Ankle sprain is a common injury in Singapore athletes as well as the active adult. Most of the time, the ankle heals with a little care (rest, taping, ice). But one rare complication of lateral ankle sprains is a condition called peroneal tendon instability.
A lateral ankle sprain means the side of the ankle away from the other leg is sprained. The two peroneal tendons go down the leg and around the back of the ankle bone. The tendons set down inside a tunnel formed by bone and connective tissue called the retromalleolar groove. A fibrous band (the superior peroneal retinaculum) goes across the tendon to hold them in the groove.
When this fibrous retinaculum is ruptured, the tendons can dislocate or pop out of the groove. The result is persistent pain along the outside aspect of the ankle bones. There may be a painful popping or snapping sensation.
Swelling may mask the symptoms of tendon displacement at first. It’s only weeks to months later when the painful symptoms don’t go away that the additional tendon damage is recognized. Early MRIs may not show peroneal tendon instability, especially if the tendon pops in and out of the groove spontaneously.
A relaxed tendon is more likely to remain in the groove. Any active movement of the ankle will force the tendon out of its protective tunnel. If the ankle is relaxed and the tendon is repositioned correctly at the time of the imaging study, then diagnosis can be delayed. Dynamic ultrasound tests are the best diagnostic tests because they will reveal the movement of the unstable tendon.
Since this problem is rare, not much is known about the best way to treat it. Conservative (nonoperative) care is only possible when the unstable tendons can reposition inside the retromalleolar groove. A cast or boot placed on the lower leg will give the tendon a chance to heal.
If conservative care is unable to achieve a stable gliding tendon or if the tendon displacement is unstable from the start, then surgery is necessary. There are several different surgical options to consider. The fibrous protective sheath (retinaculum) can be reinforced or reconstructed. The groove can be reshaped (deepened) and rebuilt. The surgeon must be careful not to destroy or disrupt the smooth gliding surface of the bone that helps form the retromalleolar groove.
The retinaculum is repaired or reconstructed depending on the severity of the damage. Incision shape, drill holes, suture type and placement, and method for protecting the groove surface are discussed. Photos of each step in the surgical procedure are provided.
In summary, traumatic displacement of the peroneal tendons is a rare but painful complication of some lateral ankle sprains. Pain and swelling may mask the presence of this problem at the time of the injury with a delayed diagnosis. A careful examination with tenderness palpated over the torn retinaculum is the best way to accurately identify the injury. Treatment is usually surgical with the surgeon’s own preferred treatment presented.