Category: Arthroscopy Introduction/Purpose: Ankle arthroscopy can be used for a variety of ankle pathology including soft tissue and bony impingement, loose bodies, osteochondral defects, ankle fractures, osteoarthritis and instability. However, complication rates associated with ankle arthroscopy range from 3.4 to 9%, with half of them consisting of neurovascular and tendon injuries due to arthroscopic portal placement. The purpose of the study is to determine the safety and efficacy of using ultrasound in topographic marking of the neurovascular structures and tendons in the foot and ankle and identification of a safe zone for arthroscopic portal creation, compared to using anatomical landmarks. Methods: Twelve cadaveric samples were divided into two groups of six. The first group underwent ultrasound assessment by a board certified radiologist, who identified zones of safety for ultrasound guided insertion of anteromedial, anterolateral and posteromedial arthroscopic portals. Ankle arthroscopy was then performed. The other group underwent similar ankle arthroscopy assessment utilizing conventional anatomical landmarks. Straws were used to delineate arthroscopy portal tracts. The cadaveric samples were then dissected. The following distances were measured between the portals and important anatomical structures: the anterolateral portal and superficial peroneal nerve (SPN) as well as extensor digitorum longus (EDL); anteromedial portal and the great saphenous vein (GSV) as well as tibialis anterior (TA); and the posteromedial portal and the flexor hallucis longus (FHL). Results: No neurovascular structures or tendons were injured in all twelve cadaveric samples. Compared with the non- ultrasonography group, the group that underwent ultrasonography assessment had statistically significant larger distance of the SPN, EDL and TA from the anterolateral and anteromedial arthroscopic portals (p values = 0.045, 0.046 and 0.025 respectively). No difference was found between the distance of the GSV from the anteromedial arthroscopic portal, as well as the distance of the FHL from the posteromedial arthroscopic portal. Conclusion: Ultrasound assessment and topographic identification of the safe zone for ankle arthroscopic portal creation is a safe and effective process that may reduce the risk of iatrogenic injury to neurovascular structures and tendons in anterior and posterior ankle arthroscopy.