Abstract
Pronation-supination movement of the forearm is very important to ensure smoothed motion during daily and sports activities. Since abnormal motions in the radioulnar joint during pronation-supination may cause distal radioulnar joint diseases, evaluation of the three-dimensional (3D) position of the radioulnar joint is necessary in order to elucidate the development and progression of the distal radioulnar joint diseases. The purpose of this study is to present an in-vivo method for analyzing 3D forearm motion with low radiation exposure and high accuracy. This method combines calibrated bi-plane X-ray imaging (frontal and lateral views) and CT scan of forearm to create 3D radius and ulna models. The 3D positions of the radius and ulna were recovered by matching the projected outline of the 3D bone model with the calibrated bi-plane x-ray image of the corresponding bone. Bi-plane X-ray images of forearms of 5 normal subjects were taken at the 90° of pronation, 45° of pronation, neutral position, 45° of supination, and 90° of supination. The relative position of the radius with respect to the ulna was evaluated during pronation-supination. Dorsal-palmar and radius-ulnar translations of radius were larger than proximal-distal translation. Maximum translation, 21.2 ± 3.8 mm, was found in dorsal-palmar direction at 90° of supination. Rotation about proximal-distal axis of radius was much larger than those about dorsal-palmar and radius-ulnar axes. Rotation angle reached its maximum value, 64.0 ± 11.1°, at 90° of supination.
