The peroneus longus and brevis arise from the posterolateral surface of the fibula and the fascia of their compartment. They run over the posterior surface of the fibular tip, where there is an adaptive fibrocartilage on the fibula, with brevis next to the bone. The tendons are kept in place by the presence of a shallow groove on the posterior fibula, the superior peroneal retinaculum (SPR) which tethers the tendons to the fibula, and a fibrocatilaginous lip, which deepens the groove where it meets the retinaculum.
On the lateral surface of the calcaneum the tendons run superficial to the calcaneofibular(CFL) and lateral talocalcaneal ligaments. Tears of the CFL create a communication between the peroneal tendon sheath and the ankle – the ability of contrast to pass from one to the other is the basis of peroneal tendonography as a method of diagnosing ankle ligament rupture. Distal to the CFL the tendons run superior (brevis) and inferior (longus) to the peroneal trochlea on the lateral calcaneal wall, retained by the inferior peroneal retinaculum (IPR). Here the sheath is thickened and stenosing tenosynovitis may occur. The peroneus brevis is inserted into the inferolateral part of the tubercle of the 5 th metatarsal. The peroneus longus turns through a sharp angle to enter a fibro-osseous tunnel on the underside of the cuboid, where there is usually an accessory ossicle, the os perineum. The longus tendon inserts into the plantar surface of the first metatarsal.
The tendons receive blood supply from vinculae which reach them from posteriorly in the calf and usually link the two tendons. Early studies found no evidence of avascular zones(Sobel 1992), but more recent work (Petersen et al 2000) suggests relatively avascular zones in brevis at the level of the SPR, and in longus at the IPR and the sharp turn to enter the cuboid tunnel. These are the commonest levels for tears.
Both tendons are plantar flexors of the ankle and evertors of the subtalar and midtarsal joints. As evertors their main opponent is tibialis posterior. In addition the peroneus longus plantarflexes the first metatarsal in opposition to tibialis anterior. Relative sparing of peroneus longus compared to tibialis anterior is probably relevant to the pathogenesis of the stiff plantarflexed first metatarsal in pes cavus. A relatively strong tibialis posterior opposed to a weaker peroneus brevis probably contributes to the development of the hindfoot varus component of cavovarus.
The incidence and prevalence of peroneal tendon problems has not been determined. In Blackburn we see 5-10 new patients a year in a population of 260,000 and 1300 new referrals, implying an incidence of the order of 30/million/year. However, this is a general foot and ankle practice without a large sports medicine component and some sporting injuries may be seen by club physiotherapists or surgeons elsewhere.
There are two main types of problems, which are related:
- Tears and tendonopathy, and the related “painful os perineum syndrome”
- Instability of the tendons at the level of the superior peroneal retinaculum
Peroneal tendon tears
Peroneus brevis tears are
- about three times commoner than those of peroneus longus
- often associated with laxity of the SPR
- also associated with a low musculotendonous junction or an accessory peroneus quartus muscle – these may make the tendon stiffer or stretch the SPR
- commonly associated with lateral ligament injuries of the ankle – about 50% also have ankle instability; peroneal tenosynovitis, tears and instability may be present in up to 70% of patients with ankle instability
- usually longitudinal, partial tears – only about 10% are complete tears
- normally centred on the level of the superior peroneal retinaculum
- probably caused by compression of the brevis tendon between the longus tendon and the fibula, especially if the tendon can be squeezed over the edge of the groove because the retinaculum is lax, or if there is a sharp ridge at the edge of the groove
Peroneus longus tears are:
- Strongly associated with pes cavus – 80% in the study by Brandes and Smith (2000) – the plantarflexed first ray may increase the stresses in the tendon
- Usually at the level of the inferior peroneal retinaculum or the point where the tendon turns under the cuboid
- Usually partial longitudinal tears
About 10% of patients have combined tears of both tendons.
Pain at the point where the peroneus longus tendon turns into the cuboid groove is sometimes known as “painful os peroneum syndrome” (POPS) (Sobel et al 1994). This may be due to:
- Acute stress fracture of the os perineum
- Chronic fracture of the os perineum, with or without peroneus longus tendonopathy or tear
- Peroneal tendonopathy or tear at the level of the inferior peroneal retinaculum, often of a stenosing type
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Transverse section through peroneal tendons at level of superior retinaculum
- R - retinaculum
- L - fibrous lip of groove
- B - peroneus brevis
- L - peroneus longus
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Development of a peroneus brevis tear
The retinaculum is lax. Peroneus brevis slips laterally, impinges on the lip and a longitudinal tear forms (arrow)
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Peroneus brevis tear - MR
- B - two parts of peroneus brevis
- L - peroneus longus
- F - fluid in paratenon
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Peroneal tendon instability
Tearing or detachment of the SPR may allow the tendons to prolapse laterally, with pain, swelling and weakness of eversion. The brevis tendon is often torn – it is thought it may be lacerated by the sharp edge of the fibular groove. A shallow fibular groove is commoner in patients with instability. There is a strong association with ankle instability.
