GUEPAR TOTAL WRIST ARTHROPLASTY FOR SURGE RY OF THE RHEUMATOID WRIST - REVIEW OF 72 CASES

Purpose of the study Total wrist arthroplasty is an alternative to art hrodesis in the treatment of the rheumatoid wrist. Material and method s Seventy-two GUEPAR total wrist arthroplasties in sixty-four patients with rheumatoid arthritis were reviewed 1 to 10 years after the opera tion (average follow-up of 4 years). GUEPAR total wrist arthroplasty i s a bicondylar prosthesis. The radial component made of polyethylene i s cemented in the radius, The carpal component made of metal is fixed by two screws in the second and the third metacarpal. This component i s constitued by two pieces : a perforated lower part permitting the pa ssage of the screws and its metacarpal fixation and a biconvex cover f ixed on the lower part by a micro-screw. Results In preoperative evalu ation, all patients had severe pain and loss of function, Post-operati vely, 89 per cent had no pain or mild pain and 96 per cent had better function. The average are of flexion-extension was 47 degrees preopera tively and 39 degrees postoperatively. There were no deep infections o r dislocations. Seventy percent of the patients were satisfied but ele ven wrists (15 per cent) required revision : 5 cases for prosthesis re vision and 6 cases for implant removal and arthrodesis. Prosthesis rev isions were justified by the unscrewing of the carpal component micro- screw : they gived good results. Arthrodesis was required for 4 radial component loosening and for 2 important bone resorptions under the ca rpal component. Radial component loosening was associated in 3 cases w ith unscrewing of the micro-screw. Radiographical analysis showed in n early all cases of this serie a bone resorption under the carpal compo nent. This resorption was 2 mm wide at an average of to 2 years and 4 mm wide at 4 years. Discussion Clinical results of this study are good but eleven wrists required revision, Nine of these revisions were due to anomalies of first prosthesis the unscrewing of the carpal compone nt micro-screw was accountable to abnormal use of polyethylene with re action of the wear products and loosening of the radial component. Thi s problem is now resolved, More disquieting is the bone resorption und er the carpal component. In fact, this resorption was constant and evo lutive. It was very likely due to micro-movements between the metacarp al screws and the carpal lower part. Also, the conception of the metac arpal fixation of this prosthesis must be revised. Conclusion In rheum atoid arthritis, wrist arthrodesis gives good results if nothings affe cts the fingers, elbow or shoulder. If they are affected, total wrist arthroplasty is an alternative, Long term loosening of total wrist art hroplasty is a significant problem so its indication must be reserved for old patients.