This study represents a new attempt to non-invasively analyze three-dimensional motions of the wrist in vivo.A volume-based registration method using magnetic resonance imaging (MRI) was developed to avoid radiation exposure. The primary aim was to evaluate the accuracy of volume-based registration and compare it with surface-based registration. The secondary aim was to evaluate contributions of the scaphoid and lunate to global wrist motion during flexionxxtension motion (FEM), radio-ulnar deviation (RUD) and radial-extensiodulnoflexion, "dart-throwing'' motion (DTM) in the right wrists of 12 healthy volunteers. Volume-based registration displayed a mean rotation error of 1.29" k 1.03" and a mean translation error of 0.21 k 0'25mm and was significantly inore accurate than surface-based registration in rotation. Different patterns of contribution of the scaphoid and lunate were identified for FEM, RUD, and DTM. The scaphoid contributes predominantly in the radiocarpal joint during FEM, in the midcarpal joint during RUD and almost equally between these joints during DTM. The h a t e contributes almost equally in both joints during FEM and predominantly in the midcarpal joint during RUD and DTM.

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