of isthmic spondylolis- should be discussed with the patient and family in great thesis: A finite element model study. Spine 2003;28:1103- detail. 1112. Annotated Bibliography This study shows that the stiffness of a spondylolisthetic motion segment decreases with increasing slip progression. Bartolozzi P, Sandri A, Cassini M, Ricci M: One-stage The authors also report that lateral bending and torsion cause posterior decompression-stabilization and transsacral in- the most resultant motion. terbody fusion after partial reduction for severe L5-S1 spondylolisthesis. Spine 2003;28:1135-1141. Classic Bibliography This retrospective study suggests that posterior decom- Boos N, Marchesi D, Zuber K, Aebi M: Treatment of se- pression with partial reduction and stabilization with pedicle vere spondylolisthesis by reduction and pedicular fixa- screw fixation and titanium cage transsacral interbody fusion tion: A 4-6 year follow up study. Spine 1993;18:1655- is a safe and effective treatment for patients with high-grade 1661. spondylolisthesis. Bradford DS, Boachie-Adjei O: Treatment of severe Beutler WJ, Frederickson MD, Murtland A, Sweeney spondylolisthesis by anterior and posterior reduction MA, Grant WD, Baker D: The natural history of and stabilization: A long-term follow-up study. J Bone spondylolysis and spondylolisthesis: 45-year follow-up Joint Surg Am 1990;72:1060-1066. evaluation. Spine 2003;28:1027-1035. Carragee EJ: Single-level posterolateral fusion, with or This is a prospective study of the natural history of without posterior decompression, for the treatment of spondylolysis and spondylolisthesis over 45 years. The authors isthmic spondylolisthesis in adults. J Bone Joint Surg Am report that patients with pars defects follow a clinical course 1997;79:1175-1180. similar to the general population and that slip progression markedly slows with each decade. Fischgrund JS, Mackay M, Herkowitz HN, Brower R, Montgomery DM, Kurz LT: Degenerative lumbar Hanson DS, Bridwell KH, Rhee JM, Lenke LG: Corre- spondylolisthesis with spinal stenosis: A prospective, lation of pelvic incidence with low- and high-grade isth- randomized study comparing decompressive laminec- mic spondylolisthesis. Spine 2002;27:2026-2029. tomy and arthrodesis with and without spinal instru- mentation. Spine 1997;22:2807-2812. This study shows that pelvic incidence is significantly higher in low- and high-grade slips compared with control Herkowitz HN, Kurz LT: Degenerative spondylolisthesis groups. Pelvic incidence also has a significant correlation with with spinal stenosis: A prospective study comparing de- Meyerding-Newman scores. compression with decompression and intertransverse ar- throdesis. J Bone Joint Surg Am 1991;73:802-808. Hanson DS, Bridwell KH, Rhee JM, Lenke LG: Dowel fibular strut grafts for high-grade dysplastic isthmic Katz JN, Lipson SJ, Chang LC, Levine SA, Fossel AH, spondylolisthesis. Spine 2002;27:1982-1988. Liang MH: Seven- to 10-year outcome of decompressive surgery for degenerative lumbar spinal stenosis. Spine This study shows that fibular strut grafting is a safe and ef- 1996;21:92-98. fective method for treating patients with partially reduced high-grade slips. The authors found no significant difference Marchetti PG, Bartolozzi P: Classification of spondy- between the use of allograft and autograft. lolisthesis as a guideline for treatment, in Bridwell KH, DeWald RL (eds): Textbook of Spinal Surgery. Philadel- La Rosa G, Conti A, Cacciola F, et al: Pedicle screw fixa- phia, PA, Lippincott-Raven, 1997, pp 1211-1254. tion for isthmic spondylolisthesis: Does posterior lum- 562 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 45 Spondylolysis-Spondylolisthesis Smith MD, Bohlman HH: Spondylolisthesis treated by a fixation and posterolateral fusion after decompression single-stage operation combining decompression with in in spondylolotic spondylolisthesis. Spine 1997;22:210- situ posterolateral and anterior fusion: An analysis of 219. eleven patients who had long-term follow-up. J Bone Joint Surg Am 1990;72:415-421. Wiltse LL, Newman PH, Macnab I: Classification of spondylolysis and spondylolisthesis. Clin Orthop Suk S, Lee C, Kim WJ, Lee JH, Cho KJ, Kim HG: Add- 1976;117:23-29. ing posterior lumbar interbody fusion to pedicle screw American Academy of Orthopaedic Surgeons 563



