TOTAL HIP-ARTHROPLASTY WITH A TITANIUM TH READED CUP - SURVIVORSHIP ANALYSIS OF 508 CUPS

The current decrease of total hip arthroplasty using a cemented polyet hylene cup point out that bone-cement interface and polyethylene wear are two weak points responsible for long term loosening. Alumina-alumi na combination can avoid one of the weak points. But fixing an alumina cup with cement doesn't avoid the second one. So from 1983 we have be en using a cup composed by a titanium alloy threaded ring with an alum ina insert. From the 508 prosthesis we fixed in between 1983 and 1989, 446 have been followed up over one year with an average follow-up 4 /- 1,6 years. The patients mean age was 61,7 +/- 12 years. 368 were pr imary THA performed mostly for osteoarthrosis, 78 were performed in re vision cases of cemented cup. All the femoral stems were cemented, we noted only two loosenings. The clinical results were satisfactory in p rimary arthroplasties (90.7 per cent satisfactory results in the R. Me rle d'Aubigne and M. Postel scoring system), whereas in revision cases of cemented cups the percentage of non satisfactory results (32.8 per cent) was very high. Nevertheless migration rate of the theaded rings was 13 per cent (n = 48/368) in primary operation. 8,11 per cent when no structural graft was needed, 22,8 per cent when grafted. Although only 17/48 have been revised up to now, the future of the last 31 rema in uncertain. In our opinion, the threaded cup should not be used in r evision cases of cemented cups. The long term fixation of a threaded c up remains a problem for the dysplasic acetabula. For the non dysplasi c non operated acetabula the mig ration factors are statistically : fe male sex, osteoporosis whatever the aetiology, a wrong primary positio nning (cup too vertical, protrusio). For all these reasons, from 1989 we have been using a press-fit titanium cup, with promising results.