The peroneocalcaneus internus tendon: case report of a rare cause of posterior ankle impingement treated by arthroscopy

A 20-year-old man, a semiprofessional hurdler, presented on the outpatient clinic with a six months history of pain posterior in the left ankle during sport activities. On physical examination there was pain palpating the posterior ankle joint and around the flexor hallucis longus (FHL) region posteromedial in the ankle during active flexion of the hallux. There was deep pain on the posterior process of the talus with a positive forced plantarflexion posterior impingement test. Magnetic resonance imaging (MRI) showed signs of posterior impingement with limited fluid distension of FHL sheath and a prominent posterior process. SPECT CT showed an increased uptake in the posterior process of the talus. Because of his complaints and high demanding level of sport activities an arthroscopic partial resection of the posterior process was suggested with a release of the FHL. The posterior arthroscopy was performed with the two posterior portals technique described by van Dijk [1]. The presumed FHL was located and the prominence of posterior process of the talus revealed. After resection of the prominence we noticed that the presumed FHL was not moving by flexion and extension of the hallux, but moved just with the mobilisation of the calcaneus. After careful inspection of the tendon, a second tendon anterior to the forementioned tendon was revealed. This tendon prooved to be the FHL, when the hallux was flexed and extended. The anatomically more posterior tendon appeared to be an accessory tendon (Figures 1 and 2). With mobilization of the hallux, there was no movement of this tendon, it only moved when the calcaneum was mobilised. We presumed that it was the peroneocalcaneus internus (PCI) tendon. An accessory posteromedial portal was made to perform a resection with the punch, scissor and shaver, because of the interference with the FHL in his tunnel (Figure 3). After this procedure the FHL could run freely in the tunnel without a sign of impingement. Postoperatively the pain was resolved. The Foot Abstract