Chapter 46 Adult Spinal Deformity Bobby K-B Tay, MD Introduction curves (> 60°) show the greatest risk for progression. In a large cohort of patients with adolescent idiopathic The evaluation and management of adult patients with scoliosis that was followed for more than 40 years, 68% spinal deformity has undergone a rapid evolution in the of patients had progression of their curvature after skel- past decade. Increasing knowledge about the natural etal maturity. Thoracic curves greater than 50° pro- history of adult spinal deformity and the biologic events gressed an average of 1° per year. Thoracolumbar that mediate the processes of spinal fusion have pro- curves progressed about 0.5° per year and lumbar vided the spinal surgeon with a greater ability to evalu- curves progressed 0.24° per year. Thoracic curves less ate and treat these complex disorders. Despite these ad- than 30° tended not to progress. vances, evaluation and optimal treatment of adult spinal deformity remains a significant challenge. In addition, Patients with degenerative scoliosis exhibited a the increasing number of technical options available to higher rate of curve progression, which on average was the spinal surgeon as well as the many spinal instrumen- about 3.3° per year. The prevalence of lumbar scoliosis tation systems available today have not made manage- in adult patients with low back pain was estimated to be ment of adult spinal deformity any less challenging. about 7.5%. The prevalence increased with age and in- cluded 15% of patients with low back pain who were It is now well established that untreated scoliosis in older than 60 years. Risk factors for curve progression the adult is not a benign condition. Common associa- include the presence of a curvature greater than 30°, tions include painful, degenerative, spinal osteoarthritis; apical rotation greater than 33%, more than 6 mm of progressive deformity; spinal stenosis with radiculopa- lateral listhesis, and poor seating of L5 on S1. thy; muscle fatigue from coronal and sagittal plane im- balance; and poor cosmesis. Accurate determination of In contrast to adolescent patients with scoliosis who pain, impairment in the quality of life, and cosmetic ef- are usually asymptomatic, adult patients with scoliosis fects of deformity are difficult to measure and compare often report back pain. In a recent European study in- among groups of patients. These factors, when weighed volving 16,394 adolescents and their parents, the lifetime against the increased complication rate of surgical treat- prevalence of low back pain was 50.9% for boys and ment, makes the decision to operate as important or 69.3% for girls with scoliosis as an independent risk fac- more important than the technique and expertise with tor. Other smaller but better designed studies have dem- which the procedure is performed. onstrated that patients with scoliosis have a higher inci- dence of back pain than age- and sex-matched controls. Prevalence and Natural History In general, the overall incidence of pain ranges from 40% to 90%, and the overall prevalence of painful de- Adult spinal deformity can arise as a sequela of un- formity ranges from 60% to 80%. The etiology of the treated adolescent idiopathic scoliosis, failed surgical or pain is multifactorial. It can arise from muscle fatigue nonsurgical treatment, or de novo spinal deformity de- on the convexity of the curvature, trunk imbalance, facet veloping in the adult. The latter can be caused by degen- arthropathy on the concavity of the curvature, and de- erative changes of the spinal column leading to instabil- generative disk disease. Back pain is more common in ity and deformity, by iatrogenic instability after patients with lumbar curves and in patients with thora- decompressive procedures for spinal stenosis and radic- columbar and lumbar curves exceeding 45° with apical ulopathy, and possibly by metabolic bone diseases such rotation and coronal imbalance. Although the incidence as osteoporosis. The prevalence of scoliosis in adults has of back pain in patients with adult scoliosis is similar to been reported to range from 1.4% to 20%. that in the general population, many studies suggest that back pain in patients with scoliosis is greater and more Clearly, scoliosis can continue to progress after skel- persistent. In addition to back pain, adult patients are etal maturity and into late adulthood. Large thoracic American Academy of Orthopaedic Surgeons 565

Adult Spinal Deformity Orthopaedic Knowledge Update 8 more likely to experience symptoms of spinal stenosis sette 14- × 36-inch weight-bearing scoliosis radiographs and radiculopathy from osteoarthritis of the spine, rota- are necessary to fully assess the extent of the primary tory subluxations, anterior listhesis, and lateral listhesis curvature as well as any compensatory curves that may of the vertebral bodies that result in stretching and/or exist. The weight-bearing radiographs also allow physi- impingement of nerve roots. Again, neurogenic symp- cians to evaluate both coronal and sagittal plane bal- toms are more common in patients with lumbar curva- ance. If surgery is contemplated, lateral supine bending tures. However, paresis or paraplegia from untreated films are obtained to assess the flexibility of secondary scoliosis has not been reported. curvatures. Occasionally, flexion and extension views are helpful to determine lumbar spine flexibility and the Decreased vital capacity and other parameters of pul- presence of sagittal plane instability. These views have monary function may occur in patients with severe tho- been sufficient in most patients for preoperative plan- racic curves (> 60°), especially in the presence of thoracic ning. Traction views may be helpful for assessing severe lordosis that effectively decreases