Range of motion of the metacarpophalangeal joint in rheumatoid patients, with and without a flexible joint replacement prosthesis, compared with normal subjects.

BACKGROUND: The metacarpophalangeal is commonly affected by rheumatoid arthritis. This may lead to joint replacement with a flexible prosthesis. The aims of this study were to determine the effects of rheumatoid arthritis on joint motion and to determine whether joint replacement needs to restore the full range of motion.
METHODS: Three-dimensional motion analysis was used to measure the range of motion of the metacarpophalangeal joint in rheumatoid patients with and without a flexible silicone arthroplasty, when performing pinch and key grips, when making a fist and when spreading the fingers. The results were compared with those from younger and older normal subjects.
FINDINGS: There appeared to be a trend for a decrease in range of motion from younger normal to older normal to rheumatoid (no prosthesis) to rheumatoid (with prosthesis) subject groups. However, statistically different (p<0.05) results were only observed for some movements (mostly involved in making a fist), in some fingers and between some subject groups. The only exception to this apparent trend was in flexion/extension when spreading the fingers into abduction.
INTERPRETATION: Making a fist is the most sensitive simple measure of range of motion in the metacarpophalangeal joint. Successful replacement of the metacarpophalangeal joint in patients with rheumatoid arthritis need not restore the normal range of motion.