Correlation between wrist loads and the distal radius volar tilt angle

Background. Based on the phenomenon of bone adaptation to mechanical stimuli (Wolff’s law) this study investigates a previously unreported correlation between the maximum wrist joint reaction force and the volar tilt angle of the distal radius. Methods. Free body analysis of the sagittal-plane forces acting on the supinated distal radius during lifting and radiographic measurements in thirty normal wrists are used to analyse the correlation between the theoretically calculated maximum wrist joint reaction force and the radiographically measured volar tilt angle. Findings. Non-statistically significant difference (p = 0.33, 95% confidence interval −0.64° to 0.22°) and statistically significant correlation (R2 = 0.74, r = 0.86, p < 0.001) between the angle of the maximum wrist force and the volar tilt angle of the distal radius and inverse relationship between the volar tilt angle and the magnitude of the maximum wrist force (R2 = 0.71, r = −0.84, P < 0.001) were found. Interpretation. The radiographically measured volar tilt angle of the distal radius appears not to differ significantly from the theoretically calculated angle of the maximum wrist joint reaction force, a possible explanation for the phylogenetical development of the volar tilt angle. Also, an inverse relationship between the volar tilt angle and the magnitude of the maximum joint reaction force was observed suggesting that wrists characterized by a low volar tilt angle may be subjected during lifting activities to maximum joint reaction forces up to 50% higher than those in wrists with a high volar tilt and emphasising the importance of accurate restoration of the volar tilt during treatment of all distal radius fractures.