When considering tendon disorders of the foot and ankle, the Achilles and posterior tibial tendons come to mind first. However, significant pathology can and does occur to the peroneal tendons as well. Indeed, peroneal tendinopathies present a diversity of unique features, which may occur in isolation or in combination. This array of tendinopathies includes paratendinitis, tendinosis, and both acute and chronic dislocation. These may be associated with a hypertrophic peroneal tubercle or possibly with the os peroneum.

The peroneal muscles both originate in the leg with the longus originating more proximally at the intersection of the upper two-thirds of the fibula, the anterior and intermuscular septa, and the deep fascia. The brevis originates at the intersection of the lower two-thirds of the fibula and the anterior and posterior intermuscular septa. The brevis lies deep to the longus in the retromalleolar groove of the fibula, and its muscle belly is usually the lower lying of the two. The peroneus longus courses distally to lie inferior to the peroneal tubercle, passes through the cuboid groove, and inserts on the base of the first metatarsal and medial cuneiform. Distal to the lateral malleolus, the peroneus brevis lies superior to the longus and inserts on the dorsal lateral aspect of the fifth metatarsal base. Accessory peroneal musculature has also been described, including the peroneus quartus.¹

The retromalleolar groove offers stability to the peroneal tendons in keeping them posterior to the fibula. However, variable depths of the retromalleolar groove have been described, and some reports have portrayed it as convex in some instances.² In addition to the retromalleolar groove, the superior and inferior peroneal retinacula provide significant restraint of the peroneal tendons. The superior peroneal retinaculum (SPR) offers the greater restraint of the two; anatomical variations have been described.³ The calcaneal fibular ligament and lateral calcaneal wall complete a fibro-osseous tunnel through which the peroneal tendons pass, contained in their common synovial sheath. The sheath then bifurcates as the tendons approach the interior peroneal retinaculum and are further separated by the peroneal tubercle.

Contributing Etiologic Factors

Acute traumatic events and chronic intermittent injuries have both been described as common etiologies of peroneal tendinopathy.⁴ Both of these mechanisms can lead to laxity of the SPR with consequent instability of the peroneal tendons. Chronic pressure from the longus may compress the brevis against the posterior fibular ridge, predisposing the brevis to injury, especially when the internal cubic content is increased, as in the presence of an accessory muscle. Distally, the peroneal tubercle and os peroneum can be involved in peroneal pathology. Although a zone of hypovascularity has been proposed as an etiologic agent of peroneal tendon injury, an anatomical study could not confirm the existence of such a zone.⁵

Pain in and about the region of the peroneal tendons may have a variety of causes. A differential diagnosis of lateral foot and ankle pain must include arthritis, sural neuritis, osteochondral lesions of the talus, and fracture of the lateral malleolus, talus, calcaneus, and fifth metatarsal. Chronic lateral ankle and/or subtalar instability may cause symptoms in this region and may be seen in conjunction with peroneal tendinopathy.

Paratendinitis and Tendinosis

The course of the peroneus longus tendon includes three turns (lateral malleolus, peroneal tubercle, and os peroneum/cuboid), and the brevis undergoes two turns (lateral malleolus and peroneal tubercle). With this in mind, it is easy to see why paratendinitis develops quite easily secondary to pressure against the osseous structures and overlying retinacular restraints. Overuse injury from chronic intermittent trauma is the leading cause.⁶ Less commonly, a particular traumatic event may play a role.⁶

Signs and symptoms of peroneal paratendinitis include edema and pain localized to palpation over the tendons. The condition is aggravated by activity, and symptoms may be reproduced by asking the patient to evert the foot against resistance or by passive inversion and plantar flexion. Treatment includes rest, ice, NSAIDs, and physical therapy. Immobilization in a short leg walking cast/boot may be used for a short period of time. Corticosteroid injection is controversial. If symptoms continue after an appropriate treatment period using the above measures, diagnostic imaging and/or surgical exploration and synovectomy are indicated. Recently, Van Dijk reported success using endoscopy (tenoscopy) in treating peroneal synovitis.⁷ Although seen in isolation, paratendinitis is more commonly seen in conjunction with other pathologies such as peroneal dislocation or tendinosis.

Tendinosis of the peroneus brevis and longus is not uncommon. Longitudinal split tears, fraying, and tendon thickening at the site of repair of old injuries are the most frequent findings. Brevis pathology is seen primarily at the retromalleolar groove area, often presenting as a longitudinal tear. Less frequently, insertional pain at the fifth metatarsal styloid process may be seen. Signs and symptoms are similar to, but more pronounced than, simple paratendinitis, especially with split tears of the tendon. Compressing the brevis against the fibula will reproduce pain.⁸ The patient may or may not have a history of injury. An association with chronic lateral ankle ligament laxity has been reported.⁹ Retromalleolar tendon tears may be associated with peroneal subluxation. MRI and ultrasound will usually confirm the presence of a tear. Major et al have reported the “chevron sign” on T2-weighted MR images to be highly suspicious for brevis tear.¹⁰ The longus can often be seen interposing itself within the tear as it compresses the brevis anteriorly against the posterior ridge of the lateral malleolus. Although peroneus longus tendinosis, including a tear, may be seen at a similar location, it is more frequently seen distally at the peroneal tubercle or lateral cuboid area. Cavovarus foot type and associated longus tears have been reported.11

