Navigation for ankle arthroscopy:: anatomical study of the anterolateral portal with reference to the superficial peroneal nerve

We aimed to navigate the surgeon regarding the localization of the main anatomical structures at the anterior part of the ankle joint, in order to find easily the safest anatomical points with reference to the superficial peroneal nerve (SPN), in particular for anterolateral portal placement in ankle arthroscopy. Sixty-three ankles in 36 fresh cadavers were dissected. In all specimens we examined (1) the distance between the SPN bifurcation and the most distal point of the lateral malleolus; and at the level of ankle joint, (2) the number of SPN, (3) the distance between the medial and intermediate dorsal cutaneous nerves, which are branches of the SPN, (4) the localization of the peroneus tertius (PT) tendon in relation to the lateral malleolus, (5) the width of the extensor digitorum longus (EDL) tendon, (6) the relationship of the PT tendon and (7) the relationship of the extensor hallucis longus (EHL) tendon with the SPN. The results were as follows: (1) In 41 ankles with bifurcation (65%) the average distance was 71.8+/-35.3 mm. (2) There were two SPN branches in 39 (62%), three branches in seven (11%) and one branch in 17 (27%) cases. (3) In 39 ankles with two branches of the SPN, the mean distance was 15.2+/-7.1 mm. (4) The lateral border of the PT tendon was positioned a mean distance of 20.8+/-3.3 mm proximal and 25.2+/-5.8 mm medial to the reference points. (5) The mean width was 10.1+/-2.9 mm. (6) In 42 ankles (67%) the distance between the lateral border of the PT tendon and the SPN was a mean of 6.2+/-6.6 mm, median of 3 mm (range 0-22 mm lateral to the tendon). (7) In 56 cases (89%) a branch of the SPN was found a mean of 6.6+/-4 mm and a median of 6 mm lateral to the EHL tendon, and in seven cases (11%) on the tendon. According to our study, in ankle arthroscopy the risk of the SPN injury is maximal in the 0-3 mm lateral to the PT tendon. To avoid injury to the SPN, the safest placement of the anterolateral portal is 4 mm lateral to the PT tendon.