Abstract
This study investigates the relationship between the quality of the arthroplasty and the radiological appearance of the interface. Of special interest is the prognostic value of sustained stability and of improvement in the interface, a phenomenon we have not previously seen.
At 1 week and at 6 and 24 months postoperatively, we assessed radiographs of 20 randomly selected patients in whom cross-linked polyethylene cups had been implanted. We classified them into three stages: in stage 0 there was no interface in any zone, in stage I less than 2 mm and in stage II more than 2 mm. This was not a comparative study, but an important feature was the sustainment and/or improvement of the interface. In 16 patients a complete ‘white-out’ of interfaces in postoperative x-rays was sustained for the duration of the study. In three patients imperfect postoperative interfaces clearly improved. In only one patient, who had developed infection, was there deterioration. Widening was seen only in cases of gross mechanical failure or sepsis.
We postulate that cross-linking of polyethylene results in virtual absence of HDP debris and that this is the main reason for interface improvement. It is polythene particles that cause osteolysis, and their elimination dramatically improves the prognosis for total joint replacement. The results reconfirm that, provided fixation is complete, cement is not the main reason for interface failure.
We believe that this method makes total joint replacement viable even in young patients.
Secretary: Dr H.J.S. Colyn, Editor: Professor M.B.E. Sweet. Correspondence should be addressed to SAOA, Box 47363, Parklands, Johannesburg, 2121, South Africa.
