Comparison of symptomatic unstable ankle with and without os subfibulare

Background: This study aimed to compare the patients background, clinical scores, condition of the lateral ligament, mechanical instabilities, and chondral lesions in ankles with symptomatic os subfibulare compared to those in ankles with chronic lateral instability without os subfibulare. Methods: Of the 212 ankles with a chronic lateral instability that were surgically treated, 72 ankles had an os subfibulare. All ankles were examined by arthroscopy during surgery. Age, sex, preoperative American Orthopaedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Scale scores, remnant condition of the lateral ligaments, and chondral lesions were compared between ankles with symptomatic os subfibulare and ankles with chronic lateral instability without os subfibulare. Results: There were no statistically significant differences between the groups in terms of the sex ratio (males: females, 35:37 vs. 53:87, n.s.) and the AOFAS Ankle-Hindfoot Scale scores (median; 75 vs. 77, n.s.). There were statistically significant differences in patient age (median: 20 vs. 24.5 years, p < 0.01), talar tilt angle (median: 9.0 degrees vs 12.0 degrees, p < 0.01), anterior drawer distance (6.2 vs. 7.0 mm, p < 0.01), chondral lesions (G0:G1:G2:G3, 35:21:66:5 vs. 40:44:27:29, p < 0.01), condition of the anterior talofibular ligament (intact: repairable remnant: poor remnant, 0:70:2 vs. 1:112:27, p < 0.01), and condition of the calcaneofibular ligament (intact: repairable remnant: poor remnant, 44:26:2 vs. 77:35:28, p < 0.01) between the groups. Conclusion: This study suggests that the condition of the lateral ligaments including mechanical instability and cartilage of the ankle were less severe in the ankles with symptomatic os subfibulare than in those with chronic lateral instability without os subfibulare. The patients' age was lower in the ankles with symptomatic os subfibulare than in those with chronic lateral instability without os subfibulare. The clinical scores and gender ratio were not statistically different between the group. (c) 2022 Published by Elsevier B.V. on behalf of The Japanese Orthopaedic Association.