Following injury, the initial healing of an injured tendon occurs over a 4-week period. It is important that the physician understand the stages of tendon healing when treating patients who have sustained a tendon injury. During the 1st week, the severed ends of the tendon become loosely joined by granulation tissue (71
). Throughout the 2nd week, paratenon vascularity increases, and during the 3rd week, collagen fibrils align longitudinally, which provides the healing tendon moderate tensile strength, and by the 4th week, edema has sufficiency diminished to allow guarded limited range of motion to begin (72
). At 4 weeks, the patient can be progressed from immobilization to a gradual return to full function as the tendon continues to heal (73
). Return to function is of extreme importance because continued immobilization increases the risk of tissue adhesions along the healing tendon as well as the risk of other comorbidities, such as deep vein thrombosis, which is a significant concern in patients who have been immobilized or have recently undergone surgery (74
The tibialis anterior is a strong dorsiflexor of the ankle and inverter of the subtalar and midtarsal joints. It becomes tendinous at the level of the distal tibial metaphysis just before becoming enclosed in a synovial sheath. The tendon passes under the superior and inferior retinacula and inserts along the medial aspect of the medial cuneiform and first metatarsal base.
Disruption of the tibialis anterior tendon is most commonly associated with open wound or laceration (76
). Closed ruptures of the tibialis anterior tendon are uncommon (77
). This is likely due to the fact that the tibialis anterior muscle functions primarily during the swing phase of gait and therefore functions in a predominately unloaded state (78
). As with other tendon ruptures, ruptures of the tibialis anterior more commonly present in male patients over the age of 45 (76
). Closed ruptures most often occur following minimal trauma in which unexpected plantarflexion eccentrically stresses a contracting tibialis anterior muscle. Commonly, this mechanism of injury is observed in soccer and tennis players (82
). Additionally, rupture of the tibialis anterior has been shown to have an association with chronic rupture of the posterior tibial tendon. Rupture of the tendon following steroid injection has also been demonstrated by a multitude of studies.
Patients suffering from tibialis anterior tendon rupture generally present reporting a weakness of the foot or ankle with associated swelling along the anteriomedial aspect of the foot and ankle (77
). Additionally, the patient may complain of a snapping sensation in the upper part of the arch and a sharp pain. On rare occasions, there may be a palpable gap in the tendon at the site of rupture (Fig. 100.6
). Ruptures of the anterior tibial tendon most commonly occur 1 to 2 cm proximal to the insertion along the medial aspect of the medial cuneiform (83
). This area has been demonstrated to have a limited blood supply. Disruption may also occur at the myotendinous junction, and several studies have demonstrated increased risk of tenosynovitis and subsequent rupture in the tibialis anterior tendon at the level of the inferior edge of the retinaculum due to the potential for abrasion as the tendon traverses the tunnel (84
). Often, there is retraction of the proximal stump, creating a bulbous enlargement above the anterior medial ankle.
The pain and weakness appear to be maximal within the first few hours of injury, but pain, swelling, and ecchymosis often resolve quickly and therefore may not be notable if there was delay in patient presentation (76
). Active dorsiflexion of the ankle is reduced in patients suffering tibialis anterior tendon rupture as compared with the contralateral side, and in these patients, dorsiflexion is accomplished via extensor hallucis and digitorum longus tendons. Clawing of the lesser digits may be observed due to the extensor substitution phenomenon (85
). With dorsiflexion, eversion of the foot may be noted due to the unopposed action of the peroneal musculature (86
). On examination of gait, the patient may be noted to walk with the heel everted during swing phase and with a mild slap of the foot upon heal contact. Additionally, the patient will demonstrate difficulty walking on heels. The patient may compensate for the loss of dorsiflexion during swing phase by adapting to a mild steppage gait (87
). Often, these patients’ symptoms mimic radiculopathy with dropfoot, and a thorough neuromuscular exam should be performed to confirm the presence of active function in the other muscles innervated by the deep and superficial branches of the peroneal nerve to rule out the possibility of a peripheral neuropathy (76
Electromyography studies can confirm the absence of motor neuropathy, and ultrasound can be utilized to confirm the diagnosis of tendon rupture (78
). Ruptures of the tibialis anterior may also be observed on CT, but these injuries are best visualized, as discussed previously, on sagittal plane MRI (Fig. 100.7
). On MRI, the tendon will appear discontinuous, with likely increased fluid signal noted along the distal course of the tendon sheath.
