Radial styloidectomy: a biomechanical study on stability of the wrist joint.

We investigated the influence of radial styloidectomy on carpal alignment and examined translation of the wrist after sequentially increased styloidectomy of 8 cadaver wrists. The radial aspect of the scaphoid fossa of the distal radius was cut obliquely at 3, 6, and 10 mm from the radial styloid guided by real-time fluoroscopy. Radiographic analysis of the changes of carpal alignment was performed with the wrist in neutral position. Force-displacement curves from the neutral to the radioulnar and palmar-dorsal directions were obtained using a multi-axis testing machine. Results demonstrated no significant malalignment of the carpal bones after radial styloidectomy. Significantly increased radial translation (>40% reduction in stiffness), however, was observed due to the loss of radial articular contact after 6- and 10-mm radial styloidectomies. Significant ulnar and palmar carpal displacement also was noted after 6- and 10-mm radial styloidectomies, with 6 specimens demonstrating moderate ulnar and palmar translation and 2 demonstrating notable increased palmar and ulnar translations. We conclude that there is a definite risk of increased carpal instability with radial styloidectomy procedures. A styloidectomy of no more than 3 to 4 mm is recommended.