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Nerve and Tendon Lacerations About the Foot and Ankle David B. Thordarson, MD, and Christopher J. Shean, MD Abstract Nerve and tendon lacerations about the foot and ankle are relatively common. Delayed repair or lack of repair of tendons can lead to foot deformi- ties, which may be especially prob- lematic for a child. 1 Most published reports are small case series of spe- cific tendon injuriesin which treatment recommendations are derived from the surgical management of pathologic conditions of the foot and ankle. Untreated tendon lacerations of the foot may have fewer sequelae than untreated lacerations of the hand; still, it is inappr opriate to equate a normal- ly functioning, lacerated tendon of a toe, for example, to a tenotomy done for a pathologic condition, such as a flexible clawtoe. 2 Similarly, an insensate digit resulting from nerve injuries in the fingers can lead to mark- edly impaired function in fine manipulation. By comparison, localized numbness in the foot caused by a distal nerve injury may be relatively innocuous, although more proximal injuries or multiple distal injuries can lead to a greater area of insensate skin and to impairment. Nerve Injuries Nerve injuries of the foot are generally caused by a penetrating wound. The sequelae of such injuries depend on the nerve injured and the level of the injury. In the foot and ankle, the main function of the nerves is to provide sensation. Generally, the tibial nerve and its branches (ie, the medial and lateral plantar nerves) inner- vate the intrinsic musculature, although the deep peroneal nerve innervates the extensor digitorum brevis and extensor hallucis brevis muscles. Denervation of these motor nerves can lead to clawing of the toes because of a resulting imbalance of intrinsic and extrinsic muscles. The long-term morbidity of nerve injuries of the foot is predominantly related tosensory nerve injury, except when a tibial nerve injury causes intrinsic muscle function loss. The two main problems associated with injuries to these nerves are the lack of sensation in the distal distribution of the nerve (Fig. 1) and the formation of a painful neuroma. When the nerve injury occurs in a weight-bearing area of the foot, the presence of a painful neuroma often leads to complex re- gional pain syndrome type I. General Principles of Nerve Surgery Nerve Repair and Reconstruction The goal of nerve repair is to in- crease the number and accuracy of axons that regenerate across the injury site. A successful repair includes the preparation of the injured nerve stumps and accurate, atraumatic nerve approximation without undue tension. The use of loupe magnification or an operating microscope is essential. Epineurial repair is recommended for neurorrhaphy about the foot and Dr. Thordarson is Vice Chair, Department of Or- thopaedic Surgery, Keck School of Medicine, Uni- versity of Southern California, Los Angeles, CA. Dr. Shean is Associate Physician, Kaiser Perma- nente, Baldwin Park, CA. None of the following authors or the departments with which theyare a ffiliated hasreceived anything of value from or owns stock in a commercial com- pany or institution related directly or indirectly to the subject of this article: Dr. Thordarson and Dr. Shean. Reprint requests: Dr. Thordarson, USC Depart- ment of Orthopaedic Surgery, GNH 3900, 1200 North State Street, Los Angeles, CA 90033. Copyright 2005 by the American Academy of Orthopaedic Surgeons. Nerve and tendon lacerations of the foot and ankle region are relatively common. Acute nerve and tendon injuries should be repaired with appropriate techniques at the time of initial wound exploration. Primary nerve repair may help minimize the risk of painful neuroma formation; primary tendon repair can lead to better functional results than delayed repair. Most chronic nerve injuries, except those to the tibial nerve or its major divisions, are managed by resection of a painful neuroma and burying the nerve ending in a protected area. Delayed reconstruction of tendon injuries is performed when correction of the functional deficit outweighs the morbidity of surgery. J Am Acad Orthop Surg 2005;13:186-196 186 Journal of the American Academy of Orthopaedic Surgeons ankle (Fig. 2). Epineurial repair is sim- pler than group fascicular repair, and it avoids the increased scarring and damage to intraneural elements caused by the additional dissection required by group fascicular repair. Except for the tibial nerve, group fascicular repair is not possible because the nerves are pure sensory and do not have multiple fascicles. In our ex- perience, protective sensation has been achieved with epineurial repair of acute tibial, medial, and lateral plantar nerves in the foot. If repair of a transected tibial nerve cannot be achieved without undue tension, then reconstruction using a simple cable graft with a reversed sural nerve autograft is indicated. Be- cause of the morbidity of the sural nerve