There is motion between the scaphoid and the lunate during the dart-throwing motion

Scaphoid and lunate mobility has been suggested to be minimal during the dart-throwing motion in studies based on serial computed tomography (CT) scans and cadaver studies. This study analyzes the direct motion between the scaphoid and the lunate during the dart-throwing motion in vivo. We examined nine individuals with standard CT scans of the wrist in radial extension and ulnar flexion. The paired CT scans were analyzed with a volume registration technique. The lunate was registered as fixed and the scaphoid as the mobile element. The motion of the scaphoid relative the lunate between the positions of radial extension and ulnar flexion was measured. There was considerable motion between the scaphoid and the lunate with both a distal to proximal translation and rotation during the dart-throwing motion, regardless of whether the scapholunate ligament was intact or not. These results suggest that aggressive dart-throwing exercises should not be implemented early on during rehabilitation following scapholunate repair.