Posterior Hindfoot Endoscopy Using 1.9-mm Diameter Needle Arthroscopy: A Cadaveric Study

CATEGORY: Ankle; Arthroscopy; Hindfoot; Sports INTRODUCTION/PURPOSE: Posterior hindfoot endoscopy is a safe and effective treatment for posterior ankle impingement syndrome (PAIS) and flexor hallucis longus (FHL) tendon disorders. As frequent coexistence of PAIS and FHL tenosynovitis has been reported, it is important to investigate FHL tendon pathology concomitantly when treating PAIS. However, the visualization of FHL tendon distal to the retinaculum is limited when using conventional rigid arthroscopy. Additionally, wound-healing problems following hindfoot endoscopy have been still reported. Recently, a novel 1.9-mm diameter needle-arthroscopic system has been introduced. Its small and semirigid features can help reduce the risk of wound complications and can make it easier to perform FHL tendoscopy. The purpose of this study was to assess whether 1.9-mm diameter needle-arthroscopy was useful for hindfoot endoscopy in a cadaveric model. METHODS: A 1.9-mm diameter arthroscopic system (NanoScope(TM), Arthrex) was used to perform a hindfoot endoscopy in 6 human donor ankles (3 pairs). The arthroscope tube is 9.5-cm long and semi-rigid, and has a 1.9-mm outer diameter. The scope's direction of view is 0°, with a 120° field of view. Posteromedial and posterolateral portals were established. Visualization and operative reach with tailored arthroscopic instruments were recorded, including posterolateral talar process, posterior talofibular ligament, intermalleolar ligament, subtalar joint, ankle joint, and flexor hallucis longus (FHL) tendon. Finally, a conventional 4.0-mm diameter arthroscope with a 30° angle was used to compare the visualization of FHL tendon. RESULTS: All significant structures were successfully visualized and reached in all specimens. In ankle joint, all of the tibial surface was visualized, but visualization of talar surface was limited. Due to its wide 120° field of view, there was no difficulty obtaining sufficient visualization in any structures. As this needle-arthroscopic system has the semirigid frame, FHL tendoscopy was easily performed via the posterolateral portal. In all specimens, the FHL tendon was visualized from the level of ankle joint to the Knot of Henry (Zone 1 and 2), and the flexor digitorum longus tendon crossing obliquely over the FHL tendon was observed (Figure). The conventional arthroscope could not be inserted into the tunnel underneath the sustentaculum tali in any specimens. CONCLUSION: Posterior hindfoot endoscopy using a 1.9-mm diameter needle-arthroscopy provides effective visualization and surgical reach of all significant structures for the treatment of PAIS. Its small and semirigid features also make the FHL tendoscopy less invasive and more accessible than conventional rigid arthroscope.