graft, delayed reconstr uction of the other nerves of the foot and ankle is not justified. Favorable outcomes can be achieved with this technique; success appears to be related to required nerve graft length. Hat- trup and Wood 3 reported that short- er nerve grafts yielded better results than long grafts when done an average of 10 months after injury. Five of seven patients with nerve grafts ≤6 cm had a good result, whereas the five grafts >6 cm had no good results. Neuroma Formation and Prevention The pathogenesis of neuroma formation consists of an injury to the en- doneurium permitting regenerating axons to escape into the surrounding tissue in a haphazard manner. Nerve repair andinterpositional nerve grafting are the best ways to minimize neuroma formation, by allowing the regenerating nerve fibers to connect with the distal portion of the nerve. Management of an established neuroma of the foot and ankle begins with nonsurgical treatment. Commonly used modalities are mechanical desen- sitization, transcutaneous electrical nerve stimulation, local corticosteroid injection, and medications. In our ex- perience, these techniques tend to pr o- vide transient, partial relief. For surgical intervention, diagnostic nerve blocks can be used to confirm the di- agnosis of neuroma and to exclude the involvement of othernerves. Although numerous surgical techniques for painful neuromas have been de- scribed, simple excision and implantation of the proximal nerve stump in a nonirritable location remains the treatment of choice. Treatment Recommendations for Nerve Injury Most nerve injuries to the foot should be treated with acute epineurial repair, followed by primary wound clo- sure. If the injury requires surgical débridement, nerve repair usually adds little morbidity to theprocedur e. In addition to minimizing the risk of subsequent sensory deficit and the development of claw toes, nerve repair also may decrease the incidence of painful neuroma. If thedistal nerve end cannot be identified or if a gap exists that precludes tension-free re- Figure 1 Dorsal (A) and plantar (B) aspects of the foot showing cutaneous innervation. Mi- nor variability between the areas supplied by each nerve is frequently present. 1 = sural nerve, 2 = superficial peroneal nerve branches, 3 = saphenous nerve, 4 = deep peroneal nerve, 5 = medial plantar nerve, 6 = lateral plantar nerve, 7 = medial calcaneal nerve. (Adapted with permission from Sarrafian SK: Nerves, in Foot and Ankle: Descriptive, Topographical, and Func- tional, ed 2. Philadelphia, PA: JB Lippincott, 1993, p 370.) David B. Thordarson, MD, and Christopher J. Shean, MD Vol 13, No 3, May/June 2005 187 pair, then the proximal nerve stump is buried in soft tissue, as with a neuroma excision. Lesions distal to the arch or in the distal forefoot generally are not repaired because of the small size of the nerve and the minimal sensory deficit. If the nerve injury is the result of a puncture wound, and if surgical treatment of the wound is unneces- sary, then the morbidity of surgery must be considered. In cases of gross wound contamination, a delayed primary nerve repair can be performed after the wound has been adequate- ly débrided. Postoperatively, the foot and ankle are immobilized for 3 weeks to protect the nerve repairs until they can tolerate mild traction. An associated tendon repair frequently results in a longer period of protection. Often patients present with a nerve injury to the plantar aspect of the foot after the wound was cleansed andsu- tured in an emergency department; the underlying nerve injury was not identified or treated. In these situa- tions, treatment decisions are based on balancing the risks and benefits of surgery because nerve grafting is often required to reestablish nerve con- tinuity. Tibial Nerve and Its Branches The tibial nerve provides the plantar sensation to the entire foot. At the proximal aspect of the flexor retinaculum of the ankle, the calcaneal branches divide from the tibial nerve and course along the medial aspect of the heel to provide sensation to the heel pad (Fig. 3). At approximately the level of the medial malleolus, the tibial nerve bifurcates into the medial and lateral plantar nerves. The medial plantar nerve provides sensation to the medial portion of the arch and to the medial three and a half digits. The lateral plantar nerve provides sensation to the lateral arch and to one and a half digits. Additionally, the medial plantar nerve provides innervation to the abductor hallucis, flex- or hallucis brevis, flexor digitorum brevis, and first lumbrical muscles. The lateral plantar nerve innervates the quadratus plantae, interossei, ad- ductor hallucis, abductor digiti min- imi, and second through fourth lumbrical muscles. The medial and lateral plantar nerves divide into common digital nerves in the midarch and, at the base of each web space, split into the proper digital nerves supplying sensation to one half of each adjacent toe of a given web space. A