Conservative therapy is indicated in elderly patients and those that are considered less active. Additionally, in those injuries that involve avulsion of the tibialis anterior insertion in which displacement of the tendon is less than 5 mm,
conservative therapy can be indicated (90
). In the management of tibialis anterior tendon ruptures, conservative therapy consists of below-knee, non-weight-bearing cast immobilization with the foot in a dorsiflexed and inverted position for approximately 4 to 6 weeks (73
). In these patients, the tendon often becomes adhered more proximally so there is often an overall decrease in dorsiflexion and strength noted in subsequent physical exams. For these patients, an ankle-foot orthosis may be indicated if loss of dorsiflexion is significant (91
Figure 100.6 Active dorsiflexion in a patient with a ruptured tibialis anterior tendon. A: Injured foot demonstrating loss of normal tendon bulge with active dorsiflexion. B: Contralateral normal foot.
Figure 100.7 Magnetic resonance imaging of a ruptured tibialis anterior tendon demonstrating the disrupted tendon ends surrounded by fluid signal.
For the majority of patients, surgical repair is indicated. This is especially true for those patients who are younger or middle aged and in those patients who wish to maintain a higher level of physical activity. In those cases in which the injury is relatively recent, and when no significant retraction is present, end-toend repair can be performed (43
). In those cases in which the tendon has avulsed from the insertion at the medial cuneiform and there has been limited retraction of the proximal portion of the tendon, the tendon can be advanced and tenodesed to the medial cuneiform by way of a drill hole or tendon anchor. If a significant gap exists between tendon ends such that primary tendon repair cannot be accomplished, a tendon graft may be employed. Several grafts have been described in the literature, including free tendon graft from the extensor digitorum longus, a tendon lengthening utilizing a split portion of the proximal, intact tibialis anterior tendon (89
), or a free peroneus brevis graft (Fig. 100.8
). When harvesting peroneus brevis as a free graft, the proximal and distal stumps of the remaining peroneus brevis tendon are sutured to the peroneus longus tendon (93
). Another technique that has been described in the literature utilizes the extensor hallucis longus. In this procedure,
the proximal stump of the tibialis anterior tendon is sutured to the adjacent extensor hallucis longus, which is severed at the metatarsophalangeal joint. The extensor hallucis longus is then rerouted to the insertion of the tibialis anterior tendon (Fig. 100.9
). Reattachment of the extensor hallucis longus-proximal tibialis anterior complex can be accomplished through a drill hole in the medial cuneiform by suturing of the tendon back onto itself, by a suture passed through the sole of the foot and tied over a button, or by means of bone anchors, screw and washer fixation, or direct anastomosis to the anterior tibial tendon stump at the cuneiform (93
). The distal aspect of the remaining extensor hallucis longus can then be anastomosed to the extensor digitorum longus tendon to the second digit or sutured to the tendon of the extensor hallucis brevis (93
Figure 100.8 Peroneus brevis tendon graft used to repair a defect in the tibialis anterior tendon. Anterolateral (A) and medial (B) views of the procedure.
Figure 100.9 Reconstruction of the tibialis anterior (TA) tendon function. A: The TA, extensor hallucis longus (EHL), and extensor hallucis brevis (EHB) tendons. B: The proximal stump of the TA tendon is sutured to the EHL tendon. The transected EHL tendon is transferred to the medial cuneiform, and the distal EHL tendon is anastomosed to EHB tendon.
