The development of an artificial finger joint

Joint replacement surgery is a challenging procedure in orthopaedic surgery that deals with pathological changes and degenerations of human joints. From the 1950s it has gained success in relieving pain and recovering motion of diseased joints where normal medication and physiotherapy has had little effect. Almost all mobile joints can be replaced by artificial ones. However, complications such as the lack of functional motion, recurrent joint deformity, implant loosening, wear and component fracture are still common and revision surgery is often required. An ideal solution for any implant system is still awaited with eager anticipation. The greatest achievements in joint replacement are probably in the area of total hip arthroplasty (THA) stimulated by Charnley?s [1] low-friction arthroplasty based on the articulating couple of metallic femoral head and polymeric acetabular cup, circa 1969. Gunston [2] employed this metal-on-plastic concept to develop a polycentric knee joint design, which is still widely accepted as the gold standard in total knee arthroplasty (TKA). Charnley?s implants reported long-term survival of about 90% at 10 years and 80% at 20 years in follow-up studies [3, 4]. Similar encouraging survival rates up to 83% at 16 years and 88% at 14 years were noted in new TKA systems [5, 6]. Joint replacement in the upper extremities has not shown the same level of accomplishment. Implant loosening is a major problem with a failure rate from 25% to 50% for condylar replacements of the elbow joint [7]. Neviasen [8] even pointed out that a constrained design of shoulder arthroplasty was so unsuccessful that over 90% of reviewed cases exhibited implant loosening, deformation or breakage. Swanson, in 1972 [9], introduced an arthroplasty replacing arthritic finger joints with a joint spacer made of silicon rubber. Swanson?s silastic implant has dominated finger joint replacement despite high fracture rate of 14% in a large series of studies with average follow-up of 8 years [10]. It is necessary to reconsider the working principles for design of implant systems for the upper extremity.