Simons Myofascial Pain & Dysfunction-The Trigger Point Manual Vol 2-The Lower Extremities

Chapter 24 / Long Extensors of Toes 483 Figure 24.4. Stretch position and spray or icing pat- the distal X marks the common location of those in the tern (thin arrows) for the long extensors of the toes. extensor hallucis longus. The thick arrow indicates the The solid circle covers the head of the fibula. The downward pressure exerted on the toes and foot to proximal X marks the common location of trigger stretch both muscles simultaneously. points in the extensor digitorum longus muscle, and ism of relief of symptoms that were due to 12. INTERMITTENT COLD WITH peripheral nerve entrapment by the mus- STRETCH cle. (Fig. 24.4) 11. ASSOCIATED TRIGGER POINTS These two long extensor muscles of the toes respond well to intermittent cold with The TrPs often appear independently in stretch. To apply this treatment to inacti- the long extensors of the toes, but also vate TrPs in either of the muscles, one may develop in conjunction with TrPs in must plantar flex the foot at the ankle and neighboring muscles. Not surprisingly, also flex the corresponding toes (Fig. the peroneus longus and brevis muscles 24.4).62 In addition, the foot should be in- are likely to develop TrPs associated with verted to achieve full lengthening of the those in the extensor digitorum longus extensor digitorum longus and everted for since all three muscles are prime agonists full lengthening of the extensor hallucis for eversion of the foot. The extensor hal- longus. For each muscle, parallel down- lucis longus and, to a lesser extent, the sweeps of vapocoolant spray or ice should extensor digitorum longus may develop cover both the full length of the muscle TrPs in association with TrPs in the tibi- and its referred pain pattern (Fig. 24.4). alis anterior muscle. In the presence of hypermobility in the The extensor digitorum longus and per- tarsometatarsal region, a two-handed oneus tertius work closely together as a stretch approach is needed so that this team in both dorsiflexion and eversion of midfoot region can be stabilized. In such the foot. Existence of active TrPs in one cases, intermittent cold could precede the apparently can induce TrPs in the other stretch rather than being applied simulta- as a result of compensatory overload of neously with it. the parallel unimpaired muscle. The use of ice for applying intermittent At times, particularly with severe per- cold with stretch is explained on page 9 petuating factors, the entire anterior of this volume and the use of vapocoolant compartment musculature harbors TrPs. spray and stretch is detailed on pages 6 7 - Thus, it is important to check the long 74 of Volume l . 6 7 extensors of the toes for TrPs if the other anterior compartment muscles are Simply applying sweeps of spray or involved. stroking with ice over the reference zone where the patient complains of pain, with-

484 Part 3 / Leg, Ankle, and Foot Pain Figure 24.5. Injection of trigger points in the right extensor digitorum longus muscle. The solid circle marks the head of the fibula. See text for description of the course of the deep peroneal nerve and anterior tibial vessels, and how to avoid them. Injection of the extensor hal- lucis longus is not generally recom- mended. out including the skin overlying the mus- with vapocoolant spray or ice stroking. cle and its TrPs, usually relieves the pain However, the advantage of their method only momentarily. Including the muscle is that it includes stabilization of the tar- and its TrPs is much more likely to abolish sometatarsal region. the pain, the restricted range of motion, and the referred deep tenderness for a long Ischemic compression and deep mas- period of time, even permanently.65 sage, two valuable techniques, are followed immediately by full passive and active The application of intermittent cold lengthening of the muscle except when with passive stretch should include cov- such stretching exercises are contraindi- erage of four agonistic muscles, the short cated by hypermobility. Additional tech- and long extensors of both the great and niques for releasing myofascial TrPs are lesser toes, effectively releasing TrP tight- discussed in Chapter 2 of this volume. ness in those muscles. The antagonist toe flexors may also need to be treated in a 13. INJECTION AND STRETCH similar manner to prevent activating their (Fig. 24.5) TrPs by unaccustomed shortening. If it is considered necessary to inject TrPs The effectiveness of this procedure is in the long extensors of the toes, one augmented by incorporating Lewit's post- should take care to avoid the deep pero- isometric relaxation35 with reflex aug- neal nerve and anterior tibial vessels. mentation,36 as described on pages 10-11 This is less difficult for TrPs in the exten- of this volume. sor digitorum longus muscle than in the extensor hallucis longus. The deep pero- Following intermittent cold with stretch, neal nerve passes across the fibula deep moist heat applied promptly over the to the extensor digitorum longus proxi- muscles that have been treated rewarms mal to the region where one usually finds the skin (and muscles if they were unin- TrPs in that muscle (Fig. 24.1). The nerve tentionally cooled] and reduces post- then accompanies the anterior tibial ves- treatment soreness. Slow active range of sels that together lie on the interosseus motion from the fully shortened to the fully membrane deep to the extensor hallucis lengthened positions of these muscles (to longus (see Fig. 19.3).27 Thus, when in- the limits of toe flexion and extension) jecting TrPs in the extensor digitorum helps further increase range of motion longus muscle (Fig. 24.5), one inserts the and incorporate full range of motion into needle close to the lateral border of the daily activities. tibialis anterior muscle and angles the needle posteriorly toward the fibula.27 Evjenth and Hamberg22 describe tech- niques that are specific for stretching the Injection of TrPs in the extensor hal- extensor digitorum longus or the extensor lucis longus muscle is generally not rec- hallucis longus muscles. These tech- ommended, and should be considered niques would be awkward to combine

Chapter 24 / Long Extensors of Toes 485 only if the taut band and TrP tenderness propriate support should be added to the have been clearly localized and their shoes. depth determined. In this case, one must be especially careful of the depth of nee- Corrective Posture and Activities dle penetration. One may have to pass the needle through the lateral portion of the If the automobile accelerator pedal places tibialis anterior to direct the needle to- the foot in a markedly dorsiflexed or ward the fibula at an angle deep enough plantar flexed position, the slope of the to reach the TrPs in the extensor hallucis pedal should be adjusted by adding an longus, but sufficiently superficial to appropriately shaped wedge pad to it in avoid the underlying deep peroneal nerve order to produce a more neutral angula- and anterior tibial vessels (see Fig. tion of the foot at the ankle. The patient 19.3).27 should be advised to stop and walk around the car every 30—60 minutes on a If TrPs are to be injected in these mus- long drive to prevent the adverse effects cles, one should warn the patient in ad- of prolonged immobilization of the leg vance that he or she may feel some numb- muscles. ness and that the muscle may become \"lazy\" following the injection. If this hap- The patient should wear low heels with pens, there is no need to worry. When a full base (not spike heels) to provide a 0.5% procaine solution is used, even if neutral angle at the ankle and a stable some procaine seeps around the nerve, base for walking, and should walk on nerve conduction will recover in 15 or 20 even surfaces. minutes; it is not uncommon for this tran- sient nerve block to occur. It is better to If excessive jogging or sports activity warn the patient ahead of time than to that involved running was responsible for confront him or her with an unexpected the development of the TrPs in these toe event. It is important to use 0.5% pro- extensors, such strenuous weight-bearing caine; if 1% or 2% procaine is injected, or activities should be avoided for a period a longer-acting local anesthetic is se- immediately after specific TrP treatment. lected, the patient may be unable to walk It is best if the patient rows, swims, or bi- out of the office for an hour or longer. cycles for exercise. If the patient insists on returning to the previous activity, a Following injection of these TrPs, ac- graded program of progressively increas- tive range of motion is performed slowly ing levels of exercise helps avoid re-expo- and repeatedly to the limits of toe flexion sure to overload beyond tolerance. and extension. Application of several sweeps of ice or vapocoolant in the mus- One should avoid both the plantar cle's lengthened position helps ensure in- flexed position and an extreme dor- activation of any residual TrPs and helps siflexed position of the foot during sleep; normalize muscle function. Prompt appli- the angle of the foot at the ankle should cation of moist heat for several minutes be in the neutral position. A pillow minimizes postinjection soreness. This placed against the feet beneath the sheet may be applied prior to active range of helps avoid excessive plantar flexion motion if it is painful. caused by heavy or tight covers, as shown for the gastrocnemius muscle in Figure 14. CORRECTIVE ACTIONS 21.11. Care should be taken in the place- ment of the pillow, however, to avoid ex- In addition to correction of systemic per- cessive dorsiflexion (shortened position petuating factors, such as those described of the muscle). in Chapter 4 of Volume l , 6 7 corrective ac- tions are recommended for the following Home Therapeutic Program specific physical stresses on these long extensor muscles of the toes. Since cooling a muscle aggravates its TrPs, the patient should wear warm socks If there is hypomobility in the joints of or stockings and slacks to keep the legs the ankle and foot, these areas should be warm. Cold, drafty locations should be mobilized. If there is hypermobility, ap- warmed, possibly by a space heater under the desk. A blanket may be needed over the legs when sitting. An electrically

486 Part 3 / Leg, Ankle, and Foot Pain heated floor pad protects from a cold 23. Ferner H, Staubesand J: Sobotta Atlas of Human floor. An electric blanket at night is help- Anatomy, Ed. 10, Vol. 1. Urban & Schwarzen- ful in maintaining body warmth and mus- cular relaxation. berg, Baltimore, 1983 (Fig. 458). 24. Ibid. (Figs. 4 6 5 , 4 6 7 ) . The patient should be instructed in an 2 5 . Ibid. (Fig. 4 6 6 ) . exercise to lengthen these long extensors 26. Ibid. (Fig. 4 6 8 ) . of the toes passively. The patient can sit 27. Ibid. (Figs. 4 7 2 - 4 7 4 ) . in a comfortable position, use one hand to 28. Ibid. (Fig. 4 8 8 ) . stabilize the leg (or to support the midfoot 2 9 . Ibid. (Fig. 503). if there is hypermobility), and use the 30. Ibid. (Fig. 504). other hand to plantar flex the ankle and flex the toes. This can be done while the 31. Jacobsen S: Myofascielt smertesyndrom (Myo- patient sits with the back supported in a fascial pain syndrome). Ugeskr Laeger 149:000- bathtub of warm water. 601, 1987. An active pedal exercise that combines toe flexion and extension with ankle 32. Jimenez L, McGlamry ED, Green DR: Lesser ray movement (see Fig. 22.13) should be per- deformities, Chapter 3. In Comprehensive Text- formed every 20-30 minutes when a per- book of Foot Surgery, edited by E. Dalton Mc- son sits or reclines for long periods. Glamry, Vol. 1. Williams & Wilkins, Baltimore, References 1987 (pp. 5 7 - 1 1 3 , see pp. 5 7 - 5 8 , 6 6 - 7 1 ) . 1. Anderson JE: Grant's Atlas of Anatomy, Ed. 8. Wil- 33. Kamon E: Electromyographic kinesiology of jumping. Arch Phys Med Rehabil 5 2 : 1 5 2 - 1 5 7 , liams & Wilkins, Baltimore, 1983 (Fig. 4-70). 2. Ibid. (Fig. 4 - 7 1 ) . 1971. 3. Ibid. (Fig. 4 - 7 2 ) . 4. Ibid. (Fig. 4 - 7 3 ) . 34. Krammer EB, Lischka MF, Gruber H: Gross anat- 5. Ibid. (Fig. 4 - 7 7 ) . 6. Ibid. (Fig. 4 - 7 9 ) . omy and evolutionary significance of the human 7. Ibid. (Fig- 4 - 1 0 6 ) . peroneus III. Anat Embryol 1 5 5 : 2 9 1 - 3 0 2 , 1979. 8. Bardeen CR: The musculature, Sect. 5. In Mor- 35. Lewit K: Manipulative Therapy in Rehabilitation of the Motor System. Butterworths, London, 1985 ris's Human Anatomy, edited by C M . Jackson, Ed. (p. 282). 6. Blakiston's Son & Co., Philadelphia, 1921 (pp. 36. Lewit K: Postisometric relaxation in combina- 512-514). 9. Basmajian JV, Deluca CJ: Muscles Alive, Ed. 5. tion with other methods of muscular facilitation and inhibition. Manual Med 2 : 1 0 1 - 1 0 4 , 1986. Williams & Wilkins, Baltimore, 1985 (pp. 351, 37. Lockhart RD: Living Anatomy, Ed. 7. Faber & 353). Faber, London, 1974 (Figs. 136, 138). 10. Bates T, Grunwaldt E: Myofascial pain in child- 38. Macdonald AJR: Abnormally tender muscle re- hood. J Pediatr 5 3 : 1 9 8 - 2 0 9 , 1 9 5 8 . gions and associated painful movements. Pain 8: 11. Broer MR, Houtz SJ: Patterns of Muscular Activity 197-205, 1980. in Selected Sports Skills. Charles C Thomas, 39. Maloney M: Personal communication, 1991. Springfield, 1967. 12. Carter BL, Morehead J, Wolpert SM, et al.: Cross- 40. Matsusaka N: Control of the medial-lateral bal- ance in walking. Acta Orthop Scand 5 7 : 5 5 5 - 5 5 9 , Sectional Anatomy. Appleton-Century-Crofts, 1986. New York, 1977 (Sects. 72-87). 4 1 . McMinn RMH, Hutchings RT: Color Atlas of 13. Clemente CD: Gray's Anatomy of the Human Body, Human Anatomy. Year Book Medical Publishers, American Ed. 30. Lea & Febiger, Philadelphia, Chicago, 1977 (pp. 282, 285). 1985 (p. 111). 4 2 . Ibid. (p. 289). 14. Ibid. (p. 112). 4 3 . Ibid. (p. 314). 1 5 . Ibid. (pp. 5 7 4 - 5 7 5 ) . 44. Ibid. (p. 318). 16. Ibid. (p. 582). 4 5 . Ibid. (p. 319). 17. Close JR: Motor Function in the Lower Extremity. 4 6 . Ibid. (p. 321). Charles C Thomas, Springfield, 1964 (p. 78). 47. Menz P, Nettle WJS: Closed rupture of the mus- 18. Duchenne GB: Physiology of Motion, translated by culotendinous junction of extensor hallucis E.B. Kaplan. J.B. Lippincott, Philadelphia, 1949 longus. Injury 2 0 : 3 7 8 - 3 8 1 , 1989. (pp. 338, 340, 341, 346, 370-371, 412). 48. Miller SJ: Principles of muscle-tendon surgery 19. Ibid. (pp. 3 4 3 - 3 4 4 , 371, 381, 4 1 6 - 1 1 7 , 421). and tendon transfers, Chapter 23. In Comprehen- 20. Ibid. (p. 345). sive Textbook of Foot Surgery, edited by E. Dalton 2 1 . Ibid, (pp. 371, 381, 4 1 6 - 1 1 7 ) . 22. Evjenth O, Hamberg J: Muscle Stretching in Man- McGlamry, Vol. 2. Williams & Wilkins, Balti- more, 1987 (pp. 714-755, see p. 737). ual Therapy, A Clinical Manual. Alfta Rehab Forlag, 4 9 . Netter FH: The Ciba Collection of Medical Illustra- tions, Vol. 8, Musculoskeletal System. Part I: Alfta, Sweden, 1984 (pp. 136-139). Anatomy, Physiology and Metabolic Disorders. Ciba-Geigy Corporation, Summit, 1987 (p. 98). 50. Ibid. (p. 99). 5 1 . Ibid. (p. 100). 52. Ibid. (p. 104). 5 3 . Ibid. (p. 107). 54. Ibid. (p. 111). 55. Perlman MD, Leveille D: Extensor digitorum longus stenosing tenosynovitis. J Am Podiatr Med Assoc 7 8 : 1 9 8 - 1 9 9 , 1988.

Chapter 24 / Long Extensors of Toes 487 56. Perry  J:  The  mechanics  of  walking.  Phys Ther 47: and  R.  Melzack,  Ed.  2.  Churchill  Livingstone,  London,  778‐801, 1967.  1989 (pp. 368‐385, see p. 378, Fig. 25.9G).  57. Perry J ,  Ireland ML, Gronley J, et al.: Predictive value  63. Smith  TF:  Common  pedal  prominences,  Chapter  6.  In  of manual muscle testing  and  gait analysis in normal  Comprehensive Textbook of Foot Surgery, edited  by  E.  ankles  by  dynamic  electromyography.  Foot Ankle Dalton  McGlamry,  Vol.  1.  Williams  &  Wilkins,  6:254‐259, 1986.  Baltimore, 1987 (pp. 252‐263, see p. 260).  58. Rasch PJ, Burke RK: Kinesiology and Applied Anatomy, 64. Streib EW, Sun SF, Pfeiffer RF: Toe extensor weakness  Ed.  6. Lea &  Febiger,  Philadelphia, 1978 (pp. 318,  330,  resulting  from  trivial  athletic  trauma.  Report  of  three  Table 17‐2).  unusual cases. Am J Sports Med 70:311‐313, 1982.  59. Reynolds MD: Myofascial trigger point syndromes in  65. Travell  J:  Ethyl  chloride  spray  for  painful  muscle  the  practice  of  rheumatology.  Arch Phys Med Rehabil spasm. Arch Phys Med Rehabil 33:291‐298, 1952.  62:111‐114, 1981.  66. Travell J ,  Rinzler SH: The myofascial genesis of pain.  60. Rohen  JW,  Yokochi  C:  Color Atlas of Anatomy, Ed.  2.  Postgrad Med 11:425‐434, 1952.  Igaku‐Shoin, New York, 1983 (p. 423).  67. Travell  JG,  Simons  DG:  Myofascial Pain and Dys- 61. Ibid. (p. 426).  function: The Trigger Point Manual. Williams  &  62. Simons  DG,  Travell  JG:  Myofascial  pain  syndromes,  Wilkins, Baltimore, 1983.  Chapter  25.  In  Textbook of Pain, edited  by  P.D.  Wall  68. Wood J: On some varieties in human myology. Proc R Soc Lond 13:299‐303, 1864.   

CHAPTER 25 Long Flexor Muscles of Toes Flexor Digitorum Longus and Flexor Hallucis Longus \"Clawtoe Muscles\" HIGHLIGHTS: REFERRED PAIN from trigger cial pain syndromes, shin splints, chronic com- points (TrPs) in the flexor digitorum longus mus- partment syndrome, and rupture of the flexor cle is felt primarily in the middle of the plantar hallucis longus tendon. Differential diagnosis re- forefoot proximal to the four lesser toes, with a quires an understanding of toe deformities. AC- spillover pattern over the plantar surface of TIVATION AND PERPETUATION of flexor dig- these toes. The TrPs in the flexor hallucis itorum longus and flexor hallucis longus TrPs longus refer pain strongly to the plantar surface can result from running on uneven ground, par- of the great toe and head of the first metatarsal. ticularly in badly worn footgear. Walking and ANATOMICAL ATTACHMENTS of the flexor running barefoot on soft sand tend to perpetuate digitorum longus are proximally, to the posterior these TrPs, as does a Morton foot structure or surface of the tibia and distally, to the base of other deviation that produces hyperpronation or the distal phalanx of each of the four lesser toes. an unstable foot. PATIENT EXAMINATION in- The flexor hallucis longus attaches proximally to cludes evaluation of gait, foot configuration, toe the posterior surface of the fibula and distally to extension range, toe flexor strength, and foot- the distal phalanx of the great toe. Its tendon gear. TRIGGER POINT EXAMINATION of the crosses deep to that of the flexor digitorum flexor digitorum longus requires the clinician to longus distal to the medial malleolus, behind exert pressure on the muscle between the back which both tendons pass. INNERVATION of of the tibia and the medial edge of the gastroc- both long flexor muscles of the toes is via nemius muscle. The examiner locates flexor hal- branches of the tibial nerve. These extrinsic toe lucis longus TrP tenderness by compressing the flexors FUNCTION to help maintain equilibrium muscle against the fibula with pressure through when body weight is on the forefoot and to help the overlying gastrocnemius aponeurosis and stabilize the foot and ankle during the midstance the soleus muscle. INTERMITTENT COLD to late stance phase of walking. The flexor dig- WITH STRETCH of these long flexor muscles of itorum longus is generally more active than the the toes requires application of vapocoolant flexor hallucis longus during vigorous sports ac- spray or ice stroking over the muscles, the sole tivities. The primary action of both of these long of the foot, and the plantar surface of the toes. flexor muscles in a \"free\" lower limb is vigorous Simultaneously, the foot is passively dorsiflexed flexion of the distal phalanx of the related toes and everted and the distal phalanges of all toes and weak flexion of the other joints of the toes. are extended. The procedure is completed with For both muscles, their assistance in controlling application of moist heat and slow active range movements of the foot in the sagittal plane and of motion. The patient is taught a passive self- in the frontal plane becomes more important stretch home program. INJECTION of flexor dig- when the position of the foot is fixed. The chief itorum longus TrPs requires consideration of the SYMPTOM of TrPs in the long flexors of the location of the posterior tibial vessels and nerve, toes is painful feet, especially when weight bear- and also of the anterior tibial vessels and deep ing. Differential diagnoses include other myofas- peroneal nerve on the other side of the interos- 488

Chapter 25 / Long Flexors of Toes 489 seus membrane. Injection of the flexor hallucis ning or jogging (at first only on smooth level sur- longus is more difficult and requires considera- faces). The patient should perform a self-stretch tion of the peroneal vessels. CORRECTIVE AC- exercise program regularly at home and prog- TIONS include replacement of badly worn ress to strengthening exercises for these mus- shoes, installation of first metatarsal pads or cles. arch supports, if indicated, and limitation of run- 1. REFERRED PAIN when patients complain that the sole of (Fig. 25.1) the forefoot is painful and tender, few cli- nicians think to examine the calf for the Trigger points (TrPs) in the flexor dig- source of the pain. itorum longus muscle refer pain and ten- derness primarily to the middle of the Myofascial TrPs in the flexor hallucis plantar forefoot proximal to the four longus muscle refer pain strongly to the lesser toes and sometimes with spillover plantar surface of the great toe and head pain to these toes (Fig. 25.1A). Only occa- of the first metatarsal (Fig. 25.16). The sionally do these TrPs refer pain to the pain may occasionally radiate proximally medial side of the ankle and calf, and for a short distance on the plantar surface, they do not refer pain to the heel. Thus, but does not extend to the heel or leg. Flexor digitorum longus trigger point Flexor hallucis longus trigger point Figure 2 5 . 1 . Pain patterns (bright red) referred from ferred by these trigger points, fled stippling illustrates trigger points (Xs) in the long flexors of the toes (right the occasional extension of the essential pain pattern, side, posterior view). The essential pain pattern (solid A, for flexor digitorum longus muscle (dark red). B, for red) shows the pain distribution characteristically re- flexor hallucis longus muscle (light red).

