CUSTOM-DESIGNED FEMORAL PROSTHESES IN TOTAL HIP-ARTHROPLASTY DONE WITH CEMENT FOR SEVERE DYSPLASIA OF THE HIP

A custom-designed femoral prosthesis was implanted with cement and a s tandard acetabular component was used to treat nineteen severely dyspl astic hips in fourteen consecutively managed patients. Components that had been custom-designed with the use of plain radiography were used because the anatomical reconstructive goals could not be achieved with commercially available implants. These goals were to match the offset of the femoral head and the length of the lower limb with those on th e normal side for patients who had unilateral involvement and to provi de an average (thirty to forty-millimeter) offset with equal limb leng ths for patients who had bilateral involvement. A retrospective clinic al and radiographic analysis was performed. The diagnoses included cox a vara (one hip), congenital dislocation (twelve hips), achondroplasia (three hips), and spondyloepiphyseal dysplasia (three hips). The mean age at the time of the reconstruction was forty-nine years (range, tw enty-two to seventy-three years), and the mean duration of follow-up w as fifty-seven months (range, twenty-seven to 108 months). In five hip s, bone-grafting of the acetabulum was needed to obtain superolateral coverage. The clinical result was excellent in eighteen hips and good in one. No revisions have been performed to date. Two femoral componen ts were possibly loose radiographically. One was associated with a def inite loosening of the acetabular cup. In addition, one other cup was possibly loose. There was a 100 per cent rate of survival if only a re vision procedure was considered as a failure. The probability of survi val of the custom-designed femoral component was 93 per cent (confiden ce interval, 95 per cent [range, 57.5 to 99.2 per cent]) at nine years if possible radiographic failures were included. The custom implants were designed with a varus neck to reduce impingement, and there was a 53 per cent average gain in the effective abductor lever arm. The use of a custom femoral component in hips with severe dysplasia allows fo r a good fit of the stem, preservation of bone stock in the superomedi al aspect of the proximal part of the femur, restoration of length of the lower limb, achievement of the desired offset, and, therefore, imp rovement of the biomechanics of the hip. The use of custom prostheses in patients in whom standard devices cannot provide anatomical restora tion is justified on the basis of clinical results and apparent cost-e ffectiveness.