Background The ulnar deviation (Ud) deformity of the metacarpophalangeal (MCP) joints is a typical deformity in the patients of rheumatoid arthritis (RA). Joint replacement arthroplasty can be indicated for the treatment of severe Ud deformity, silastic prosthesis being widely used with generally good results . There are few, however, previous reports focusing on the relationship between the range of motion (ROM) of the MCP and PIP joints after the surgery.
Objectives The objective of this study was to investigate the influence of silastic replacement arthroplasty of MCP joint replacement on post-operative extension range of PIP joint of the same finger.
Methods RA patients who underwent silastic replacement arthroplasty of at least 1 MCP joint except for thumb for the treatment of Ud deformity were reviewed. There were 80 hands of 65 patients, average age of whom was 70.1 (32.4 - 86.1) years old, 56 patients being female and 9 being men. The ROM of the PIP joints before and after surgery was collected from the medical records, and the relationship between the post-operative change of ROM in PIP joints and post-operative ROM of in the MCP joint of same finger was examined. Paired-t test and the correlation coefficient were used for statistical analysis.
Results The mean active extension range of PIP joints in index to little finger changed from -0.68° (-56.0–30.0) to 0.92° (-52.0–30.0)° [P=0.55], -5.64° (-104.0–30.0) to -8.44° (-56.0–30.0) [P=0.03], -3.44° (-112.0–32.0) to -8.91° (-94.0–40.0) [P=0.08], and -9.81° (-96.0–30.0) to -17.2° (-76.0–30.0) [P=0.07], respectively. There was an indication of a decrease in post-operative extension range of PIP joint except for the index finger. The ROM of the PIP joint was reduced only in the little finger, but was significantly increased in the index and middle finger. Correlation coefficients between the active flexion range of the MCP joint and the active extension range of the PIP joint of index to little finger was 0.34, 0.19, 0.08, and 0.33 respectively, no correlation being found.
Conclusions Post-operative decline in active extension of the PIP joint might be a compensatory change accompanying a shift of the arc of motion of the replaced MCP joint to a more extended position . However, since the correlation between extension deficit of PIP join and MCP joint flexion range was not actually observed, it is unlikely that a decrease in the extension of the PIP joint is a result of compensation. There is a possibility that the procedure such as intrinsic tendon release, bone shortening by resection of metacarpal head, and centralization of extensor tendon , might influence the postoperative PIP joint motion. It is necessary to pay attention to changes in the ROM of the PIP joint after joint replacement arthroplasty of MCP joint.
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Disclosure of Interest None declared