490 Part 3 / Leg, Ankle, and Foot Pain 2. ANATOMICAL ATTACHMENTS AND both sides of it. The fibers of this muscle CONSIDERATIONS continue to converge on its tendon as it (Fig. 25.2) crosses the posterior surface of the lower end of the tibia. The tendon then crosses The two long (extrinsic) flexor muscles of the posterior surface of the talus and the the toes share the deep posterior compart- inferior surface of the sustentaculum tali ment of the leg with the tibialis posterior of the calcaneus—deep to the tendon of and the popliteus muscles.41 the flexor digitorum longus muscle. In the sole of the foot, the tendon of the flexor The flexor digitorum longus muscle hallucis longus courses forward between lies on the back of the tibia deep to the the two heads of the flexor hallucis brevis soleus and gastrocnemius and medial to muscle to attach distally to the base of the the tibialis posterior. Proximally it at- terminal phalanx of the great (first) toe.16 taches to the posterior surface of the mid- dle two-quarters of the tibia,43 beginning Occasionally, the peroneocalcaneus internus distal to the soleus attachment (Fig. 25.2) muscle runs from the posterior aspect of the fibula and including the intermuscular septum under the sustentaculum tali together with the that is shared with the tibialis posterior flexor hallucis longus tendon and inserts on the muscle. The fibers of this pennate muscle calcaneus.16,49 A sesamoid bone may develop in converge on the tendon that passes be- the tendon of the flexor hallucis longus where it hind the medial malleolus in a groove passes over the talus and calcaneus.12 shared with the tendon of the tibialis pos- terior muscle, but in a separate compart- Supplemental References ment and in a separate synovial sheath. As its tendon approaches the navicular Photographs present the flexor digitorum bone and passes into the sole of the foot, longus and the flexor hallucis longus from be- it crosses superficial to the flexor hallucis hind,39,47 and drawings show the tendons at the longus tendon from which it receives a ankle from behind,6 and from a posteromedial strong tendinous slip. At approximately view.7 Views from behind portray both muscles midsole, the quadratus plantae muscle in relation to the posterior tibial artery and joins the flexor digitorum longus ten- nerve,4,21,42 and in relation to only the posterior don, which then divides into four ten- tibial artery.40 Other posterior views include dons, each of which passes through an the peroneal artery,21,40,42 the tibialis posterior opening in the corresponding tendon of muscle,442 and the tendon crossover in the the flexor digitorum brevis. Distally foot.40,42 A schematic drawing in a posterior each of the four tendons attaches to the view of the leg and a plantar view of the foot base of the distal phalanx of its corre- portray the muscles, the tendon crossover, and sponding lesser toe.12,16 tendinous attachments to the toes.8 Variations are not uncommon. The flexor dig- A photograph from a medial and plantar view shows both the flexor digitorum longus and the itorum longus muscle may be more or less divided flexor hallucis longus muscles.48 Drawings pres- ent the tendons at the ankle from the medial view5 into separate fasciculi for the individual toes.\" and with tendon sheaths.17, 22 The plantar view reveals the course of the tendons in the foot and One of the more common anomalous muscles of their attachments to the toes.7,9,25,48 the leg is the flexor accessorius longus digitorum, The entire length of the flexor digitorum longus is presented in 14 cross sections,15 and the flexor which spans from the fibula or tibia to the tendon hallucis longus is presented in 13 cross sections.14 Both muscles are presented in three cross sections of the flexor digitorum longus or to the quadratus through the proximal, middle, and distal thirds of the leg,24 in a single cross section at the lower part plantae.16,30,49,55 of the middle third of the leg,2 and in one cross section just above the middle of the leg.41 The lat- The flexor hallucis longus muscle lies ter cross section portrays the relation of the deep distal and lateral to the flexor digitorum posterior compartment to the other compartments longus (Fig. 25.2) and the tibialis poste- of the leg.41 rior. It also lies deep to the soleus and gastrocnemius muscles. This pennate muscle attaches proximally to the infe- rior two-thirds of the body of the fibula, to the interosseous membrane, and to in- termuscular septa shared with muscles on

Chapter 25 / Long Flexors of Toes 491 Figure 25.2. Attachments of the long flexors of the toes, right side, seen from behind. The flexor digitorum longus is dark red, and the flexor hallucis longus is medium red. Flexor Fibula digitorum Flexor longus hallucis longus Tibia ,Calcaneus Flexor hallucis Flexor digitorum longus tendon longus tendon Posterior views locate the bony attachments of 4. FUNCTION both long flexor muscles of the toes to the fibula and tibia.3, 23, 37,43 Plantar views of the foot locate The flexor digitorum longus and the the tendinous attachments on the toes.10,26,38,43 flexor hallucis longus muscles function during walking to stabilize the foot and 3. INNERVATION ankle in midstance to late stance, playing a role in mediolateral balance. They assist The flexor digitorum longus receives fi- other plantar flexors in enabling the indi- bers from a branch of the tibial nerve that vidual to transfer weight to the forefoot, contains fibers from the L5 and S1 spinal and they help in the maintenance of equi- nerves. The flexor hallucis longus is in- librium when weight is on the forefoot. nervated by a branch of the tibial nerve that contains fibers from the L5, S1, and S2 The flexor digitorum longus flexes the spinal nerves.16 distal phalanx of each of the four lesser toes; the flexor hallucis longus flexes the distal phalanx of the great toe. They both

492 Part 3 / Leg, Ankle, and Foot Pain assist in plantar flexion and inversion of landing of an upward two-leg jump. Running in the foot when the foot is free to move. soft sand calls for powerful toe-curling action.45 Actions 5. FUNCTIONAL (MYOTATIC) UNIT The flexor digitorum longus and the flexor hal- lucis longus act primarily as flexors of the distal The agonists for these long flexors of the phalanges of their respective toes with important toes are the short flexors of the toes, the additional actions of assisting plantar flexion and flexors digitorum and hallucis brevis. The inversion of the foot.16,45 antagonists of these flexors are the long (extrinsic) and short (intrinsic) extensors Direct electrical stimulation of the flexor dig- of the toes. itorum longus muscle with the limb free caused forceful flexion only of the distal phalanges of the The prime ankle plantar flexors are the four lesser toes; the middle and proximal phalan- gastrocnemius and soleus muscles, which ges could easily be extended. Stimulation of the are assisted by these long flexors of flexor hallucis longus muscle similarly caused the toes, the tibialis posterior, peroneus powerful flexion of the distal phalanx and rela- longus, and peroneus brevis. The prime tively weak flexion of the proximal phalanx of the muscles for inversion of the foot are the great toe.19 tibialis anterior and tibialis posterior, which these extrinsic toe flexors can also Functions assist. Standing 6. SYMPTOMS Without flexor hallucis longus function, it is diffi- Patients complain that their feet hurt cult for the individual to maintain equilibrium when they walk. The pain occurs in the when standing on the toes.27 sole of the forefoot and on the plantar sur- faces of the toes. These people have Walking frequently obtained custom-made inserts (orthoses) to reduce stress on the foot. Electromyographic studies showed that, during Most patients like the inserts and retain ambulation, the flexor hallucis longus13,18,51 and them even after the TrPs causing the pain flexor digitorum longus18,51 muscles were active have been inactivated. primarily when body weight was concentrated on that same limb, at the time when these muscles The TrPs in these long extrinsic flexors could position and stabilize the foot and ankle of the toes may occasionally cause pain- during midstance to late stance. The flexor hal- ful contraction of these muscles similar to lucis longus muscle was slightly active in flat- the calf cramps of gastrocnemius TrPs. footed subjects at heel-off but negligibly so in nor- However, toe flexor \"cramping\" is more mal subjects. Flexor hallucis longus activity at likely to be caused by TrPs of the intrinsic that time in the flatfooted subjects could help pre- flexors of the toes. vent excessive dorsiflexion of the great toe.13,29 Differential Diagnosis Perry and associates44 found that, among seven normal subjects, the peak intensity of electrical The medial ankle pain sometimes re- activity of the long flexor muscles of the toes dur- ferred by flexor digitorum longus TrPs ing fast gait, free gait, and slow gait approximated can present symptoms easily mistaken for the activity elicited by a manual muscle testing ef- a tarsal tunnel syndrome if the clinician fort of fair + , fair + , and fair, respectively, for is not aware of this referred pain pattern most subjects. and fails to examine the muscle for TrPs. Following tibial nerve block and loss of motor Other Myofascial Pain Syndromes function in the plantar flexors (including the flexor digitorum longus and the flexor hallucis The referred pain patterns of the flexor longus) subjects noted inability to transfer weight digitorum longus (Fig. 25.1A) and tibialis to the forward part of the foot, making it difficult posterior (see Fig. 23.1) both appear on to lean forward with the weight solely on one the sole of the foot and plantar surface of limb.52 the toes. However, TrP pain from the flexor digitorum longus concentrates on Running and Sports Activities the sole, whereas pain referred from the The flexor digitorum longus is important in \"drive\" for sports. For instance, Kamon32 found it to be vigorously active during the take-off and

Chapter 25 / Long Flexors of Toes 493 tibialis posterior concentrates over the of the foot in the presence of a flexible pes Achilles tendon and its pain distribution valgus deformity (flat foot). Pronation of on the sole is only a spillover, not an es- the subtalar joint allows hypermobility sential, pattern. The pain patterns of the and unlocking of the midtarsal joint, flexor digitorum longus and the abductor which, in turn, leads to hypermobility of digiti minimi (see Fig. 26.3A) both appear the forefoot.31 The long flexors of the toes on the lateral side of the sole, but that of then act earlier and longer than in normal the abductor digiti minimi is usually re- gait.29 Instead of stabilizing the forefoot, stricted to the region of the head of the this abnormal activity usually overpow- fifth metatarsal and does not cause pain ers the smaller intrinsic lumbrical and in- in the toes. The essential patterns of the terosseous muscles, as well as the quad- flexor digitorum longus and the adductor ratus plantae. Loss of quadratus plantae hallucis (see Fig. 27.2A) are quite similar, function allows adducto varus deviation but the adductor hallucis pattern does not of the fifth toe and possibly of the fourth include spillover patterns to the toes or toe. Flexor stabilization is the most com- leg. The pain syndromes of the flexor dig- mon etiology of hammer toes.31 itorum longus and the interossei (see Fig. 27.3) could be confusingly similar if sev- Flexor substitution develops when the eral interosseous muscles were involved. triceps surae muscles are weak and the An interosseous TrP refers pain primarily deep posterior and lateral leg muscles try to the corresponding toe and in a longitu- to substitute for this weakness. This sub- dinal band at the base of the toe, espe- stitution occurs in a high-arched and cially on the plantar surface. supinated foot in the late stance phase of gait when the flexors have gained Pain referred from flexor digitorum mechanical advantage over the interossei; brevis TrPs (see Fig. 26.3B) runs trans- it usually produces total flexion (clawing) versely across the sole of the foot in the of all toes without adducto varus of the region of the metatarsal heads. The pain fourth and fifth toes. If triceps surae from neither the flexor hallucis longus strength is inadequate for heel lift, this ac- nor the flexor digitorum longus has this tion readily leads to a hammer-toe syn- transverse orientation. drome. Flexor substitution is the least common of the three mechanisms (flexor The essential pain patterns of both the stabilization, flexor substitution, and ex- flexor hallucis longus (Fig. 25.16) and the tensor substitution) that can produce flexor hallucis brevis (see Fig. 27.26) in- clawtoes and hammer toes.31 Extensor volve the plantar surface of the great toe, substitution is reviewed under Section 6 but the pattern of the flexor hallucis in Chapter 24. brevis extends around the medial side of the foot and has a spillover pattern across Toe curling may result from spasticity following the dorsal surface of the great toe. traumatic brain injury or any cerebrovascular ac- These ambiguities should be resolved by palpating all suspected muscles for cident. Simply releasing the flexor hallucis longus taut bands, TrP spot tenderness, and re- production of the patient's pain com- and flexor digitorum longus tendons provided sat- plaint. isfactory relief in only about one-fourth of 41 feet. Toe Deformities Additional release of the flexor digitorum brevis Hammer toes and clawtoes. Hammer toe and clawtoe deformities (described in often achieved a more functional result.33 Chapter 24 of this volume) may result from overactivity of the long flexor mus- Hallux valgus. Snijders and co-work- cles of the toes by either of two mecha- ers50 used a force plate to study the bio- nisms, flexor stabilization or flexor sub- mechanical effects of an increased val- stitution.31 gus angle of the great toe (hallux valgus) and of an increased varus angle of the Flexor stabilization most commonly first metatarsal bone (spread foot) dur- occurs when the long flexors of the toes ing standing and push-off. They found attempt to stabilize the osseous structures that the greater the valgus angle of the great toe, the more the force exerted by the flexor hallucis longus tended to fur- ther increase the abnormal angle. This

4 9 4 Part 3 / Leg, Ankle, and Foot Pain matched the observation that if a woman is aggravated by the presence of a Morton succeeded in reaching the age of 20 years (mediolateral rocking) foot structure (see with a valgus angle of 10° or less, she was Chapter 20, pages 381-383 for details.) unlikely to develop bunions later.50 This finding strongly reinforces the impor- When the foot excessively pronates tance of wearing, from early childhood (due to a hypermobile midfoot, flexible through adulthood, footwear that exerts pes valgus deformity, muscular imbal- no pressure directed laterally on the great ance, or some other cause), the flexor dig- toe. itorum longus and flexor hallucis longus can become overloaded and develop Shin Splints and Chronic Compartment Syndrome TrPs. These muscles may also become overloaded in a high-arched supinated Garth and Miller28 examined 17 athletes who pre- foot with triceps surae weakness. sented for treatment of incapacitating pain and soreness located posteromedially along the mid- In a study of 100 patients who had in- dle third of the tibia (over the attachment and curred a motor vehicle accident that acti- belly of the flexor digitorum longus muscle). vated TrPs in numerous muscles, the Symptoms were provoked and aggravated by re- flexor hallucis longus was rarely in- petitive weight bearing. Similar symptoms are re- volved.11 ferred to as shin splints,28 medial tibial stress syn- drome,28 and chronic compartment syndrome.*4 Sev- Perpetuation enteen asymptomatic athletes served as controls. The symptomatic athletes consistently had a mild Impaired mobility of the joints of the foot claw deformity of the second toe with abnormal can perpetuate TrPs in these muscles. displacement of its arc of motion toward exten- sion of the metatarsophalangeal (MP) joint. Exam- A common error among joggers and iners found weakness of the lumbrical muscles.28 runners is to continue to use a shoe after It appears as if the relatively stronger flexor dig- it has developed excessive wear on the itorum longus muscle became overloaded because sole and heel. Loss of cushioning and of inadequate MP joint stabilization caused by the flexibility produces excessive strain on lumbrical weakness, which resulted in clawing of the joints and muscles, including the long the lesser toes rather than in effective stabiliza- flexors of the toes. Walking and running tion. Symptoms were relieved by a treatment regi- on soft sand, especially barefoot, heavily men consisting of toe flexion exercises, reduced loads the flexor digitorum longus; this ac- athletic activity, and metatarsal and arch pads to tivity can perpetuate, or activate, TrPs in compensate for the weak lumbrical action. The this muscle. athletes apparently were not examined for TrPs in the sore muscle to assess their contribution to the An inflexible shoe sole prevents normal athletes' conditions. extension of the MP joints during walking and running. This stiffness of the sole ef- Tendon Rupture fectively lengthens the lever arm against which these two long flexor muscles of Spontaneous rupture of the flexor hallucis longus the toes function, and thus overloads tendon can occur during overload without evi- them. dence of previous disease or injury.48 Even though surgical repair does not always restore function of 8. PATIENT EXAMINATION the great toe, the authors46 concluded that, in cases of laceration or rupture, surgical repair While the patient is walking, the exam- seems justified. iner should look for a hyperpronating an- kle or foot. One should also examine the 7. ACTIVATION AND PERPETUATION feet for a long second, short first metatar- OF TRIGGER POINTS sal (Morton foot structure). The patient's shoe may show a wear pattern character- Activation istic of this foot structure (see Chapter 20, page 383), or evidence of excessive wear, The TrPs in the flexor digitorum longus indications of excessive wear include: and flexor hallucis longus muscles can be asymmetry between the two shoes, cracks activated, and are then perpetuated, by between the midsole and edge of the running or jogging on uneven ground or shoe, a definite lean of the shoe either in- on laterally slanted surfaces. The problem ward or outward when set on a level sur- face, loss of the sole pattern in sports

Chapter 25 / Long Flexors of Toes 495 Figure 25.3. Palpation of trigger points in the long is first directed anteriorly to encounter the back of the flexors of the toes on the right. A, flexor digitorum tibia solidly and then laterally between the tibia and longus, patient in side-lying position. Large arrow gastrocnemius to exert pressure on the flexor dig- shows the direction of pressure. This muscle is lo- itorum longus. B, palpation of trigger point tenderness cated between the posterior face of the tibia and the in the flexor hallucis longus in an anterior direction soleus/gastrocnemius muscles. With the knee bent through the soleus muscle and through the aponeuro- and the foot plantar flexed, the gastrocnemius muscle sis between the soleus and gastrocnemius, patient in can be pushed posteriorly away from the tibia to ex- prone position. pose the flexor digitorum longus more fully. Pressure shoes, and a flattened or expanded heel the plantar-flexed position is likely to be pattern of the shoe. particularly painful in the presence of TrPs in the corresponding flexor muscle. The patient's feet should be examined Passive extension range of motion of the for muscular imbalances, for restriction of great toe is restricted in the presence of motion (including joint play), and for hy- flexor hallucis longus involvement,36 permobility, as well as for the presence of and passive extension of the four lesser deviations, such as ankle equinus, flat toes is restricted when the flexor dig- foot, or a high-arched rigid foot. itorum longus harbors TrPs. The clinician examines the foot for toe 9. TRIGGER POINT EXAMINATION configuration and tenderness. The exam- (Fig. 25.3) ination includes the distal phalanges of all toes for flexion weakness, as de- For palpation of TrPs in the flexor dig- scribed by Kendall and McCreary.34 itorum longus muscle, the patient lies on Weakness of the flexor digitorum longus the involved side and the clinician uses and the flexor hallucis longus affects flat palpation (Fig. 25.3A) to exert pres- flexion of the distal phalanx of the cor- sure between the tibia and the soleus/gas- responding toes, and weakness of the trocnemius muscles on the medial side of flexor digitorum brevis affects flexion of the leg (see Fig. 19.3, cross section). With the middle phalanx in the four lesser the knee bent to 90° and the foot plantar toes. In addition, the involved muscle flexed, the gastrocnemius muscle can be often exhibits a ratchety or breakaway pressed posteriorly away from the tibia to weakness when the examiner tests its expose the flexor digitorum longus to strength during a lengthening contrac- more effective palpation. The clinician tion. Maximum flexion effort of the great first exerts pressure toward the back of toe or four lesser toes with the foot in