tibial nerve injury that leads to denervation of the entire plantar aspect of the foot or the majority of the plantar aspect of the foot is poorly tolerated. The nerve injury should be ex- Figure 2 Epineurial repair. Note that only epineurial sutures are placed, with no group fascicular repair (deep sutures) performed. (Adapted with permission from Wiglis EFS: Nerve repair and grafting, in Green DP [ed]: Operative Hand Surgery, ed 2. Philadelphia, PA: Churchill Livingstone, 1988, p 1381.) Figure 3 Medial view of the ankle showing the tibial nerve dividing into the medial and lateral plantar nerves, with the medial calcaneal branches evident. (Adapted with permission from Sarrafian SK: Nerves, in Foot and Ankle: Descriptive, Topographical, and Functional, ed 2. Philadelphia, PA: JB Lippincott, 1993, p 384.) Nerve and Tendon Lacerations About the Foot and Ankle 188 Journal of the American Academy of Orthopaedic Surgeons plored and repaired. Nunley and Ga- bel 4 reported on five patients treated with sural nerve grafting of tibial nerve injuries. Results were evaluat- ed by the return of superficial sensation, healing of plantar ulceration, and absence of neurogenic pain. The authors noted that ultimate recovery might require up to 4 years. Dellon and Mackinnon 5 reported successful results in all eight patients with tibial nerve deficits. They concludedthat grafting the tibial nerve can restore at least some sensibility to the plantar foot. Hattrup and Wood 3 used an interfascicular grafting technique for delayed neural reconstruction inthree cases of tibial nerve grafts; they reported one good, one fair, and one poor result. Transection of the calcaneal branches leads to localized numbness of the heel pad. Most patients tolerate this well if the sensation of the plantar forefoot remains intact. However, lacerations of the calcaneal branches frequently occur immediately adjacent to the weight-bearing surface of the foot; these lacerations may lead to painful neuromas. Kim and Dellon 6 reported on a series of 15 patients with heel pain resulting fr om calcaneal neuromas. They recommended using an extended tarsal tunnel incision to per- mit identification of all calcaneal nerves and nerve implantation into the flexor hallucis longus muscle after neuroma resection. This approach yielded good or excellent results in 14 of 15 patients. Reflex sympathetic dystrophy can occur after transection of calcaneal branches along the medial aspect of the heel. Because the sensory deficit is well tolerated, transecting the involved branch closer to its split from the tibial nerve results in the same sensory deficit but removes the painful neur oma from the weight- bearing aspect of the foot. Transection of the medial or lateral plantar nerve in the proximal portion of the arch leads to a bothersome area of numbness in the plantar aspect of the foot, with the patient los- ing all protective sensation supplied by the injured nerve in the distal region of the foot. Isolated laceration of the lateral plantar nerve is better tolerated. If sensation is present in half the foot distally, options include sim- ply cutting the neuroma back to a less painful area or performing a nerve repair, which usually requires harvesting a sural nerve graft. In most cases, nerve repair has led to recovery of protective sensation of the isolated portion of the foot. Digital Nerves Injury to a single common digital nerve in the distal forefoot is generally well tolerated because it is the traumatic equivalent of excising a Morton neuroma. In one study of injuries to the flexor hallucis longus tendon, four patients underwent associated primary repair of lacerated nerves (three proper digital nerves, one medial plantar nerve). 7 Normal sensation was achieved in only one patient after repair of the proper digital nerve. The sensory deficit in the other three patients had little effect on total function, although the nerve injuries were associated with a hyper- sensitive scar. In another study focus- ing on tendon injuries, digital nerves were noted to be lacerated in six patients and were repaired in three. 2 Mild, decreased pin-prick sensation was noted in all six, but no patient reported symptomatic numbness. If the transection occurs in a weight-bearing area, typically the only treatment required is transection of the nerve branch at a more proximal level and burying it in the arch musculature. Johnson et al 8 reported on 33 feet in which a longitudinal plantar incision was used to excise a stump neuroma after excision of a Morton neuroma. The proximal end of the nerve was allowed to retract into the more proximal arch. Twenty- two patients (67%) had complete relief or marked improvement in their pain; three (9%) had improvement with persistent pain. Eight patients (24%) had no improvement or worse pain at an average of 67 months after surgery. Wolfort and Dellon 9 performed a prospective study of 17 re- current interdigital neuromas resected through a plantar incision with