Kinematics of the proximal interphalangeal joint of the finger after surface replacement

Nine fresh-frozen normal human cadaveric long fingers were used to compare the kinematics of the proximal interphalangeal joint (PIP) before and after a resurfacing metal-polyethylene prosthetic replacement (Avanta prosthesis , San Diego, CA) using the magnetic Isotrak system (Polhemus Navigational S ystems, Colchester, VT). The kinematics of the PIP joint after replacement were similar to that of the normal joint. The maximum angular displacement was 5 degrees for lateral deviation and 9 degrees for rotation during the p assive flexion and extension motion. The center of rotation after implant i nsertion was nearly identical to the center of rotation of the normal joint . This anatomically designed PIP prosthesis has potential to restore normal motion to the finger PIP joint while resisting physiologic out-of-plane fo rces such as pinch and grasp. (J Hand Surg 2000;25A:305-312. Copyright (C) 2000 by the American Society for Surgery of the Hand.).