Progressive Collapsing Foot Deformity: Multi-bone Modeling and Joint Level Measurements.

Abstract

Purpose: The objective of this study was to characterize joint level morphology and alignment differences across stages of progressive collapsing foot deformity (PCFD) within the talocrural, subtalar, talonavicular, and calcaneocuboid joints using multi-bone statistical shape modeling (SSM) and joint distance measurements from weightbearing computed tomography (WBCT) scans. This was achieved by employing multi-bone SSM in conjunction with precise joint measurement analysis, utilizing WBCT scans to investigate the intricate changes within the talocrural, subtalar, talonavicular, and calcaneocuboid joints.

Methods: A retrospective analysis was conducted on patients with PCFD who failed conservative treatment. Two groups of 20 feet each were formed for flexible PCFD and rigid PCFD, with 27 additional feet identified as asymptomatic controls. All 67 participants underwent a WBCT scan, and 3D models were created as inputs for multi-bone SSM and joint distance measures.

Results: The first principal component analysis mode contained 45.8% of the variation in the population while the second mode contained 13.3% of the variation and the third mode contained 6.4% of variation accounting for 65.6% of the overall variation in the multi-bone model. Joint space distance measurement differences were observed between all three groups for all articulations. The primary difference between flexible PCFD and rigid PCFD multi-bone SSM was a statistically significant medial shift of alignment of the talar neck, resulting in worsened peritalar subluxation.

Conclusion: PCFD is quantifiably variable across a clinical population when evaluating joint level measurements as well as morphologic and alignment variations. Talonavicular joint malalignment severity may be a clinical key in distinguishing between stages of PCFD.