Failure characteristics of the isolated distal radius in response to dynamic impact loading.

Abstract

We examined the mechanical response of the distal radius pre-fracture and at fracture under dynamic impact loads. The distal third of eight human cadaveric radii were potted and placed in a custom designed pneumatic impact system. The distal intra-articular surface of the radius rested against a model scaphoid and lunate, simulating 45° of wrist extension. The scaphoid and lunate were attached to a load cell that in turn was attached to an impact plate. Impulsive impacts were applied at increasing energy levels, in 10 J increments, until fracture occurred. Three 45° stacked strain gauge rosettes were affixed along the length of the radius quantifying the bone strains. The mean (SD) fracture energy was 45.5 (16) J. The mean (SD) resultant impact reaction force (IRFr) at failure was 2,142 (1,229) N, resulting in high compressive strains at the distal (2,718 (1,698) µε) and proximal radius (3,664 (1,890) µε). We successfully reproduced consistent fracture patterns in response to dynamic loads. The fracture energy and forces reported here are lower and the strains are higher than those previously reported and can likely be attributed to the controlled, incremental, dynamic nature of the applied loads.