Eckert and Davis (1976) described three types of retinacular deficiency:
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type 1 – the retinaculum is detached from the lateral aspect of the peroneal groove |
type 2 – the retinaculum is elevated from the lateral edge of the groove in continuity with the periosteum of the lateral malleolus, producing a lesion similar to the Bankhart lesion in the shoulder. In our limited experience this is by far the commonest finding. |
type 3 – similar to type 2 except that a flake of bone is elevated with the soft tissue sleeve – this may show on an oblique Xray of the acutely injured ankle and allows bony fixation |
Clinical features
Patients with peroneal tendon problems usually present with pain, swelling and sometimes clicking or popping on the posteromedial aspect of the ankle or the lateral aspect of the hindfoot. Those with longus tears may localise the pain to the entry to the cuboid tunnel (POPS) or occasionally under the midfoot. There may be a history of an ankle “sprain”, especially with brevis tears.
Examination will demonstrate tenderness over the tendon – typically behind the malleolus with brevis tears and at the entry to the cuboid tunnel or at the IPR with longus tears. Getting the patient to actively rotate the foot may produce obvious tendon prolapse onto the lateral aspect of the malleolus. With lesser degrees of instability there may be no obvious prolapse but the brevis tendon may be felt to slide laterally, usually in eversion. A brevis tendon which becomes prominent laterally often has a longitudinal tear.
Resisted contraction of each tendon may reproduce thepatient’s pain. Active movement may produce a grating or creaking sensation over the tendons.
There may be varying amounts of synovial swelling. Pes cavus suggests a longus tear.
Imaging
Plain radiography is not usually very helpful. Oblique views of an acutely injured ankle may show an avulsion fragment lying lateral to the lateral malleolus – this represents a flake of bone avulsed with the SPR.
Both ultrasound and MR can show the tendons well and demonstrate tears. Both modalities can assess the ankle ligaments. MR also enables assessment of the depth of the peroneal groove and will demonstrate intra-articular problems in the ankle such as osteochondral injuries. Tendonopathy shows as enlargement, high signal or a “flame” shape to the tendon. Tears show as multipart or chevron-shaped tendons, and part or all of the tendon may be subluxed laterally.
There have been no comparative studies of the accuracy or utility of ultrasound and MR.
Non-surgical treatment
Simple analgesics or NSAIDs may be used for pain and synovitis. Physical modalities such as ice, ultrasound or interferential therapy may be used to settle acute symptoms. An ankle brace may be useful in the acute situation or occasionally pallliatively. Patients with flexible cavus deformities and a longus tear may benefit from orthotics.
There have been no reports, other than anecdotal, of the outcome or usefulness of non-surgical treatment. We would generally try non-surgical treatment for patients without overt instability, but would generally advise the correction of SPR instability as primary treatment.
Surgery
Peroneal tendon tears
Most authors have reported debridement and suture of longitudinal tears, with tubulisation of the remaining tendon. Krause et al (1998) recommended repair for tears of peroneus brevis where more than 50% of the tendon was intact, but where there was less than 50% tendon remaining they excised the abnormal segment and attached the ends to the peroneus longus.
Where there is a complete tear with discontinuity of the tendon ends repair without tension is usually impossible except in the acute setting, and the ends of the tendon should be sutured to the adjacent tendon. Obviously, complete tears of both tendons preclude this, and a tendon transfer is required – flexor digitorum longus transfer has been reported in two patients by Borton et al (1998)
Peroneus longus tears at the os peroneum may be debrided and repaired. A fragmented os peroneum is usually excised. Occasionally a defect in the tendon needs to be bridged with a tendon graft (plantaris).
Peroneus brevis tears often have associated SPR laxity and this should be repaired at the same time as the tendon (see below). Stenosing tenosynovitis of peroneus longus may require release of the IPR and/or reduction of the peroneal tubercle.
Van Dijk (1998) described endoscopic debridement and suture of the peroneal tendons. There have been no comparative studies with open surgery.
Superior peroneal retinaculum laxity
Many different types of operation have been described to correct SPR laxity:
- Sliding bone graft to the lateral edge of the groove
- Deepening of the groove by removing underlying cancellous bone and depressing the cortical floor of the groove
- Bankhart-type repair of the type-2 retinacular lesion
- Rotational osteotomy of the distal fibula
- Various forms of retinacular tightening or re-insertion
Obviously, these are not all mutually exclusive. Our standard stabilisation procedure is a Bankhart-type repair. The retinaculum is opened longitudinally, close to where the attachment to the fibular groove should be. The bare area on the lateral malleolus is freshened and one or two suture anchors inserted close to the edge of the groove. The avulsed tissue sleeve is reattached to these and the retinaculum plicated, usually also onto the suture anchor(s). If the groove is shallow, a posterior trapdoor is elevated and cancellous bone removed from the posterior part of the lateral malleolus to allow the floor of the groove to be lowered and the edges of the trapdoor evened. Debridement and repair or tenodesis of tendon tears is usually required.
All reports of stabilisation are small, usually 10-20 patients. Overall, about 85-90% of patients get satisfactory functional results, and some have returned to top-level sport. The rate of recurrent instability is 5-10%. Other complications include neuromas, infection and lateral ankle pain.
Symptomatic ankle instability can be corrected through the same incision, usually with a Brostrom-Gould procedure.
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