An Anatomical Equivalence Study of the Capitate and the Second Metatarsal Head as a Donor for Lunocapitate Articular Reconstruction.

PURPOSE: To evaluate the anatomical equivalence of the proximal articular surface of the capitate and the second metatarsal head as potential donor-recipient surfaces for lunocapitate reconstruction.

METHODS: Ten capitates and 10 second metatarsals were excised from the bilateral hands and feet of five cadaver specimens. Frontal and sagittal photographs were obtained for each specimen, and articular parameters, including head width, length, thickness, and radius of curvature, were measured using standardized two-dimensional analysis. Morphological equivalence was assessed using paired two one-sided tests with predefined equivalence margins. Sagittal analysis included both radial and ulnar views, as well as crossed-orientation comparisons to simulate nonipsilateral grafting conditions. Three-dimensional surface analysis of a representative specimen was conducted for qualitative validation.

RESULTS: Equivalence was demonstrated for head width in the frontal view. In sagittal analyses, the radius of curvature consistently met equivalence criteria across both ipsilateral and crossed-orientation comparisons. Three-dimensional analysis demonstrated close overall surface congruity after rigid registration, supporting the two-dimensional findings.

CONCLUSIONS: Critical articular parameters, specifically head width and radius of curvature, demonstrated robust anatomical equivalence between the proximal articular surface of the capitate and the second metatarsal head across multiple orientations. These findings provide an anatomical rationale for considering the second metatarsal head as a donor for lunocapitate reconstruction.

CLINICAL RELEVANCE: Anatomical equivalence of articular geometry, particularly curvature, supports rational donor-site selection for capitate reconstruction when preservation of joint congruity is prioritized.