Association Between Talar Morphology and Subchondral Bone Sclerosis in the Medial Gutter of Patients With Chronic Lateral Ankle Instability.

BACKGROUND: Chronic lateral ankle instability (CLAI) is associated with an increased risk of posttraumatic osteoarthritis, with early degenerative changes often beginning in the medial gutter. Although altered loading toward the anteromedial talus has been reported, the contribution of talar morphology to early subchondral adaptation remains unclear. This study aimed to investigate the association between talar morphology and subchondral bone sclerosis in the medial gutter using quantitative computed tomography (QCT). METHODS: Twenty-seven patients with CLAI (34 ankles) who underwent arthroscopic ligament repair and 30 control patients (34 feet) without ankle trauma or deformity were retrospectively analyzed. QCT was used to quantify volumetric bone mineral density (BMD). The talar side of the medial gutter was divided into 8 subregions, and BMD ratios were calculated by normalizing regional BMD to fibular BMD. Radiographic and axial computed tomography-based morphologic parameters, including anterior opening angle of the talus (AOT), posterior width (PW), anterior width, and trochlea tali length, were measured. Group comparisons and Spearman correlation analyses were performed. RESULTS: BMD ratios in the medial gutter were significantly greater in the CLAI group than in controls, particularly in anterior regions (areas 1, 2, and 5; all P < .05). Compared with controls, CLAI patients demonstrated a larger AOT and smaller PW, as well as significantly greater talar tilt angle (11.6° vs 4.6°; P < .01) and anterior drawer distance (7.2 mm vs 5.1 mm; P < .01). In the CLAI group, significant positive correlations between BMD ratio and AOT (r = 0.48-0.60) and significant negative correlations with PW (r = -0.41 to -0.49) were observed after false-discovery-rate correction. No consistent morphology-BMD associations were observed in controls. CONCLUSION: In CLAI, subchondral bone density is increased in the anterior medial gutter and is associated with a larger AOT and smaller PW, suggesting anteriorly biased loading patterns and localized subchondral adaptation. These findings suggest an association between talar morphology and region-specific subchondral adaptation in CLAI. LEVEL OF EVIDENCE: Level III, comparative study.