If diagnosed early, peroneal tendinosis/tears may be treated with four to eight weeks of immobilization and limited weight-bearing followed by physical therapy. The majority of peroneal tendon split tears will likely require surgical repair of any associated subluxation. However, smaller (1 to 2 cm) bucket handle-type tears or tendon thickening may require simple debridement. Larger longitudinal split tears require both debridement and surgical repair. If flattening of the tendon exists, tubularization of the tendon is indicated.¹²

Peroneal Dislocation

Although thought of primarily as a skiing injury, peroneal tendon dislocation was first described in a ballet dancer by Monteggia in 1803.¹³ A variety of sports have actually been implicated, including wrestling, football, tennis, basketball, and running. Basically, any activity that may result in a sudden forceful reflex contraction of the peroneal musculature can result in acute peroneal tendon dislocation. Various positions of the foot at the time of injury have been described and theorized.¹⁴ Chronic dislocation may be a result of a prior injury or may be insidious in onset. Congenital dislocation of the peroneal tendons may also occur.

Acute peroneal dislocation must be ruled out in any patient sustaining a lateral ankle injury. Often the diagnosis can be made only after edema reduction. The peroneus longus is the most common tendon involved. It is important to note that the SPR is not actually torn with this injury; rather, a “false pouch” forms over the fibula by a lifting of the periosteum where the SPR intersects it. Eckert and Davis have eloquently described this and have also provided a classification of the acute injury, which may include an elevation of the posterior fibrous lip of the fibula, as well as a small fibular avulsion fracture (Figure 2).¹⁵

A period of nonweight-bearing immobilization may be tried with grade I injuries with the foot in slight plantar flexion. Diagnostic imaging must confirm the reduction of the peroneal tendons before immobilization is undertaken. Otherwise, surgical repair is the treatment of choice, especially in active individuals.¹⁴ The SPR is incised, the peroneal tendon(s) are relocated, the false pouch is eliminated, and the fracture fragment, if present, repaired.

Patients with chronic peroneal dislocation will usually present with a history of “snapping” or “popping” about the lateral ankle. As stated earlier, a history of trauma may or may not be a factor. Symptoms of lateral instability may also be reported. Often this condition is asymptomatic, in which case continued observation is indicated. However, if pain and/or disability exist, surgery is the treatment of choice.¹⁴ A multitude of surgical procedures have been described for chronic dislocation. These range from delayed primary repair of the SPR, or recreation of it with a soft tissue sling, to groove-deepening procedures with a fibular sliding graft or osteoperiosteal flap. If delayed primary repair is not possible, a worthwhile alternative is the Jones procedure, which uses a slip of the Achilles tendon to “recreate” the SPR.¹⁶ Groove deepening is accomplished by raising an osteoperiosteal flap and removing cancellous bone to deepen the groove, followed by flap replacement (Figure 3).¹⁷ Although fibular sliding grafts also deepen the groove, this procedure exposes the tendons to rough, bleeding cancellous bone, which could predispose them to injury.

Lateral Calcaneus and Cuboid Pain

If pain is more distal at the lateral calcaneus, hypertrophy of the lateral calcaneal tubercle may be present. This may result in tendinosis or paratendinitis of the peroneal tendons, most commonly the peroneus longus. Occasionally, the tendon may be completely engulfed. Pain localized to palpation over the area is present, often aggravated by inversion. Axial calcaneal radiographs and CT scans are quite helpful in evaluating the tubercle. Although symptomatic treatment, including a short period of immobilization, may provide relief, reduction of the tubercle and repair of any associated tendon pathology may be necessary. Occasionally, it may be necessary to anastomose the longus to the brevis.

Finally, the most distal peroneal tendon pathology is over the lateral cuboid, involving the peroneus longus and the os peroneum. The os peroneum is a fibrocartilaginous sesamoid found within the peroneus longus tendon. It is ossified in about 20% of patients and may be multipartite. Acute pain over the cuboid area following trauma, especially inversion injuries, may be seen. Alternatively, chronic pain may stem from an old injury or from repeated inversion stress to this area. Oblique radiographs of the foot best define an ossified os peroneum, and MR imaging is helpful in evaluating the condition of the peroneus longus.⁶ Osseous findings may include fracture of the os peroneum, with or without displacement, or separation of a partite sesamoid. Partial or complete rupture of the peroneus longus may be seen. Diastasis of the os peroneum with superior migration of the proximal fragment is highly suspicious of rupture or significant attrition of the peroneus longus. In cases of non- or minimally displaced fractures that are diagnosed early, cast immobilization may be beneficial. However, if significant displacement exists or significant peroneal longus injury is present, surgery is often undertaken. Likewise, chronic cases are less likely to respond to nonoperative care.

Surgery consists of excision of the os peroneum and repair of the longus. Transfer of the longus to the brevis should be considered if the longus is judged to be beyond repair.

Summary

Numerous peroneal tendon disorders exist. These may occur in isolation or in combination. Determining the location of symptoms (retromalleolar, lateral calcaneal, or lateral cuboid) is beneficial in making a differential diagnosis and determining treatment. Diagnostic imaging is quite helpful in determining the degree of injury to the tendon(s). Newer techniques, including tenoscopy, promise to dramatically improve treatment of these disorders.

References

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