Repair of Dislocating Peroneal Tendons: Perspective 2

Florian Nickisch

Scott B. Shawen

Robert B. Anderson

ANATOMY

The peroneus longus and brevis muscles are the two major structures within the lateral compartment of the leg, both arising from the proximal fibula (FIG 1A).
Both structures become tendinous before crossing the ankle joint and remain in a common sheath. As they course distally, the tendon of the peroneus brevis lies against the posterior surface of the distal fibula, anterior and medial to the tendon of the peroneus longus.
Distal to the fibula, each tendon enters a distinct tendon sheath, separated by the peroneal tubercle.
Posterior to the distal fibula, both tendons are stabilized in the retrofibular groove by the superior peroneal retinaculum (SPR) (FIG 1B).

The posterior surface of the distal fibula is covered by a layer of fibrocartilage to allow smooth gliding of the peroneal tendons. The depth and width of the retrofibular (peroneal) groove is highly variable. A definite groove is present in about 80%. In the remaining cases, the posterior surface of the fibula is flat or convex.⁵ A fibrocartilage rim on the lateral border of the fibula that adds an additional 2 to 4 mm to the depth of the sulcus is often present.

FIG 1 • A. Lateral view of the ankle showing the peroneal tendons as well as the superior and inferior peroneal retinacula. Note the vertical orientation of a portion of the SPR that corresponds to the orientation of the calcaneofibular ligament. B. Superior view of the ankle region shows the relationship of the fibular groove, SPR, peroneal tendons, and cartilaginous ridge. (A: From Davis WH, Sobel M, Deland J, et al. The superior peroneal retinaculum: an anatomic study. Foot Ankle Int 1994;15:273; B: From Coughlin MJ, Mann RA, eds. Surgery of the Foot and Ankle, ed 7. St. Louis: Mosby, 1999:819.)

The SPR, the primary restraint to peroneal instability, is composed of a band of the deep fascia that is continuous with the periosteum of the distal fibula but does not attach to the fibrocartilage rim or the posterolateral edge of the bone.¹¹ It is extremely variable in width and thickness, and five distinct insertional patterns have been described, the most common being a band to both the Achilles tendon and the calcaneus.³
The fiber orientation of the SPR is parallel to those of the calcaneofibular ligament, and therefore inversion injuries of the calcaneofibular ligament may also cause injury to the SPR.⁶,⁹

PATHOGENESIS

Acute subluxation or dislocation of the peroneal tendons usually occurs while the foot is forcefully dorsiflexed with the peroneal muscles strongly contracted; it commonly occurs during a forward fall in Alpine skiing or in springboard diving.⁸
Resisted plantarflexion and inversion while the peroneals contract may also cause subluxation or dislocation of the peroneal tendons, and in this case, it is commonly associated with lateral instability of the ankle.
Peroneal dislocation may also occur as a sequela to severe calcaneal fractures with lateral displacement of the calcaneus.⁵,⁷
Peroneal dislocations can be classified into three grades depending on the pathoanatomy of the injury⁴:
- Grade I: SPR stripped off fibula; peroneus longus dislocated anteriorly
- Grade II: fibrous rim avulsed from posterolateral aspect of fibula along with SPR; peroneus longus dislocated anteriorly
- Grade III: bony rim avulsion fracture attached to SPR with anterior dislocation of peroneus longus
As a result of subluxation or dislocation, inherent injuries to the tendons can occur. Depending on the location of the tendon injury, they are divided into zones I, II, and III.
- Zone I injuries are defined as those involving the fibular groove and most often affect the peroneus brevis tendon. As the tendons sublux in the groove, the brevis is forced onto the sharp posterolateral bony ridge of the distal fibula, causing a longitudinal split in the tendon from the strain of a 45-degree course change as well as compression by the overlying longus tendon.
- Zone II injuries are located between the tip of the fibula and the cuboid tunnel.
- Zone III injuries are located in the cuboid tunnel and primarily involve the peroneus longus tendon and possibly a painful os peroneum.

NATURAL HISTORY

If diagnosed early, in acute peroneal dislocation, the tendons can be manually reduced and held in a reduced position for a 4- to 6-week period of immobilization. In this situation, functional rehabilitation leads to maintenance of tendon reduction and complete recovery in about 50% of cases.¹
With delayed diagnosis and treatment, recurrent subluxation and chronic dislocation are common and may lead to degeneration and tearing of the peroneal tendons.¹⁰

PATIENT HISTORY AND PHYSICAL FINDINGS

Most patients present well beyond the acute phase complaining of vague posterolateral ankle pain that radiates proximally with or without a popping sensation during activity.¹²
There may be a history of forced dorsiflexion trauma associated with a pop on the lateral aspect of the ankle.
Often, a history of an inversion-supination sprain and possible lateral ankle instability is reported.⁹
On physical examination, peroneal tendinopathy is characterized as fullness along the tendons with diffuse tenderness. Localized tenderness over the posterior ridge of the fibula should raise suspicion for progression of the injury to a peroneal tendon split tear.
Pain may be elicited with inversion stretch or active resisted eversion.
Tendon subluxation typically presents as snapping or popping and pain with eversion against resistance. The peroneal tunnel compression test consists of having the patient perform this motion while palpating the posterior border of the fibula. Circumduction of the ankle may demonstrate dislocation of the tendons with eversion and dorsiflexion and spontaneous relocation with plantarflexion and inversion (FIG 2).

FIG 2 • Dislocated peroneal tendons during resisted eversion.
Chronic dislocation of the tendons is characterized by a palpable ridge over the lateral distal fibula often associated with chronic swelling.
Eversion strength may be limited by pain. Significant weakness of active eversion without much pain should raise suspicion for a complete tear of the peroneal tendons.
A complete examination of the ankle should also include evaluation of associated injuries, ruling out differential diagnoses. This includes (but is not limited to) the following:
- Lateral ankle instability: history of frequent sprains, cavovarus foot, increased laxity with anterior drawer or inversion stress test compared to the contralateral side
- High ankle sprain (syndesmotic sprain): pain over anterior ankle syndesmosis, pain with provocative maneuvers (calf squeeze test, external rotation stress test)
- Painful os trigonum or posterior talar process fracture: pain with forced plantarflexion, pain with resisted plantarflexion of the great toe