Isoelastic arthroplasty of the metacarpophalangeal joints in rheumatoid arthritis: a preliminary report.

The Isoelastic prosthesis for the metacarpophalangeal joint was used in 68 rheumatoid joints. The average follow-up period was 3 years and 3 months. The subjective score for pain, appearance, and usefulness as well as the functional outcome was determined by means of a modified Green test. All subjective scores improved postoperatively, whereas function did not change significantly. Preoperative range of motion values were not available. The extension deficit after operation was 26 degrees, the average flexion 63 degrees, and the total range of motion 37 degrees. Grip strength improved only slightly. Complications included four cases of delayed wound healing and four metacarpal fractures after operation. The Isoelastic prosthesis gives satisfactory results in rheumatoid arthritis patients. The intraoperative insertion is easy and the material is well tolerated. In vivo, the implant itself is rigid enough to resist ulnar drift, although osteolysis around the plastic surface has caused recurrence of ulnar deformity.