PATEL, B.A.*; CARLSON, K.J.; Stony Brook University; Stony Brook University: Hand Postures, Locomotion and Bone Density in the Primate Wrist

Bone adapts to loads it incurs in part by remodeling, which alters bone mineral density. Because mineral density is directly proportional to the compressive strength of bone, the location of maximum load on a joint surface can be estimated by characterizing the local distribution of density on a joint surface. Computed tomographic osteoabsorptiometry (CTO) permits non-invasive quantification of bone density at joint surfaces by measuring optical density over the joint surface. Optical densities serve as the basis for constructing contour maps that can reveal patterns in joint force transmission and loading history (M�ller-Gerble, 1989). This method has been widely used in clinical research, but it has yet to be fully embraced by functional morphologists. We employ CTO to investigate subchondral bone density patterns in the primate wrist. Distal radii of catarrhine primates exhibiting different forms of locomotion and hand postures were examined. Contour maps of optical densities were superimposed onto 3D reconstructions, generated from serial CT scans, to measure the magnitude and location of maximum density relative to anteroposterior and mediolateral reference planes. Pairwise comparisons between taxa reveal marked differences. In particular, bipedal humans had a diffuse pattern of maximum density, while quadrupedal non-human primates had a dorsally concentrated pattern of maximum density. There is relatively less distinction in the concentration and location of maximum density between quadrupeds. Different hand postures during locomotion may have an impact on density distribution within the joint surface, but this effect appears small relative to the difference between quadrupeds and bipeds. This study also demonstrates the utility of CTO in functional morphology studies. Research funded by Sigma Xi GIAR.