Various circular arc radii of the distal volar radius and the implications on volar plate osteosynthesis.

The purpose of this anatomical study was to explore the different circular arc radii of the distal volar radius and provide more detailed anatomic information that will further the understanding of volar plate osteosynthesis. The profiles of the volar distal radii of 100 cadaver specimens were measured with a common profile gauge. Profiles were copied onto paper and then matched to a best-fit circular arc template to determine the radius of curvature on the radial and ulnar sides of the distal volar radius. The mean circular arc radius of the distal volar surface was 2.6 cm (+/-1 cm, 1-6 cm) on the radial side and 2.3 cm (+/-1 cm, 1-6 cm) on the ulnar side. A significant difference (P<.01) was noted in the radii of curvature of the distal radius in 55% of the study population. In 37% of these cases, the circular arc radius flattens toward the ulnar side. In 63%, it flattens toward the radial side. This characteristic may lead to a false rotation position of the distal fracture fragment following volar plate osteosynthesis. In addition, suboptimal or incorrect plate position may result due to the discrepancy between the plate radius of curvature and the radius of curvature of either the radial or ulnar volar radius.