Following open repair, short-leg cast immobilization is typically preferred, with non-weight-bearing from approximately 4 to 6 weeks. If grafting techniques have been employed, then the patient is generally casted for a full 6 weeks. Once the case is removed, the patient may be transitioned to a CAM walker or other protective device for a variable period while physical therapy for range-of-motion and strengthening exercises is initiated.
EXTENSOR HALLUCIS LONGUS
It is rare to rupture the extensor hallucis tendon, but such injuries can occur when a sudden plantarflexory force is applied to the extending hallux. More commonly, injuries to the extensor hallucis longus tendon are due to lacerations of the tendon as it traverses the relatively unprotected dorsum of the foot. In fact, this tendon is the most commonly lacerated extensor in lawn mower injuries (Fig. 100.10
). Several studies have demonstrated that avulsion injuries at the base of the distal phalanx can occur, but these injuries are rare and are associated with sports that involve running and jumping (97
In the evaluation of extensor hallucis longus tendon injury, the clinical examination is of key importance. Patients who have sustained extensor hallucis longus injury will demonstrate weakness in extension of the great toe on the effected side. In some instances, the extensor hallucis brevis can generate some active motion of the hallux, and therefore, it is important to rule out motion at the first metatarsophalangeal joint that is due to brevis function. Additionally, the clinician may also notice the loss of the tented appearance of the skin at the at the first metatarsophalangeal joint as compared with the contralateral side, which suggests loss of extensor hood function. Furthermore, extensor tendon pathology is easily evaluated with the use of longitudinal ultrasonography (98
There is much discussion with regard to extensor hallucis longus repair. Some authors have advocated conservative therapy in the treatment of extensor hallucis longus pathology, citing the well-observed phenomenon that extensor tendons tend to heal spontaneously (100
). Other authors have suggested that surgical repair of the extensor hallucis longus tendon to provide for increased postinjury function should be attempted
). In these instances of surgical repair, an end-to-end anastomosis is usually possible when treated early (104
). In these instances, nonabsorbable suture is utilized to secure the repair site. When retraction has occurred, a tendon-passing instrument can be introduced proximally into the tendon sheath to draw the proximal stump distally. Patients suffering extensor tendon injury in which there has been a delay in repair or in those instances in which significant retraction has occurred often require tendon grafting to provide for surgical repair (105
). In these cases, a free graft from the extensor hallucis brevis may be utilized in either an end-to-end or side-to-side fashion (Fig. 100.11
Figure 100.10 A: A laceration caused by a piece of sheet metal was sutured without appreciating the lacerated extensor hallucis longus tendon. B: Interphalangeal joint extension is lacking, but the metatarsophalangeal joint will exhibit dorsiflexion due to the extensor hallucis brevis.
Figure 100.11 Repair of an extensor hallucis longus (EHL) laceration with an extensor hallucis brevis (EHB) graft. A: Creation of a turndown flap from the proximal stump of the EHL. B: EHB graft sutured to EHL. C: Side-to-side anastomosis of the flap to the graft. D: The graft and flap combination is secured to the distal stump of the EHL tendon.
Following surgical repair of extensor hallucis longus tendon injuries, the patient should be placed in a short-leg, non-weight-bearing cast with the ankle at 90 degrees and the hallux at neutral position or in slight dorsiflexion for approximately 4 weeks (58
). Following this immobilization, the patient should initiate progressive weight-bearing with strengthening exercises. In those cases in which the extensor hallucis has been completely avulsed from the base of the distal phalanx, surgical repair is generally indicated and post repair these patients are placed in a short-leg, non-weight-bearing case for approximately 6 weeks with the hallux in extension (Fig. 100.12
Figure 100.12 Radiograph demonstrating an avulsion of the base of the distal phalanx created by the extensor hallucis longus tendon.