MRI Evaluation of Cervical, Spring, and Interosseous Talocalcaneal Ligament Orientation in Progressive Collapsing Foot Deformity.

Background: Progressive collapsing foot deformity (PCFD) is a complex condition characterized by progressive ligamentous and osseous changes in the hindfoot, midfoot, and forefoot. Although osseous changes at the subtalar and transverse tarsal joints have been well studied, ligamentous anatomy in PCFD is less understood. This study evaluates the cervical, interosseous talocalcaneal, and superomedial fibers of the spring ligament in patients with PCFD vs controls using magnetic resonance imaging (MRI) analysis.

Methods: Nonweightbearing MRI and weightbearing radiographs of 39 patients (23 PCFD, 16 controls) were retrospectively reviewed. MRIs measured the coronal plane orientation of the interosseous talocalcaneal, cervical, and superomedial spring ligaments relative to the subtalar joint middle facet. Radiographic data included anteroposterior (AP) talonavicular coverage percentage, AP talocalcaneal angle (Kite), lateral talar-first metatarsal angle (Meary), talar declination angle, and calcaneal pitch. Two observers measured each radiographic and MRI angle. Statistical analysis included an independent t test and intraclass correlation coefficient (ICC) to assess interobserver reliability.

Results: PCFD patients demonstrated significantly more horizontal ligament orientations than controls, with reduced cervical (25.5 vs 45 degrees, P < .001), superomedial spring (11.5 vs 23.1 degrees, P < .001), and interosseous talocalcaneal ligament angles (39.5 vs 49.0 degrees, P = .005). Radiographically, PCFD patients had decreased talonavicular coverage (64.5% vs 80.9%, P < .001), increased Meary angle (22.2 vs -2.3 degrees, P < .001), increased talar declination (37.0 vs 20.6 degrees, P < .001), increased Kite angle (20.7 vs 17.2 degrees, P = .079), and decreased calcaneal pitch (15.5 vs 24.6 degrees, P < .001). Interobserver reliability was excellent, with ICC values exceeding 0.94 for all measurements except interosseous talocalcaneal ligament angle (ICC = 0.83).

Conclusion: On nonweightbearing MRI, PCFD patients showed more horizontal orientation of key subtalar ligaments than controls; whether these differences persist under physiologic load should be confirmed with weightbearing imaging.