Three-dimensional quantitative comparative analysis of trapezial-metacarpal joint surface curvatures in human populations

Trapezial-metacarpal (TM) joint surfaces appear to be shallower in Asian than in white postmortem specimens, and the frequency of TM osteoarthritis seems to be substantially lower in Asian TM joints. This study tested the hypothesis that there are significant differences among human populations in TM joint surface curvature and that populations of Asian descent have less curvature than those of recent European descent. The sample included trapeziums and first metacarpals from skeletons of 80 individuals of recent European and Asian descent and from skeletons of 34 African and 9 Australian aboriginal individuals. We scanned the surfaces using a laser digitizer to generate 3-dimensional models of each articular surface. We calculated dorsovolar, radioulnar, and root mean square curvatures by fitting modeled quadric surfaces to the TM joint surfaces. We tested pairwise comparisons of mean curvatures between populations for statistical significance using a standard resampling method (ie, bootstrapping). We also made pairwise comparisons of mean curvatures between males and females for a combined African and European sample. Mean dorsovolar metacarpal curvature was significantly higher in the European sample than in the Asian, African, and Australian samples. Mean root mean square curvature of the trapezial surface was significantly higher in the European sample than in the Asian sample. The European sample had the highest root mean square and dorsovolar trapezial curvatures of all the populations. We found no significant differences between male and female specimens. A tendency toward higher mean dorsovolar curvature of both the metacarpal and trapezial surface in the European sample may help to explain the higher frequency of TM osteoarthritis reported in Europeans. The greater TM curvatures affect basal thumb joint mechanics in thumb opposition and therefore may be a factor in the development of osteoarthritis at this joint in Europeans.