Cervical Ligament Insufficiency in Progressive Collapsing Foot Deformity: It May Be More Important Than We Know

Background: Subluxation at the subtalar joint is one of the major radiographic features that characterize progressive collapsing foot deformity (PCFD). Although it is recognized that the cervical ligament plays an important function in maintaining the subtalar joint's stability, its role and involvement in PCFD is largely unknown. The purpose of this study was to assess the prevalence of cervical ligament insufficiency in patients with PCFD and to establish if the degree of its pathology changes with increasing axial plane deformity.Methods: This study retrospectively reviewed magnetic resonance imaging (MRI) of 78 PCFD patients and age- and gender-matched controls. The structures evaluated were the cervical, spring, and talocalcaneal interosseous ligaments. Structural derangement was graded on a 5-part scale (0-4), with grade 0 being normal and grade 4 indicating a tear of greater than 50% of the cross-sectional area. Plain radiographic parameters (talonavicular coverage angle [TNC], lateral talo-first metatarsal [Meary] angle, calcaneal pitch, and hindfoot moment arm) as well as axial plane orientation of the talus (TM-Tal) and calcaneus (TM-Calc) relative to the transmalleolar axis and talocalcaneal subluxation (Diff Calc-Tal) were correlated with the cervical ligament MRI grading system.Results: The overall distribution of the degree of cervical ligament involvement was significantly different between the PCFD and control groups (P < .001). MRI evidence of a tear in the cervical ligament was identified in 47 of 78 (60.3%) feet in the PCFD group, which was significantly higher than the control group (10.9%) and comparable to that of superomedial spring (43.6%) and talocalcaneal interosseous (44.9%) ligaments. Univariate ordinal logistic regression modeling demonstrated a predictive ability of TM-Calc (odds ratio [OR] 1.17, 95% CI 1.06-1.30, P = .004), Diff Calc-Tal (OR 1.15, 95% CI 1.06-1.26, P = .002), TNC (OR 1.08, 95% CI 1.03-1.13, P = .003), and Meary angle (OR 1.05, 95% CI 1.02-1.10, P = .006) in determining higher cervical ligament grade on MRI.Conclusion: This study found that cervical ligament insufficiency is more often than not associated with PCFD, and that an increasing axial plane deformity appears to be associated with a greater degree of insufficiency.