TOTAL HIP-ARTHROPLASTY WITH USE OF AN ACETABULAR REINFORCEMENT RING IN PATIENTS WHO HAVE CONGENITAL DYSPLASIA OF THE HIP - RESULTS AT 5 TO 15 YEARS

The purpose of our study was to examine the clinical and technical pro blems associated,vith reconstruction of the hip in patients who had co ngenital dysplasia and to offer recommendations for their solution. We reviewed the records on 123 consecutive total hip arthroplasties that had been performed by one of us (M. E. M.), between 1981 and 1986, fo r the treatment of coxarthrosis due to congenital dysplasia of the hip . A minimum of five years of follow-up was required for inclusion in t he study, The study group consisted of seventy patients who had had a total of eighty-seven reconstructions. According to the classification of Crowe et al,, eleven hips had type-IV acetabular dysplasia; sixty- five, type-m; and eleven, type-II. Acetabular reconstruction was perfo rmed with use of the Muller acetabular roof-reinforcement ring and a p olyethylene cup, which was inserted with cement. Autologous graft from the femoral head was used in forty-two hips. Femoral reconstruction w as performed with use of the Muller straight-stem component for congen ital dysplasia of the hip in eighty hips and with use of a standard Mu ller straight-stem component in seven hips, At an average of 9.4 years (range, five to fifteen years) postoperatively, the result was descri bed as excellent for sixty hips (69 per cent), as good for twenty-thre e (26 per cent), as fair for two (2 per cent), and as poor for two. Ni ne (10 per cent) of the hips had been revised. One revision had been p erformed because of aseptic loosening of the acetabular component; one , because of aseptic loosening of the femoral component; one, because of aseptic loosening of both components; and six, because of infection . Of the unrevised hips, three had had superior migration of the aceta bular component of less than five millimeters, and mild protrusio had developed in one. Two hips had a continuous radiolucent line around th e acetabular construct. Two hips had had subsidence of the femoral ste m of less than three millimeters; one had a complete, non-progressive radiolucent line at the bone-cement interface; and four had a radioluc ent line at the proximal part of the bone-cement interface. Six hips h ad evidence of endosteal osteolysis. Six hips had grade-III or IV hete rotopic ossification according to the system of Brooker et al, These r esults compare favorably with others in the literature. We recommend r estoration of the anatomical hip center with the use of an acetabular roof-reinforcement ring and a polyethylene cup inserted with cement fo r the reconstruction of a deficient acetabulum, The acetabular reinfor cement ring prevents resorption of bone graft and migration of the cup , which are major causes of failure of the cup in patients who have ha d a reconstruction of a deficient acetabulum, Bone graft should be use d medially and superiorly as needed to augment bone stock notably. Cem ent should not be used to fill acetabular defects as we believe that i t contributes to aseptic loosening.