496 Part 3 / Leg, Ankle, and Foot Pain the tibia and then laterally against the Figure 25.4. Intermittent cold with stretch of the right flexor digitorum longus. It is difficult to flexor digitorum longus and flexor hallucis longus, pa- elicit local twitch responses from this tient prone and knee flexed to 90°. Parallel sweeps of deep muscle, but spot tenderness is read- the vapocoolant or ice follow the direction of the ar- ily identified by the patient's reaction, rows. All five toes are extended together with dorsi- and the expected pattern of referred pain flexion of the ankle. As a final stretch, the foot is also may be evoked. everted. If the tarsometatarsal joints are hypermobile, intermittent cold is applied first, and then one hand is For examination of TrPs in the flexor used to stabilize these intermediate joints while the hallucis longus muscle, the patient lies other extends the toes. This stretch can be effectively prone and the clinician uses flat palpa- augmented with postisometric relaxation. tion, applying deep pressure at the junc- tion of the middle and lower thirds of patient lies prone with the knee flexed to the calf, just lateral to the mid-line, 90° as the clinician passively dorsiflexes against the posterior face of the fibula and everts the foot and extends the distal (Fig. 25.36). The pressure of palpation phalanges of all five toes, only as far must be projected through the soleus as the onset of resistance. The patient muscle, as well as through the thick apo- breathes in deeply and, at the same time, neurosis that becomes the Achilles ten- gently attempts to flex the toes against the don. Tenderness can be attributed to the resistance provided by the clinician's flexor hallucis longus only if the exam- hand. Then, the patient slowly exhales iner is sure the overlying muscles are and concentrates on relaxing while the free of tender TrPs. clinician applies the ice or vapocoolant spray in parallel sweeps distally over 10. ENTRAPMENTS both sides of the calf, the sole of the foot, and the plantar surface of all toes. The cli- No nerve entrapment has been identified nician then gently presses the foot toward as due to TrPs in the flexor digitorum dorsiflexion and eversion, and the toes longus or the flexor hallucis longus. How- into extension, to take up any slack that ever, the anomalous flexor digitorum ac- develops in the muscles, without causing cessorius longus can cause a tarsal tunnel pain. This sequence is repeated until no syndrome.49 further range of motion is gained. 11. ASSOCIATED TRIGGER POINTS The use of ice for applying intermittent cold with stretch is explained on page 9 The associated muscles most likely to harbor active TrPs, when one finds them in the long flexors of the toes, are: the tibi- alis posterior, also a primary invertor and accessory plantar flexor of the foot, and the long and short extensors of the toes, an- tagonists to the toe-flexion function of the flexor digitorum longus and flexor hal- lucis longus. The short (intrinsic) flexors of the toes may also develop TrPs as part of the functional unit. 12. INTERMITTENT COLD WITH STRETCH (Fig. 25.4) To inactivate TrPs in the flexor hallucis longus and flexor digitorum longus mus- cles, simultaneous intermittent cold with stretch of both muscles (Fig. 25.4) can be combined with postisometric relaxation as described by Lewit and Simons.35 The

Chapter 25 / Long Flexors of Toes 497 Figure 25.5. Injection of trigger points in the long angled anteriorly toward the back of the tibia. B, in the flexors of the toes, right side. A, in the flexor digitorum flexor hallucis longus muscle. The needle is angled longus muscle. The trigger point is spanned and fixed laterally toward the back of the fibula. See Figure 19.3 by the fingers of the operator's left hand. The needle is for a cross-sectional view of this region. of this volume and the use of vapocoolant is described in Section 14 of this chap- spray and stretch is detailed on pages 6 7 - ter. 74 of Volume l . 5 3 Techniques that aug- ment relaxation and stretch are reviewed Evjenth and Hamberg20 describe and il- on pages 10-11 of this volume. lustrate a stretch technique for each of the long flexor muscles of the toes, but it is In the presence of hypermobility in not convenient to use with ice or vapo- the tarsometatarsal region, a two-handed coolant spray, since the stretch requires stretch approach is needed so that this two hands. However, the advantage of midfoot region can be stabilized. In such their method is that it includes stabiliza- cases, the application of intermittent cold tion of the tarsometatarsal region. The in parallel sweeps can precede the stretch Lewit technique, described previously in rather than being applied simultaneously this chapter and in Chapter 2 of this vol- with it. ume, is sometimes remarkably effective by itself without cooling. The combina- Following application of vapocoolant tion is usually very effective. spray or ice stroking with stretch, the cli- nician applies moist heat over the treated 13. INJECTION AND STRETCH muscles to rewarm the cooled skin while (Fig. 25.5) the patient relaxes. After several minutes of heat application, the patient performs The flexor digitorum longus frequently slow active range of motion from full harbors multiple TrPs (like the long finger plantar flexion to full dorsiflexion of the flexors) and these may separately involve ankle with full flexion and extension of individual digitations for the toes. There- the toes for several cycles, to take advan- fore, one can easily overlook some TrPs in tage of reciprocal inhibition and to nor- this muscle. Injection requires precise lo- malize sarcomere length and restore full calization of the TrPs and full knowledge functional range of motion. of relevant anatomy. The cross-sectional view in Figure 19.3 shows clearly how To maintain the gains achieved, the the flexor digitorum longus lies between patient then learns and practices how to the tibia in front and the tibial nerve with self-stretch the affected muscles pas- the posterior tibial vessels behind. The sively as a home exercise. This exercise

498 Part 3 / Leg, Ankle, and Foot Pain anterior tibial vessels and the deep pero- Before leaving the clinic, the patient neal nerve also travel deep to the flexor learns and practices as a home program digitorum longus and are shielded by the the passive self-stretch exercise described interosseous membrane and in some parts in the next section. of the leg by the tibialis posterior muscle. 14. CORRECTIVE ACTIONS For injection of TrPs in the flexor dig- itorum longus muscle, the patient lies on Corrective first metatarsal pads are added the involved side (as for palpation) and to the shoe if the patient has a Morton the clinician carefully localizes the spots (mediolateral rocking) foot structure (see of TrP tenderness between the examining Chapter 20, Peroneus Longus, pages 389- fingers (Fig. 25.5A). By angling the needle 392). Arch supports may also be needed toward the posterior surface of the tibia for an excessively pronated foot or for a through the medial edge of the soleus hypermobile foot. muscle, the clinician minimizes the dan- ger of penetrating the tibial nerve and If hypomobility of the foot is a factor, posterior tibial vessels. Because of this normal joint play and motion should be oblique approach, a needle as long as 63 restored. mm (21/2 in) may be needed. Needle pene- tration of a TrP is confirmed by a pain re- Corrective Posture and Activities sponse (jump sign) of the patient. With probing movements, the clinician infil- The patient should wear comfortable trates the cluster of TrPs with approxi- shoes that have adequate shock absorp- mately 1 mL of 0.5% procaine in isotonic tion (a rubber sole or a foam insert inside saline. the shoe) and adequate flexibility of the distal sole. New shoes should be tested at The TrPs in the flexor hallucis longus the time of purchase to ensure adequate are even more difficult to inject precisely space in the vamp for the addition of an than those in the flexor digitorum longus, insert without cramping the toes. One and alternative non-invasive methods of should replace worn-out shoes and those therapy should be tried before injecting with poor flexibility of the distal sole. An this muscle. Figure 19.3 illustrates the in- extremely stiff sole that prevents exten- timate association between the peroneal sion of the metatarsophalangeal joint of blood vessels and the medial portion of the great toe should be avoided. The pa- this muscle. To inject TrPs in the flexor tient's heel should fit snugly inside the hallucis longus muscle, the patient lies shoe to provide mediolateral stability; if prone (Fig. 25.5B) and the clinician local- needed, lateral pads should be added in- izes the TrP tenderness as closely as pos- side until the heel of the shoe fits well. sible by deep palpation through the gas- High heels and spike heels should be trocnemius and soleus muscles. A needle avoided completely. 63 mm (21/2 in) long may sometimes be re- quired. When injecting, it is advisable to If patients with active TrPs in the flexor angle the needle somewhat laterally away digitorum longus or the flexor hallucis from the peroneal vessels toward the pos- longus are runners or joggers, initial man- terior surface of the fibula. It may be nec- agement concentrates on inactivating the essary to contact the fibula gently to con- TrPs, correcting anatomical and bio- firm the location of the needle and to en- mechanical imbalances, and improving sure sufficient depth of penetration to the stamina of deconditioned muscles. If reach the TrPs in this muscle. The clini- these measures are inadequate, the run- cian infiltrates each TrP with 1 mL or less ners should be encouraged to substitute of 0.5% procaine in isotonic saline. non-weight-bearing activities, such as rowing, swimming, or bicycling. Running Promptly following injection, moist should first resume on a flat, even sur- heat is applied over the calf for several face, initially with limited distance that minutes to minimize postinjection sore- progresses by increments that are within ness. The patient then actively contracts tolerance. If the only running surface and stretches the muscle slowly through available is slanted from side-to-side, its fully shortened and fully lengthened then equal time should be allotted to run- positions for several cycles.

Chapter 25 / Long Flexors of Toes 499 ning on a medial and a lateral slant dur- 6. Blakiston's Son & Co., Philadelphia, 1921 (pp. ing one exercise session.1 521-523). Running on soft sand should be 13. Basmajian JV, Deluca CJ: Muscles Alive, Ed. 5. avoided until TrPs are inactivated and muscles are conditioned. Williams & Wilkins, Baltimore, 1985 (p. 378). 14. Carter BL, Morehead J, Wolpert SM, et al.: Cross- Home Therapeutic Program Sectional Anatomy. Appleton-Century-Crofts, For passive self-stretch, the patient is in- structed to rest the heel on the floor or on New York, 1977 (Sects. 74-86). a stool, then to grasp the toes with the an- 15. Ibid. (Sects. 7 4 - 8 7 ) . kle dorsiflexed, and gradually to extend 16. Clemente CD: Gray's Anatomy of the Human Body, the toes. If there is hypermobility in the tarsometatarsal region, the patient should American Ed. 30. Lea & Febiger, Philadelphia, use the other hand to stabilize this region. Alternating periods of actively flexing the 1985 (pp. 578-579). toes against resistance, relaxing, and pick- 17. Ibid. (p. 583, Fig. 6 - 8 1 ) . ing up the slack (Lewit technique) facili- 18. Close JR: Motor Function in the Lower Extremity. tate full stretch. Figure 16.13B in the Hamstring chapter illustrates self-stretch Charles C Thomas, Springfield, 1964 (Fig. 65, p. of the long flexor muscles of the toes in combination with hamstring stretch. The 78). Lewit technique is described in detail in 19. Duchenne GB: Physiology of Motion, translated by Chapter 2 of this volume. E.B. Kaplan. J.B. Lippincott, Philadelphia, 1949 The patient will benefit by walking in a swimming pool, taking long strides, with (pp. 372-374). the body submerged to approximately 20. Evjenth O, Hamberg J: Muscle Stretching in Man- waist level. This requires use of these sta- bilizer muscles in a slowed time frame ual Therapy, A Clinical Manual. Alfta Rehab Forlag, and does not overstress them because of the buoyant effect of the water. A mild ex- Alfta, Sweden, 1984 (pp. 154, 156). ercise for toe flexor strengthening is that 2 1 . Ferner H, Staubesand J: Sobotta Atlas of Human of picking up objects (marbles or Kleenex) with the toes. One should follow this ex- Anatomy, Ed. 10, Vol. 2. Urban & Schwarzen- ercise with lengthening of the muscles. More vigorous strengthening is obtained berg, Baltimore, 1983 (Figs. 461, 462). by having the patient walk slowly with a 22. Ibid. (Fig. 4 6 4 ) . long stride on dry sand, if the soleus and 23. Ibid. (Fig. 4 6 9 ) . other plantar flexor muscles can tolerate 24. Ibid. (Figs. 4 7 2 - 4 7 4 ) . this stress. 25. Ibid. (Fig. 4 9 9 ) . 26. Ibid. (Fig. 500). References 27. Frenette JP, Jackson DW: Lacerations of the 1. Anderson A: Personal communication, 1991. flexor hallucis longus in the young athlete. J 2. Anderson JE: Grant's Atlas of Anatomy, Ed. 8. Wil- Bone Joint Surg [Am] 5 9 : 6 7 3 - 6 7 6 , 1 9 7 7 . liams & Wilkins, Baltimore, 1983 (Fig. 4-72). 28. Garth WP Jr, Miller ST: Evaluation of claw toe 3. Ibid. (Fig. 4 - 8 1 ) . 4. Ibid. (Figs. 4 - 8 4 , 4 - 8 6 ) . deformity, weakness of the foot intrinsics, and 5. Ibid. (Fig. 4 - 8 7 ) . posteromedial shin pain. Am J Sports Med 17: 6. Ibid. (Fig. 4 - 8 9 ) . 7. Ibid. (Fig. 4 - 9 5 ) . 821-827, 1989. 8. Ibid. (Fig. 4 - 9 9 B ) . 9. Ibid. (Fig. 4 - 1 0 2 ) . 29. Gray EG, Basmajian JV: Electromyography and 10. Ibid. (Fig. 4 - 1 0 7 ) . 11. Baker BA: The muscle trigger: evidence of over- cinematography of leg and foot (\"normal\" and flat) during walking. Anat Rec 1 6 1 : 1 - 1 6 , 1 9 6 8 . load injury. J Neurol Orthop Med Surg 7 : 3 5 - 4 4 , 30. Hollinshead WH: Anatomy for Surgeons, Ed. 3., 1986. Vol. 3, The Back and Limbs. Harper & Row, New 12. Bardeen CR: The musculature, Sect. 5. In Mor- ris's Human Anatomy, edited by C M . Jackson, Ed. York, 1982 (p. 783). 31. Jimenez L, McGlamry ED, Green DR: Lesser ray deformities, Chapter 3. In Comprehensive Text- book of Foot Surgery, edited by E. Dalton Mc- Glamry, Vol. 1. Williams & Wilkins, Baltimore, 1987 (pp. 5 7 - 1 1 3 , see pp. 66-68). 32. Kamon E: Electromyographic kinesiology of jumping. Arch Phys Med Rehabil 5 2 : 1 5 2 - 1 5 7 , 1971. 33. Keenan MA, Gorsi AP, Smith CW, et al.: Intrin- sic toe flexion deformity following correction of spastic equinovarus deformity in adults. Foot Ankle 7 : 3 3 3 - 3 3 7 , 1987. 34. Kendall FP, McCreary EK: Muscles, Testing and Function, Ed. 3. Williams & Wilkins, Baltimore, 1983 (pp. 134, 135). 35. Lewit K, Simons DG: Myofascial pain: relief by post-isometric relaxation. Arch Phys Med Rehabil 65:452-456, 1984. 36. Macdonald AJR: Abnormally tender muscle re- gions and associated painful movements. Pain 8: 197-205, 1980. 37. McMinn RMH, Hutchings RT: Color Atlas of Human Anatomy. Year Book Medical Publishers, Chicago, 1977 (pp. 281, 285). 38. Ibid. (p. 289). 39. Ibid. (p. 315).

500 Part 3 / Leg, Ankle, and Foot Pain 40. Ibid. (p. 316).  49. Sammarco GJ, Stephens MM: Tarsal tunnel syndrome  41. Netter  FH:  The Ciba Collection of Medical Illustrations, caused by the flexor digitorum acces‐sorius longus. J Bone Joint Surg [Am] 72:453—454, 1990.  Vol.  8,  Musculoskeletal  System.  Part  I:  Anatomy,  50. Snijders  CJ,  Snijder  JGN,  Philippens  MMGM:  Physiology  and  Metabolic  Disorders.  Ciba‐Geigy  Corporation, Summit, 1987 (p. 98).  Biomechanics  of  hallux  valgus  and  spread  foot.  Foot  42. Ibid. (p. 103).  Ankle 7:26‐39, 1986.  43. Ibid. (p. 107).  51. Sutherland  DH:  An  electromyographic  study  of  the  44. Perry  J, Ireland  ML, Gronley J, et al.: Predictive  value  plantar  flexors  of  the  ankle  in  normal  walking  on  the  of  manual  muscle  testing  and  gait  analysis  in  normal  level. J Bone Joint Surg [Am] 48:66‐71, 1966.  ankles  by  dynamic  electromyography.  Foot Ankle 52. Sutherland  DH,  Cooper  L,  Daniel  D:  The  role  of  the  6:254‐259, 1986.  ankle  plantar  flexors  in  normal  walking.  J Bone Joint 45. Rasch PJ, Burke RK: Kinesiology and Applied Anatomy, Surg [Am] 62:354‐363, 1980.  Ed.  6.  Lea  &  Febiger,  Philadelphia,  1978  (pp.  320‐321,  53. Travell  JG,  Simons  DG:  Myofascial Pain and Dys- 330, Table 17.2).  function: The Trigger Point Manual. Williams  &  46. Rasmussen  RB,  Thyssen  EP:  Rupture  of  the  flexor  Wilkins, Baltimore, 1983.  hallucis  longus  tendon:  case  report.  Foot Ankle 54. Wiley  JP,  Clement  DB,  Doyle  DL,  et  al.: A  primary  10:288‐289, 1990.  care  perspective  of  chronic  compartment  syndrome  of  47. Rohen  JW,  Yokochi  C:  Color Atlas of Anatomy, Ed.  2.  the leg. Phys Sportsmed 75:111‐120, 1987.  Igaku‐Shoin, New York, 1988 (p. 424).  55. Wood J: On some varieties in human myology. Proc R 48. Ibid. (p. 425).  Soc Lond 73:299‐303, 1864.   

