Is the postero-medial portal safe in posterior ankle arthroscopy?

Background: Posterior ankle arthroscopy is considered to pose a risk of neurological and vascular complications. Some authors consider the postero-medial portal to be risky and recommend using only the postero-lateral portal. The aim of this study was to analyze the margin of error offered by posterior ankle arthroscopy portals.

Material And Methods: Twenty MRI studies of the ankle joint were analyzed. The paths of the postero-medial and postero-lateral portals were drawn. Next, the path of the probe was diverged to aim at the neurovascular bundle and the angle of deviation was measured. We analyzed the distance between the probe located directly laterally to the flexor hallucis longus tendon and the neurovascular bundle.

Results: The mean angle of deviation leading to collision with neurovascular bundle structures was 53.3° (range 37-70°) and 30.75° (range 22-41°) for the postero-medial and postero-lateral portals, respectively, p<0.05. The mean minimal distance between and the probe and the bundle was 12 mm (range 5-15 mm) and 13 mm (range 8-18 mm) for the postero-medial and postero-lateral portals, respectively, p>0.05.

Conclusions: 1. The postero-medial arthroscopic portal is at least as safe as the postero-lateral one in posterior ankle arthroscopy. 2. Keeping instruments strictly laterally to the flexor hallucis longus tendon leaves at least 5 mm distance from the neurovascular bundle.