[Guépar's total radio-carpal prosthesis in the surgery of the rheumatoid wrist. Apropos of 72 cases reviewed].

PURPOSE OF THE STUDY

Total wrist arthroplasty is an alternative to arthrodesis in the treatment of the rheumatoid wrist.

MATERIAL AND METHODS

Seventy-two GUEPAR total wrist arthroplasties in sixty-four patients with rheumatoid arthritis were reviewed 1 to 10 years after the operation (average follow-up of 4 years). GUEPAR total wrist arthroplasty is a bicondylar prosthesis. The radial component made of polyethylene is cemented in the radius. The carpal component made of metal is fixed by two screws in the second and the third metacarpal. This component is constitued by two pieces: a perforated lower part permitting the passage of the screws and its metacarpal fixation and a biconvex cover fixed on the lower part by a micro-screw.

RESULTS

In preoperative evaluation, all patients had severe pain and loss of function. Post-operatively, 89 per cent had no pain or mild pain and 96 per cent had better function. The average arc of flexion-extension was 47 degrees preoperatively and 39 degrees postoperatively. There were no deep infections or dislocations. Seventy percent of the patients were satisfied but eleven wrists (15 per cent) required revision: 5 cases for prosthesis revision and 6 cases for implant removal and arthrodesis. Prosthesis revisions 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 carpal component. Radial component loosening was associated in 3 cases with unscrewing of the micro-screw. Radiographical analysis showed in nearly all cases of this serie a bone resorption under the carpal component. 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 component micro-screw was accountable to abnormal use of polyethylene with reaction of the wear products and loosening of the radial component. This problem is now resolved. More disquieting is the bone resorption under the carpal component. In fact, this resorption was constant and evolutive. It was very likely due to micro-movements between the metacarpal screws and the carpal lower part. Also, the conception of the metacarpal-fixation of this prosthesis must be revised.

CONCLUSION

In rheumatoid arthritis, wrist arthrodesis gives good results if nothings affects the fingers, elbow or shoulder. If they are affected, total wrist arthroplasty is an alternative. Long term loosening of total wrist arthroplasty is a significant problem so its indication must be reserved for old patients.