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Coaxial portals for posterior ankle arthroscopy: An anatomic study with clinical correlation on 29 patients.

PURPOSE
The authors performed a cadaveric study on 10 ankles and retrospectively reviewed 29 arthroscopic synovectomies to determine the trajectory, minimal safe distances, and complications using a new approach for posterior ankle arthroscopy.


TYPE OF STUDY
Anatomic study and case series.


MATERIALS AND METHODS
A posterolateral portal was established immediately posterior to the peroneal tendon sheath. While staying within the posterior ankle capsule, an inside-out technique was then used to establish the posteromedial portal directly behind the medial malleolus adjacent to the posterior tibial tendon. The cadaveric ankles were frozen, sectioned, and photographed to measure the proximity of neurovascular structures to these coaxial portals. From 1988 to 1994, arthroscopic synovectomy was performed on 23 patients (29 ankles) with hemophilia using these modified portals.


RESULTS
Results of the anatomic study showed that the posterior tibial nerve and posterior tibial artery were located a mean distance of 5.7 mm (SEM, 0.6 mm) and 6.4 mm (SEM, 0.7 mm) from the edge of the cannula, respectively. Neither penetration nor contact of nerve or vessel was observed at either posterior portal. In the 29 clinical cases, posterior capsular synovectomy was achieved arthroscopically with no detectable complications at an average 45-month follow-up.


CONCLUSIONS
Our anatomic data show that the coaxial portals described here are essentially equidistant to the neurovascular structures compared with conventional portals. Our clinical results suggest that his technique for posteromedial and posterolateral portals is safe, effective, and reproducible.