Persistent Pain After Ankle Sprain: Is A Peroneal Tendon Injury The Cause?

   In a follow-up to the last column (see “A Guide To Treating Ankle Sprains From Start To Finish, pg. 92, June issue), I would like to discuss common secondary injuries that often occur in relation to ankle injuries, especially sprains. One of the most common and often misdiagnosed secondary complications of ankle sprains is a tear or injury to the peroneal tendon(s).    Since the tendons are in such close proximity to the lateral ankle and the lateral ankle is most often injured during a sprain, there is a tendency to perceive the two painful regions as one. Accordingly, some pay less attention to the peroneal tendons than the lateral collateral ligaments. This is not to say that it is simple to differentiate an ankle sprain with or without peroneal injury at the initial visit. However, if the patient continues to have pain two to three weeks after an initial sprain, practitioners should consider the peroneal tendons as a possible cause of pain.    The cause of peroneal injury with ankle sprains is not truly and fully understood. What is understood is that the peroneal tendons act as evertors of the ankle and also act as mild stabilizers of the medial column and first ray through the attachment of the peroneus longus to the base of the first metatarsal. The peroneal tendons are most commonly stretched with inversion of the ankle. Accordingly, they are most prone to injury with an inversion type of injury. However, in our institute research, we have found three potential causes of peroneal injury.

How Can Peroneal Tendon Injuries Occur?

   The first is the most common finding of injury to the peroneal tendon or peroneal retinaculum during an inversion injury. The peroneus brevis tendon is pushed between the peroneus longus and the fibula, and the inversion may snap the tendon against the side of the fibula. This results in a retinaculum tear and linear tear of the peroneal tendon.    A second cause of injury is from a severe fixed strain on the peroneal tendon while the foot is in a fixed position. We have noted that this injury commonly occurs with skiing injuries, snowboarding injuries, horseback riding injuries and water skiing injuries. In all such cases, the foot is in a locked position of full dorsiflexion and eversion in the buckle. During the injury, the foot has an isometric overload of the peroneal tendon resulting in tear. The difference in this type of tear is that it is often more severe with a potential complete tear or severe split tearing. This may involve either the peroneus brevis or longus tendon, although the brevis is more commonly injured.    The last and probably most common presentation is in the case of chronic ankle instability with a poorly treated ankle injury. The peroneal tendons are under constant strain to try to stabilize the lateral ankle instability, and the brevis tendon begins to fray from the overload. This leads to a longitudinal tear or split longitudinal tear. This type of injury is a chronic low-grade injury that responds well to surgery. It is essential in all cases of peroneal injury to consider instability of the ankle as a primary cause and treat the underlying instability of the ankle, if present, at the same time as the peroneal repair.

Essential Diagnostic Considerations

   Peroneal injuries are often missed as the patient presents with very faint complaints. There is no screaming or yelling, and the pain is often a dull, low-grade ache that gets progressively worse over months. These patients often say the pain is worse with exercise. However, the patient may relate no true cause for the pain and if you do not ask the patient directly, he or she may not even recall a previous ankle sprain or injury. Indeed, the main sprain may have been many years prior to the present presentation period. There is rarely a dislocation of the peroneal tendon noted and practitioners may note stable range of motion and strength.    Often, there is a positive anterior drawer test of the ankle and there may or may not be a positive talar tilt test noted. There is usually pain directly over the peroneal tendons to pressure. More commonly, the pain is at the distal 2 to 3 cm of posterior fibula and around the plantar bend of the distal fibula. One may or may not be able to initiate subluxation or dislocation of the tendon with forced resistance against dorsiflexion and eversion of the ankle.    Diagnostic testing may include radiographs of the foot and ankle. The practitioner should rule out fractures and loose bodies about the foot and ankle. Avulsion fracture of the distal tip of the fibula may be a cause for peroneal pain and potential tear. One should also be able to note a fracture of the os peroneum on radiographs as a source of pain. Also be sure to check for calcaneal and metatarsal alignment. Although most ankle sprains occur in patients with pes planus, those with a severe calcaneal varus and/or a plantarflexed first metatarsal and ankle instability may have an overload on the peroneal tendons due to the abnormal lateral foot position.    The mainstay of peroneal tendon injury diagnosis is the use of advanced diagnostic studies such as magnetic resonance imaging (MRI) or diagnostic musculoskeletal ultrasound. At our institute, when an ankle sprain does not respond to care at three weeks, we will usually check the peroneal tendons with an ultrasound. Cross-sectional images are best in such cases and will usually show flattening, a split or what is often called a C-shaped tendon posterior to the fibula with peroneus brevis injury. In cases of a split tear, one will see the peroneus longus tendon sitting between the split pieces of the brevis tendon and/or the brevis tendon may be partially dislocated lateral to the fibular edge with one split medial and one split lateral to the lateral fibular border.    When it comes to obtaining MRIs in these cases, clinicians will see similar findings on cross-sectional imaging but a more defined knowledge of the extent of tear and length of tear may be perceived.

