Os Trigonum: Should You Treat It Surgically?
Yes. Christopher Corwin, DPM says surgical excision, when properly indicated, addresses the cause of os trigonum pain, offers a lower risk of recurrence and facilitates a quick recovery and return to activity.
The os trigonum is the second most common accessory bone in the foot. Asymptomatic os trigonum rarely requires treatment. However, in the case of symptomatic os trigonum, especially when the pain arises from an ankle injury, it can be difficult sometimes to discern between os trigonum and a fracture of the posterolateral process of the talus (Stieda’s process).
Injuries to the posterolateral process of the talus are relatively common in athletes who participate in football, soccer, basketball, gymnastics and dance. These injuries can be debilitating to the athlete.
Symptoms with os trigonum injuries typically involve pain in the deep posterior aspect of the ankle when the athlete places the foot in extreme plantarflexion. Football punters and soccer players may state they have no pain when running but extreme pain when kicking the ball. Dancers may have pain going on pointe.
Keys To The Diagnostic Workup
The mechanism of os trigonum injury varies but it is commonly associated with plantarflexion type ankle injuries. The posterior process of the talus gets pinched between the posterior aspect of the distal tibia and the posterosuperior aspect of the calcaneus. This leads to a fracture. Inversion ankle sprains that affect the posterior talofibular ligament can also cause avulsion fractures as the posterior talofibular ligament inserts into the lateral tubercle of the talus.
Physicians often diagnose these fractures after the resolution of anterolateral ankle pain. With these injuries, patients often note an ache in the deep posterior or posterolateral ankle that has not gotten better.
Physical examination reveals pain with palpation on the deep posterolateral aspect of the ankle. Forced plantarflexion to end range of motion often reproduces the symptoms as the posterior process of the talus is impinged between the tibia and calcaneus. This is a relatively reliable diagnostic tool.
Much less useful is the classically described test of dorsiflexion and plantarflexion of the hallux in an attempt to elicit pain in the deep posterior ankle via movement of the flexor hallucis longus tendon against the Stieda’s process. We have found this test to be positive less than 10 percent of the time.
Radiographs may show an avulsion of the posterior process or an os trigonum to be present. Magnetic resonance imaging (MRI) evaluation clearly demonstrates injury with inflammatory fluid surrounding the os trigonum and stress related changes in the bone that show an increased signal in the lateral posterior process on T2 weighted images.
Pertinent Pearls On Surgical Management And Post-Op Protocol
One should attempt conservative therapy first. This includes immobilization, activity modification, athletic taping to prevent end range of plantarflexion and possible steroid injection. Should these options fail, surgical intervention is warranted in the active, symptomatic individual or in athletes competing in sports that require plantarflexion type of movement. Surgical management of the symptomatic os trigonum and the fractured posterolateral process of the talus involves the same surgical procedure.
One would perform surgery with the patient under the anesthesia of choice. Surgery often involves general or spinal anesthesia. Ensure the patient is in a full lateral position with a beanbag and use a thigh tourniquet to achieve hemostasis. Make a 3 to 4 cm curved incision on the posterior aspect of the peroneal tendons and center the incision at the level of the posterosuperior aspect of the calcaneus. Pay careful attention to avoid the sural nerve, which runs in the area and is often protected posteriorly in the subcutaneous fat.