Comparative Analysis of Structural Differences in Progressive Collapsing Foot Deformities with and without Hallux Valgus
Authors: Wang Chien-Shun , Behrens Andrew , Talaski Grayson M. , Casas Erik Jesus Huanuco , Carvalho Kepler A.M. , Acker Antoine , Valvecchi Tommaso Forin , Schweitzer Karl M. , Easley Mark E. , de Cesar Netto Cesar 
Published: December 2024

Category: Bunion; Hindfoot Introduction/Purpose: Progressive collapsing foot deformity (PCFD) and Hallux Valgus (HV) are common foot and ankle pathologies, each associated with over-pronation. Although hindfoot pronation is known to potentially increase forefoot pronation, not all patients with PCFD ultimately develop HV deformity. This study aims to explore the structural differences in patients with PCFD, with and without HV deformities, using weight-bearing computed tomography (WBCT). We hypothesize that specific structural variations exist, which could potentially inform and enhance future therapeutic strategies and preventive measures for HV deformity in patients with PCFD. Methods: Adult PCFD patients underwent WBCT at our institution between May 2023 and December 2023 were included. Semi-automatically measured parameters include Meary angle (axial and sagittal), calcaneal inclination angle, hindfoot moment arm, hindfoot angle, axial talonavicular angle, intermetatarsal angle, HV angle were recorded. WBCT manual measurement include foot and ankle offset, angle between inferior facet of the talus and the ground (inftal-hor), angle between inferior and superior facets of the talus (inftal-suptal), angle between inferior facet of the talus and superior facet of the calcaneus (inftal-supcal), and forefoot arch angle. Additionally, using the ground as a reference, the coronal plane pronation of the navicular, medial cuneiform, first metatarsal base, and first metatarsal head were also recorded. HV deformity was defined as having a Hallux Valgus Angle (HVA) greater than 15 degrees. Pronation/valgus were defined as positive values. Results: Our study included 58 patients (72 feet), 33 feet with HV and 39 without HV. In the coronal plane, the PCFD with HV group exhibited higher inftal-suptal angle (p=0.001), and higher pronation of the first tarsal-metatarsal joint (p=0.006), first metatarsal bone(p=0.002), and first metatarsal head(p< 0.001). Additionally, this group also demonstrated higher navicular-cuneiform joint supination (p < 0.001). In axial plane, the axial talar-1st metatarsal angle higher in the PCFD without HV group (p=0.043). Nominal logistic regression analysis indicated parameters include 1st metatarsal head rotation (p< 0.001), medial cuneiform rotation(p< 0.001), inftal-suptal angle (p< 0.001), axial talar-1st metatarsal angle (p< 0.001), navicular rotation (p=0.007), first metatarsal base rotation (p=0.012), and inftal-hor angle (p=0.016) are significantly correlated with the presence of HV in PCFD patients. (R2 (U)=0.79) Conclusion: Our findings reveal distinct structural differences in PCFD patients with HV compared to those without, which corroborates our hypothesis. Significant correlations exist between HV presence and rotation of the navicular, medial cuneiform, first metatarsal base, and first metatarsal head. Talus morphology, including inftal-suptal and inftal-hor angles, also correlated with HV deformity. Talar-first metatarsal angle was the only traditional two-dimensional radiographic parameter that correlated with HV deformity. Based on our findings, PCFD patients displaying these features might need HV preventive measures. Prospective longitudinal studies or dynamic research may be required to further elucidate the relationships between these two deformities.