Relationship Between First Tarsometatarsal Joint Displacement, Plantar Tarsometatarsal Ligament Morphology, and Hallux Valgus Angle.

BACKGROUND: This study aimed to examine whether the morphology of the articular surface of the first tarsometatarsal (TMT) joint, plantar tarsometatarsal ligament (PTML), and hallux valgus angle (HVA) were associated with plane-specific TMT joint displacement. METHODS: Nine Thiel-embalmed cadavers (18 feet) were included. HVA was measured using a goniometer. The capacity for TMT joint motion (mobility) was operationalized as displacement of the first metatarsal relative to the medial cuneiform under manual stress, measured ultrasonographically in the dorsal, plantar, and medial imaging planes. PTML morphology (length, width, and thickness) and TMT joint articular surface morphology (type classification) were assessed, and their associations with plane-specific TMT joint displacement were analyzed. RESULTS: No significant differences in dorsal, plantar, or medial displacement were observed between Type III and the other articular surface morphologies after adjustment for multiple comparisons. Similarly, PTML length, width, and thickness were not significantly associated with displacement in any direction. Although HVA was positively associated with plantar displacement before adjustment, this association did not remain significant after FDR correction. CONCLUSIONS: In this small exploratory cadaveric study, no statistically significant associations were identified between first TMT joint displacement and articular surface morphology, PTML morphology, or HVA after accounting for within-cadaver clustering and multiple comparisons. These findings should be interpreted cautiously because of the small sample size and limited range of HVA severity. LEVEL OF EVIDENCE: Level IV, Descriptive laboratory study.