The daily educational pearl – Superior peroneal retinaculum tear

33 yo woman present with a painful ankle after an eversion injury while playing
netball.

Superior peroneal retinaculum tear

- relatively rare injury after forced dorsiflexion + eversion injury of the ankle – common in ballet dancers, skiers

Anatomy:
The superior peroneal retinaculum is a fibrous structure that runs from the distal fibula to the posterolateral aspect of the calcaneus and maintains the peroneal tendons against the fibular groove.
It is formed as a confluence of superficial fascia, the sheath of peroneal tendons, and periosteum of distal fibula (about 2 cm proximal to fibula tip) formed from thickening of fascia that arises off the posterior margin of distal 1-2 cm of the fibula and runs posteriorly to blend with the Achilles tendon sheath.

Pathology:

- rupture of the retinaculum is followed by either anterior subluxation or dislocation of the tendons (complete peroneal tendons dislocation occurs in 0.5% injuries)

- commonly misdiagnosed as ankle sprain

- important to be diagnosed correctly and be immobilized and referred to Orthopaedics as they often need operative repair conservative treatment only has a 50% recurrence rate)
- chronic peroneal tendon dislocation is often associated with recurrent ankle sprains due to anterolateral instability of the ankle, which lead to incompetency of peroneal retinaculum, and subsequent tendon subluxation and degenerative changes and longitudinal splitting in the peroneus brevis tendon

Clinical exam:
- tenderness posterior to the lateral malleolus;
- subluxation of the peroneal tendons may be provoked by having the patient dorsiflex the foot from a position of dorsiflexion and eversion
- prominence of the tendon w/ dorsiflexion and internal rotation

Xrays:
- need to assess mortise view of the ankle
- look for shell-like avulsion fracture of the lateral malleolus which indicates disruption of the peroneal retinaculum (50% of cases)

MRI is of greatest value in evaluating soft tissue structures.

Non Operative treatment:
- ensure that the tendons are reduced before immobilization

- place in plantar flexion in slightly inverted below knee cast for 6 weeks

- all should have follow-up in the Orthopaedics / Trauma clinic, not with their GP

 

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