Lateral plantar nerve neuropraxia after FHL tendoscopy: case report and anatomic evaluation

FHL tendoscopy has been described as minimally invasive method used to create some pathologies or facilitate some surgeries. As we have encountered lateral plantar nerve neurapraxia, we investigate the cause of lateral nerve injury during Zone 2 flexor digitorum longus (FHL) tendoscopy with a cadaveric model.

Eight feet of 4 embalmed cadavers were used for this study. Posterior ankle endoscopy (Zone 1 FHL tendoscopy) was performed with posteromedial and posterolateral portals. A 4.0-mm metal rod was inserted into the Zone 2 tendon health through the posteromedial portal. The distance between the posteromedial portal and the posterior tibial nerve was measured with the ankle in neutral position. Then, the shortest distance between the posterior tibial nerve and the rod was measured with the ankle in three positions: 20 degrees plan-tarflexion, neutral, and the 20 degrees dorsiflexion.

The average distance between the posterior tibial nerve and the posteromedial portal was 9.3 mm. The average shortest distance between the posterior tibial nerve and the metal rod was 5 mm with the ankle in 20 degrees dorsiflexion.

Ankle dorsiflexion brings the posterior tibial nerve in contact with the arthroscope during Zone 2 tendoscopy.

In order to avoid potential nerve injury during Zone 2 FHL tendoscopy, ankle dorsiflexion should be avoided.