CHAPTER 26 Superficial Intrinsic Foot Muscles Extensor Digitorum Brevis, Extensor Hallucis Brevis, Abductor Hallucis, Flexor Digitorum Brevis, Abductor Digiti Minimi \"Sore Foot Muscles\" HIGHLIGHTS: REFERRED PAIN and tender- proximal phalanx of the fifth toe. The flexor dig- ness from trigger points (TrPs) in either of the itorum brevis also attaches, proximally, to the tu- short extensor muscles of the toes, the extensor berosity of the calcaneus and, distally, by sepa- digitorum brevis or the extensor hallucis brevis, rate tendons, to the middle phalanx of each of project locally over the dorsum of the foot. Pain the four lesser toes. FUNCTION: The abductor and tenderness referred from TrPs in the abduc- hallucis and the flexor digitorum brevis are ac- tor hallucis muscle center along the medial side tive from midstance through toe-off in walking. of the heel with spillover to the instep and to the These and other intrinsic muscles stabilize the back of the heel. Pain and tenderness referred foot for single-limb balance and for propulsion. from TrPs in the abductor digiti minimi concen- The extensor digitorum brevis, through its at- trate along the plantar aspect of the fifth meta- tachments to the tendons of the extensor dig- tarsal head and may spill over onto the sole itorum longus, acts to extend the phalanges of nearby and onto the distal lateral side of the the second, third, and fourth toes. The extensor forefoot. Both pain and tenderness from the hallucis brevis extends the proximal phalanx of flexor digitorum brevis center over the heads of the great toe. The abductor hallucis usually the second to fourth metatarsals. ANATOMICAL flexes and may abduct the proximal phalanx of ATTACHMENTS of the three digitations of the the great toe. Tension of the abductor hallucis extensor digitorum brevis are, proximally, to the aggravates hallux valgus after it has developed. calcaneus and, distally, to the lateral surfaces of The flexor digitorum brevis flexes the second the corresponding tendons of the extensor dig- (middle) phalanges of the four lesser toes. The itorum longus muscle and via the extensor ap- abductor digiti minimi abducts and assists flex- paratus to the intermediate and distal phalanges ion of the proximal phalanx of the fifth toe. of the second, third, and fourth toes. The exten- SYMPTOMS of patients with TrPs in the short sor hallucis brevis also anchors proximally to the flexors of the toes include sore feet and pain on calcaneus, and distally, directly to the dorsal walking and, if the TrPs are severe, deep aching surface of the proximal phalanx of the great toe. pain at rest. The differential diagnosis should in- Proximal attachments of both the abductor hal- clude identification of similar referred pain pat- lucis and the abductor digiti minimi are to the tu- terns of other myofascial pain syndromes, plan- berosity of the calcaneus. The distal attachment tar fasciitis, congenital muscular hypertrophy, of the abductor hallucis is either to the medial and avulsion fracture at the muscular attach- side or to the plantar aspect of the proximal pha- ment. PATIENT EXAMINATION entails looking lanx of the great toe; the distal attachment of the for an antalgic gait, painfully restricted stretch abductor digiti minimi is to the lateral side of the range of motion, and diffuse deep tenderness of 501

502 Part 3 / Leg, Ankle, and Foot Pain the plantar aponeurosis. ENTRAPMENT of the cleansing of the foot. Effective injection depends posterior tibial nerve and/or its branches may be on precise localization of the taut band and its caused by the abductor hallucis muscle itself, by TrP by flat or pincer palpation and then on pene- fascial bands associated with it, or by an acces- tration of the TrP with the needle. Only the ab- sory abductor hallucis. For INTERMITTENT ductor hallucis is so thick as to require deep pal- COLD WITH STRETCH to inactivate TrPs in the pation to locate the tenderness of its TrPs close two short extensors of the toes, the operator ap- to the bone. The posterior tibial artery and nerve plies sweeps of ice or vapocoolant spray down- and their branches pass deep to the abductor ward over the anterolateral leg and dorsum of hallucis muscle below the medial malleolus and the foot to the toes and simultaneously flexes all must be considered. Intermittent cold with five toes. Application of parallel sweeps of inter- stretch followed by a moist hot pack and then full mittent cold over the medial side and plantar range of motion complete the TrP injection pro- surface of the foot during passive extension of cedure. CORRECTIVE ACTIONS include en- the great toe releases TrP tightness of the ab- couraging the patient to buy shoes that fit and to ductor hallucis muscle. Parallel sweeps of ice or use cushioned soles when standing or walking vapocoolant spray over the sole of the foot from on hard surfaces. Learning to use the Toe the heel to the toes with passive extension of the Flexor Self-stretch Exercise in a home program lesser toes releases tightness of the flexor dig- is important for TrPs in the long or short flexors itorum brevis. The ankle may be held in the neu- of the toes. Patients with TrPs in the superficial tral position for all of these procedures, which plantar muscles of the foot can benefit by using are concluded with prompt application of moist the Golf-ball Technique and the Rolling-pin heat and active full range of motion. INJECTION Technique as an integral part of their home AND STRETCH of these superficial foot mus- treatment program. cles should be preceded by hydrogen peroxide 1. REFERRED PAIN more specifically, that it referred pain to (Figs. 26.1-26.3) the instep. The superficial intrinsic foot muscles re- Abductors of First and Fifth Toes fer pain and tenderness to the foot but not to the ankle or above it. When patients The pain and tenderness referred from say they \"sprained\" an ankle and com- TrPs in the abductor hallucis muscle plain of foot but not ankle pain, one (Fig. 26.2) center along the medial side of should look for trigger points (TrPs) in the the heel with spillover to the instep and intrinsic foot muscles as a cause of the additional extension to the back of the pain. Krout63 pointed out that the myofas- heel medially. This contrasts with the cial TrPs in foot muscles that refer pain pain and tenderness usually referred by and tenderness to weight-bearing areas on soleus TrPs (see Fig. 22.1 on page 429), the sole of the foot are most troublesome which covers all of the back and bottom to patients. of the heel. Short Extensors of Toes (Intrinsic Myofascial TrPs sometimes occur in the abduc- Extensors) tor hallucis muscle in children and were identi- fied as the source of their heel pain.18 In a study of The composite referred pain pattern of painful feet caused by myalgic spots in muscles, TrPs in the extensor digitorum brevis and Good47 found the abductor hallucis to be responsi- extensor hallucis brevis muscles covers ble for heel pain in 10 of 100 cases. Kelly54,55 re- the mid-dorsum of the foot (Fig. 26.1).101 ported that a myalgic lesion in the abductor hal- lucis muscle produced cramps in the foot. In children, TrPs are occasionally found in these short extensors of the toes. The chief pain pattern referred from The referred pain pattern in children is TrPs in the abductor digiti minimi con- similar to that seen in adults.18 Kelly55 ob- centrates along the plantar aspect of the served that a myalgic lesion in the exten- fifth metatarsal head and may spill over sor digitorum brevis muscle produced cramps in the foot and later reported,56

Chapter 26 / Superficial Intrinsic Foot Muscles 503 Extensor hallucis brevis Extensor digitorum brevis Figure 26.1. Pain and tenderness referral pattern red locates the essential pain pattern nearly always {bright red) of trigger points (Xs) in the extensor hal- experienced when these trigger points are active. Red lucis brevis (darker red) and in the extensor digitorum stippling indicates occasional extension of the essen- brevis (light red) muscles of the right foot. Solid bright tial referred pain pattern of these muscles. onto the adjacent sole. The plantar spill- subjects. The flexor hallucis brevis (a over pattern may also include some of the deep intrinsic muscle) accounted for 40, distal lateral side of the forefoot (Fig. and the flexor digitorum brevis for 12, of 26.3A). the 100 cases. Superficial Short Flexor of Toes 2. ANATOMICAL ATTACHMENTS AND CONSIDERATIONS Pain and tenderness are projected from (Fig. 26.4) TrPs in the flexor digitorum brevis to the sole over the heads of the second to The reader is referred to Figure 18.2 in fourth metatarsal bones with occasional this volume for a drawing of the bones of extension over the head of the fifth meta- the foot. Review of this figure and of the tarsal (Fig. 26.36). The referred pain does ligamentous and other soft tissue struc- not extend back as far as the center of the tures of the foot should facilitate an un- sole, nor forward onto the toes. The bony derstanding of the relationship between portion of the plantar forefoot is \"sore\" structure and function. and tender, leading to the complaint of \"sore foot.\" Short Extensors of Toes In his study of 100 patients com- The extensor digitorum brevis and the plaining of painful feet caused by myalgic extensor hallucis brevis lie on the dor- spots in foot muscles, Good47 found the sum of the foot deep to the tendons of the short flexors of the toes to be responsible extensor digitorum longus.87 They attach for this complaint in more than half of the proximally to the superior surface of the

504 Part 3 / Leg, Ankle, and Foot Pain Figure 26.2. Pattern of pain and tenderness (bright heel is solid red and the spillover pattern to the instep red) referred from trigger points (Xs) in the abductor is stippled red. B, attachments of the abductor hal- hallucis muscle (darker red) of the right foot. A, the lucis. essential referred pain pattern to the medial side of the calcaneus (Fig. 26.4A) distal to the groove dons may be absent, and rarely the whole extensor for the peroneus brevis tendon and they digitorum brevis muscle is missing.12 Examination attach also to adjacent ligamentous struc- of the extensor digitorum brevis muscle of a still- tures. Together, these muscles form four born infant for terminal motor innervation re- bellies. The most medial, the extensor vealed a multipennate muscle with an oval end- hallucis brevis, presents the most distinct plate band around each central tendon.25 belly. The medial tendon anchors distally to the dorsal surface of the proximal pha- Abductors of First and Fifth Toes lanx of the great toe and often unites with the tendon of the extensor hallucis The abductor hallucis muscle is subcuta- longus. The remaining three tendons neous along the posterior half of the me- unite with the lateral surfaces of the ex- dial border of the foot,88 covering the en- tensor digitorum longus tendons to form trance of the plantar vessels and nerves the extensor apparatus of the second, into the sole. It anchors proximally to the third, and fourth toes, but rarely of the medial process of the tuberosity of the fifth toe (Fig. 26.4A).12,27 This extensor ap- calcaneus (Fig. 26.4B), to the flexor reti- paratus anchors to the intermediate and naculum of the ankle, to the plantar apo- distal phalanges. Not all sources mention neurosis, and to the intermuscular sep- an attachment of the extensor apparatus tum shared with the flexor digitorum to the proximal phalanges of the lesser brevis. Its tendon joins with that of the toes;27 however, some authors12, 32 describe medial head of the flexor hallucis brevis specific fibrous attachments (from the and is usually said to attach distally to margins of the long extensor tendons) to the medial side of the base of the proxi- the dorsum of the proximal phalanges. mal phalanx of the great toe (Fig. 26.4B).27 However, a study of just this issue An additional slip of the extensor digitorum showed that in only one-fifth of 22 speci- mens was the attachment to the medial brevis muscle occasionally attaches to a metatar- side of the first phalanx. In the others, the sophalangeal articulation, to the fifth toe, or to a dorsal interosseous muscle.27 One or more ten-

Chapter 26 / Superficial Intrinsic Foot Muscles 505 Figure 26.3. Patterns of referred pain and tender- ductor digiti minimi (light red). B, flexor digitorum ness (bright red) and location of trigger points (Xs) in brevis (darker red). two superficial intrinsic muscles of the right foot: A, ab- tendon attached directly or indirectly to from pain by surgical excision of the muscle.35 its plantar surface.17 The authors35 described the muscle as non-tender preoperatively. An accessory abductor hallucis may extend from the fascia superficial to the posterior tibial Superficial Short Flexor of Toes nerve above the medial malleolus to attach to the middle of the main abductor hallucis muscle.19,50 The flexor digitorum brevis muscle lies in the middle of the sole of the foot and is The abductor digiti minimi is subcuta- covered only by skin and the central part neous along the length of the lateral bor- of the plantar aponeurosis (Fig. 26.4B). der of the foot (Fig. 26.4S). It anchors The flexor hallucis brevis muscle, more proximally to the width of the tuberosity deeply situated, is a topic in the next of the calcaneus26 between the medial and chapter. The flexor digitorum brevis cov- lateral processes of that tuberosity, to the ers the lateral plantar vessels and nerves. deep surface of the lateral plantar fascia, It anchors proximally to the medial pro- and to the fibrous band that extends from cess of the tuberosity of the calcaneus, to the calcaneus to the lateral side of the the plantar aponeurosis, and to contigu- base of the fifth metatarsal.12,27 Distally, it ous intermuscular septa. This muscle di- joins the flexor digiti minimi brevis to at- vides into four tendons, one to each of the tach to the lateral aspect of the base of the lesser toes.27 Distally, each tendon splits proximal phalanx of the fifth toe. Some- at the base of the proximal phalanx to al- times fibers of this abductor muscle at- low passage of the corresponding tendon tach to the base of the fifth metatarsal44 in of the flexor digitorum longus, then re- such large numbers that the proximal half unites, splits again, and attaches to both of the muscle appears much bulkier than sides of the middle phalanx.27 the distal half. The tendon of the flexor digitorum brevis of the A patient with gross congenital hypertrophy of fifth toe may be absent (38%), or replaced by a one abductor digiti minimi muscle obtained relief small muscle attached to the long flexor tendon

506 Part 3 / Leg, Ankle, and Foot Pain Calcaneus Extensor Proximal hallucis phalanx Extensor brevis digitorum of the Abductor great toe brevis digiti minimi Flexor digitorum Extensor digitorum brevis longus Abductor tendon hallucis (cut) Plantar Proximal aponeurosis phalanx of the (cut) great toe Calcaneus Figure 26.4. Dorsal and plantar views: superficial in- light red. B, plantar muscles, most superficial layer. trinsic muscles of the right foot and their skeletal at- The abductor hallucis is dark red; the flexor digitorum tachments. A, dorsal muscles. The extensor hallucis brevis is light red; and the abductor digiti minimi is me- brevis is dark red and the extensor digitorum brevis is dium red. (33%), or may be represented by a muscle coming Dorsal View. The extensor digitorum brevis and from the quadratus plantae.27 extensor hallucis brevis are seen from the dorsal view in drawings2, 38 and in pictures of dissec- Supplemental References tions.77,92 The extensor digitorum brevis appears in a drawing,4 and the abductor digiti minimi and Plantar View. Drawings present the abductor extensor digitorum brevis appear in a photograph digiti minimi and abductor hallucis muscles from of a dissection76 from the dorsal view. the plantar view8,28,39, 43 and some include the flexor digitorum brevis muscle.2839 A photograph The two short extensors of the toes, drawn from of a dissection also presents the plantar aspect of the dorsal view, appear with the dorsalis pedis ar- these three muscles.93 Drawings portray, in plan- tery and with the medial branch of the peroneal tar view, the three plantar muscles of this chapter nerve.87 A photograph of a dissection shows the (namely, the abductor digiti minimi, abductor hal- same structures.73 lucis, and flexor digitorum brevis) with the plan- tar digital nerves and arteries,6 with the medial Lateral View. Drawings present the abductor and lateral plantar nerves,88 and with just the two digiti minimi and extensor digitorum brevis from toe abductors (but not the short flexor of the toes) the lateral88 and dorsolateral76 views. A photo- and the medial and lateral plantar nerves.7 A graph of a dissection shows the same muscles and drawing shows the path of the posterior tibial ar- the extensor hallucis brevis from the lateral tery, medial and lateral plantar arteries, and me- view.72 dial and lateral plantar nerves deep to the abduc- tor hallucis muscle as they enter the sole.42 A pho- Medial View. A photograph of a dissection tograph of a dissection includes the abductor shows the abductor hallucis from the medial hallucis and abductor digiti minimi with nerves view.78 A drawing shows the nerves and vessels and arteries79 and with nerves.74 that pass deep to the abductor hallucis as they enter the sole of the foot.5

Chapter 26 / Superficial Intrinsic Foot Muscles 507 Cross Sections. The relation of the abductor hal- branch of the lateral plantar nerve94 by fi- lucis and extensor digitorum brevis muscles to ad- bers from the second and third sacral spi- jacent structures can be seen in a series of six se- nal nerves.27 rial cross sections of the foot,21 the extensor hal- lucis brevis in five serial sections,20 the abductor 4. FUNCTION digiti minimi in four sections,23 and the flexor dig- itorum brevis in three sections.22 Photographs of During ambulation, muscles of the foot all five muscles of this chapter appear in four function to permit flexibility for shock ab- cross sections through the foot.83 Drawings of all sorption and balance, and to provide ri- five muscles appear in a cross section through the gidity and stability for propulsion. head of the talus,40 and drawings of the abductor digiti minimi and abductor hallucis with tendons In general, the intrinsic muscles of the of the other three appear in a cross section foot function as a unit. The electromy- through the metatarsal bones,41 similar to Figure ographic (EMG) activity of these muscles 27.9 in the next chapter of this volume. closely parallels the progressive supina- tion at the subtalar joint during level, up- Sagittal Sections. A photograph of a sagittal sec- hill, and downhill walking. These mus- tion through the medial part of the talus presents cles stabilize the foot at the subtalar and the abductor hallucis.80 One through the second transverse tarsal joints during propul- toe shows the flexor digitorum brevis.81 One sion.68 through the fifth toe includes the abductor digiti minimi and the extensor digitorum brevis mus- The abductor hallucis and flexor dig- cles.82 itorum brevis muscles are generally more active and may contribute to static arch Skeletal Attachments. The skeletal attachments support in flatfooted persons; however, in- of all five muscles of this chapter are marked on trinsic foot muscle activity is not required the bones of the foot as seen from the dorsal and for static support of the arches in the nor- plantar views.10,11,70,75 The dorsal view shows the mal foot.49 These muscles are recruited attachments of the abductor digiti minimi, abduc- during the walking cycle to compensate tor hallucis, extensor digitorum brevis, and the for lax ligaments and special stresses.49 extensor hallucis brevis.45 A medial view presents the attachments of the abductor hallucis.9 A sche- The abductor hallucis acts as a flexor matic drawing of the plantar view portrays attach- and abductor of the proximal phalanx of ments and the course of the abductor digiti the great toe. The flexor digitorum brevis minimi, abductor hallucis, and flexor digitorum flexes the middle phalanx of each of the brevis.44 four lesser toes. The abductor digiti minimi abducts and assists flexion of the Surface Contours. Photographs reveal the skin proximal phalanx of the fifth toe. The ex- contours produced by the underlying extensor tensor digitorum brevis extends the sec- digitorum brevis muscle from a lateral view3,66 ond, third, and fourth toes. The extensor and from the lateral and anteromedial views.71 hallucis brevis extends the proximal pha- Photographs show the presence of the abductor lanx of the great toe. digiti minimi and abductor hallucis muscles from the plantar view,37 and the extensor digitorum Actions brevis from the lateral view.66 The extensor digitorum brevis, through its attach- 3. INNERVATION ments to the tendons of the extensor digitorum The extensor digitorum brevis and the ex- tensor hallucis brevis receive their inner- longus, extends all three phalanges of the second, vation via branches of the deep peroneal nerve by fibers from the fifth lumbar and third, and fourth toes. The extensor hallucis first sacral spinal nerves. The abductor hallucis and the flexor digitorum brevis brevis extends only the proximal phalanx of the are innervated via branches of the medial plantar nerve by fibers also from the fifth great toe.27 lumbar and first sacral spinal nerves.27 The laterally placed abductor digiti The abductor hallucis may flex and/or abduct minimi is supplied through the first the proximal phalanx of the great toe.27,51 In only one-fifth of 22 specimens was the attachment of the abductor hallucis found to be in a position for abduction of the great toe; in the others, it acted primarily as a flexor.17 Electrical stimulation of this muscle produced primarily flexion and some abduction of the proximal phalanx with compen- satory extension of the distal phalanx of the great toe.31

508 Part 3 / Leg, Ankle, and Foot Pain The flexor digitorum brevis flexes the second toe by footwear and, therefore, are more vulnera- (middle) phalanx of the four lesser toes.27 Electri- ble to bunion formation. cal stimulation of this muscle confirmed that it forcefully flexes only the second phalanx and that Based on a review of the literature and on their simultaneous stimulation of the extensor dig- own experience, Reinherz and Gastwirth81 con- itorum longus produced extension of the proximal cluded that radical excision of the abductor hal- phalanges with strong clawing of the toes.31 lucis should be avoided whenever possible be- cause of its large size, importance in first ray sta- The abductor digiti minimi abducts and assists bilization, and the potential for deformation of flexion of the proximal phalanx of the fifth toe.27 foot structure in absence of the muscle. Electrical stimulation produced lateral deviation with some flexion of this toe.31 5. FUNCTIONAL (MYOTATIC) UNIT Functions The long and short extensors and flexors of the toes work together as a functional Electromyographic activity was generally negligi- unit in conjunction with the lumbricals ble in the abductor hallucis, flexor digitorum and interossei. Since a major action of the brevis, and the abductor digiti minimi in 14 nor- abductor hallucis is flexion, it forms a mal subjects while standing, but activity was functional unit with the flexors hallucis marked when the subjects rose on tiptoes.\" brevis and longus and also with the deep Marked activity in the abductor hallucis of a few adductor hallucis. subjects was associated with an unnecessary habit of \"digging in\" with the great toe. The activity 6. SYMPTOMS was immediately abolished when the subject straightened the toe.14 In five other normal sub- Patients with active TrPs in any of the jects, the additional stress of standing on only one three superficial muscles in the sole of foot failed to activate the abductor hallucis mus- the foot (the two abductors and the flexor cle.33 digitorum brevis) complain primarily of intolerably sore feet and are determined Neither the abductor hallucis nor the flexor dig- to find relief. They usually have tried all itorum brevis contributes to static support of the sorts of shoes and insert devices. The arch of the normal foot, even under a load of 180 orthoses are often uncomfortable and kg (400 lbs).13 In another study, all six subjects quickly discarded because of the tender- with flat feet evidenced EMG activity of the abduc- ness of the muscles against which they tor hallucis that showed a marked increase unilat- press. Many of these patients are said to erally when they stood on that foot and ceased have \"fallen arches.\" The patients have a when they stood on the other foot.33 limited walking range and their friends may note that they tend to limp. After in- In the normal walking subject, the abductor hal- activation of the TrPs, appropriate arch lucis and flexor digitorum brevis muscles become supports are usually tolerated and often active at midstance and continue activity to toe- helpful in relieving perpetuating stresses off in normal subjects. In subjects with flat feet, on the muscles. EMG activity of these muscles is more intense and usually appears from heel-strike to toe-off.16 The deep aching pain at rest is a dis- tressing symptom that often drives the pa- Basmajian15 conducted an EMG study of 10 sub- tient to seek relief by surgical procedures. jects with hallux valgus and found that there was no EMG activity of the abductor hallucis during Differential Diagnosis abduction effort. He explained in detail how the lateral deviation of the first phalanx caused in- For detailed descriptions and discussions creased leverage of the abductor hallucis for fur- of foot problems, the reader is referred to ther lateral deviation when activated as a flexor. McGlamry's comprehensive two-volume Duranti and associates33 found that the abductor textbook.69 hallucis in patients with hallux valgus was more active during weight bearing than in normal sub- Other Myofascial Pain Syndromes jects, but this might only aggravate the problem considering its displaced line of pull. Those indi- Two other myofascial pain syndromes viduals in whom the abductor hallucis functions might be mistaken for TrPs in the exten- only as a flexor, and in whom it is not attached in sor hallucis brevis and extensor dig- a position to produce abduction, are more vulner- itorum brevis muscles (Fig. 26.1) that re- able to the effects of valgus deviation of the first