the anterior-posterior deformities, but in deformities less than 60°, bending chest diameter. In one study, up to 35% of patients with films provide a better assessment of curve flexibility. A thoracic curves reported cardiopulmonary symptoms. fulcrum bending view (in which the PA radiograph is However, significant alterations in vital capacity as a re- taken with the patient in the lateral decubitus position sult of restrictive lung disease have not been observed un- with the apex of the curvature over a large bolster) or a til the curve magnitude exceeds 90° to 100°. In addition, push-prone radiograph (in which the pelvis of the prone there is no evidence to suggest that an adult patient with patient is stabilized while the surgeon applies lateral previously normal pulmonary function after skeletal ma- pressure to the major curve) can help access thoracic turity will experience deterioration in pulmonary function curve flexibility. with progression of the curvature without a preexisting history of smoking or some other pulmonary disease. In general, curve magnitude and patient age are the main predictors of curve flexibility. Every 10° increase Finally, the psychologic impact of chronic pain and in curve magnitude over 40° results in a 10% decrease deformity must be considered. In a world where appear- in curve flexibility. Every 10-year increase in age de- ance and health become increasingly important for so- creases the flexibility of the structural curve by 5% and cial acceptance and well-being, the inability of individu- the lumbosacral fractional curve by 10%. als to function at the level of their peers because of pain or deformity can create a huge psychologic burden. The MRI is reserved to evaluate rapidly progressive influence of spinal deformity on psychologic well-being curves and to determine the cause of any neurologic ab- has not been determined in the adult population. Small normalities on physical examination. Myelography is series of patients with adult scoliosis have been reported helpful for evaluating the neural elements in patients to show a significant negative impact of the spinal defor- with severe rotational deformity and in those with metal mity on patients’ perception of health. implants that may obscure the clarity of MRI scans. Dis- kography has been recommended by some authors as a Patient Assessment means of evaluating discogenic pain. This is especially relevant in the evaluation of patients with low back pain History and Physical Examination and lumbar scoliosis to help determine the distal extent of fusion, especially in patients with disk degeneration A complete history followed by a careful physical exam- and axial low back pain. A positive diskogram in a pa- ination (including a complete neurologic examination) tient with a degenerated disk below the anticipated fu- is essential in a patient with adult spinal deformity. The sion levels would be a relative indication to extend the importance of social and family history and occupa- fusion to encompass the involved degenerated disk. tional history cannot be overstated. Depression, sub- However, there are no prospective studies to confirm or stance abuse, and chronic smoking in patients with adult refute the efficacy of this rationale because the results spinal deformity can result in a less than ideal outcome of provocative diskograms seem to depend to a great after major spinal reconstructive surgery. Overall, the extent on the interpretation and the technique of the evaluation of the adult with scoliosis is much more diffi- examiner. cult than that of adolescents because the usual criteria for surgical treatment are more difficult to interpret. In Preoperative pulmonary function testing is useful for addition, the surgical treatment of scoliosis in adults car- patients with thoracic curves exceeding 70°, patients ries a higher rate of complications and involves a longer with a history of pulmonary disease (chronic smokers), recovery period than in adolescents. Proper patient se- and patients who will require thoracoplasty. Adults who lection is critical for achieving a successful result. undergo thoracoplasty experience a 27% decline in pul- monary function by 3 months postoperatively, which, in Imaging Studies contrast to adolescents, does not improve appreciably after 2-year follow-up. Thus, an adult patient with bor- Standard PA and lateral full-length spine radiographs are an essential part of the evaluation process. Long cas- 566 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 46 Adult Spinal Deformity derline pulmonary function may not tolerate thoraco- which can result from malnutrition. Use of sequential plasty or thoracotomy. compression devices or foot pumps to minimize the risk of deep venous thrombosis, mobilization with the assis- Treatment tance of physical therapy, and aggressive respiratory therapy should be routine. Other useful adjuncts to sur- Nonsurgical Treatment gery include an autologous blood exchange program, the use of the Cell Saver autologous blood recovery sys- The initial treatment of patients