Finger motion analysis of the patients with cervical myelopathy.

Methods: Pinch motion between the thumb and the index finger in myelopathy hand was analyzed using micro-reflective markers and the VICON system. Objective: To clarify the disturbance in small finger motions of the myelopathy hand.

Background: Specificity of hand dysfunction of the patients with cervical myelopathy was recently recognized as the myelopathy hand. The author established the video-based finger motion analysis system and have been applied it to some disease with abnormal pattern in finger movement.

Methods: The subjects included 11 normal persons (normal group; mean age, 30.2 years) and 9 patients with cervical myelopathy caused by spondylosis, ossification of the posterior longitudinal ligament, or disc herniation (myelopathy group; mean age, 56.0 years). All patients exhibited myelopathy hand, which was defined by two specific signs: the finger escape sign and the inability to grip and release rapidly with the fingers. Fourteen 3-mm micro-reflective markers were placed on the dorsal surface of the thumb and the index finger, and on the dorsal hand. Repeated pinching of a small ball, coin, and small rod was recorded by four infrared video cameras with the movement of each marker tracked in three dimensions. The flexion angle of the thumb IP and MCP joints, and the DIP, PIP, and MCP joints of the index finger were calculated as the angle between the vector joining the markers.

Results: When pinching the ball, the mean maximum flexion angle and arc of motion of the index DIP and PIP joints were significantly larger in the myelopathy group than in the normal group, while there was no difference in the MCP joint. In the thumb, the maximum flexion angle and the arc of motion of the thumb MCP joint were significantly larger in the myelopathy group than in the normal group. In addition, the arc of motion of the thumb IP joint was larger in the myelopathy group than in the normal group. Similar results were obtained when pinching the coin and small bar.

Conclusions: Overall, the patients with myelopathy hand exhibited a larger flexion angle in the two distal finger joints when pinching small objects.