implantation of the proximal end of the nerve into an intrinsic muscle in the arch of the foot. At a mean follow-up of 34 months, 10 of 13 patients had excellent relief and had returned to their r egular jobs. Twenty per cent had good r elief of symptoms but had gone to work at different jobs than previ- ously held and had had to change their shoe wear. Super ficial Peroneal Nerve The superficial peroneal nerve ex- its the deep fascia in the distal lateral aspect of the leg and forms two branches that supply sensation to most of the dorsal aspect of the foot (Figs. 1 and 4). The lateral of thesetwo branches becomes the dorsal interme- diate cutaneous nerve; it suppliessen- sation to most of the dorsal and mid- portion of the foot as well as to the third and sometimes fourth web space. The medial branch becomes the dorsal medial cutaneous branch; it supplies sensation to the medial dorsal aspect of the foot as well as to the medial aspect of the great toe and the second web, although there is some variability between the exact areas of innervation. Acute management of a laceration of the superficial peroneal nervebranch should include nerve exploration and epineurial repair if the two ends can be identified. The management of a subacute injury to the superficial peroneal nerve depends on the level of pain and on the degree of sensory deficit. Numb- ness on the dorsal aspect of the foot usually is well tolerated; in most cases, delayed repair is not warranted. However, nerve injuries at the ankle level frequently lead to a neuroma that is irritated by shoe wear or ankle movement. Transecting the nerve above the ankle and burying it in the anterior compartment musculature David B. Thordarson, MD, and Christopher J. Shean, MD Vol 13, No 3, May/June 2005 189 provides adequate symptomatic relief from irritation from shoe wear or motion of the ankle. Deep Peroneal Nerve The deep peroneal nerve supplies sensation to the first dorsal web space (Figs. 1 and 4) and innervation to the extensor digitorum brevis and extensor hallucis brevis muscles. Denervation of the extensor hallucis brevis and extensor digitorum brevis muscles can weaken toe extension but generally is well tolerated. The most frequent complaint after deep peroneal nerve laceration is a painful neuroma on the dorsal aspect of the foot. In the presence of acute lacerations, epineurial repair minimizes the risk of a painful neuroma. In a subacute setting or in the presence of a nerve injury with segmental loss or inability to identify the two ends, transecting the nerve proximal to the ankle and burying it in the anterior compartment of the leg has led to good symptomatic relief. In a series of 19 dorsal foot neuromas resulting from superficial or deep peroneal nerve injuries in 11 patients, 10 treatment included resection of the neuroma with implantation of the nerves into the anter olateral compartment. Excellent results were reported for 9 of 11 patients after an average of 29 months. The authors recommended anterolateral compartment fasciotomy to avoid potential problems since the anterolateral compartment muscles, shrunken by dis- use, regain normal size as pain re- solves. Saphenous Nerve The saphenous nerve is a small cutaneous nerve branch that follows the saphenous vein along the anterome- dial aspect of the ankle. Generally, an injury results in a small area of decreased sensation over the medial border of the hindfoot, and occasion- ally into the medial midfoot, which is well tolerated. Acute epineurial repair is difficult because the nerve is small. A painful neuroma should be treated with nerve transection proximal to the ankle joint and buried in an adjacent muscle, such as the soleus. Sural Nerve The sural nerve is a wholly sensory nerve providing sensation to the lateral border of the foot. Numbness in its area of distribution generally is well tolerated; thus, the nerve frequently is harvested for nerve grafting elsewhere in the body. If a sural nerve injury is identified in an acute traumatic wound, epineurial repair may decrease the incidence of a painful neuroma. Alternatively, an acute injury may be treated with the same methods as those for delayed treatment: transection of the nerve 5 to 7 cm proximal to the ankle to minimize pressure over the neuroma from shoe wear or irritation from motion of the ankle. Figure 4 The dorsal cutaneous nerves of the foot. The branches of these nerves correspond to the areas of innervation (Fig. 1), but some minor variability in their distribution frequently is present. (Adapted with permission from Sarrafian SK: Cr oss-sectional and topographic anatomy, in Foot and Ankle: Descriptive, Topographical, and Functional, ed 2. Philadelphia, PA: JB Lippincott, 1993, p 419.) Nerve and Tendon Lacerations About the Foot and Ankle 190 Journal of the American Academy of Orthopaedic Surgeons Tendon Lacerations Acute tendon lacerations about the foot and ankle most commonly are caused by penetration of the plantar aspect of the foot by