Biomechanical Evaluation of Distal Radius Fracture Stability

Objectives/Hypotheses: (a) To determine the radiographic correlation between an artificially created dorsal comminution (via a wedge osteotomy) and dorsal tilt (clinical instability) and (b) to determine the efficacy of cast immobilization in maintaining reduction of the simulated fracture pattern as a predictor of successful treatment in the clinical setting. Study Design: Biomechanical cadaveric study. Setting: Level I trauma center. Methods: In ten fresh cadaveric upper extremities, sequential dorsal wedge osteotomies (25, 50, and 75 percent of the distal radial diameter) were performed, each followed by measurement of tilt and radial inclination on posteroanterior and lateral radiographs before and after applying a load simulating the physiologic static forces of the forearm. In the last five specimens, the osteotomies were reduced and casted after the load application for each osteotomy, and radiographic measurements were again taken under loaded and unloaded conditions. Results: In the uncasted loaded group (n = 10), average tilt changed from an initial 9 degrees palmar to 3 degrees palmar after the first osteotomy and became dorsally angulated (11 and 30 degrees) after the second and third osteotomies, respectively. Casting and loading resulted in a palmar tilt of 10, 6, and 3 degrees for the 25, 50, and 75 percent osteotomies, respectively. Conclusion: Increasing wedge osteotomies across the midline axis of the radius resulted in dorsal tilt and radial inclination changes representative of clinically unstable fractures that require more aggressive treatment protocols. However, in our experimental setting, casting maintained reduction of stable and unstable osteotomy patterns.