Rheumatoid arthritis: current trends in diagnostics, conservative treatment, and surgical reconstruction

Abstract

CONCEPTS AND DEVELOPMENT In 1962, an orthopedic research department was instituted at Blodgett Memorial Medical Center Grand Rapids, Michigan, to develop implants for arthroplasty of the small joints of the extremities (3, 4). The basic concept of implant resection arthroplasty was developed on the premises that a nonfixed, flexible, low-modulus silicone implant coudl adapt to the biomechanical variances of loading forces to help distribute and decelerate the loads to the contiguous bone and therefore could be useful as an adjunct to resection arthroplasty procedures. The ideal design was developed after years of flex and load testing, and was named the "distributing-load flexible hinge". (Dow Corning Corp., Midland, Michigan, USA). The basic concept can be summarized as: "bone resection + implant + encapsulation = functional joint". The flexible hinged implant acts as a dynamic spacer to maintain internal alignment and spacing of the reconstructed joint and as an internal mold that supports the healing capsuloligamentous system around the implant while early motion is started. Join stability is achieved through reconstruction of the ligamentous and musculotendinous systems. The implant becomes stabilized by the "encapsulation process" and no permanent fixation is required. Controlled postoperative motion in a dynamic brace is essential to guide the orientation of the healing capsular structures to obtain a functional balance of mobility and stability in the desired arc and alignment. Favourable bone remodeling around silicone implants has been noted in the MP and PIP joints as evidenced by maintenance of the shape of the cut end of the bone with metaphyseal cortical thickening and production of new bone around the intramedullary stem (10). However, fractures or cutting of the implant by sharp bone edges and implant abrasion can occur, especially in patients with severe rheumatoid disease, recurrent synovitis, incomplete correction of deformities or abusive patterns of daily activity. A High Performance (HP) silicone elastomer with improved resistance to tear propagation was developed in 1974. The fracture rate of HP silicone hinged implants in our clinic was approximately 5% at the level of the fingers and wrist, and was reported to be as high as 25% by other clinics. To correct this problem, a research project was initiated in 1976 to develop bone liners (grommets) to shield the implant midsection. The research facilities included Blodgett Memorial Medical Center Orthopedic Research Department, Michigan State University College of Veterinary Medicine, Clemson University College of Engineering, American Edwards, National Aeronautics and Space Administration, and the research laboratories of Dow Corning Corporation. A laboratory study, in vivo animal trials, and human clinical studies were done to evaluate ingrowth and press-fit fixation, semicircular and circumferential designs, and nine different materials (porous polyethylene, Proplast, pyrolytic carbon, stainless steel, stainless steel mesh, ion-bombarded cobalt-chromium, smooth cobalt-chromium, titanium, and glutaraldehyde-prepared bovine pericardium). The titanium press-fit circumferential design provided the best implant protection and bone response (Fig. 25.1). Approximately 2,000 circumferential titanium grommets have been used in our clinic for the first metatarsophalangeal joint since 1985, and the MP joints since 1987; excellent implant protection and good bone tolerance have been obtained to date. In 1985, we reported that particulate synovitis and cystic bone changes can occur around abradedsilicone implants due to the so-called "frustrated macrophage", which after ingesting particles, releases a variety of osteolytic enzymes. This phenomenon was especially seen with carpal bone implants overloaded with excessive compressive and shear stresses, implant oversize or subluxation, carpal instability, and excessive activity (7). It is felt that while HP silicone is more tear resistant, it is also more likely to generate wear particles from abrasion when used for spacer implants (carpal bones and single stem toe), and that the reactions could be related to the physical size of particles, and not their chemical composition. In 1986, we therefore developed titanium implants for the thumb basal joint, scaphoid, lunate, radial head and single stemmed toe which we have used since that time with very promising results. Particle related synovitis occurs less frequently with flexible hinged implants such as the finger, wrist and double-stemmed toe. The use of titanium grommets has decreased implant wear and further improved the durability of the latter procedures. The synovitis and nonseptic osteolysis associated with hip and knee total joint procedures, is now recognized as a polyethylene particulate problem. Although there have been a few reports in the literature suggesting a relationship between silicone implants and a broad spectrum of connective tissue diseases, systemic illness and autoimmune phenomena, the causal relationship has not been proven. It is known that rheumatoid patients are at excess risk to develop lymphomas, leukemia and myelomas possibly due to the immunological abnormality of rheumatoid arthritis (1). The participation of antigen-specific lymphocytes or antibodies in silicone particle-induced macrophage reactions has not been demonstrated in ongoing studies. Animal and human autopsy studies have shown that if migration of silicone particles occurs, it is limited to regional lymph nodes with no evidence of systemic dissemination. We have undertaken an indepth research study on the particle problem with the engineering and biology departments of a local university. We are using an in vitro model to try to duplicate the macrophage reaction in an effort to further understand and find solutions to the particle-induced reactions which can occur from metals, plastics, or elastomers.