Functional implications of radial diaphyseal curvature.

A recent study (Galtés et al.: Am J Phys Anthropol 135 (2008) 293-300) demonstrated that during pronation, pronator teres exerts a favorable force for radial lateral bending. On the basis of this finding, we hypothesized that the pattern of muscular loading exerted on the radius by this muscle might play a role as a mechanical stimulus involved in radial bowing. The current work relates the hypertrophy of the forearm muscles to the degree of lateral curvature of the radial diaphysis. The analysis is based on an original osteometrical index to estimate radial curvature, and it applies a visual reference method to grade the osteological appearance of 10 entheses of 104 radii from archaeological and contemporary samples. Using these morphological data as an indirect method to measure the association between muscular hypertrophy and bone curvature, this study reveals that the pattern of muscular loading exerted on the apex of the radial shaft by the pronator teres muscle may play an important role as a mechanical stimulus involved in diaphyseal bowing.