Comparative Analysis of Subtalar Ligaments Between Patients With Talocalcaneal Coalition and Control Subjects Using 3-Dimensional Magnetic Resonance Imaging.

PURPOSE: The purpose of this study was to find the differences in the subtalar ligaments between patients with talocalcaneal (TC) coalition and control subjects using 3-dimensional isotropic magnetic resonance imaging. METHODS: Magnetic resonance imaging of 27 ankles with TC coalition and 27 age- and sex-matched controls were retrospectively reviewed. Absence of cervical ligament, anterior capsular ligament (ACL), interosseous TC ligament (ITCL), and partial or complete absence of 3 roots of the inferior extensor retinaculum was analyzed. Thickness and width of ACL and ITCL were measured when possible. RESULTS: Absence of ACL and ITCL was significantly more frequent in TC coalition patients than in controls (59.2% vs 7.4%, P < 0.0001; 44.4% vs 7.4%, P = 0.004). Absence of cervical ligament and 3 roots of the inferior extensor retinaculum did not differ between the 2 groups. Thickness and width of ACL were significantly smaller in TC coalition patients than in control subjects (0.81 ± 0.23 vs 1.27 ± 0.41 mm, P < 0.0001; 5.26 ± 1.17 vs 7.07 ± 1.46 mm, P = 0.001). Thickness and width of ITCL did not differ between the 2 groups. In the TC coalition group, the absence of ACL and ITCL did not differ according to coalition type, patient demographics, and magnetic resonance imaging units. CONCLUSIONS: Anterior capsular ligament and ITCL are frequently absent in TC coalition patients. Even when present, the ACL is attenuated in TC coalition patients compared with controls.