Interpretation of variant morphological patterns in the hallucal cuneometatarsal joint

Abstract

First cuneometatarsal joints are normally characterized by a single articulating facet. In some cases, however, they may bear some degree of division into two, or even three, distinct facets. Typically, double facets at this joint are interpreted as evidence of partial or complete division of the medial cuneiform earlier in development, though evidence to support this interpretation is limited. The purpose of this study was to examine the relationship between double facets and bipartition by comparing the sex ratio in double-faceted medial cuneiforms from two Euro-American skeletal samples, with the unbalanced sex ratio found in cases of complete bipartition of the medial cuneiform. Upon examination, no statistically significant differences were found in double-facet frequency between females and males, and the sex ratio differed significantly from that seen in known cases of bipartite medial cuneiform. These results suggest that the existence of double facets distally on the medial cuneiform is likely not exclusively indicative of developmental bipartition, a conclusion also supported by reports of divided distal surfaces in non-bipartite medial cuneiforms in some prenatal specimens. Furthermore, medial cuneiforms bearing three facets distally to the first metatarsal sometimes occur, possibly more frequently in individuals of advanced age. Ultimately, understanding distal facet patterns on the medial cuneiform may hold significance for understanding joint mobility and susceptibility to hallux valgus deformity in hominins from both bioarchaeological and paleoanthropological perspectives.