Description of anatomical differences in 3D bone morphology between female individuals with progressive collapsing foot deformity and asymptomatic controls.

Background: Progressive collapsing foot deformity (PCFD) represents a multifaceted three-dimensional condition. However, there has been limited discussion regarding how the morphology of each bone affects PCFD.

Purpose: To determine morphological differences within each bone of the foot and ankle in females affected by PCFD compared to asymptomatic controls.

Study design: Comparative cross-sectional study.

Methods: We hypothesized the medial column bones would exhibit the most substantial shape differences between groups. We developed multiple statistical shape models (SSMs) to analyze the 3D shape of the distal tibia, distal fibula, talus, calcaneus, navicular, cuboid, cuneiforms, and metatarsals. We quantified and compared results between 23 female PCFD patients and 23 asymptomatic females.

Results: SSM analyses revealed significant modes of variation across several bones. Notably, the fibula showed reduced fibular tip height in PCFD patients. The talus exhibited decreased lateral and posterior processes and an inferior, adducted talar head shift. The calcaneus had a narrowed posterior facet and anteriorly shifted anterior-medial facet. In PCFD patients, the navicular tuberosity was displaced toward the body with medial-inferior articular defects. The cuboid showed increased prominence of the tuberosity and beak.

Conclusion: These SSM results provide novel characterization of the 3D shape of bones from tibia to metatarsals in PCFD and asymptomatic females. Patients with PCFD exhibited distinct 3D shape differences in the distal fibula, talus, calcaneus, navicular, and cuboid, suggesting that PCFD is primarily characterized by deformities of the hindfoot bones.