Abstract
PURPOSE: Congruency of the proximal radioulnar joint (PRUJ) is important in the rotation of the forearm while any compromise would significantly impair the elbow function. The purpose of this study is to determine the morphological features of the radial head and investigate its role in the congruency of the PRUJ during forearm rotation. The hypothesis is that the PRUJ is more congruent in the maximal pronation and supination positions than in the neutral position. METHODS: Thirty sets of computed tomography images of the elbow were acquired, and a three-dimensional model of the proximal radius and ulna was generated. The radius of curvature of the radial head and the radial head at the maximal pronation, neutral positions and maximal supination were calculated and compared with a one-way analysis of variance. RESULTS: The point on the radial head contacting the middle point of radial head at the maximal pronation and supination was located at the ends of the semi-major axis of the ellipse, while it was located at one end of the semi-minor axis at neutral position. The radii of curvature of the pronation, neutral and supination points of the radial head were 14.72 ± 1.51, 9.74 ± 1.49 and 14.58 ± 1.70 mm, respectively. The value of the neutral point was significantly smaller than that of the pronation and supination points. CONCLUSIONS: This study quantitatively evaluated the morphology of the radial head and suggested that the best congruency of the PRUJ was achieved at maximal pronation and supination, while the neutral position was associated with the least congruency. LEVEL OF EVIDENCE: Basic Science Study.