Efficacy of dynamic external fixation for treatment of distal radius fractures using 3D kinematic analysis

The purpose of this study was to investigate the kinematics of external fixation devices used for distal radius fractures. Dynamic external fixator devices that are placed across the wrist joint facilitate fracture healing by allowing force transmission across the fracture site and articular cartilage repair by allowing wrist motion. If external fixation devices are to be used dynamically, then their actual effect on wrist kinematics should be determined. Unfortunately, there has been no agreement among authors regarding normal carpal kinematics. This study investigated several parameters, global wrist flexion/extension, angles between carpal bones, and the instantaneous screw axis (ISA), in an attempt to quantify normal kinematics and the kinematics of wrists with external fixators attached. The results of this study show that the center of rotation of the wrist is not limited to the proximal head of the capitate as previously suggested. It also shows that the global range of motion of the wrist is limited with the application of any of the dynamic external fixators tested. Finally, the intercarpal bone joint angles are altered with the application of an external fixator. The radial-lunate joint has an increased range of motion with an external fixator attached in order to compensate for the constraints imposed by the external fixator.