Palmar tilt changes due to distal radius fractures and radiocarpal instability: a biomechanical study.

ABSTRACT

OBJECTIVE: To investigate the impact of dorsally angulated malunited distal radius fractures on the stability of the radiocarpal joint. METHODS: Eight fresh upper limb specimens from 4 human cadavers were obtained, in which radial osteotomy was performed to prepare models of Frykman I distal radius fracture. Pressure-sensitive film was applied to study the changes in the contact area distribution and the pressure load across the radiocarpal joint in response to palmar tilt variation, and the lateral radiograph of the wrist was taken at the end of pressure loading. RESULTS: When the dorsal tilt exceeded 10 degrees, the radioscaphoid and radiolunate articular contact areas were markedly decreased (P<0.01) and shifted to the dorsal aspect of the radiocarpal joint, where the pressure load was significantly increased (P<0.01). A dorsal radiocarpal subluxation was liable to occur on the sagittal plane when the dorsal tilt exceeded 40 degrees. CONCLUSION: A dorsal tilt over 10 degrees is the most primary cause of radiocarpal instability after a dorsal deformity due to distal radius fractures.