EFFECT OF DISTAL RADIUS FRACTURE ALIGNMENT ON FOREARM ROTATION

Abstract

This study examined the effect of wrist fracture deformities on the work and kinematics of forearm rotation in vitro.

An osteotomy was performed on eight fresh frozen upper extremities just proximal to the distal radioulnar joint and a three-degree of freedom modular implant designed to simulate distal radius fracture deformities was secured in place. This allowed for accurate adjustment of dorsal angulation, dorsal displacement, and radial shortening. The study was divided into two parts, the first phase examining the effects of distal radius deformity and the second sectioned the TFCC and repeated the testing, reviewing the effects of a progressive soft tissue injury in conjunction with distal radius deformity.

The magnitude of muscle activity required to achieve the motion, namely the work of rotation, was affected by the degree of simulated malunion and whether the TFCC was intact or sectioned. Increasing dorsal angulation caused a significant reduction in forearm pronation and supination. Once the TFCC ligaments were sectioned, the range of motion was restored to the pre-injured state for both pronation and supination. Dorsal displacement decreased the forearm range of motion significant at 10mm from native (p=0.02) and 5mm (p=0.03) for intact pronation. Radial shortening of 5mm or less had no effect on forearm rotation. However, 7.5mm of radial shortening could not be achieved in any of the specimens until the TFCC was divided.

Our results reveal that a significant loss of forearm rotation can be expected if a radius fracture exceeds thirty degrees dorsal angulation or 10mm of dorsal displacement. Radial shortening greater than 7.5mm could only be achieved concomitant with a TFCC rupture. This and further study in this area, should assist clinicians in developing treatment strategies for their patients with fractures and deformities of the distal radius.