Chapter 26 / Superficial Intrinsic Foot Muscles 509 fer pain and tenderness to the proximal Signs: Examination reveals tenderness part of the dorsum of the foot in front of over the medial insertion of the plantar the lateral malleolus. The referred pain fascia on the calcaneus29,99 and/or diffuse pattern of the extensor digitorum longus tenderness along the entire medial plan- (see Fig. 24.1A) is quite similar but ex- tar aspect of the foot.99 The patient experi- tends farther distally and may spill over ences plantar pain on passive extension to include the toes and the lower leg. The of the great toe.95,99 A calcaneal spur is pattern referred by TrPs in the peroneus usually an incidental finding that corre- longus and peroneus brevis muscles (see lates poorly with pain. One treats the fas- Fig. 20.1A) differs in that it appears more ciitis without regard to the spur.95,96 Sud- on, and behind, the lateral malleolus than den complete rupture of the plantar apo- in front of it. neurosis usually occurs only after a number of local steroid injections.29,99 Three other myofascial pain syndromes may be mistaken for that of the flexor dig- Treatment: The one treatment for plan- itorum brevis muscle (Fig. 26.36). This tar fasciitis most strongly emphasized is transverse plantar pattern covers the rest for the foot in the form of reduced ac- heads of the second, third, and fourth tivity29'95,99—to the point of using crutches metatarsals. The most similar pattern is for a few days29—and lessening of stress that of the adductor hallucis (see Fig. on the plantar fascia by using stiff-soled 27.2A), which covers the same region but wooden shoes temporarily95 or by adhe- also extends proximally to the instep. The sive strapping of the foot.100 An essential flexor digitorum longus pain pattern (see part of several treatment programs is Fig. 25.1A) is more longitudinal than stretching the heel cord (gastrocnemius/ transverse in orientation, is located more soleus muscles).29,99, 1 0 0 Orthotic correc- laterally on the sole, and extends farther tions include a low soft (or hard) medial proximally than that of the flexor dig- longitudinal arch support, heel wedges, itorum brevis. The plantar pain referred and a Steindler heel that replaces with from TrPs in an interosseous muscle (see sponge rubber the part of the shoe under Fig. 27.3) is more longitudinally oriented the tender area of the heel.96, 1 0 0 Several and involves the corresponding toe to a authors recommend oral anti-inflam- major degree. The toe pain helps distin- matory medication.96,99,100 Local injection guish the involvement of multiple inter- of steroids gives inconsistent results and osseus muscles from active TrPs in the may be associated with rupture of the flexor digitorum brevis muscle. plantar aponeurosis.29,99 Ultrasound ap- plied with 10% cortisone, when com- Plantar Fasciitis bined with passive stretching of the tri- ceps surae and rest, can be effective con- Symptoms: The patient complains of servative therapy.87 Surgical release of the pain in the region of the plantar aponeu- plantar fascia is a last resort and rarely rosis and/or of pain in the heel,29,99,100 used 2 9 , 5 3 , 9 6 , 9 9 , 1 0 0 which has led to the term \"policeman's heel.\"53 The patient is likely to say, Cause: Plantar fasciitis is generally at- \"the undersurface of my foot hurts, near tributed to repeated traction with micro- the middle.\"52 The pain is insidious in tears of the plantar aponeurosis,100 which onset29,99 and not associated with a spe- produce an inflammatory degeneration of cific movement or event, but often is the plantar aponeurosis at its site of at- felt after a sudden increase in an ath- tachment on the medial tubercle of the lete's level of activity.99 Pain is most calcaneus.53,96 Tension overload is caused marked on arising in the morning. The by a tight Achilles tendon that increases first 10-12 steps are severely painful tension on the aponeurosis,99, 1 0 0 excessive until the plantar fascia and the muscles walking, running, or jumping,96,99 and pes have been stretched.29,96, 99 The pain planus with pronation of the foot on worsens again toward evening96 and af- weight bearing.99 Lewit65 points out that ter sports activities that require running tightness of the plantar aponeurosis may or jumping.29,99,100 result from tension of the muscles that anchor to it. These are intrinsic muscles that function as flexors of the toes: the ab-

510 Part 3 / Leg, Ankle, and Foot Pain ductor hallucis, flexor digitorum brevis, oped.62 The muscle imbalance produced and abductor digiti minimi. Myofascial by the deviation tends to aggravate the TrPs cause chronic shortening of muscles condition further.15,98 that harbor them. Congenital Hypertrophy: One case of The fact that many of the symptoms congenital hypertrophy of the abductor and signs of plantar fasciitis are also char- digiti minimi35 and three cases of congen- acteristic of several myofascial pain syn- ital hypertrophy of the abductor hallucis dromes raises the question as to whether muscle34 are reported. In each case, the TrPs may be contributing significantly to enlarged muscle caused pain and consid- the chronic overload of the plantar apo- erable difficulty in finding suitable foot- neurosis in many of these patients. The wear; it was identified at surgery and re- muscles most likely to be involved are the sected with no adverse results reported. intrinsic flexors of the toes, the gastrocne- The nature of the mass should be readily mius, and the soleus. The area of heel identifiable by palpation during volun- pain and tenderness of plantar fasciitis tary flexion of the great toe or abduction matches partly the referred patterns of the of the fifth toe and by EMG evaluation. soleus (see Fig. 22.1), quadratus plantae (see Fig. 27.1), and abductor hallucis Avulsion Fracture: An avulsion fracture muscles (see Fig. 26.2A). The distribution of the dorsolateral aspect of the calcaneus of pain and tenderness along the plantar secondary to a pull-off mechanism by the fascia fits the pattern produced by TrPs in extensor digitorum brevis muscle is not the flexor digitorum longus muscle (see rare. A 10% incidence was found in a 1- Fig. 25.1A). The intrinsic flexors of the year review of all emergency room cases toes can be overloaded by a sudden in- of ankle trauma.24 Such fracture is likely crease in running and jumping activities. to result from an inversion injury of the The pain produced on passive extension foot and is treated with supportive band- of the great toe in plantar fasciitis is also ages, elevation, and early range of motion characteristic of TrPs in the abductor hal- exercises.84 lucis muscle. Compartment Syndromes Structural Problems Myerson85 reviewed the anatomy of the Flat Feet: It is important to distinguish four compartments of the forefoot: the between a fixed flat foot due to tarsal coa- central (plantar), medial, lateral, and in- lition and a relaxed pronated flat foot. terosseous (dorsal) compartments. He The former generally requires surgery. noted a dearth of literature and lack of The latter usually responds to conserva- recognition of these syndromes, which tive therapy. In either case, surgical cor- may result when a cast is applied to an rection is indicated only if necessary to injured foot. relieve pain.46 Out-toeing (walking with the foot abducted and everted) is often Other Problems considered so undesirable that the foot posture should be straightened. However, Articular dysfunction in the foot can dis- in case of flat feet, Lapidus64 makes the turb mechanics and produce imbalances point that the out-toeing serves a useful that cause pain at many sites. purpose and is best left uncorrected. 7. ACTIVATION AND PERPETUATION Bunions: The prevalence of bunions OF TRIGGER POINTS and hallux valgus is highly variable among different ethnic groups and appar- Activation ently has a significant, if not predomi- nant, hereditary component. The bunion A shoe with a tight cap or vamp (a tight fit protrusion may be accentuated by a com- between the shoe and the forefoot) re- bination of varus deviation of the first stricts toe movement. This constriction metatarsal and valgus deviation of the can overload the superficial intrinsic foot great toe. This combination may require muscles and activate TrPs in them. Once surgery for correction when it has devel- it has initiated the TrPs, the same condi- tion also perpetuates them. The muscle overload associated with a fracture of the

Chapter 26 / Superficial Intrinsic Foot Muscles 511 ankle or other bones of the foot, espe- dle phalanx is painfully limited, the ab- cially when a cast has immobilized the ductor digiti minimi may be shortened by foot for some time, can also activate TrPs TrPs. The same passive extension testing in the short flexors of the toes. applies to the second, third, and fourth toes for TrPs in the flexor digitorum Injuries to these muscles caused by brevis.58 Pressing the proximal phalanx of bruising, banging, stubbing the toes, fall- the great toe toward extension57 similarly ing, and other traumas short of fracture tests for painfully restricted range of mo- can initiate TrPs in them. tion and serves as a sign of TrP involve- ment of the abductor hallucis and flexor Patients who have a (mediolateral) hallucis brevis. Asking the patient to rocking foot because of a Morton foot press down hard against the examining structure may develop TrPs in the abduc- finger tests for significant weakness. tor digiti minimi and in the abductor hal- lucis muscles. Palpation of the painful areas estab- lishes whether these areas also exhibit Perpetuation tenderness that may be referred from TrPs. Since chronic TrP tension in a mus- Although some pronation of the foot dur- cle induces tenderness at the attachment ing the stance phase of gait is normal, of the muscle, patients with TrPs in the hyperpronation, when uncorrected, can intrinsic flexors of the toes are likely to be contribute to perpetuation of TrPs in the tender in front of the calcaneus where the intrinsic foot muscles. plantar aponeurosis attaches. Either hypermobility or hypomobility The patient's feet should be examined of the joints of the foot can perpetuate for restricted motion (including restric- TrPs in these superficial intrinsic muscles tion of joint play) and for hypermobility. of the foot. They should also be examined for struc- tural deviations, such as hindfoot varus Shoes with an inflexible sole (wooden or valgus, forefoot varus or valgus, sole or shoes with a steel bar along the equinus, hypermobility or malposition of length of the sole) can immobilize the foot the first ray, short first (relatively long sufficiently to perpetuate TrPs in the su- second) metatarsal, excessively higb arch, perficial intrinsic foot muscles. hallux valgus, and hammer toes. A hard slippery surface under a desk The dorsalis pedis and posterior tibial chair with wheels can overload the toe pulses should be palpated to assess the flexors that must repeatedly help pull the status of arterial circulation. The skin and chair close to the desk. nails should be examined for lesions. Edema should be noted. Walking or running on uneven terrain and on surfaces that slope transversely The clinician should examine the pa- can perpetuate TrPs in the intrinsic mus- tient's shoes for a tight cap, a rigid sole, a cles of the feet. pointed front of the shoe, and for a nega- tive heel height. Systemic factors that can be responsible for perpetuating these TrPs are presented 9. TRIGGER POINT EXAMINATION on pages 115-155 of Volume l . 1 0 2 (Fig. 26.5) 8. PATIENT EXAMINATION Myofascial TrPs in the superficial intrin- sic muscles of the foot are examined by Observation of the patient's gait may re- flat palpation against underlying struc- veal an antalgic limp that alerts one to ask tures (Fig. 26.5). The TrPs are identified about sore feet if the patient has not al- primarily by the patient's jump response ready volunteered this complaint. While to exquisite spot tenderness in a taut the patient walks without shoes, the clini- band. These muscles rarely exhibit local cian should look for excessive supination twitch responses to snapping palpation. or excessive pronation. The overlying tendons complicate palpa- tion of the short extensors of the toes; the If plantar flexion of the lesser toes and/ flexor digitorum brevis lies deep to the or the great toe is limited by pain, the ex- tensor digitorum brevis59 or extensor hal- lucis brevis60 may be shortened by taut bands associated with TrPs. If passive ex- tension of the fifth toe applied at the mid-

512 Part 3 / Leg, Ankle, and Foot Pain Figure 26.5. Examination to locate trigger points in locates the most distal location of trigger points in the the superficial intrinsic muscles of the right foot. A, the extensor hallucis brevis muscle. B, palpation of the thumb palpates the most distal location of trigger abductor hallucis muscle for trigger points, points in the extensor digitorum brevis muscle; the X thick plantar aponeurosis, and the abduc- In two cases, a congenitally hypertrophied ab- tor hallucis is a surprisingly thick muscle. ductor hallucis muscle and, in another, an ac- The thickness renders its deeper fibers cessory muscle belly attached to the abductor relatively inaccessible and may require hallucis caused entrapment symptoms.34 Good- strong deep palpation rather than gentler gold and associates48 demonstrated the value of flat palpation to elicit tenderness from its electrodiagnosis in establishing the diagnosis of deep TrPs. nerve entrapment in tarsal tunnel syndrome and cited a case in which a fibrotic edge of the The abductor digiti minimi is usually abductor hallucis muscle was responsible. most effectively examined by pincer pal- Wilemon103 reported two patients in whom fi- pation along the lateral edge of the sole of brous bands of the abductor hallucis constricted the foot. The examiner should explore all or parts of the posterior tibial nerve. Rask90 both distal to and proximal to the base of relieved entrapment symptoms by injecting a the fifth metatarsal for taut bands and TrP TrP where the medial plantar nerve passes be- tenderness. tween the abductor hallucis muscle and the tu- berosity of the navicular. 10. ENTRAPMENTS The symptom of a painful heel has been at- The posterior tibial nerve and its two tributed to entrapment of the branch of the lat- branches, the medial and lateral plantar eral plantar nerve to the abductor digiti minimi nerves, may become entrapped against muscle as the nerve passes deep to the abduc- the medial tarsal bones by the abductor tor hallucis muscle. Kenzora61 reported relief of hallucis muscle as the nerves pass deep to six patients obtained by following the course of the muscle.42 These nerves pass deep to the nerve through its fibrovascular tunnel deep the abductor hallucis just below the me- to the abductor hallucis muscle with a curved dial malleolus, immediately distal to the hemostat and gently spreading it a few times to flexor retinaculum of the tarsal tunnel. release constrictions of the nerve. Rondhuis Entrapment of the nerves in that area by and Huson94 identified entrapment of the the taut bands of TrPs in the abductor hal- branch of the lateral plantar nerve that supplies lucis muscle may be responsible for a tar- the flexor digitorum brevis where the nerve sal tunnel syndrome. passes between the abductor hallucis muscle

Chapter 26 / Superficial Intrinsic Foot Muscles 513 and the medial head of the quadratus plantae deep intrinsic muscles. The whole foot is muscle. These authors94 found no evidence for sore, especially the distal plantar surface entrapment in the region of the plantar fascia including the midsole region. that would have been needed to substantiate the usual explanation offered for entrapment of Flexor digitorum brevis TrPs are likely this nerve. On the other hand, surgical release to be associated with similar involvement of the tibial nerve and the medial and lateral of the long (extrinsic) flexors of the toes plantar nerves as they passed through and deep and sometimes of the deeper flexor hal- to the abductor hallucis muscle relieved symp- lucis brevis. On the other hand, the ab- toms of entrapment in 9 of 10 patients.1 The ductor digiti minimi is more likely to possible [likely] role of myofascial TrPs in the present as a single-muscle syndrome due abductor hallucis was apparently not consid- largely to a tight shoe of inadequate ered in these patients with heel pain. width. An accessory abductor hallucis attached, 12. INTERMITTENT COLD WITH proximally, to the fascia superficial to the pos- STRETCH terior tibial nerve about 4 cm proximal to the (Fig. 26.6) tip of the medial malleolus, passed deep to the nerve and partially encircled it to end, distally, In all the intermittent cold-with-stretch in the middle of the main abductor hallucis procedures described later in this chap- muscle.19 In this patient, at age 24 years, the ter, the process will be facilitated if the muscle suddenly and inexplicably caused pain- operator incorporates the Lewit postiso- ful neurapraxic entrapment of the posterior tib- metric relaxation technique with augmen- ial nerve. Symptoms were relieved by surgical tation, as described in Chapter 2, pages excision of the accessory abductor hallucis 10-11. Other treatment techniques are muscle. The authors19 did not report on the also described in Chapter 2. The use of presence or absence of preoperative tenderness ice for applying intermittent cold with in the muscle. In another case,50 the muscle did stretch is explained on page 9 of this vol- cause aching pain, which was relieved surgi- ume and the use of vapocoolant spray and cally. Examination for a TrP component of the stretch is detailed on pages 67-74 of Vol- pain was not reported. ume l . 1 0 2 Edwards and coauthors34 reported that three pa- If the patient has hypermobility in the tients—aged 7, 14, and 20 years, respectively— tarsometatarsal region, that region needs complained of painful feet, could not find shoes to be stabilized during the stretch of the that would fit, and had a palpable mass that oblit- intrinsic muscles of the toes. In such erated the longitudinal arch. At surgery, two pa- cases, the intermittent cold can be ap- tients were found to have a three times normal plied prior to, rather than during, the sized abductor hallucis, and the third was found stretch. to have an accessory muscle belly of the same muscle, which compressed the posterior tibial Since some patients have cold feet to nerve. begin with, it is critical to feel the warmth of the skin before applying intermittent 11. ASSOCIATED TRIGGER POINTS cold. The skin must be warmed either re- flexly with a dry hot pad on the abdomen The TrPs in the extensor digitorum brevis or by direct application of heat to the feet. and extensor hallucis brevis muscles are Skin temperature should be rechecked af- often associated with TrPs in the corre- ter several cycles of intermittent cold ap- sponding long (extrinsic) extensor mus- plication. cles of the toes. One usually finds that, with involvement of the abductor hal- After each of the procedures described lucis, TrPs also appear in the neighboring in this chapter, the operator should rewarm the skin of the patient's foot with a moist heating pad and then have the pa- tient actively exercise the treated muscle through several slow cycles of the com-

514 Part 3 / Leg, Ankle, and Foot Pain Figure 26.6. Intermittent cold patterns (thin arrows) stretch the flexor digitorum brevis (and quadratus and stretch positions for trigger points in the superficial plantae). Only the toes need be extended, while the foot muscles. The thick arrows show the direction in foot remains in the neutral position at the ankle. The which pressure is exerted to stretch the muscle pas- ice or spray pattern includes the pain reference zone sively. The Xs mark the location of trigger points in the on the plantar surface of the toes. D, if one wishes to muscles being stretched. A, flexion of all toes to combine intermittent cold with stretch of the flexor stretch the extensor digitorum brevis and extensor digitorum brevis and the flexor hallucis brevis (Fig. hallucis brevis, with plantar flexion of the foot to 27.7), the operator should also extend the great toe. stretch the long extensors of the toes also. When only When the tarsometatarsal region is hypermobile, inter- the toes are flexed (without ankle plantar flexion), ap- mittent cold should be applied prior to the passive plication of intermittent cold above the ankle is unnec- stretch so that one hand can stabilize the midfoot essary. B, extension of the great toe to stretch the ab- while the other hand moves the toes. ductor hallucis. C, extension of the four lesser toes to plete range of shortening and lengthening and over the dorsum of the foot before of that muscle. taking up the slack by pressing gently on all five toes to flex them. The operator Short Extensors of Toes continues the cycle of applying cold in parallel sweeps, and then taking up any To release TrP tightness of the extensor slack that develops in the short extensors digitorum brevis and extensor hallucis of the toes, until no further gains occur. brevis muscles using intermittent cold The skin should be covered no more than with stretch, the patient lies supine with two or three times and then rewarmed to pillows as needed for comfort and with avoid chilling of the underlying muscle. the foot at the end of the table (Fig. 26.6A). The clinician applies a few paral- To release tension in the short exten-. lel sweeps of ice or vapocoolant spray sors of the toes, the ankle can be left in a down the anterolateral aspect of the ankle neutral position. Adding plantar flexion of the ankle, as in Figure 26.6A, also

