S5 IMPLANT ARTHROPLASTY OF THE HAND IN JAPAN

Abstract

Development of newer finger implant in Japan started with hinged Ceramic implant in early 1980’ and was abandoned its use in early stage (Doi 1984 and Minami 1988). Although silicone finger implant has been most popular, breakage of the implant, particle induced inflammation and implant subsidence continued to be the problems of the silicone implant. In turning to new century, there was another enthusiasm of developing new finger implant in Japan. Surface replacement was chosen for the PIP joints, however, most of design for the MP joint had constrained mechanism, including ball and socket joint with stem allows piston motion and semi-hinged joint with much freedom. Currently available finger implants in Japan will be discussed briefly.

The author developed cement-less surface finger implants (Self Locking Finger Joint, SLFJ) for the MP (including thumb) and PIP. Characteristics of the implant include,(1) the joints anchor(stem) has tapered screw with two long legs which spread intramedullary allows fixation without cement and thus change the position during the operation for optimum collateral tension, (2) joint design that preserve collateral ligament and surface contour, (3) simultaneous replacements of both MP and PIP are possible. Over 500 joins in 200 patients have been operated during last seven years. Of 50 cases operated by author with minimum of 4 years follow up, 34 cases were available for evaluation. There were 98 joints: 72 MP, 12 PIP and 14 MP of the thumbs. Average follow up was 5 years and 5 months (4 years ~ 6 years and 6 months). Fixation of the joints anchor were stable, only three joints showed marked loosening. Breakage of the joint anchors was found in 7 MP and 2 PIP; 5 out of 9 breakage of the legs were occurred during the operation. In x-ray evaluation, about half of the joint anchors were found securely fixed to the bone within 2 years. Dislocations of the joints were found in 4 MP joints in 3 cases (3 were early dislocation and were found to be technical failure and one late dislocation) and 2 PIP joints (one early and one late dislocation). Five MP implants were removed because of progressive flexion contracture and 3 MP and 2 PIP were re-operated. Range of motion of ext/flex averaged −25/70 in MP and −20/65 in PIP.