a sharp object or by a sharp object dropped onto the dorsum. Most of these wounds are clean, with limited contamination. Treatment of the tendon injury depends on whether it is identified acutely or after a delay. In the acute setting, standard wound management should be used, including appropriate tetanus prophylaxis and débridement of any devitalized tissue. Motor strength of underlying tendinous structures should be as- sessed to define whether a tendon injury has occurred (Figs. 5 and 6). Achilles Tendon The gastrocnemius and soleus muscles function, through the Achil- les tendon, as the major ankle plantar flexors and stabilizers of the ankle joint. The maximum excursion of the Achilles tendon is approximately 4 cm; thus, lacerations of this tendon tend to retract 4 cm or more. 11 An acute laceration of the Achil- les tendon should be relatively easily identifiable following penetration of the posterior aspect of the ankle region (Fig. 5, A). Despite con- troversy regarding surgical versus nonsurgical treatment of an acute Achilles tendon rupture, an acute tendon laceration should be repaired surgically since the patient requires a surgical procedure to repair the skin laceration. Many suture techniques have been de- scribed; one preference for an acute repair is to use a Krackow suture 12 Figure 5 A, The lateral aspect of the ankle showing the posterior position of the Achilles tendon and location of peroneal tendons as they course along the posterior and inferior aspects of the fibula to their respective insertions. B, The dorsal aspect of the foot and ankle showing the course of the extensor tendons and the tibialis anterior tendon. C, The medial aspect of the ankle showing the relationship of the tibialis posterior, flexor digitorum longus, and flexor hallucis longus tendons. (Panel A adapted with permission from Netter FH: Muscles of leg: Lateral view, in Colacino S [ed]: Atlas of the Human Body. Summit, NJ: CIBA-GEIGY, 1989. Panel B adapted with permission from Sarrafian SK: Cross-sectional and topographic anatomy, in Foot and Ankle: Descriptive, Topographical, and Functional, ed 2. Philadelphia, PA: JB Lip- pincott, 1993, p 423. Panel C adapted with permission from Netter FH: Tendon sheaths of ankle, in Colacino S [ed]: Atlas of the Human Body. Summit, NJ: CIBA-GEIGY, 1989.) David B. Thordarson, MD, and Christopher J. Shean, MD Vol 13, No 3, May/June 2005 191 with a no. 2 nonabsorbable braided suture (Fig. 7). If the laceration is directly off bone, additional supple- mentation with suture anchors to the posterior calcaneus may be ad- vantageous. Wickes et al 1 noted that, in a series of 21 Achilles tendon lacerations in children, results were generally good with earlier repair. Delayed treatment of the Achilles laceration may require an Achilles tendon reconstruction procedure because the proximal muscle-tendon unit will retract, leading to a large gap of scar tissue. If more than 6 weeks have passed since the injury, Achil- les reconstruction with either turn- down flaps or V-Y advancement of gastrocnemius fascia, or a flexor hallucis longus muscle augmentation, frequently is necessary. 13 Tibialis Anterior Tendon The tibialis anterior tendon (Fig. 5, C) functions eccentrically after heel strike to control acceleration of the foot and concentrically, contracting after toe-off, to assist in foot clearance during the swingphase of gait. It provides approximately 80% of the dorsiflexion power of the ankle. 14 Loss of function can result in a slapping gait upon heel strike and a tendency toward tripping during the swing phase of gait, or in a steppage gait in which the hip is flexed more than normal during the swing phase to prevent catching the toes of a nondorsi- flexed foot. A tender, bulbous mass proximal to the laceration is frequently palpable at the level of tendon retraction. Patients have weak dorsiflexion and no palpable tension of the tibialis anterior tendon along the anterior aspect of the ankle with dorsiflexion of the ankle. Tr eatment o f acute laceration should include end-to-end repair. 2,12,15-17 Pri- mary repair is possible a minimum of 6 weeks after injury and should be attempted for up to 3 months after injury. The distal end of the laceration is usually found in the re- Figure 6 Plantar aspect of the foot showing the course of the flexor digitorum longus and flexor hallucis longus tendons. (Adapted with permission from Netter FH: Muscles of the sole of the foot: Second layer, in Colacino S [ed]: Atlas of the Human Body. Summit, NJ: CIBA- GEIGY, 1989.) Figure 7 The Krackow stitch. (Adapted with permission from Armagan O, Sher eff MJ: Ten- don and injury repair, in Myerson M [ed]: Foot and AnkleDisorders. Philadelphia, PA: WB Saunders, 2000, p 945.) Nerve and Tendon Lacerations About the Foot and Ankle 192 Journal of the American Academy of Orthopaedic Surgeons gion of the skin laceration. The proximal end can retract 3 cm or more. It should be possible to place a hemostat beneath the extensor retinaculum to pull the lacerated tendon into the wound. Nonabsorbable sutures then can be woven through the tendon using a Kessler, Bunnell, or Krackow suture technique. If the tendon is frayed, an additional small- er monofilament suture can be used to oversew the tendon ends, creating a smoother surface and increasing the strength of the repair. 