Chapter 26 / Superficial Intrinsic Foot Muscles 515 stretches and releases TrPs in the long ex- spray over the sole of the foot from the tensors of the toes and requires additional heel to the toes while gently extending downward application of cold in a pat- the lesser toes to take up any slack in the tern that includes all of the anterolateral muscle. With a repeat application of in- leg. termittent cold, the operator takes up any further slack that develops in the muscle. Abductors of Toes The operator immediately applies a moist heating pad for rewarming. To inactivate TrPs in the abductor hal- lucis muscle by intermittent cold with One can easily modify this procedure stretch, the patient lies on the affected for the flexor digitorum brevis to include side or prone with the foot hanging over both the abductor hallucis and flexor hal- the end of the treatment table and with lucis brevis muscles (Fig. 26.6D). Sweeps the ankle in a neutral position (neither of intermittent cold cover the entire plan- plantar flexed nor dorsiflexed). The oper- tar surface of the foot including the great ator applies the vapocoolant spray or ice toe and the medial border of the foot. All in parallel sweeps distally over the me- five toes are passively extended together. dial side of the foot and medial portion of the sole from the back of the heel to the Evjenth and Hamberg36 describe and il- tip of the great toe (Fig. 26.6B). Then the lustrate stretch techniques for the abduc- operator presses the proximal phalanx of tor hallucis, extensor hallucis brevis, and the great toe into extension and repeats the flexor digitorum brevis muscles, none the application of intermittent cold while of which is readily combined with appli- taking up any slack that develops. The cation of intermittent cold because the process may be repeated until no further hand covers the essential pain patterns gains are realized; however, it is impor- where intermittent cold should be ap- tant after two or three cycles to rewarm plied. These techniques, however, do pro- the skin (and, possibly, the muscle) with vide stabilization of the foot and are use- a moist heating pad. Because the abductor ful when using postisometric relaxation hallucis often acts only as a flexor and not alone. as an abductor, and because hallux valgus is such a common problem, extension 13. INJECTION AND STRETCH without adduction is applied to the proxi- (Fig. 26.7) mal phalanx. It is helpful to combine ex- tension of the toe with deep slow massage If less invasive procedures (for example, of the muscle in a distal direction to help intermittent cold with stretcb, Lewit post- stretch its fibers. isometric relaxation, and ischemic com- pression) are not sufficiently effective, Inactivation of TrPs in the abductor TrP injection should be considered. The digiti minimi follows closely this same basic procedure for injecting TrPs in any procedure except that the ice or vapocool- muscle is found on pages 74-86 in Vol- ant spray covers the lateral rather than the ume l . 1 0 2 medial side of the foot, and adduction of the fifth toe is emphasized as much as ex- When injecting any TrPs in the foot, the tension. injection site should be scrubbed care- fully with alcohol or a more powerful io- Inactivation of TrPs in these superficial dine antiseptic. If the individual works intrinsic abductors may also be effec- on a farm or has a garden where there tively accomplished with deep stripping may be exposure to animal feces, the feet massage or with postisometric relaxation. should be thoroughly scrubbed with hy- drogen peroxide, which kills tetanus Short Flexors of Toes spores. After injection, pressure is ap- plied promptly for hemostasis and the To release tension caused by TrPs in the needle puncture site is covered with a flexor digitorum brevis muscle, the pa- snug adhesive bandage to ensure sealing tient lies comfortably on the affected side of the wound. These extra precautions of with the ankle in tbe neutral position, as hydrogen peroxide and the bandage are in Figure 26.6C. The operator applies sev- not generally used when injecting TrPs in eral parallel sweeps of ice or vapocoolant other regions of the body, but are impor-

516 Part 3 / Leg, Ankle, and Foot Pain Figure 26.7. Injection of trigger points in superficial tensor hallucis brevis. B, in the abductor hallucis on muscles of the right foot. A, most distal site for exten- the medial side of the foot. C, in the abductor digiti sor digitorum brevis trigger points. The X locates the minimi on the lateral side of the foot. most distal site for injection of trigger points in the ex- tant when injecting through the skin of tor palpates for any TrP tenderness re- the foot. maining in the muscle and similarly in- jects any residual TrPs. After the injection of TrPs in any of the following muscles, the clinician applies The X in Figure 26.7A locates the re- intermittent cold with passive stretch, as gion of TrPs in the extensor hallucis described for each muscle in the previous brevis. The injection procedure is the section, and follows this promptly by ap- same as for the extensor digitorum brevis plication of moist heat for a few minutes described previously, except for the loca- to reduce the likelihood or the severity of tion of needle penetration. postinjection soreness. The patient then performs several cycles of slow active Abductors of Toes range of motion through the fully short- ened and fully lengthened positions of For injection of TrPs in the abductor hal- the injected muscle in order to equalize lucis muscle, the patient lies on the in- sarcomere lengths and to normalize mus- volved side (Fig. 26.76). The clinician cle function. cleanses the foot as described previously, locates precisely the taut band and TrP by Short Extensors of Toes flat palpation, and inserts the 37-mm (l1/2- (Fig. 26.7) in) long 22-gauge needle that is usually used on a 10-mL syringe. Although one For injection of TrPs in the extensor dig- might expect the TrPs in the abductor hal- itorum brevis muscle, the patient lies su- lucis to be close to the surface, this is a pine with pillows and a blanket as surprisingly thick muscle. The main TrPs needed for comfort (Fig. 26.7A). The oper- often lie close to the bone, so it is usually ator locates the taut band and TrP by necessary to advance the needle to the flat palpation, marks its location, and periosteal level and then to explore the stretches the skin for hemostasis by muscle for active TrPs just short of that spreading apart the fingers on both sides depth. These deep TrPs in the muscle are of the TrP. A 37-ram (l1/2-in) long 22- easily overlooked. Needle encounter with gauge needle will reach any of these su- the TrP usually gives the operator a feel- perficial TrPs; a 25-mm (1-in) needle may ing of penetrating hard rubber and evokes suffice. When the patient exhibits a jump a pain response on the part of the patient; sign and/or the toes extend, which indi- in this muscle, a local twitch response, cates a local twitch response, the operator when it occurs, is indicated by flexion of injects the TrP with 0.5% procaine solu- the great toe. The clinician then injects tion prepared by dilution with isotonic the 0.5% procaine solution into the TrP saline. Before completely withdrawing and, on probing further, may find a clus- the needle, by sliding the skin, the opera- ter of TrPs to be injected.

Chapter 26 / Superficial Intrinsic Foot Muscles 517 When injecting this muscle, one must Patients should ensure, when buying know the location of the posterior tibial new shoes, that the shoes are large artery and nerve and their branches that enough. They should take a foam sole in- pass behind the medial malleolus and sert to the store and place it in the shoe then deep to the abductor hallucis muscle when trying the shoe on for size. The near where it attaches to the calcaneus.5 shoes should provide snug heel support and preferably some ankle support, a flex- For injection of TrPs in the abductor ible sole, a cap (vamp) that is high digiti minimi muscle, the patient lies on enough, a toe that is not sharply pointed, the uninvolved side and is made comfort- and a moderate-height (not negative, able (Fig. 26.7C). After cleansing the foot, high, or spike) heel. Athletic shoes de- the clinician locates the taut band and its signed to fit and support the feet and an- TrPs by either flat or pincer palpation of kles are now widely accepted as stylish this muscle. It is not very thick, unlike for more general use. Shoes designed for the abductor hallucis, and its taut bands specific activities should be selected on and TrPs are generally easily localized. that basis. High-quality athletic shoes are They may be either in front of, or behind, worth the price.30 the base of the fifth metatarsal, which is palpable as a bony protuberance along the Corrective Posture and Activities lateral border of the foot. The TrPs are in- jected with 0.5% procaine solution wher- Walking on a hard surface with stiff, slip- ever they are found in the muscle. Needle pery, leather-soled shoes overloads the penetration of TrPs in this muscle is muscles of the feet. This problem is aggra- likely to cause a local twitch response as vated in persons with flat arches.97 It is shown by a variable combination of ab- much better either to wear shoes with re- duction and flexion of the fifth toe. silient heels and soles, such as running shoes, or to add a foam sole insert inside 14. CORRECTIVE ACTIONS the shoe. The addition must not cramp (Figs. 26.8 and 26.9) the foot and prevent normal toe move- ment. Wearing crepe soles that are too Corrective pads are installed inside the flexible to support the metatarsal area, shoe under the first metatarsal head to however, can be troublesome, possibly in- compensate for a Morton foot structure jurious.97 (see Chapter 20, pages 389-391), espe- cially for patients with TrPs in the abduc- Adequate space in the shoe is an impor- tor digiti minimi muscle. Arch supports tant consideration when buying new may be needed for a hypermobile foot. shoes. Since few people have perfectly Other structural deviations of the foot matched feet, new shoes should be fitted should be corrected or shoes must be on the larger foot. modified to provide good overall support for dynamic balance and comfort. Unless the patient has structural defor- mities, orthoses are usually unnecessary If hypomobility is a factor, normal joint after the TrPs causing the foot soreness play and range of motion should be re- have been inactivated. The patients need stored. soft cushioning, not hard orthoses. The cushioning is ineffective if the added ma- Corrective Body Mechanics terial makes the shoe too tight and re- stricts normal movement. Many patients find that, as they age, their feet become larger. Shoes that did fit Corrective Exercises years before are too tight and no longer comfortable. Old shoes should be re- Walking in dry sand is vigorous exercise placed with new ones that do not cramp for intrinsic foot muscles and can easily and squeeze the foot and do not limit toe be overdone. Walking in wet sand with movement. Feet not only increase in special attention to \"toe-off\" provides a length, but the forefoot tends to widen milder strengthening exercise. with age.97 This change may relate to in- creased laxity of ligaments and/or loss of Picking up marbles with the toes im- intrinsic muscle tone. proves strength and coordination of the toe muscles.89

518 Part 3 / Leg, Ankle, and Foot Pain Figure 26.8. Passive Toe Flexor Self-stretch Exer- cise for use at home by the patient with trigger points in the short (and long) flexors of the toes. The patient pulls all five toes into extension with one hand. If the patient has any hypermobility in the tarsometatarsal region, that region should be stabilized by the patient's other hand. Home Treatment Program Figure 26.9. Self-application of ischemic compres- (Figs. 26.8 and 26.9) sion and massage of plantar intrinsic foot muscles. A, using the Golf-ball Technique, rolling the golf ball back The Toe Flexor Self-stretch Exercise for and forth under the foot while applying pressure with use at home by the patient with TrPs in the body weight, positioned to treat the flexor dig- the short or long flexors of the toes is pic- itorum brevis and sometimes the quadratus plantae tured in Figure 26.8. In its simplest form, muscles. B, using the Rolling Pin Technique with the the patient simply relaxes the leg and foot foot flat to massage the toe flexors. C, using the Roll- muscles as much as possible, grasps the ing Pin Technique to treat the abductor digiti minimi toes, and gently pulls them into extension muscle with the foot inverted. and the foot into dorsiflexion. By coordi- nating contraction and relaxation with The addition by the patient of active toe respiration in accordance with Lewit's extension and ankle dorsiflexion contrib- postisometric relaxation technique (Chap- utes the effect of reciprocal inhibition to ter 2, page 11), the effectiveness of the further release the flexor muscle being stretch is markedly improved. The patient stretched. The patient can achieve a simi- should be instructed to stabilize the lar effect by slowly performing full active midfoot if there is any hypermobility in range of motion through several cycles. that region. In addition, it may be helpful for the patient to perform the passive Figure 26.9 illustrates home versions of stretch while seated in a bathtub or self-administered ischemic compression Jacuzzi® with the leg and foot immersed in warm water.

Chapter 26 / Superficial Intrinsic Foot Muscles 519 and deep stripping massage of the super- Pagliano and Wischnia89 illustrate a set ficial plantar muscles. When using the of foot-strengthening exercises, several of Golf-ball Technique of Figure 26.9A, the which can be applied to both extrinsic patient places sufficient body weight on and intrinsic flexors and extensors of the the golf ball to locate the tender spots in toes. the muscles. Then the patient can either apply steady ischemic compression or References roll the ball over the tender spot (TrP] along the taut band to perform a modifica- 1. Albrektsson B, Rydholm A, Rydholm U: The tion of stripping massage, as described in tarsal tunnel syndrome in children. J Bone Joint detail in Cbapter 2, page 9. With this golf- Surg [Br] 6 4 : 2 1 5 - 2 1 7 , 1 9 8 2 . ball technique, the patients can apply as much pressure as desired, for as long as 2. Anderson JE: Grant's Atlas of Anatomy, Ed. 8. desired, without overloading the hand Williams & Wilkins, Baltimore, 1983 (Fig. 4- muscles. This technique is especially use- 77). ful for applying effective pressure to the flexor digitorum brevis and to that part of 3. Ibid. (Fig. 4 - 7 8 B ) . the abductor digiti minimi that lies deep 4. Ibid. (Fig. 4 - 7 9 ) . to the plantar aponeurosis. 5. Ibid. (Fig. 4 - 8 7 ) . 6. Ibid. (Fig. 4 - 9 3 ) . Figure 26.96 shows how to use the 7. Ibid. (Fig. 4 - 1 0 0 ) . Rolling-pin Technique in a similar man- 8. Ibid. (Fig. 4 - 1 0 2 ) . ner. This is less specific as to the location 9. Ibid. (Fig. 4 - 1 0 3 ) . of the applied pressure, but is probably 10. Ibid. (Fig. 4 - 1 0 6 ) . easier to apply. Foot flat, as shown in this 11. Ibid. (Fig. 4 - 1 0 7 ) . drawing, applies pressure to the flexor 12. Bardeen CR: The musculature, Sect. 5. In Mor- digitorum brevis, flexor hallucis brevis, and the abductor hallucis. ris's Human Anatomy, edited by C M . Jackson, Ed. 6. Blakiston's Son & Co., Philadelphia, Figure 26.9C shows the advantage of 1921 (pp. 514, 524-528, 530). rolling the foot to one side to treat mus- 13. Basmajian JV, Deluca CJ: Muscles Alive, Ed. 5. cles along the sides of the foot more effec- Williams & Wilkins, Baltimore, 1985 (pp. 3 4 2 - tively; namely, the abductor digiti minimi 345). when inverting the foot, and the abductor 14. Ibid. (p. 3 4 9 ) . hallucis when everting the foot. Both ver- 1 5 . Ibid. (pp. 3 5 1 , 3 5 2 ) . sions of the Rolling-pin Technique can be 16. Ibid. (pp. 3 5 1 , 3 7 9 ) . used for self-administered ischemic com- 17. Ibid. (pp. 3 5 3 , 3 5 4 ) . pression or modified stripping massage. For the latter, the pin is rolled very 18. Bates T, Grunwaldt E: Myofascial pain in slowly throughout the length of the ten- childhood. J Pediatr 5 3 : 1 9 8 - 2 0 9 , 1 9 5 8 . der part of the muscle. 19. Bhansali RM, Bhansali RR: Accessory abductor The active Toe-stretch Exercise pro- hallucis causing entrapment of the posterior vides a general purpose flexion-extension tibial nerve. J Bone Joint Surg [Br] 6 9 : 4 7 9 - 4 8 0 , stretch for the toe muscles in the same 1987. way that the Artisan's Finger-stretch Ex- ercise (Fig. 35.8, Volume l ) 1 0 2 provides a 20. Carter BL, Morehead J, Wolpert SM, et al.: general purpose active flexion-extension Cross-Sectional Anatomy. Appleton-Century- stretch exercise for the finger muscles. Crofts, New York, 1977, (Sects. 82-86). The patient sits on a chair and extends the legs, feet on the floor in front, then ac- 2 1 . Ibid. (Sects. 8 2 - 8 7 ) . tively fully inverts and plantar flexes the 22. Ibid. (Sects. 8 3 - 8 5 ) . foot while strongly curling the toes, and 23. Ibid. (Sects. 8 3 - 8 6 ) . then slowly transitions to everting and dorsiflexing the foot fully while strongly 24. Cavaliere RG: Ankle and rearfoot—calcaneal extending the toes. This should be re- fractures, Chapter 28, Part 3. In Comprehensive peated at least five times, with a pause be- Textbook of Foot Surgery, edited by E. Dalton tween each cycle. McGlamry, Vol. 2. Williams & Wilkins, Balti- more, 1987 (pp. 8 7 3 - 9 0 3 , see pp. 8 8 1 , 8 8 5 ) . 25. Christensen E: Topography of terminal motor innervation in striated muscles from stillborn infants. Am J Phys Med 3 8 : 6 5 - 7 8 , 1 9 5 9 . 26. Clemente CD: Gray's Anatomy of the Human Body, American Ed. 30. Lea & Febiger, Phila- delphia, 1985 (p. 293, Fig. 4-220). 27. Ibid. (pp. 575, 5 8 4 - 5 8 7 ) . 28. Ibid. (p. 585, Fig. 6 - 8 2 ) . 29. Coker TP Jr, Arnold JA: Sports injuries to the foot and ankle, Chapter 57. In Disorders of the Foot, edited by M.H. Jahss, Vol. 2. W.B. Saun- ders Co., London, 1982, (pp. 1 5 7 3 - 1 6 0 6 , see pp. 1604-1605). 30. Drez D: Running footwear: examination of the training shoe, the foot, and functional orthotic devices. Am J Sports Med 8 : 1 4 0 - 1 4 1 , 1 9 8 0 .

520 Part 3 / Leg, Ankle, and Foot Pain 3 1 . Duchenne GB: Physiology of Motion, translated 61. Kenzora JE: The painful heel syndrome: an en- trapment neuropathy. Bull Hosp Jt Dis Orthop by E.B. Kaplan. J.B. Lippincott, Philadelphia, Inst 4 7 : 1 7 8 - 1 8 9 , 1987. 1949 (pp. 373-374, 376). 62. Kenzora JE: A rationale for the surgical treat- 32. Ibid. (p. 4 1 2 ) . ment of bunions. Orthopedics 7 7 : 7 7 7 - 7 8 9 , 33. Duranti R, Galletti R, Pantaleo T: Electromy- 1988. 63. Krout RR: Trigger points [letter]. J Am Podiatr ographic observations in patients with foot syndromes. Am J Phys Med 6 4 : 2 9 5 - 3 0 4 , 1985. Med Assoc 77:269, 1987. 34. Edwards WG, Lincoln CR, Bassett FH, et al.: 64. Lapidus PW: Some fallacies about intoeing and The tarsal tunnel syndrome: diagnosis and outtoeing. Orthop Rev 7 0 : 7 3 - 7 9 , 1981. treatment. JAMA 2 0 7 : 7 1 6 - 7 2 0 , 1 9 6 9 . 6 5 . Lewit K: Manipulative Therapy in Rehabilitation of 35. Estersohn HS, Agins SW, Ridenour J: Congeni- the Motor System. Butterworths, London, 1985 tal hypertrophy of an intrinsic muscle of the (p. 284). foot. J Foot Surg 2 6 : 5 0 1 - 5 0 3 , 1987. 66. Lockhart RD: Living Anatomy, Ed. 7. Faber & 36. Evjenth O, Hamberg J: Muscle Stretching in Man- ual Therapy, A Clinical Manual. Alfta Rehab Faber, London, 1974 (Fig. 138). Forlag, Alfta, Sweden, 1984 (pp. 150, 155, 67. Maloney M: Personal communication, 1991. 159). 68. Mann R, Inman VT: Phasic activity of intrinsic 37. Ferner H, Staubesand J: Sobotta Atlas of Human muscles of the foot. J Bone Joint Surg [Am] 46: Anatomy, Ed. 10, Vol. 2. Urban & Schwarzen- 469-481, 1964. 69. McGlamry ED (Ed): Comprehensive Textbook of berg, Baltimore, 1983 (Fig. 381). 38. Ibid. (Fig. 4 8 9 ) . Foot Surgery, Vols. I & II. Williams & Wilkins, 3 9 . Ibid. (Fig. 4 9 1 ) . 4 0 . Ibid. (Fig. 4 9 2 ) . Baltimore, 1987. 4 1 . Ibid. (Fig. 4 9 3 ) . 70. McMinn RMH, Hutchings RT: Color Atlas of 4 2 . Ibid. (Fig. 4 9 7 ) . 4 3 . Ibid. (Fig. 4 9 8 ) . Human Anatomy. Year Book Medical Publishers, 4 4 . Ibid. (Fig. 5 0 0 ) . 4 5 . Ibid. (Fig. 5 0 3 ) . Chicago, 1977 (p. 289). 71. Ibid. (p. 3 1 8 ) . 46. Goldner JL: Advances in care of the foot: 1800 72. Ibid. (p. 3 2 1 ) . to 1 9 8 7 . Orthopedics 1 0 : 1 8 1 7 - 1 8 3 6 , 1987. 73. Ibid. (p. 3 2 2 ) . 74. ibid. (p. 325B). 4 7 . Good MG: Painful feet. Practitioner 7 6 3 : 2 2 9 - 75. McMinn RMH, Hutchings RT, Logan BM: Color 232, 1949. Atlas of Foot and Ankle Anatomy. Appleton-Cen- 48. Goodgold J, Kopell HP, Spielholz NI: The tar- tury-Crofts, Connecticut, 1982 (p. 28). 76. Ibid. (p. 54). sal-tunnel syndrome: objective diagnostic cri- 77. Ibid. (p. 56). teria. N Engl J Med 2 7 3 : 7 4 2 - 7 4 5 , 1965. 78. Ibid. (p. 58). 79. Ibid. (p. 64). 49. Gray EG, Basmajian JV: Electromyography and 80. Ibid. (pp. 7 2 - 7 3 ) . 8 1 . Ibid. (p. 74). cinematography of leg and foot (\"normal\" and 82. Ibid, (p- 75). flat) during walking. Anat Rec 7 8 7 : 1 - 1 6 , 1 9 6 8 . 83. Ibid. (pp. 8 2 - 8 3 ) . 84. Morse HH, Lambert L, Basch D, et al.: Avulsion 50. Haber JA, Sollitto RJ: Accessory abductor hal- lucis: a case report. J Foot Surg 78:74, 1979. fracture by the extensor digitorum brevis mus- cle. J Am Podiatr Med Assoc 7 9 : 5 1 4 - 5 1 6 , 1989. 5 1 . Hollinshead WH: Functional Anatomy of the Limbs and Back, Ed. 4. W.B. Saunders, Philadel- 85. Myerson M: Diagnosis and treatment of com- partment syndrome of the foot. Orthopedics 13: phia, 1976, (p. 358, Table 20-1). 711-717, 1990. 52. Hoppenfeld S: Physical examination of the foot 86. Netter FH: The Ciba Collection of Medical Illustra- by complaint, Chapter 5. In Disorders of the Foot, edited by M.H. Jahss, Vol. 1. W.B. Saun- tions, Vol. 8, Musculoskeletal System. Part I: ders Co., Philadelphia, 1982 (pp. 1 0 3 - 1 1 5 , see Anatomy, Physiology and Metabolic Disorders. pp. 108-110). 53. Hoppenfeld S, deBoer P: Surgical Exposures in Ciba-Geigy Corporation, Summit, 1987 (p. Orthopaedics: The Anatomic Approach. J. B. Lip- 109). 87. Ibid. (p. 111). pincott Co., Philadelphia, 1984 (p. 528). 8 8 . Ibid. (p. 113). 54. Kelly M: The nature of fibrositis. II. A study of 89. Pagliano J, Wischnia B: Fabulous feet: the foundation of good running. Runner's World pp: the causation of the myalgic lesion (rheumatic, traumatic, infective). Ann Rheum Dis 5 : 6 9 - 7 7 , 39^41, Aug. 1984. 1946. 90. Rask MR: Medial plantar neurapraxia (jogger's foot). Clin Orthop 7 3 4 : 1 9 3 - 1 9 5 , 1978. 55. Kelly M: Some rules for the employment of lo- 91. Reinherz RP, Gastwirth CM: The abductor hal- cal analgesic in the treatment of somatic pain. lucis muscle [Editorial]. J Foot Surg 2 6 : 9 3 - 9 4 , Med J Austral 7 : 2 3 5 - 2 3 9 , 1947. 1987. 56. Kelly M: The relief of facial pain by procaine 92. Rohen JW, Yokochi C: Color Atlas of Anatomy, (Novocaine) injections. J Am Geriatr Soc 11: Ed. 2. Igaku-Shoin, New York, 1988 (p. 426). 586-596, 1963. 9 3 . Ibid. (pp. 4 2 7 , 4 2 8 ) . 57. Kendall FP, McCreary EK: Muscles, Testing and 94. Rondhuis JJ, Huson A: The first branch of the Function, Ed. 3. Williams & Wilkins, Baltimore, lateral plantar nerve and heel pain. Acta Morphol Neerl-Scand 2 4 : 2 6 9 - 2 7 9 , 1 9 8 6 . 1983 (p. 131). 5 8 . Ibid. (p. 133). 5 9 . Ibid. (p. 139). 60. Ibid. (p. 140).

