The biomechanical analysis of the hand in rheumatoid arthritis patients with MCP arthroplasty

Abstract

Rheumatoid arthritis (RA) is a chronic inflammatory disease, causing extreme deformity, pain and swelling of joints, severely affecting quality of life. Arthroplasty has had considerable success in larger joints such as the hip. The most frequently used artificial finger joints rely on a silicone elastomer component for their flexibility. However, success of these implants has been mixed; with fracture rates for the elastomer component reported to be up to 82%. It is currently unknown why fracture of the elastomer occurs so frequently. Motion analysis was used to determine range of motion (ROM) of the metacarpophalangeal (MCP) joints in patients with rheumatoid arthritis, both without and with arthroplasty, to determine how the procedure affects motion of the joint. A 12 camera motion capture system was used to capture hand kinematic data. Preliminary experiments determined the best positions for reflective markers for measuring motion. Subjects consisted of a control population (20) and a patient population (10 without surgery and 10 with). Data were processed to give maximum, minimum and ROMs of flexion/extension and abduction/adduction at all MCPs during four movements: pinch grip, key grip, fist clench and hand spread. Results showed ROM was decreased by ageing, further by RA, and further again by replacement surgery. MCP surgery patients produced significantly lower ROMs than all other groups, suggesting the implants may not restore movement.