Peroneus brevis tear

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Peroneus brevis tendon tears are acute or chronic, and may be asymptomatic or associated with lateral ankle pain and/or instability. They commonly occur at the level of the retromalleolar groove.

Epidemiology

Small published case series include patients ranging from 13 to 65 years of age . Cadaveric studies have shown a prevalence of ~25% (range 11-37%) .

Injuries of the peroneus brevis are more common than those of peroneus longus . Tears of both peroneus tendons simultaneously are less common .

Clinical presentation

Small studies suggest that ~50% of peroneus brevis tears diagnosed by imaging are asymptomatic .

Most symptomatic tears (~60%) occur following a reported trauma, most often a lateral ankle sprain (60%) . However, injury may also occur slowly as a degenerative process without isolated episode .

Symptoms can include pain, swelling, and erythema at the lateral ankle which worsens with activity. There is a suspected high rate of peroneal tendon injury in those with chronic ankle instability. There is also an association with systemic conditions e.g. rheumatoid arthritis, diabetes, or local steroid injection .

Pathology

The peroneus brevis tendon is positioned between the peroneus longus tendon and the retromalleolar groove of the fibula, likely predisposing it to injury from mechanical wear, particularly in dorsiflexion.

Traumatic episodes and tendon dislocation can lead to degeneration. Other anatomical variants can predispose to injury:

As the brevis tear develops, the longus tendon moves forward into the space which further antagonises the injury and prevents healing.

One surgical review stated 40% of those undergoing brevis repair had longus tears at surgery, which are likely secondary to degenerative change following migration .

Radiographic features

Ultrasound

Ultrasound has a high sensitivity (100%) and specificity (85%) for identifying tendon tears :

  • partial tear: discontinuity and partial retraction of affected tendon fibers with fluid in the sheath, normal appearance proximal and distal to the tear
  • longitudinal fissures: two "hemi-tendon" appearance at the apex of the malleolus affecting the deep fibers first
  • full-thickness: typical appearance of a rupture
MRI

MRI has variable reported accuracy for clinically or surgically confirmed injury, with positive predictive value as low as 48% and sensitivity/specificity as high as 83% and 75%, respectively .

MR findings that suggest peroneus brevis tear include:

  • morphologic abnormality of peroneus brevis tendon :
    • complete discontinuity: should be confirmed on at least two planes
    • C-shape or "boomerang" appearance: tendon enveloping adjacent peroneus longus tendon
    • focal tendon caliber change: should be confirmed on at least two planes
    • separation into discrete subtendons
  • abnormal tendon positioning: anterior dislocation or subluxation most common
  • +/- tenosynovitis: most (54%) peroneus brevis tears are associated with fluid signal the tendon sheath, which should be confirmed on multiple planes

Treatment and prognosis

Management of symptomatic peroneal tendon tears is initially non-operative, often using anti-inflammatories and rest/immobilization .

Operative treatment may be considered in those with persistent symptoms or for those with ankle instability with debridement or if required tenodesis to the adjacent peroneus longus tendon.

Differential diagnosis

  • normal variant bifurcated peroneus brevis tendon: differentiate by identifying muscle fibers attaching to the tendon slips
  • peroneus quartus tendon insertion simulating a tear on imaging

See also