Myelopathy hand: new evidence of the classical sign.

STUDY DESIGN

Motion analysis on video files that captured grip and release cycles with fingers.

OBJECTIVE

To reveal the kinematic characteristics of finger motion in cervical myelopathy.

SUMMARY OF BACKGROUND DATA

Myelopathy patients are often unable to smoothly move their fingers in grip and release cycles. Although paradoxical wrist motion (trick motion) and lack of finger coordination are well-known phenomena in myelopathy patients, it is not known which types of myelopathy patients present with these kinematic characteristics, and it is not known why they occur.

METHODS

Thirty patients with myelopathy were evaluated before and after decompressive surgery and compared with 42 healthy controls. The subjects were asked to grip and release with their fingers as rapidly as possible for 15 seconds. Movies taken with a digital camera were divided into 3 animation files of 5-seconds each. Three physicians independently counted the number of finger grip and release cycles of those files in a blinded manner; they also evaluated trick motion of the wrist and lack of finger coordination.

RESULTS

Both the frequency of trick motion and that of uncoordinated finger motion were significantly higher in the preoperative myelopathy group than in the control group (trick motion, 11.7% vs. 4.8% and uncoordinated finger motion, 15.6% vs. 7.1%), but were the same in the pre- and postoperative myelopathy groups. In the preoperative myelopathy group, the number of grip and release cycles of uncoordinated finger motion files, especially ulnar delay type, was significantly smaller than that of coordinated finger motion files, which meant uncoordinated finger motion was related to the severity of myelopathy.

CONCLUSION

Both uncoordinated finger motion and trick motion of the wrist were more frequent in myelopathy patients than in healthy controls, and uncoordinated finger motion was associated with severity of myelopathy, whereas trick motion was not associated with either severity of myelopathy or level of cord compression. These findings contradict the conventional idea that trick motion is associated with the severity of myelopathy.