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

Abstract

Category: Hindfoot; Midfoot/Forefoot Introduction/ Purpose: 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 its integrity of it changes with increasing axial plane deformity. We hypothesized that there will be a higher prevalence of cervical ligament insufficiency in a PCFD cohort compared to that of a control group. Additionally, we hypothesized that those with higher degrees of cervical ligament insufficiency will have a more severe abduction deformity and talocalcaneal subluxation. Methods: This study retrospectively reviewed magnetic resonance imaging (MRI) of 78 PCFD patients and age- and gender- matched controls. A radiologist specializing in musculoskeletal disorders evaluated the structural derangement of the cervical ligament into five grades (Grade 0 indicating normal and Grade 4 indicating a tear greater than 50% of the cross-sectional area), as previously described. To compare its involvement in PCFD, two commonly involved ligaments (spring and interosseous) in PCFD were also evaluated. Plain radiographic parameters, including the talonavicular coverage angle (TNC), lateral talo-1st metatarsal (Meary’s) 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, Table 1). MRI evidence of a tear (Grades 3 or 4) 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 greater than that of superomedial spring (43.6%) and talocalcaneal interosseous (44.9%) ligaments. Univariate ordinal logistic regression modelling demonstrated a predictive ability of TM-Calc (Odds ratio [OR]: 1.17, 95% confidence interval [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’s angle (OR: 1.05, 95% CI: 1.02-1.10, p=.006) in determining higher cervical ligament grade on MRI (Figure 1). Conclusion: We found that cervical ligament insufficiency is a significant component of PCFD and is more common than anticipated in this study. Based on the radiographic findings in the current study, cervical ligament insufficiency appears to be primarily associated with axial plane midfoot and hindfoot deformity. If its biomechanical properties are established in the future studies, we think the reconstruction of the cervical ligament may be a potential adjunct surgical procedure for PCFD patients with significant axial plane deformity.