Chapter 26 / Superficial Intrinsic Foot Muscles 521 95. Sammarco GJ: The foot  and ankle in classical  ballet  99.  Tanner  SM,  Harvey  JS:  How  we  manage  plantar  and  modern  dance,  Chapter  59.  In  Disorders of the fasciitis. Phys Sportsmed 76:39‐47, 1988.  Foot, edited  by  M.H.  Jahss,  Vol.  2.  W.B.  Saunders  Co.,  Philadelphia,  1982  (pp.  1626‐1659,  see pp.  100. Torg JS, Pavlov H, Torg E: Overuse injuries in sports:  1654‐1655).  the foot. Clin Sports Med 6:291‐320, 1987.  96. Seder  JI:  How  I  manage  heel  spur  syndrome.  Phys 101. Travell J, Rinzler SH: The myofascial genesis of pain.  Sportsmed 75:83‐85, 1987.  Postgrad Med 77:425‐434, 1952.  97. Sheon RP: A joint‐protection guide for nonar‐ticular  102. Travell  JG,  Simons  DG:  Myofascial Pain and Dys- rheumatic  disorders.  Postgrad Med 77: 329‐338,  function: The Trigger Point Manual. Williams  &  1985.  Wilkins, Baltimore, 1983.  98. Shimazaki K, Takebe K: Investigations on the origin  103. Wilemon  WK:  Tarsal  tunnel  syndrome:  a  50‐year  of  hallux  valgus  by  electromyographic  analysis.  survey of the world literature and a report of two new  Kobe J Med Sci 27:139‐158, 1981.  cases. Orthop Rev 8:111‐117, 1979.   

CHAPTER 27 Deep Intrinsic Foot Muscles Quadratus Plantae and Lumbricals, Flexor Hallucis Brevis, Adductor Hallucis, Flexor Digiti Minimi Brevis, and Interossei \"Vipers' Nest\" HIGHLIGHTS: REFERRED PAIN and tender- third, fourth, and fifth toes. Medially, both heads ness induced by trigger points (TrPs) in the of this muscle join where they attach to the lat- quadratus plantae muscle project to the plantar eral aspect of the base of the proximal phalanx surface of the heel. The oblique and transverse of the large toe. The four bipennate dorsal inter- heads of the adductor hallucis refer to the plan- ossei anchor, proximally, to the shafts of adja- tar surface of the forefoot in the region of the cent metatarsal bones. Distally, the first dorsal metatarsal heads. Referral from the flexor hal- interosseous attaches to the medial side and the lucis brevis covers the region of the head of the second attaches to the lateral side of the base of first metatarsal bone on its plantar and medial the proximal phalanx of the second toe; both join aspects, and may spill over to include all of the the dorsal aponeurosis of the extensor digitorum first toe and much of the second toe. The TrPs longus tendon of that toe. The third and fourth in the interossei refer pain and tenderness pri- dorsal interossei attach distally to only the lateral marily along that side of the toe to which each side of the third and fourth toes in a similar fash- muscle attaches and to the plantar surface of ion. The three plantar interossei extend from the the corresponding metatarsal head. ANATOMI- bases of the third, fourth, and fifth metatarsal CAL ATTACHMENTS of the quadratus plantae bones to the medial aspect of the bases of the are to the calcaneus proximally and to the ten- proximal phalanges of the third, fourth, and fifth don of the flexor digitorum longus distally. The toes. FUNCTION of the intrinsic muscles of the lumbricals extend from the digitations of the foot is primarily related to stabilizing the foot for flexor digitorum longus tendon to the extensor propulsion. The quadratus plantae aligns the hood of each of the four lesser toes. The flexor pull of the flexor digitorum longus into pure flex- digiti minimi brevis extends from the base of the ion and assists it in flexing the four lesser toes. fifth metatarsal to the proximal phalanx of the The lumbricals flex the proximal phalanges of fifth toe. The two parts of the flexor hallucis the four lesser toes and extend the two distal brevis extend from a common proximal attach- phalanges. The flexor digiti minimi brevis flexes ment onto the adjacent surfaces of the cuboid the proximal phalanx of the small toe. Similarly, and lateral cuneiform bones to distal attach- the flexor hallucis brevis flexes the proximal ments by two tendons, one to each side of the phalanx of the great toe. The adductor hallucis proximal phalanx of the large toe. Each distal adducts and assists flexion of the great toe and tendon of the flexor hallucis brevis muscle con- assists in maintaining transverse plane stability. tains a sesamoid bone. The oblique head of the The dorsal and plantar interossei, respectively, adductor hallucis anchors to the bases of the abduct and adduct the lesser toes and stabilize second, third, and fourth metatarsals. The trans- the forefoot. SYMPTOMS caused by TrPs in the verse head of this muscle attaches to the plantar deep intrinsic muscles of the foot include im- paired walking because of pain and often intoler- metatarsophalangeal (MP) ligaments of the 522

Chapter 27 / Deep Intrinsic Foot Muscles 523 ance to corrective orthoses inserted in the shoe. JECTION AND STRETCH of the quadratus The clinician may need to distinguish symptoms plantae, flexor hallucis brevis, and adductor hal- of the deep intrinsic muscles from those of other lucis are performed with the patient lying on the myofascial pain syndromes, plantar fasciitis, ar- same (affected) side; the quadratus plantae and ticular dysfunction of the foot, and an injured the flexor hallucis brevis muscles are ap- sesamoid bone. PATIENT EXAMINATION in- proached with the needle from the medial as- cludes looking for an antalgic gait; for exces- pect of the foot. The adductor hallucis is ap- sive supination or pronation; for restricted proached through the sole of the foot. Both the range of motion or hypermobility of the toes, dorsal and plantar interossei are injected forefoot, and hindfoot; for weakness of the through the dorsum of the foot. CORRECTIVE toes; for a Morton foot structure; for the loca- ACTIONS include restoration of normal joint tion and thickness of calluses; and for improp- play and range of motion of articulations in the erly designed and fitted shoes. INTERMIT- foot. Only well-designed, well-fitted shoes of TENT COLD WITH STRETCH generally works high quality are recommended. Appropriate sup- well for TrPs in the quadratus plantae, flexor hal- ports are added to the shoes to correct for struc- lucis brevis, flexor digiti minimi brevis, and ad- tural problems of the foot. A self-stretch exercise ductor hallucis muscles. However, TrPs in the program and the Golf-ball or Rolling-pin Tech- interossei and lumbricals may be inactivated nique are recommended to the patient. more readily by deep massage or injection. IN- 1. REFERRED PAIN strange \"fluffy\" feeling of numbness and (Figs. 27.1-27.3) a sense of swelling of the skin over the re- gion of the metatarsal heads. Myofascial trigger points (TrPs) in the quadratus plantae muscle usually refer Medial to the oblique head of the ad- pain and tenderness only to the plantar ductor hallucis, TrPs in the flexor hallucis surface of the heel (Fig. 27.1). brevis muscle refer pain and tenderness primarily to the region of the head of the Pain and tenderness referred from TrPs first metatarsal on both its plantar and me- in either the oblique or transverse head of dial aspects (Fig. 27.26), with a spillover the adductor hallucis muscle (Fig. 27.2A) pattern that may include all of the great toe are felt in the distal portion of the sole of and much of the second toe. Kelly38 de- the foot, primarily in the region of the scribed pain radiating from a \"fibrositic\" first through fourth metatarsal heads. The lesion [TrP] in the flexor hallucis brevis TrPs in the transverse head of the ad- muscle as causing cramps in the foot. ductor hallucis are likely to cause a Figure 2 7 . 1 . Pain pattern (bright red) referred from a trigger point (X) in the deeply placed quadratus plantae muscle (darker red) of the right foot. Solid red portrays the essential referred pain pat- tern; red stippling shows the spillover of the essential pattern. The lumbrical mus- cles are not colored.

524 Part 3 / Leg, Ankle, and Foot Pain Adductor Flexor hallucis hallucis brevis Figure 27.2. Pain patterns {bright red) referred from essential pattern appears as red stippling. A, adductor trigger points (Xs) in two deep intrinsic muscles of the hallucis muscle, oblique and transverse heads (light right foot, as viewed during examination. Essential re- red). B, flexor hallucis brevis muscle (dark red). ferred pain patterns are solid red and a spillover of the An isolated pain pattern for the flexor and then was abolished so that he could again digiti minimi brevis is not established; it appears to be similar to that of the abduc- walk normally. Kellgren also reported37 that injec- tor digiti minimi muscle (see Fig. 26.3A). tion of approximately 0.2 mL of a 6% hypertonic As in the interossei of the hand, TrPs in interosseous muscles of the foot refer solution of sodium chloride into the first dorsal pain and tenderness largely to the side of the digit to which the tendon attaches; interosseous muscle caused pain in the lateral however, in the case of the foot, these TrPs also refer pain both to the dorsum half of the foot and in the calf of the leg. and to the sole of the foot along the distal portion of the corresponding metatarsal. 2. ANATOMICAL ATTACHMENTS AND Figure 27.3A illustrates this pattern for CONSIDERATIONS the first dorsal interosseous muscle from (Figs. 27.4 and 27.5) the dorsal view and Figure 27.36 shows it from the plantar view.70,71 In addition, The reader is referred to Figure 18.2 in TrPs in the first dorsal interosseus muscle this volume for a drawing of the bones of may produce tingling in the great toe; the the foot. Careful review of this figure disturbance of sensation can include the along with anatomical considerations of dorsum of the foot and lower shin. The muscles and ligaments may help the plantar interossei produce a pattern reader understand the relationship be- comparable to that of the dorsal interos- tween the structure and function of the sei. The separate pain patterns of the lum- foot. bricals are not confirmed, but it is likely that their patterns are similar to that of The quadratus plantae and the lumbri- corresponding interossei. cals, both muscles of the second muscular layer on the plantar aspect of the foot, at- Kellgren36 reported a patient who complained of tach to tendon slips of the flexor dig- itorum longus (Fig. 27.4A). The quadratus pain in and under the metatarsal heads and in the plantae (flexor accessorius) muscle has two heads. Its larger, medial head at- outside of the foot and ankle; the patient expe- taches proximally to the medial side of the calcaneus, and the flat tendinous lat- rienced pain with each step and walked with a eral head attaches proximally to the lat- eral side of that bone and to the long plan- limp. When the tender region in the third interos- tar ligament. The two heads are separated by the long plantar ligament and converge seous space was infiltrated with 3 mL of procaine distally at an acute angle to join the lat- eral margin of the tendon and the tendon solution, the pain was reproduced momentarily

Chapter 27 / Deep Intrinsic Foot Muscles 525 Figure 27.3. Typical pain pattern (bright red) re- Dorsal and plantar ferred from a trigger point (X) in the right first dorsal interossei, interosseous muscle. The dorsal interosseous mus- plantar view cles are medium red and the plantar interosseous muscles are light red. A, dorsal view. B, plantar view, slips of the flexor digitorum longus.14,52 The third layer of muscles on the plan- The lateral plantar vessels and nerve lie tar aspect of the foot includes the longitu- between this muscle and the superficial dinally oriented short flexors of the great layer of intrinsic muscles. and fifth toes, the transverse head of the adductor hallucis and the more longitudi- Sometimes the lateral head of the quadratus nally oriented oblique head of this ad- plantae, or even the entire muscle, is missing. The ductor muscle (Fig. 27.4B).14 muscle also varies as to the number of digital flexor tendons that receive its muscular slips.14 The flexor digiti minimi brevis attaches proximally to the base of the fifth meta- Starting at a proximal attachment to tarsal and distally to the lateral side of the flexor digitorum longus tendon near the base of the proximal phalanx of the the midplantar region, the lumbricals ex- fifth toe (Fig. 2 7 . 4 6 ) . 1 4 , 3 0 tend distally to the expansion of the ex- tensor digitorum longus tendon of each of When the deeper fibers of the human flexor the four lesser toes (Fig. 27.4A).14,52 Each digiti minimi brevis attach to the ligament that lumbrical arises from two adjacent ten- joins the fifth metatarsal and cuboid, and then ex- dons except the first, which arises along tend distally to the lateral part of the distal half of the medial surface of the flexor digitorum the fifth metatarsal, they are sometimes identified longus tendon to the second toe. The lum- as the opponens digiti minimi,14, 30, 76 an arrange- brical tendons pass on the plantar side of ment that is characteristic in apes. the deep transverse metatarsal ligaments to reach their distal attachments on the The adductor hallucis muscle has two medial surface of the extensor expansion. heads (Fig. 27.4B). The oblique head At times, they may be attached to the slants diagonally across the first four met- bone of the first phalanx. One or more atarsal bones. It anchors proximally onto lumbricals may be absent.14 the bases of the second, third, and fourth metatarsal bones and onto the sheath of the tendon of the peroneus longus; it at-

526 Part 3 / Leg, Ankle, and Foot Pain Adductor hallucis, transverse head Lumbricals Flexor Proximal digiti phalanx Quadratus minimi plantae brevis Sesamoid bones Adductor hallucis, Calcaneus 5th metatarsal oblique head Cuboid bone Flexor hallucis brevis Flexor digitorum longus tendon 1 st metatarsal bone Long plantar ligament Figure 27.4. Anatomical attachments of intermedi- muscular layer: flexor hallucis brevis (dark red), ob- ate-depth plantar muscles of the right foot, plantar lique and transverse heads of the adductor hallucis view. A, in second muscular layer: quadratus plantae (medium red), and flexor digiti minimi brevis (light {dark red) and lumbricals (medium red). B, in third red). taches distally to the lateral aspect of the and lateral cuneiform bones (Fig. 27AB) base of the proximal phalanx of the large and to the adjacent part of the attachment toe together with the lateral part of the of the tibialis posterior tendon. Distally, flexor hallucis brevis. The transverse head the two heads attach to the medial and spans the space superficial to the second lateral aspects of the base of the proximal through fourth metatarsal heads. Its fas- phalanx of the large toe. A sesamoid bone ciculi attach laterally to the plantar is present in each tendon at its distal at- metatarsophalangeal (MP) ligaments of tachment. An additional slip of the flexor the third, fourth, and fifth toes and to the hallucis brevis may attach to the proximal transverse metatarsal ligaments of the phalanx of the second toe.14 same digits. Medially, fasciculi of the transverse head join to attach to the lat- The interossei are located in the fourth eral aspect of the base of the proximal muscular layer on the plantar aspect of phalanx of the large toe, blending with the foot. Figure 27.5A. shows attacbments the tendon of the oblique head.14,29 of the dorsal interossei. Their action is relative to the midline of the second toe. Valvo et,al.75 found that the conjoined tendon of The four dorsal interossei are each bipen- the two heads of the adductor hallucis muscle nate muscles located between two meta- consistently passed through the bifurcation in the tarsal bones. Each dorsal interosseous most medial deep transverse metatarsal ligament. anchors proximally to the two adjacent At times, a portion of the muscle may attach to the metatarsal bones and attaches distally to first metatarsal bone, forming an opponens hal- the base of the proximal phalanx and to lucis muscle.14 the aponeurosis of the tendon of the ex- tensor digitorum longus on the side of the The two heads of the flexor hallucis toe toward which it pulls.14 (The first dor- brevis anchor proximally by a common sal interosseous attaches to the medial tendon to adjacent surfaces of the cuboid side of the proximal phalanx of the sec- ond toe; the remaining three tendons are

Chapter 27 / Deep Intrinsic Foot Muscles 527 Metatarsal 3rd, 2nd, and bones 1 st plantar interossei 4th, 3rd, 2nd, and 1 st Metatarsal dorsal bones Dorsal interossei aponeuroses Cut ends of toe extensors Figure 27.5. Anatomical attachments of the interos- (dark red). B, plantar view of the plantar interossei sei in the deep (fourth) layer on the plantar aspect of (light red). the right foot. A, dorsal view of the dorsal interossei attached to the lateral sides of the second, servations on 115 feet. They35 found that 8 8 % of third, and fourth toes.) Manter44 contends the dorsal interossei and 93% of the plantar inter- that the dorsal interossei rarely continue ossei originated not only from bone but also from dorsally into the extensor aponeurosis. soft tissue, including the epimysium of other mus- cles, a slip of the peroneus longus tendon, or the The three plantar interossei appear in ligamentous network. This ligamentous network Figure 2 7 . 5 6 . Each muscle anchors proxi- comprises intertwining fibers of the tarsometatar- mally to the base of the related metatarsal sal joint capsules, the intermediate and long plan- and attaches distally to the medial side of tar ligaments, and the peroneal sheath. The me- the base of the proximal phalanx of the dial head of the first dorsal interosseous in all ten corresponding toe and usually to the dor- subjects received a slip of the peroneus longus sal aponeurosis of that extensor digitorum tendon. In other studies, 64.3% of 115 feet35 and longus tendon.14 The pennate belly of 63.5% of 149 feet44 exhibited this structure. Con- each plantar interosseous muscle lies sistently, the muscles of the fourth ray (the second along the plantar surface of its corre- plantar and the fourth dorsal interossei) were the sponding metatarsal, as seen in Figure largest of the interossei, extended the furthest 27.58 and in the cross-sectional view of proximally, and had the most extensive areas of Figure 27.9. origin.35 Most noteworthy, 73% of the individual muscles studied arose partly from another muscle Kalin and Hirsch35 point out that, although most or muscles, usually a crossover between dorsal and plantar interosseus muscles. This interweav- current anatomy texts make no mention of the ing of origins was least common among interossei along the sides of the foot and most common fact, the interossei characteristically have exten- among the more centrally located interossei. In apes, the longitudinal axis of the foot passes sive soft tissue origins that should significantly through the third digit as in the human hand. In man, the axis of the foot now passes through the influence their function across the tarsometatarsal second toe. This recent evolutionary change prob- joints and ensure that the interossei contract in a coordinated manner to perform their role as stabi- lizers of the forefoot. These authors reported a de- tailed study of 69 interosseous muscles in ten feet of ten different subjects and made additional ob-