with back pain and tem (Haemonetics, Braintree, MA) at the time of sur- scoliosis should not differ from the treatment of patients gery, carefully monitored intraoperative hypotension, with mechanical back pain in the absence of deformity. routine neurologic monitoring, and an experienced an- A relative indication for nonsurgical treatment includes esthesia staff that can manage the blood loss and fluid patients who physically cannot tolerate the amount of shifts that occur during complex spinal reconstruction. surgery necessary to properly address their pain, defor- Finally, redosing of antibiotics every 4 hours or after mity, and neurologic dysfunction. A physical therapy 1,500 mL of blood loss to maintain the antibiotic con- program should be instituted to improve aerobic capac- centration above the minimum inhibitory concentration ity, strengthen muscles, and improve flexibility and joint is recommended. motion. Although local heat application, analgesics, and bracing all may aid in the amelioration of symptoms, It is important to remember that the amount of cor- they do not prevent curve progression. Corticosteroid rection obtained in the adult patient is secondary to the injections in the form of nerve root blocks, facet injec- achievement of coronal and sagittal plane balance. Tho- tions, and epidural steroid injections may be of consider- racic rib prominence is best corrected with thoraco- able value in the arsenal of conservative management of plasty rather than with overcorrection of the thoracic adult spinal deformity. In patients who are not surgical curve. The choice of fixation used to achieve correction candidates, spinal bracing during ambulation may pro- and balance is extremely important because osteoporo- vide some symptomatic relief to improve functionality. sis is often present in the adult patient. Segmental fixa- tion provides improved purchase in weakened bone and Surgical Treatment creates a large area for force transmission in the correc- tion of deformity. The indications for surgery in the adult patient with scoliosis include thoracic curve greater than 50° to 60°, The use of thoracic pedicle screws in the treatment with chronic pain that is unrelieved by conservative of traumatic conditions of the spinal column has be- management; significant loss of pulmonary function not come more popular as experience with the technique in- attributable to underlying pulmonary disease; docu- creases. The primary benefit of pedicle screw fixation is mented curve progression with coronal or sagittal plane the ability to shorten the length of fusion across the in- imbalance; symptomatic deformity that is unacceptable jured level while still having significant three- to the patient; and lumbar curvature with associated dimensional control over the spinal deformity to be able back or radicular pain or symptoms of spinal stenosis. to reduce it. Pedicle screw fixation may also provide a more secure anchor at the cephalad extent of the fusion Adult patients have a greater risk of experiencing compared with that provided by hooks. The use of trans- surgical complications than adolescents. Major compli- pedicular fixation in the thoracic spine is still controver- cations include pseudarthrosis in 5% to 27% of patients, sial because the presence of deformity makes insertion residual pain in 5% to 15%, neurologic injury in 1% to of screws more difficult and hazardous. In addition, in 5%, infection in 0.5% to 5%, and thromboembolism in the presence of osteoporosis, the spinal lamina is often 1% to 20%. the most secure point of fixation. In such instances, ex- cellent correction of thoracic curves can be obtained To avoid the detrimental effects of prolonged immo- with a combination of laminar hooks and sublaminar bilization, surgical procedures should be designed to wires. In contrast to adolescent scoliosis, adult curva- provide maximum stability and thus allow early mobili- tures tend to be less flexible and adult patients tend to zation with minimal external support. Combined proce- have osteoporosis and less healing potential. Thus, pedi- dures are preferable to staged procedures if this is tech- cle screw fixation alone does not substitute for appro- nically and physiologically feasible. Combined anterior- priate anterior column releases and fusion. posterior spinal reconstructive surgery has a lower infection rate than staged procedures as a result of pa- Intraoperative somatosensory-evoked potential and tient malnutrition at the time of the posterior proce- motor-evoked potential monitoring are especially help- dure. ful when there is a possibility of extensive blood loss, hypotension, significant deformity correction, and stiff Normalization of nutritional status does not occur curvatures. When this type of monitoring is not avail- until 6 to 12 weeks after the index procedure. If surgical able, a wake-up test should be performed after instru- procedures need to be staged, the use of hyperalimenta- mentation and correction of the curvatures. Combined tion or enteral nutritional supplementation between stages is recommended to help decrease complications, American Academy of Orthopaedic Surgeons 567