Key Treatment Pearls

   Conservative care for peroneal tendon injuries has had very low success in our hands. I believe the main reason for this is that the brevis tendon, which is most commonly injured, cannot coil and heal itself due to the longus tendon sitting within the substance of the torn region. Therefore, in most cases, the clinician may emphasize a period of casting or bracing but these options are not commonly successful. In cases of a poor surgical candidate, one may attempt treatment with a custom ankle foot orthosis or functional orthosis.    The mainstay of treatment for peroneal injury is repair of the torn tendon with possible ankle stabilization if necessary. Peroneal repair is quite simple to perform on the brevis tendon and is more difficult on the longus tendon. The longus tendon will often tear lateral to the cuboid or plantar to the cuboid region, and therefore is a more difficult area to treat and repair.    When dealing with both brevis and longus tears, the surgeon should repair both tendons with debridement of the torn region in a linear fashion and coiling of the tendon onto itself. I prefer to use an Arthrocare Topaz mini coblation probe to debride the tendon and also to fenestrate the tendon in the region of tear. This will increase vascularity to the region and we have found an increase in the strength of the repair. I also prefer to use a thin nylon suture and repair the tendon with a baseball-type, running and locking stitch pattern. This decreases a reaction to the suture material and minimizes the number of knots.    I pay a great deal of attention to the position of the brevis tendon following repair. If the tendon does not sit well posterior to the fibula and seems prone to dislocation laterally, I will use a burr and deepen the posterior fibular groove. This is rarely necessary if there is adequate and stable repair to the peroneal retinaculum.    When it comes to ankle stabilization, I prefer a modified Brostrom type stabilization in primary ligament injury or tendon allograft ligament repair if there has already been a primary repair that has failed or re-injury has occurred. It is rare to require a calcaneal osteotomy or metatarsal osteotomy but the surgeon may need to perform these procedures concurrently with the ankle stabilization if necessary. The podiatric surgeon should remove a non-healing os peroneum after a period of casting and immobilization.    Following surgery involving tendon repair, podiatric physicians should have the patient use a non-weightbearing cast for three weeks. This should be followed by a weightbearing cast for three weeks. At six weeks, the patient can use an ankle brace and you can refer him or her to physical therapy. These patients may begin athletic activity at three months. They should use an ankle brace for one month at all times following cast removal and subsequently for athletic activity for three months.

Final Notes

   With proper attention to detail, peroneal tendon repair is a highly successful and fairly simple procedure. If patients with a sprain have continued lateral ankle pain and posterior fibular pain, the podiatric physician should have a high index of suspicion for possible peroneal tendon injury. Dr. Baravarian is the Co-Director of the Foot and Ankle Institute of Santa Monica. He is an Associate Professor at UCLA Medical Center and is the Chief of Podiatric Surgery at Santa Monica/UCLA Medical Center. Dr. Baravarian may be reached at bbaravarian @mednet.ucla.edu. For further reading, see “Detecting The Cause Of Chronic Ankle Pain” in the March 2002 issue of Podiatry Today.