The traumatic dislocation of the peroneal tendons of a Real Madrid forward in November last year, the surgical repair and his speculated return to sport have been reported extensively in the media and followed by Spring on Foot at the ISEH. Whilst ankle soft tissue inversion trauma most commonly injures the lateral ligament complex, problems affecting the peroneal tendons, which course behind the outer aspect of the ankle, are less well known, as Mr Michael Oddy, ISEH Consultant Trauma & Orthopaedic Surgeon reports:

"The two peroneal tendons, longus and brevis, arise as muscles in the outer aspect of the leg and are restrained behind the outer fibula bone in a tunnel formed by the shape of a bony groove, a restraining ridge of cartilage and the peroneal retinaculum ligaments. The brevis tendon continues along the side of the heel bone to join the base of the fifth metatarsal and acts to evert or twist the foot upwards and outwards. The longus, which courses under the foot to join the base of the first metatarsal and medial cuneiform bones, causes pronation of the foot twisting it down and outwards. They also both act as dynamic muscle restraints against spraining twisting forces and thereby add stability to the ankle.

The peroneal tendons can undergo the same pathological processes that others such as the better known Achilles’ tendon suffer: intrinsic painful tendon damage or tendinopathy and tendon sheath inflammation or synovitis.  Acute injuries are generally either due to rupture or dislocation leading to the peroneal tendons lying in front of the fibula. There can similarly follow a pattern of more chronic instability of the tendons which over time can lead to further structural damage. The peroneal tendons are more at risk of both acute and chronic damage with a foot which is higher arched and associated with a heel bone in varus, being tilted towards the midline of the body which can be more susceptible to recurrent sprains.

The mechanism of injury causing peroneal tendon dislocation tends to be with a foot positioned in upward dorsiflexion and inward tilting inversion whilst the tendons are contracting with force. This can occur in sports with forced or high speed twisting such as soccer, rugby, basketball or racket sports. Clinical features are similar to an ankle sprain with pain, swelling and bruising over the outer aspect of the ankle, possibly with an initial popping sound.

A plain X-ray is useful initially to exclude an ankle malleolar fracture and can sometimes show a flake of bone next to the fibula where the peroneal retinaculum has caused an avulsion fracture. More sensitive imaging such as an Ultrasound or Magnetic Resonance Imaging (MRI) scan is essential in confirming the injury and detailing its anatomy. In the acute setting, the peroneal retinaculum can tear within its ligamentous substance, avulse from its bony attachment on the fibula or with its bony attachment as an avulsion fracture. Recurrent peroneal tendon instability can also be associated with bony anatomical features of a shallow fibula groove which can also be delineated with a Computerised Tomography (CT) scan.

Non-operative treatment of peroneal tendon dislocation can really only be considered for a first time presenting new injury where the tendons can be re-located by positioning the ankle in downward plantar-flexion and inversion inward tilting in a plaster cast for four to six weeks to restrain their position behind the fibula to allow the retinaculum to heal. Thereafter protection with a brace or taping combined with a physical therapy programme can be successful in a proportion of cases. The role of surgery is to prevent the physical instability with recurrent tendon dislocation which can otherwise lead to progressive tendon structural deterioration as well as the impaired biomechanical effects on the ankle function.

In the acute setting, surgical treatment involves either a direct repair of the retinaculum or its re-attachment to the fibula which often requires small bone anchors to snug the ligament back into position onto the bone. Rehabilitation usually requires a two to four week period in a plaster cast followed by progressive weaning from a pneumatic walker boot or ankle brace with a return to full contact sports being rare before three to four months post surgery. Chronic instability commonly requires the depth of the fibula groove to be deepened either by elevating a strip of the edge of the fibula as a bony lip or by increasing the concavity of the fibula from within by drilling out its centre and tamping the surface in like the collapse of a sink-hole. Similarly, assessing for a varus or inward tilting heel bone position sometimes requires a calcaneal heel bone osteotomy to re-align the axis of the ankle to prevent a recurrent inward spraining force or at least the use of functional insole orthoses to lift the outer side of the foot.

The peroneal tendons are an often overlooked cause of outside lateral ankle sports injury being overshadowed by fractures, lateral ligament sprains and even Achilles’ tendon pain; yet they can present one of the greatest challenges due to the range of injury pathology, the spectrum of time to presentation and also their relationship to ankle and hindfoot alignment".