18 In cases of delayed identification, especially more than 3 months after injury, it is often impossible to pri- marily repair the two ends of the tibialis anterior tendon. A dorsiflexion- assist ankle-foot orthosis is acceptable nonsurgical treatment in elderly patients or those with low functional de- mand. Surgical treatment consists of either a sliding tendon graft or an adjacent tendon transfer (eg, extensor hallucis longus) to span thegap 12 (Fig. 8). A sliding tendon graft involves harvesting half the width of the tendon proximally and turning this down to span any remaining gap in the tibialis anterior tendon. The repair can be augmented by anchoring the tibialis anterior tendon to the medial aspect of the foot into the medial cu- neiform or dorsal navicular distal to the extensor retinaculum. No marked weakness has been noted with this method. The new insertion is distal to the extensor retinaculum, which acts as a pulley for the tibialis anterior tendon. Postoperatively, patients should be kept in a short leg, nonwalking cast for 4 weeks, followed by 2 to 4 weeks in a walking cast or boot. Floyd et al 2 reported on three children who underwent repair of a tibialis anterior tendon; all regained good function. Simonet and Sim 16 noted excellent results in four of five tibialis anterior tendon laceration repairs. In an earlier publication, good results were reported with open repair of the tibialis anterior tendon acutely following laceration. 15 Five of eight patients had a good outcome; two had a poor outcome and one, a fair outcome, but these three patients had multiple tendon lacerations. Grif- fiths 17 noted unsatisfactory results in untreated laceration of the peroneal, tibialis posterior, and tibialis anteri- or tendons. Peroneal Tendons The peroneus brevis tendon is the major everter of the foot;the peroneus longus serves as an accessory everter and also as a plantar flexor of the first metatarsal (Fig. 5, A). Acute laceration of the peroneal tendons should be repaired as part of the repair of the skin laceration. Weakness of either or both of these tendons can lead to an inversion deformity of the foot. 1,17 It may be difficult to differentiate between the tendons if both are lacerated at the level of the lateral malleolus. The peroneus brevis muscle has a lower lying muscle belly and is anterior to the peroneus longus at the level of the lateral malleolus. Distal- ly, the peroneus longus tendon can be identified by placing gentle traction on the tendon and palpating plantar flexion of the first metatarsal. Repair of these tendons is similar to that of the tibialis anterior tendon. Lacera- tions of the superior peroneal retinaculum also should be repaired at the Figure 8 Extensor hallucis longus transfer for chronic, irreparable tibialis anterior tendon laceration. Note that the distal extensor hallucis longus stump is tenodesed to the extensor hallucis brevis, while proximally the extensor hallucis longus is used as tendon graft ma- terial to repair the distal stump of the tibialis anterior tendon. The proximal tibialis anterior tendon is placed under tension at time of repair. (Adapted with permission from Armagan O, Shereff MJ: Tendon and injury repair, in Myerson M [ed]: Foot and Ankle Disorders. Phil- adelphia, PA: WB Saunders, 2000, p 950.) David B. Thordarson, MD, and Christopher J. Shean, MD Vol 13, No 3, May/June 2005 193 same time to pr event peroneal tendon subluxation. Delayed identification of lacerated peroneal tendons still warrants surgical intervention when pain or functional limitation, such as an inversion deformity, exists. In chronic cases, especially more than 3 months after injury, a primary repair may be difficult. A side-by-side tenodesis or sliding graft to the adjacent peroneal tendon may be performed to repair any gap in the tendons. Flexor hallucis longus repair also has been de- scribed. 19 Tibialis Posterior Tendon The primary function of the tibialis posterior tendon (Fig. 5, C) is pow- erful inversion of the heel. It is most active during the heel rise portion of gait, when it locks the hindfoot in varus to stabilize the foot for the toe- off portion of the gait cycle. An acute laceration of this tendon should be repaired. 20 A flatfoot deformity has been noted in patients with untreated acute lacerations of the tibialis posterior tendon, resulting from loss of hindfoot inversion and the unopposed pull of the peroneus brevis tendon. 