The patient granted permission for the publication of this case report.
A 61-year-old woman was referred to our hospital 3 years after undergoing surgery for a left trimalleolar fracture of the ankle due to a road traffic accident. She underwent immediate open reduction and internal fixation at a local hospital. Left ankle pain persisted and about 10 months after the primary surgery she developed numbness along the medial aspect of the left ankle and over the sole of the foot. The implants were removed at about 1 year after the primary surgery, but the left ankle pain did not improve and the numbness worsened. She was referred to us for further investigation.
Her main complaint was a tingling/reduced sensation and paresthesia on the plantar and medial aspects of the forefoot to the middle foot area along the main distribution of the medial plantar nerve. There was tenderness and swelling over the ankle joint and the proximal posterior aspect of the medial malleolus (Fig. 1). Tinel's-sign was positive over the proximal posterior aspect of the medial malleolus. No motor deficit or deformity of the toes was detected. Plain radiographs revealed severe joint space narrowing between the tibia and talus, indicating osteoarthritic change in the left ankle in the standing position on anterior-posterior view (Fig. 2a) and lateral view (Fig. 2b). Computed tomography (CT) images showed an osteophyte of the posteromedial aspect of the distal tibia on coronal view (Fig. 3a) and axial view (Fig. 3b) and on three-dimensional (3D) CT imaging (Fig. 3c). Magnetic resonance (MR) images showed the osteophyte impinging on the tibial nerve on T1-weighted (Fig. 4a), T2-weighted (Fig. 4b), and short T1 inversion recovery (STIR) images (Fig. 4c) on coronal view, and on T2 (Fig. 4d) and STIR (Fig. 4e) images on axial view.
We diagnosed TTS with traumatic osteoarthritis of the ankle. Therefore, we opted to perform excision of the osteophyte to decompress the tibial nerve and ankle arthroscopic arthrodesis because endoscopic techniques can accelerate recovery and reduce morbidity compared with the open procedure. The preoperative Japanese Society for Surgery of the Foot (JSSF) score was 30/100 points (pain 0/40, function 20/50, alignment 10/10).
The patient was positioned supine with the affected limb in a stirrup and traction in place. Two standard portals (anterolateral and anteromedial) were used. Fibrous tissue was seen filling the ankle joint space (Fig. 5a) and synovitis was severe. The fibrous tissue was removed and synovectomy was performed with an arthroscopic shaver. Cartilage was almost completely denuded and subchondral bone was exposed at the articular surface of the tibial plafond and talar trochlea (Fig. 5b). Using a surgical abrader, we denuded all remaining articular cartilage and established beds of bleeding cancellous bone (Fig. 5c). A curvilinear incision was then placed along the course of the tibial nerve posterior to the medial malleolus. Fixation between the distal tibia and talus was established using 3 cannulated partially threaded screws. After fixation, the flexor retinaculum was released, exposing the osteophyte in the posteromedial side of the distal tibia pushing the tibial nerve from the anterior aspect (Fig. 6a). Scarring around the nerve was also noted with redness and swelling of the nerve. The osteophyte was removed (Fig. 6b). CT images soon after surgery confirmed successful removal of the osteophyte on coronal view (Fig. 7a) and axial view (Fig. 7b) and on a 3D CT image (Fig. 7c).
A non-weightbearing below-knee cast was applied for 2 weeks for immobilization. This immobilization was maintained for another 2 weeks but with weightbearing permitted. After a total of 4 weeks of immobilization with the lower leg cast, the cast was removed and an ankle brace was attached to the left foot and ankle. The patient started a mobilization protocol with progressive passive and active range of motion exercises at 4 weeks after surgery. Bony union of the ankle was achieved about 6 weeks after surgery.
Two years after decompression of the right tarsal tunnel and neurolysis of the tibial nerve, the patient reported major improvements in the dysesthesia along the entire plantar surface of the foot. She was not taking any medication, as radiographs showed complete union between the tibia and the talus on weightbearing on antero-posterior view (Fig. 8a) and lateral view (Fig. 8b). There was no tenderness or swelling over the ankle joint or the proximal posterior level of the medial malleolus (Fig. 9). Tinel's sign was negative over the proximal posterior level of the medial malleolus. At that time, The JSSF score had improved to 89/100 points (pain 40/40, function 39/50, alignment 10/10).