The surgical treatment of chronic ankle instability (CAI) relies chiefly on anterior talo-fibular ligament (ATFL) repair (with or without augmentation) or anatomical reconstruction with a tendon graft. Arthroscopy enables not only a complete assessment and the same-stage treatment of concomitant articular lesions, but also an accurate assessment of ligament lesions. Pre-operative imaging studies (MRI, CT, US) may fail to provide sufficient detail about chronic ATFL lesions to guide the decision between repair and reconstruction. The aim of this study was to develop an arthroscopic classification of chronic ATFL lesions designed to assist in selecting the optimal surgical technique.

Sixty-nine anterior ankle arthroscopy videos recorded before surgery for CAI were studied retrospectively. ATFL dissection was performed in all patients. Based on the video analysis, five ATFL grades were identified: 0, normal ATFL thickness and tension; 1, ATFL distension with normal thickness; 2, ATFL avulsion with normal thickness; 3, thin ATFL with no resistance during the hook test; and 4, no ATFL, with a bald malleolus. Intra- and interobserver reproducibility of the arthroscopic classification of chronic ATFL lesions was evaluated by computing the kappa coefficients (κ) after assessment by two independent observers.

All 69 ATFLs were classified as abnormal (none was grade 0). Each ATFL could be matched to a grade. Intra-observer agreement was good for both observers: κ was 0.67 with 75% of agreement for one observer and 0.68 with 76% of agreement for the other observer. Inter-observer agreement was fair to good, with κ values ranging from 0.59 to 0.88 and agreement from 70% to 91%.

Arthroscopic ATFL dissection is a simple procedure that provides a highly accurate assessment of ATFL lesions and mechanical resistance, focussing chiefly on the superior ATFL. Grade 1 and 2 lesions can be repaired using the Broström-Gould procedure, whereas grade 3 and 4 lesions require anatomic reconstruction with grafting.

This arthroscopic classification of chronic ATFL lesions confirms the diagnostic role for arthroscopy in assessing the ligaments in patients with CAI. It is helpful for determining the best surgical technique for stabilising the ankle. These results must be confirmed in a larger study.