21 Identification of a tibialis posteri- or tendon laceration may not occur for months after injury. Primary repair is impossible, and a secondary flexible flatfoot deformity may have developed. In such cases, a flexor digitorum longus tendon may be used for reconstruction, similar to using a tibialis posterior tendon advancement for repair of an attritional rupture. A calcaneal osteotomy may be considered ifa secondary flexible flatfoot deformity has developed. If there is a fixed flatfoot deformity, appropriate nonsurgical treatment (eg, an ac- commodative orthotic) is indicated. Acute repair of a tibialis posterior tendon laceration can lead to a good result, as demonstrated by Floyd et al. 2 One patient had a good result after repair, whereas the second patient had a planovalgus foot deformity that developed in the 5 years following an untreated laceration. Goldner et al 21 reported on three patients with untreated acute lacerations; all reported weakness of the foot and subsequent loss of the arch with increased physical activity. Flexor Hallucis Longus Tendon The function of the flexor hallucis longus tendon (Figs. 5, C and 6) is plantar flexion of the great toe interphalangeal joint; it also serves as a dy- namic stabilizer of the metatarsophalangeal joint. Lacerations therefor e lead to decr eased great toe flexion strength. This may be less pronounced if the laceration is proximal to the knot of Henry because significantinterconnec- tions between the flexor hallucis longus and flexor digitorum longus tendons are usually present. When possible, primary surgical r e- pair of a lacerated flexor hallucis longus tendon should be attempted acutely. Gr eat car e should be taken not to overtighten the flexor hallucis longus; doing so can result in a claw toe deformity from excessive tension. In cases of delayed identification with weakness of gr eat toe flexion, marked retraction of the flexor hallucis longus may be present; thus, a primary repair is not possible. Tenodesis of the flexor hallucis longus to the flexor hallucis brevis near the metatarsophalangeal joint may be used. 7 However, little morbidity has been reported with flexor hallucis longus transfer for repair of chronic ruptures of the Achil- les tendon. In this case, the flexor hallucis longus is transected above the point wher e decussations of flexor hallucis longus to flexor digitorum longus fiber are usually present, at the knot of Henry. 12 An untreated laceration of the flex- or hallucis longus does not always lead to impaired function. Frenette and Jackson 7 reported on 10 patients identified as athletic. The laceration was not repaired in four patients, and none had subsequent disability. How- ever, laceration of both the flexor hallucis longus and flexor hallucis brevis tendons was thought to impair function, and repair was advocated in these cases. Repair was easier when lacerations were distal to the insertion of the flexor hallucis brevis tendon. Floyd et al 2 reported that 10 of 13 patients with lacerations of the flexor hallucis longus underwent primary repair; two others had secondary repair. Nine of the 12 patients treated with repair had active metatarsophalangeal joint flexion; 3 had none. Flexor Digitorum Longus Tendon The primary function of the flex- or digitorum longus tendon (Fig. 6) is flexion of the lesser toes. Laceration of this tendon is well tolerated b ecause of the presence of the flexor digitorum brevis muscles; they generally pr event significant toe deformity from occur - ring after isolated laceration of the flex- or digitorum longus. With a laceration pr oximal to the quadratus plantae, some residual strength of the flexor digitorum longus may persist via this muscle. The flexor digitorum longus is commonly used as a tendon transfer for chronic ruptured tibialis posterior tendons, with minimal long- term morbidity. If, during wound exploration following acute laceration of thefoot, the flexor digitorum longus is found to be lacerated, and if repair can be easily performed, repair should be done. Floyd et al 2 reported on five patients who underwent primary repair of the flexor digitorum longus tendon and one who had secondary repair. All had good active motion of the involved toes without deformity. De- layed repair would rarely be indicated because laceration of the tendon proximal or distal to the knot of Hen- ry is generally well tolerated. Extensor Hallucis Longus Tendon The main function of the extensor hallucis longus tendon (Fig. 5, B) is to extend the great toe, especially the interphalangeal joint. Laceration of Nerve and Tendon Lacerations About the Foot and Ankle 194 Journal of the American Academy of Orthopaedic Surgeons this tendon typically results in a flexed position of the great toe, which is generally well tolerated during shoe wear; however, it can lead to tripping because of weak dorsiflexion in the swing phase of gait as the toe sits in a plantarflexed position. Acute identification of a laceration of the extensor hallucis longus tendon requires treatment with appropriate tendon repair techniques to prevent deformity. 