Snapping Plantaris Tendon

A fit and healthy 30-year-old male sales executive presented with an 18-month history of painful snapping around the posterior aspect of right ankle after sustaining a twisting injury during skateboarding. He said that he had felt a “pop” at the time of injury and there had been some swelling initially. Over the 18 months since the injury, the posterior ankle pain had increasingly limited his activities. He was unable to play competitive soccer and even jogging was becoming progressively difficult. The pain was associated with a click that was reproducible on active ankle movement. He no longer noticed any swelling around the ankle and had no symptoms of instability or locking. On physical examination his hindfoot alignment and arches were normal. He was able to demonstrate the snapping over the posterior aspect of the ankle on resisted plantarflexion, and this was accompanied by pain (videos are available as supplementary files). We were surprised to note that the snapping seemed to be occurring around the posteromedial aspect of the Achilles tendon. It was possible to prevent the snap by pressing onto the posteromedial aspect of the midsubstance of the Achilles (where the plantaris is usually found) with the examiner’s thumb. The Achilles itself was intact and nontender. There was no ankle instability and there was full power of the tibialis posterior and peroneal tendons with no pain and no subluxation/dislocation on stressing them. He had slight tightness in his gastrocnemius on Silfverskiold’s test. Radiographs of the foot and ankle were normal and an MRI, which had been ordered by the referring physician, showed no ligamentous or osteochondral injuries, and there was no evidence of plantaris subluxation or Achilles tendinopathy on the static images. A dynamic ultrasound was ordered and this confirmed the initial suspicion of plantaris subluxation (Figure 1). The patient was keen to explore all nonoperative options before considering surgery; therefore anti-inflammatory medications and physiotherapy with particular attention paid to eccentric gastrocnemius stretching were tried. Unfortunately, after 3 months this did not improve the situation and as he was unable to play soccer or jog more than 1 km, we elected to operate. The operative procedure was performed under general anesthesia with the patient placed prone on the operating table. The plantaris tendon subluxation was reproducible by the operating surgeon intraoperatively with forced dorsiflexion of the ankle. Tendinoscopy of the Achilles tendon was performed using a 4.5 mm, 30-degree angled arthroscope via a distal lateral and a proximal medial portal as described by Steenstra and van Dijk. There were technical difficulties in the confident identification of the plantaris tendon as it appeared to be more anterior and distant from the Achilles compared to the situation that one finds when performing Achilles tendinoscopy and plantaris release/excision for Achilles tendinopathy, therefore a posteromedial longitudinal incision was extended from the posteromedial portal and dissection was performed to expose the plantaris and Achilles tendons (Figure 2). After excision of the tendon, the snapping around the Achilles could no longer be demonstrated. The wound was closed in layers, and the patient was allowed to bear weight as tolerated immediately after surgery. 549048 FAIXXX10.1177/1071100714549048Foot & Ankle InternationalHan et al research-article2014