Background: The purpose of this study was to investigate scaphoid motion within the
scapho-trapezio-trapezoidal (STT) joint during wrist motion in the presence of STT joint osteoarthritis
Methods: We studied 11 wrists with STT OA and 5 normal wrists. Computed tomography (CT)
images were acquired in five wrist positions (maximum active flexion, extension, radial deviation,
ulnar deviation, and neutral position). The 3-dimensional surface models of the radius and scaphoid
were constructed and the motion of scaphoid relative to the radius was calculated.
Results and Conclusions: During wrist flexion/extension motion, the scaphoid rotated mostly in
the flexion/extension plane. The angle tended to be smaller in STT OA than in normal. During
wrist radioulnar deviation, the scaphoid was in an extended position in neutral wrist in STT OA.
The motion of scaphoid in STT OA was divided into two types: a rigid type and mobile type. The
mobile type rotated closer to the flexion/extension plane than the rigid type. Taking into account
scaphoid motion during wrist movement before surgery may provide better results in the treatment
of STT OA.