Adult Spinal Deformity Orthopaedic Knowledge Update 8 somatosensory-evoked potential and motor-evoked po- formity to obtain a balanced correction of the curvature. tential monitoring is superior to single modality tech- Curvatures that exceed 90° to 100° are often associated niques in the assessment of real-time root and spinal with rigid ankylosis of the spine and severe coronal im- cord function. With the development of intercostal mus- balance. In patients with this degree of deformity, a cle and rectus abdominis intraoperative electromyo- three-stage posterior-anterior-posterior procedure or a graphic monitoring, thoracic pedicle screws can be vertebral resection procedure is required to gain suffi- tested to minimize the risk of perforation into the spinal cient spinal mobility and to gain sufficient curve correc- canal or the neural foramen. tion to obtain spinal balance. Before any surgical procedure, both surgeon and pa- Patients with spinal stenosis should have decompres- tient must have realistic expectations for the outcome of sion of the stenotic levels before instrumentation and the operation. Most studies report a 69% to 95% reduc- correction of the curvatures. Patients with severe lum- tion in the severity of pain and a 30% to 40% correction bar spinal stenosis who also have decompensation in the of deformity. sagittal plane can be treated with staged posterior and anterior surgery. In these patients, decompression of the In general, the approach to the surgical treatment of stenotic levels should be performed before restoration adult spinal deformity is based on accepted methods of of sagittal balance. Restoration of lordosis in these pa- choosing fusion levels, placement of instrumentation, tients before decompression of the stenotic levels may and curve reduction techniques that were derived from result in a neurologic deficit. experience in the treatment of adolescent spinal defor- mities. These techniques are then modified to take into Once the spinal deformity is corrected with the appro- consideration the various challenges presented by adult priate release and instrumentation, a meticulous spinal fu- patients. These surgical challenges include the presence sion with bone grafting should be performed.Autogenous of spinal stenosis, stiffer deformities, sagittal plane im- graft from the local fusion bed and the iliac crest are balance, less potential for healing, osteoporosis, the need placed over the decorticated posterior elements. to extend the fusion to the sacrum because of stiff frac- tional curvatures in the lower lumbar spine or the pres- Degenerative Lumbar Scoliosis ence of spinal stenosis, and discogenic pain. In addition, an anatomic correction of the spinal deformity is not of- Degenerative lumbar scoliosis can result from untreated ten achieved or warranted in the adult patient. The goal idiopathic scoliosis, but it more frequently occurs inde- of surgical correction is to obtain a balanced spine in pendently as a sequela of the aging process in combina- the sagittal and coronal planes. tion with osteoporosis. Many patients with degenerative lumbar scoliosis have a combination of both mechanical Fusion levels are often determined from the weight- back pain and spinal stenosis. Patients may also present bearing PA radiographs, with modifications determined with radiculopathy because the neural foramen are nar- by lateral bending and weight-bearing lateral radio- rowed at the concavity of the spinal deformity. Fortu- graphs. Some general guidelines exist. All of the struc- nately, most of these patients are well balanced in the tural curves should be included in the fusion. The end sagittal and coronal planes despite the magnitude of the vertebra of the fusion should be within the Harrington curvature, and their main symptoms are the result of stable zone and should be neutrally rotated when the neural compression. Decompression of the stenotic spi- deformity corrects on lateral bending. The first unfused nal canal and neural foramen often results in significant disk space at the caudal end of the fusion should be improvement in pain and function in these patients. Un- flexible on lateral bending. The fusion should not be less the decompressed segments are severely ankylosed, stopped within the apex of the thoracic kyphosis or ad- these levels should be fused to prevent progression of jacent to a kyphotic motion segment. the scoliosis (Figure 1). The entire deformity does not need to be included in the fusion as long as the patient Curves less than 60° to 70° on the Cobb measure- is balanced in the sagittal and coronal planes. However, ment without significant coronal or sagittal plane dec- fusion levels should be chosen so as not to end the fu- ompensation can be treated effectively using a single sion at a listhetic level, the apex of the curvature, or a posterior approach. In patients with this type of spinal kyphotic segment. If instrumentation is used and the pa- deformity, radical