528 Part 3 / Leg, Ankle, and Foot Pain ably contributes to the large variety of anatomical brevis,7,24,46,49 and the dorsal and plantar interos- variations.44 sei.46,49 Supplemental References 3. INNERVATION The quadratus plantae, as listed here, was some- Of the muscles covered in this chapter, times indexed and labeled as the flexor acces- only the flexor hallucis brevis and the sorius muscle. first lumbrical are supplied by the medial plantar nerve, which contains fibers from Plantar View Without Major Vessels or Nerves. the fifth lumbar and first sacral spinal nerves. The other muscles of this chapter Drawings portray the quadratus plantae,2,14 the are supplied by the lateral plantar nerve lumbricals,2,14 the flexor digiti minimi brevis,5,15 that carries fibers from the second and the adductor hallucis,15 the flexor hallucis third sacral spinal nerves.14 These mus- brevis,5,15 and both the dorsal and plantar inter- cles include the quadratus plantae, the o s s e i 5 1 6 2 5 8 0 without vessels or nerves. Photo- second, third, and fourth lumbricals, the graphs record the quadratus plantae,47,52, 65 the flexor digiti minimi brevis, the adductor lumbricals,4,7,51,52,64,65,67 the flexor digiti minimi hallucis, and all interossei. b r e v i s , 5 1 - 5 3 , 6 4 - 6 6 the adductor hallucis,47,48,53,66 the flexor hallucis brevis,47,48,53,66 and both the dorsal 4. FUNCTION and plantar interossei47,48, 54 without major vessels or nerves. During upright activities, muscles of the foot provide flexibility for shock absorp- Plantar View With Vessels or Nerves. Drawings tion and balance, and rigidity for the sta- show the medial and lateral plantar nerves in rela- bility needed during propulsion. In gen- tion to the quadratus plantae,4,23,57,59 the lumbri- eral, the intrinsic muscles of the foot c a l s , 2 3 , 5 7 , 5 9 the flexor digiti minimi brevis,4,59 function as a unit. The electromyographic the adductor hallucis,4,59 the flexor hallucis (EMG) activity of these muscles closely brevis,4,57,59 and plantar interosseous muscles.59 parallels the progressive supination at the One drawing59 also shows the medial and lateral subtalar joint during level, uphill, and plantar arteries; this drawing includes the sesa- downhill walking. These muscles stabi- moid bones in the flexor hallucis brevis tendons lize the foot at the subtalar and transverse at the first MP joint. tarsal joints during propulsion.42 It has been suggested that the interossei help Dorsal View. Dorsal view drawings present the the toes adjust to variations in terrain, dorsal interossei without vessels or nerves16,25'60 and that through their extensive soft tis- and with the deep peroneal veins and artery.58 A sue origins they may serve a role as stabi- photograph shows the dorsal interossei very lizers of the forefoot, \"rendering the tar- clearly.50 sometatarsal joints rigid when weight is carried on the ball of the foot.\"35 Medial View. Seen from the medial view without blood vessels or nerves, the quadratus plantae and Actions flexor hallucis brevis appear in a drawing3 and the quadratus plantae appears in a photograph.63 The quadratus plantae muscle assists the flexor digitorum longus in flexion of the Cross Sections. A series of cross sections identi- terminal phalanges of the four lesser fies the relations to surrounding structures of the toes.14,27,28,61 Because of the angle at which quadratus plantae,10 lumbricals, flexor digiti it attaches to the flexor digitorum longus minimi brevis, dorsal and plantar interossei,12 ad- tendon, the quadratus plantae centers the ductor hallucis,13 and the flexor hallucis brevis.\" line of pull of the flexor digitorum longus A section through the metatarsals identifies the on the fifth and, to a lesser extent, on the flexor digiti minimi brevis, flexor hallucis brevis, fourth and third toes. The line of pull by adductor hallucis, and the dorsal and plantar in- the flexor digitorum longus on the second terossei.22 toe is relatively straight and needs no cor- rection.28,34 The quadratus plantae pro- Sagittal Sections. A sagittal section through the duces flexion of the four lesser toes even second toe shows the surroundings of the ad- in the absence of flexor digitorum longus ductor hallucis,55 and one through the fifth toe shows those of the flexor digiti minimi brevis.58 Skeletal Attachments. Marks on the bones iden- tify the skeletal attachments of the quadratus plantae,6,7,24,49 the flexor digiti minimi brevis,7,24,49 the adductor hallucis,7,24,46,49 the flexor hallucis

Chapter 27 / Deep Intrinsic Foot Muscles 529 activity. The quadratus plantae also pro- According to Basmajian and Deluca,9 vides proximal stability to the lumbrical an important role of the intrinsic muscles muscles of the foot.34 is stabilization of the foot during propul- sion, acting mainly at the subtalar and The four lumbricals in the foot flex the transverse tarsal joints. The excessively proximal phalanges at the MP joints and pronated foot requires greater intrinsic extend the two distal phalanges at the in- muscle activity for stabilization than does terphalangeal (IP) joints of the four lesser the normal foot.42 toes.14,28,61 This action is analogous to the actions of the lumbricals in the hand.14 The quadratus plantae changes the posteromedial pull of the flexor dig- The flexor digiti minimi brevis muscle itorum longus into that of pure flexion of flexes the proximal phalanx of the small the toes and may be especially valuable in toe at the MP joint.14,61 flexing the toes when the weight-bearing foot is dorsiflexing at the ankle.28 The adductor hallucis adducts the great toe (draws it toward the second Normal function of the flexor hallucis toe).27, 61 It also assists in flexion of the brevis apparently helps prevent clawing proximal phalanx of the great toe and in of the great toe. Clawing of the great toe maintaining transverse plane stability.14 with hallux varus may result from sever- The oblique head of this muscle, on stim- ance of the lateral tendon of the flexor ulation, produced adduction that was hallucis brevis when the lateral sesamoid more forceful than that of the lateral head bone is removed during a McBride surgi- of the flexor hallucis brevis.17 cal procedure.74 The flexor hallucis brevis flexes the The lumbricals add leverage for the proximal phalanx of the great toe at the toes to dig in more effectively when walk- MP joint.14,61 On stimulation, the medial ing on soft sand, and they apparently head of this muscle abducted the proxi- function in conjunction witb the interos- mal phalanx and the lateral head ad- sei to provide stabilization of the forefoot. ducted it toward the second toe.17 Although the lumbricals do not cross the tarsometatarsal joints, they influence the The actions of the dorsal and plantar in- stability of those joints (in conjunction terossei are in relation to the longitudinal with contraction of the quadratus plantae) axis of the second toe. The dorsal interos- when weight is carried on the ball of the sei abduct the second, third, and fourth foot, as during push-off at the end of toes (they abduct the second toe in each stance phase.35 The lumbricals may also direction away from its own long axis, and function during the swing phase of gait to they abduct tbe third and fourth toes away prevent excessive extension of the MP from the second toe). The dorsal interossei joints that would otherwise be created by also flex the proximal phalanges and the extensor digitorum longus.33 weakly extend the two distal phalanges through the extensor mechanism of the The interossei show vigorous electrical second, third, and fourth toes.14,17,27,31,61 activity from midstance to toe-off;32, 42 they Some authors have noted an absence of in- contribute to stabilization of the forefoot terosseus attachment to the extensor when the heel is off the ground and the mechanism, which would leave only the foot is subject to extension at the tarsome- lumbricals to extend the IP joints.33 tatarsal joints late in stance phase and during push-off. In addition, tbe interos- The plantar interossei adduct the third, sei help the toes adjust to variations in fourth, and fifth toes toward the second terrain.35 Jarrett and associates33 suggest toe and also are flexors of the proximal that the interossei function during the phalanges.14,27,61 They may act as exten- stance phase of gait to check the pull of sors of the distal phalanges of the third, the flexor digitorum longus and brevis, fourth, and fifth toes, but only if they in- thereby allowing straight toe function for sert into the extensor mechanism.31 stabilization against the ground. Functions The adductor hallucis helps stabilize the forefoot (metatarsal head region) in Muscle activity is not necessary to sup- the transverse plane. port the arches of the fully loaded foot at rest.42

530 Part 3 / Leg, Ankle, and Foot Pain 5. FUNCTIONAL (MYOTATIC) UNIT may disappear after inactivation of these TrPs, especially in younger patients. The quadratus plantae, flexors digitorum longus and brevis, lumbricals, and inter- DIFFERENTIAL DIAGNOSIS ossei function as a team to flex the four lesser toes and to control their extension. Other Myofascial Pain Syndromes Their antagonists are the extensors dig- itorum longus and brevis. Because patients often have active TrPs in several foot and leg muscles at the same The flexor digiti minimi brevis, abduc- time, one sees many combinations of pain tor digiti minimi, the fourth lumbrical, referral patterns. and the third plantar interosseus muscles function together to flex the fifth toe. Quadratus Plantae. The quadratus plan- They are opposed by the tendon slips of tae TrPs refer pain and tenderness to the the extensors digitorum longus and brevis bottom of the heel (Fig. 27.1), whereas that attach to the fifth toe. both the gastrocnemius TrP1 (see Fig. 21.1) and flexor digitorum longus TrPs The adductor hallucis and flexor hal- (see Fig. 25.1) refer pain and tenderness lucis brevis form a functional unit to con- to the instep, anterior to the heel. The trol the positioning of, and the force ex- heel referral pattern of soleus TrP1 (see erted by, the great toe. Fig. 22.1) is more extensive than that of the quadratus plantae. The soleus TrP re- The dorsal and plantar interossei to- ferral covers not only the plantar surface gether with the lumbricals control abduc- of the heel, but usually extends over the tion and adduction efforts of the four back of the heel and part of the way up lesser toes. the Achilles tendon. The pattern of the tibialis posterior TrPs (see Fig. 23.1) may 6. SYMPTOMS spill over to the heel, but focuses primar- ily on the Achilles tendon above the heel. Patients with TrPs in the deep intrinsic Pain and tenderness referred from the ab- foot muscles are likely to present with ductor hallucis muscle (see Fig. 26.2) marked limitation of walking due to pain, concentrates along only the medial border and they may complain of numbness of of the heel, whereas the quadratus the foot and a feeling that it is swollen. plantae referral pattern covers the plantar The altered sensation usually includes surface of the heel. the entire distal end of the foot and is not limited to only one toe. This altered sen- Adductor Hallucis. The adductor hal- sation is especially likely to arise from lucis refers pain and tenderness to the TrPs in the flexor digiti minimi brevis, plantar surface of much of the forefoot flexor hallucis brevis, or adductor hal- (Fig. 27.2A), but gastrocnemius TrP1 (see lucis muscles. Patients with TrPs in these Fig. 21.1) usually refers more proximally muscles often have tried orthoses inserted to the instep. Distinguishing the more re- in the shoes, but usually quickly remove stricted pain and tenderness of interos- them because of intolerably greater pain seous TrPs (that usually include a strong from the increased pressure on the TrPs pattern to one toe) ordinarily is not much and tender reference zones. of a problem. Both the flexor digitorum longus (see Fig. 25.1) and the flexor dig- Muscular imbalances and articular dys- itorum brevis (see Fig. 26.3B) refer pain functions of the foot may lead to prob- and tenderness to the plantar surface of lems in any proximal segment of the the forefoot in an area that could easily be body, including the knee, hip, pelvis, and confused with the pattern of the adductor spine. hallucis. When the pain complaint in- cludes the plantar surface of the forefoot, The pain complaints of patients with the former two muscles and the adductor involvement of the deep foot intrinsic hallucis should be examined. muscles are often combined with myofas- cial patterns of TrPs in other muscles that Flexor Hallucis Brevis. Flexor hallucis refer pain to the foot. brevis TrPs refer pain and tenderness mainly to the region of the head of the Active or latent TrPs in the dorsal inter- first metatarsal with only a spillover pat- osseus muscles can be associated with hammer toes. The deformation of the toes

Chapter 27 / Deep Intrinsic Foot Muscles 531 tern to the great toe (Fig. 27.2B), whereas To our knowledge, the possible contribution to TrPs in the tibialis anterior muscle refer hallux valgus by TrPs in the adductor hallucis primarily to the great toe itself (see Fig. (which could shorten the muscle without in- 19.1). Tbe extensor hallucis longus TrPs creased EMG activity) has not been investigated. refer only to the dorsal side of the head of the first metatarsal bone (see Fig. 24.18), Alfred and Bergfeld1 reviewed stress fractures and not to the medial and plantar sides as of the foot. Stress fracture of the calcaneus can oc- does the flexor hallucis brevis. The re- cur at any age and cause chronic heel pain that ferred pain pattern of the flexor hallucis eludes diagnosis because it usually requires a longus TrPs (see Fig. 25.18) usually in- bone scan for diagnosis. Stress fracture of the na- cludes only tbe plantar surface of both the vicular is rare and is easily disregarded because first metatarsal head and the great toe. arch pain is so common in adults. Usually the pa- tient with the latter stress fracture has pain and Interossei. The ray-specific pain pat- swelling along both the dorsum of the foot and the tern of TrPs in an interosseous muscle medial arch that are worse after activity and at the (Fig. 27.3A and B), which includes both end of the day. Metatarsal stress fractures cause the plantar region of the corresponding aching pain in the forefoot and are found often metatarsal head and the adjacent side of among military recruits and ballet dancers. The the corresponding toe, is not likely to be key to diagnosis is spot tenderness over the af- confused with the pain pattern discussed fected metatarsal.1 previously under the adductor hallucis muscle, unless several adjacent interossei Manoli and Weber43 investigated why three pa- harbor active TrPs. tients with calcaneal fractures developed clawing of the lesser toes as a late sequela. Examination of Myofascial TrPs in a dorsal interos- 17 lower limb specimens revealed a previously seous muscle can contribute to a hammer unidentified separate compartment of the hind- toe deformity, apparently by weakening foot, a calcaneal compartment that contains the the muscle. quadratus plantae muscle. The authors concluded that the clawtoe deformities were late sequelae to Other Conditions an unrecognized calcaneal compartment syn- drome that led to contracture of the quadratus The reader is referred to McGlamry's two- plantae muscle. The authors proposed a surgical volume textbook for comprehensive in- technique for release of this compartment in case formation on conditions that affect the such a compartment syndrome developed in asso- foot.45 Other conditions deserving consid- ciation with a calcaneal fracture. eration include plantar fasciitis, hallux valgus, stress fractures, calcaneal com- The pattern of heel pain characteristic of TrPs partment syndrome, nerve entrapment, in the quadratus plantae may also be caused by articular dysfunction, and an injured ses- entrapment of the first branch of the lateral plan- amoid bone. tar nerve. An extensive anatomical study showed that the most likely location of entrapment was The pain and tenderness caused by TrPs of the where the nerve coursed between the abductor hal- lucis muscle and the medial head of the quadratus quadratus plantae muscle may masquerade as plantae m u s c l e . 6 8 The mechanism of entrapment was not clear. plantar fasciitis. Chapter 26 reviews this condi- Articular dysfunction (either hypermobility or tion on pages 509-510. hypomobility) of the foot can seriously disturb foot mechanics and produce imbalances that may Hallux valgus is a progressive deformity that cause pain in many locations, ranging from the feet to the head and neck. can relate to contracture of numerous periarticular Other structural deviations can be a source of structures of the first MP joint. These structures disturbed foot mechanics. Such deviations in- clude: hindfoot varus or valgus, forefoot varus or include (but are not limited to) the lateral collat- valgus, equinus, hypermobility or malposition of eral ligament and the joint capsule, the adductor the first ray, and an excessively high arch. hallucis muscle and tendons, the lateral head of the flexor hallucis brevis, and its fibular sesamoid.69 An Injury of a sesamoid bone in the flexor hallucis brevis tendon can disable an athlete.82 A specific EMG study revealed that in subjects with hallux single injury rarely initiates the pain; it appears to result from repetitive stress. The pain is usually valgus, while the adductor hallucis activity was markedly decreased, the abductor hallucis activ- ity was nil, and so a weak adductor force was oper- ative.9 Adductor hallucis tenotomy has been re- ported to be effective in relieving hallux valgus.74

532 Part 3 / Leg, Ankle, and Foot Pain poorly localized about the MP joint of the great and fourth tarsometatarsal joints is com- toe. With gentle pressure, the examiner can elicit mon and easily determined.41 local tenderness over the sesamoid bone and can usually elicit pain about the joint with passive ex- The Morton foot structure and other tension of the great toe. The symptoms may be causes of a hyperpronated foot, when un- caused by sesamoiditis, osteochondritis, simple corrected, may contribute significantly to stress fracture of the sesamoid, or a displaced ses- the perpetuation of TrPs in the intrinsic amoid fracture, and are ordinarily responsive to foot muscles. Pronation during early conservative therapy.62 stance is normal; it is hyperpronation that becomes a problem. Deviation of the second toe so that it overlapped the great toe resulted from traumatic rupture of An inflexible sole of the shoe (a both the dorsal lateral MP collateral ligament and wooden sole or shoe with a steel bar the second interosseous tendon in two cases.26 placed the length of the sole) limits move- Surgical repair was required in both cases. ment of the forefoot sufficiently to perpet- uate TrPs in deep intrinsic muscles. 7. ACTIVATION AND PERPETUATION OF TRIGGER POINTS Systemic conditions including gout of the great toe (podagra) that may perpetuate Activation TrPs in the intrinsic foot muscles are con- sidered on pages 115-155 of Volume I. 73 The factors that activate and perpetuate TrPs in the superficial intrinsic muscles 8. PATIENT EXAMINATION of the foot, discussed in Chapter 26 on pages 510-511, are also likely to do the The status of arterial circulation is exam- same to these deep intrinsic muscles. A ined by palpating for the dorsalis pedis tight shoe cap (vamp) that has an inade- and posterior tibial pulses. The skin and quate vertical dimension of the shoe cov- nails are examined for lesions, and the ering the forefoot restricts toe movement skin is examined for color, temperature, and can be a major activator and perpetu- and edema. ator of TrPs in most of the deep intrinsic toe muscles. The TrPs in the interossei The clinician should observe the patient are more likely to be activated and perpet- walking barefoot, noting particularly ex- uated by a shoe that is too short than by a cessive supination or pronation of the foot. tight vamp. An antalgic gait alerts one to ask about sore feet, if the patient has not already volun- TrPs can be activated in these muscles teered this complaint. The patient may re- at the time of a fracture of the ankle or spond, \"Yes, of course, but don't every- other bones of the foot. The TrPs are then one's feet hurt?\" He or she cannot remem- aggravated by a cast that immobilizes the ber when the feet did not hurt; it has foot for some time. become an accepted part of life.72 Other traumas to these deep intrinsic The patient with active TrPs in the foot muscles, such as bruising, banging, deep muscles of the forefoot is unable to stubbing toes, and falling, can also acti- hop on the sore foot. vate TrPs in them. The clinician examines the feet for con- Perpetuation figuration and for restricted range of mo- tion of the toes in flexion and extension. Walking in soft sand, walking or running Myofascial TrPs painfully restrict the on uneven or sloped surfaces, chilling the stretch range of motion; strength and ac- feet in cold water, or wearing wet socks in tive contraction in the shortened position cold weather can aggravate and perpetu- are also usually limited by pain. ate these TrPs, especially when the mus- cles are fatigued. The two-part screening test described by Lewit41 for detection of restricted joint Impaired mobility of the joints of the movement in the feet is simple and effec- foot can perpetuate TrPs in the intrinsic tive. In the first part, the patient rests the foot muscles that cross those joints. heel of the relaxed foot on the examining Blockage of motion in the second, third, table and the clinician grasps a side of the forefoot in each hand, then tries to rotate the forefoot around the long axis of the foot. The center of rotation passes