An Anatomical Evaluation of the Trapezium and Its Relationship to Basilar Joint Osteophytic Change.

Background: To perform a comprehensive osteologic investigation into trapezium anatomy and investigate the relationship between anatomical factors and osteophyte formation, focusing on sex-specific differences.

Methods: This was a cadaveric study involving 1233 trapezia and first metacarpals. Two subgroups ("Control" and "Main Study") were established. The "Control" cohort was used to identify features of the trapezium in specimens devoid of osteophytic change. The prevalence and severity of osteophytic change were investigated in the "Main Study" cohort. Sex differences were specifically assessed. Regression analyses were used to identify factors associated with osteophyte formation.

Results: Three discrete surface morphologies exist at the trapezium trapeziometacarpal (TM) facet: heart, quadrilateral, and bean. Controlling for height, men have a larger trapezium TM facet surface area. However, the trapezium assumes the same off-center saddle shape in both sexes. The presence of osteophytes at the basilar joint is a common finding; no differences in osteologic prevalence exist between sexes. The progression of osteophytic change complements the radiographic Eaton-Littler classification system. The trapezium TM facet increases the surface area with incremental osteophyte involvement, with the degree of surface area expansion correlated with increases in the severity of osteophytic change. Increased age, increased surface area, bean morphology, and decreased volar joint depth are associated with more severe osteophyte formation.

Conclusions: Anatomical features of the trapezium may contribute to osteophyte development. Although the prevalence of osteophytic disease appears equal between sexes, sex differences exist in some anatomical parameters. These differences may help explain the increased prevalence of symptomatic basilar joint disease in women.