Posterior arthroscopic approach to the ankle: An anatomic study

Purpose: The purpose of this study is to verify the safety of a new technique for a posterior arthroscopic approach to the ankle. This technique was recently described in literature. The technique uses a modified posteromedial portal, a different way of introducing the instruments into the portal, and the tendon of the flexor hallucis longus (FHL) as a landmark to work in the posterior compartment. Type of Study: Anatomic study. Methods: The technique was performed on 10 (4 fresh and 6 fresh-frozen) below-knee amputation specimens, which were then dissected. The instruments were left in place, and anatomic dissections were performed to determine the relationship to the surrounding neurovascular structures. Then the instruments were removed, and the distance of the neurovascular structures from the posteromedial portal was recorded. Another medial portal, 1 cm more proximal, was also created to measure the distance of this latter portal from the nervous structures. Results: None of the anatomic dissections showed injuries to the neurovascular bundle either during penetration of the instruments or during procedures in the posterior compartment laterally to the tendon of the FHL. This latter is the landmark to prevent damage to the more medially located nerves and vessels. The new posteromedial. portal is located, on average, 13.3 mm (range, 11 to 17 mm) from the posterior tibial nerve, 14.7 mm (range, 8 to 20) from the calcaneal branch (which may be single or multiple, and may vary as needed the height of bifurcation from the posterior tibial nerve), and 17.3 mm (range, 15 to 21 mm) from the posterior tibial artery. A posteromedial portal located 1 cm more proximally is on average 2.9 mm closer to the nervous structures. Conclusions: Based on these anatomic data, there appears to be relatively little risk to the surrounding neurovascular structures with this new technique. Therefore, this technique appears to be relatively safe in the treatment of intra-articular and extra-articular pathology.