facetectomies and osteotomies of tient still has lumbar lordosis, mild distraction between ankylosed segments will allow sufficient mobility to the pedicle screws at the concavity of the curvature achieve curve correction and balance. Curvatures helps to enlarge and stabilize the neuroforamen. greater than 70° are often associated with coronal and sagittal plane decompensation. These deformities are Patients with long fusions to the sacrum should also best treated with a combined anterior-posterior ap- have selective anterior fusion at the L4-5 and L5-S1 seg- proach. Anterior releases and fusions of the most struc- ments, with structural grafting to maximize fusion rates tural portions of the curvature followed by posterior re- and decrease the possibility of failure of the sacral leases and osteotomies with or without rib resections screws. will, in most patients, allow sufficient mobility of the de- 568 American Academy of Orthopaedic Surgeons

Orthopaedic Knowledge Update 8 Chapter 46 Adult Spinal Deformity Figure 1 PA (A) and lateral (B) weight-bearing radiographs of the lumbar spine of a 50-year-old woman with degenerative scoliosis and spinal stenosis who was treated with lumbar laminectomy radical facetectomies, instrumentation with correction of scoliosis, and spinal fusion. Postoperative PA (C) and lateral (D) weight-bearing radiographs of the same patient after decompression and fusion. In general, arthrodesis to the sacrum for idiopathic or in those in whom previously placed sacral screws scoliosis should be avoided if possible. Long fusions to have failed, iliac fixation is usually necessary. In the the sacrum are associated with a higher rate of pseudar- adult patient, Luque-Galveston fixation is associated throsis, fixed sagittal deformity, instrumentation failure, with a high rate of pseudarthrosis (30% to 40%). Al- and limited function. Indications to extend the fusion to though iliac fixation with iliac screws is biomechanically the sacrum include lumbosacral pain secondary to de- strong, iliac screws can be prominent in very thin indi- generative disk disease below a lumbar curvature when viduals (Figure 2). a decision has been made to correct the lumbar curve, an unbalanced lumbosacral curvature with lumbar scoli- Salvage Procedures in Adult Patients osis for which balance in the lumbosacral curve is not achieved (as assessed using appropriate side bending ra- The indications for revision scoliosis surgery in the adult diographs), and the presence of substantial degenera- include painful pseudarthrosis, progressive deformity tion of the motion segments of L4-5 and L5-S1 anteri- from pseudarthrosis or inadequate fusion levels, flat- orly and posteriorly. In selected patients with a fixed back syndrome from distraction implants across the lumbosacral fractional curve, fusion to the sacrum can lumbar spine, symptomatic adjacent segment degenera- be avoided by an end plate osteotomy at L4 or L5 (with tion or vertebral body fracture, and unacceptable resid- concave osteophyte excision) to make the end vertebra ual deformity. horizontal, reduce the fractional curve, and create a sta- ble end vertebra above the pelvis. The goals of surgery are the same as in primary sur- gery—to obtain a solid arthrodesis, achieve three- When performing long fusions to the sacrum in dimensional spinal balance, and provide rigid internal adults, a combined approach is recommended to maxi- fixation. The management of pseudarthrosis in the adult mize the fusion rate, reestablish lumbar lordosis, and patient with scoliosis depends on the level of the pseud- prevent implant failure across the lumbosacral junction. arthrosis, the presence or absence of deformity, the se- Two-stage surgery is preferable with the anterior diskec- curity of preexisting fixation, and especially the pres- tomies and fusion, with structural grafts or cages per- ence or absence of pain. A painful pseudarthrosis formed first followed by posterior fusion and instrumen- associated with progressive deformity and loss of fixa- tation. tion is a clear indication for spinal revision surgery via a combined approach. However, thoracic pseudarthrosis Many techniques are available to secure fixation that is not associated with deformity or loss of fixation across the lumbosacral junction. These include sacral can be adequately managed by single-stage anterior and screws placed in a bicortical fashion, sacral screws with posterior repair with copious autogenous bone grafting. intrasacral rods, iliac wing screws, Galveston technique, and convergent and divergent sacral screws. Bicortical Adult patients may present with curve progression sacral screw fixation with structural anterior fusion at above or below a previous fusion that was done in child- L5-S1 appears to be an adequate anchor for most long hood or adolescence. This condition may be secondary fusions to the sacrum. In patients with poor bone stock to crankshaft phenomena or the primary fusion being too short. For minor degrees of deformity in young American Academy of Orthopaedic Surgeons 569