2,7,18 Although the maximum excursion has been reported as 2 to 4 cm, the tendon in fact may retract 5 cm or more, perhaps because of repetitive motion of the ankle. De- layed identification, especially of more than 3 months, usually precludes an end-to-end repair. A side- to-side tenodesis with the distal end of the extensor hallucis longus to the extensor hallucis brevis tendon, or to an adjacent extensor digitorum longus tendon, may be required. A few authors have noted good outcomes with repair of the extensor hallucis longus tendon. Floyd et al 2 noted that 11 of 13 patients who underwent repair of the lacerated extensor hallucis longus had active interphalangeal joint extension. Holmes 22 also noted functional impairment with laceration of the extensor hallucis longus and recommended both primary and delayed repair. Howev- er, some authors think that an unre- paired laceration of the extensor hallucis longus tendon is well tolerated. 17 Extensor Digitorum Longus An isolated laceration of the second through fourth extensor digitorum longus tendons (Fig. 5, B) usually does not cause major problems if the extensor digitorum brevis remains intact. An isolated laceration of the extensor digitorum longus to the fifth toe typically results in a flexed toe deformity because of the absence of the extensor digitorum brevis tendon. Acute repair of these subcutaneous tendons is easily achieved at the time o f repair of a dorsal foot laceration. Delayed recogni- tion of these injuries does not require repair provided the extensor digitorum brevis muscle is intact. Other- wise, a claw toe deformity, resulting from unopposed pull of the flexor tendons, can develop, with flexion of the metatarsophalangeal, proximal interphalangeal, and distal interphalangeal joints. However, patients with significant claw toe deformity after unidentified extensor digitorum longus laceration may require a delayed repair or reconstruction with tenodesis to the adjacent intact extensor tendon. In one study, seven of eight patients noted to have extensor digitorum longus lacerations underwent primary repair, with minimal sub- jective complaints at follow-up. 2 Wickes et al 1 reported that extensor digitorum longus lacerations are well tolerated because the adjacent tendons serve as an internal splint. Summary Acute lacerations in the foot and ankle region requir e careful physical ex- amination to identify underlying nerve and tendon injuries. Acute nerve and tendon injuries identified at the time of wound exploration should be repaired without undue tension with appropriate nerve and tendon repair techniques. Early tendon repair generally provides good results. Delayed tendon repair requir - ing tendon reconstruction, tendon transfers, or osteotomies to restore normal foot function is more chal- lenging. Delayed repair may be avoided with appropriate acute rec- ognition of the damaged structures. References 1. W ickes M, Harbison J, Patterson D: Ten- don injuries about the foot and ankle in children. AustNZJSurg1980;50:158-161. 2. Floyd DW, Heckman JD, Rockwood CA: Tendon lacerations in the foot. Foot Ankle 1983;4:8-14. 3. Hattrup SJ, Wood MB: Delayed neural reconstruction in the lower extremity: Results of interfascicular nerve grafting. Foot Ankle 1986;7:105-109. 4. Nunley JA, Gabel GT: Tibial nerve grafting for restoration of plantar sensation. Foot Ankle 1993;14:489-492. 5. Dellon AL, Mackinnon SE: Results of posterior tibial nerve grafting at the ankle. J Reconstr Microsurg 1991;7:81-83. 6. Kim J, Dellon AL: Neuromas of the calcaneal nerves. Foot Ankle Int 2001;22: 890-894. 7. Frenette J, Jackson D: Lacerations of the flexor hallucis longus in the young ath- lete. J Bone Joint S ur g Am 1977;59:673-676. 8. Johnson JE, Johnson KA, Unni KK: Per- sistent pain after excision of an interdigital neuroma. J Bone Joint Surg Am 1988; 70:651-657. 9. Wolfort SF, Dellon AL: Treatment of re- current neuroma of the interdigital nerve by implantation of the proximal nerve intomuscle in the arch of the foot. J Foot Ankle Surg 2001;40:404-410. 10. Dellon AL, Aszmann OC: Treatment of superficial and deep peroneal neuromas by resection and translocation of the nerves into the anterolateral compartment. Foot Ankle Int 1998;19:300-303. 11. Hintermann NB, Nigg B, Sommer C: Foot movement and tendon excursion: An in vitro study. Foot Ankle Int 1994;15: 386-395. 12. Armagan O, Shereff M: Tendon injury and repair, in Myerson M (ed): Foot and Ankle Disorders. Philadelphia, PA: WB Saunders, 2000, pp 942-971. 13. Wapner KL, Pavlock GS, Hecht PJ, Naselli F, Walther R: Repair of chronic Achilles tendon rupture with flexor hallucis longus tendon transfer. Foot Ankle 1993;14:443-449. 14. Frey C, Shereff M: Tendon injuries about the ankle in athletes. Clin Sports Med 1988;7:103-118. 15. Lipscomb P: Injuries of the extensor tendons in the distal part of the leg and in the ankle. J Bone Joint Surg Am 1955; 37:1206-1213. 16. Simonet W, Sim L: Boot-top tendon lac- David B. Thordarson, MD, and Christopher J. Shean, MD Vol 13, No 3, May/June 2005 195

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