20 Jahres Ergebnisse der Kombination von beschichteter RM-Pfanne und CLS-Schaft. Langzeitbeobachtung einer komplett zementfreien Hüftprothesenimplantation

A total of 93 consecutive cementless hip arthroplasties were performed between January 1986 and July 1989 in 80 patients at the Orthopedic Clinic Kassel using the coated RM-cup and the CLS-stem. 48 total hip replacements were inserted in 41 men and 45 THR in 39 women. The average age at the time of the index arthroplasty was 50 years for men and 54 years for women. Corresponding to the low mean age of the patients the preoperative diagnosis was osteoarthritis in 55.9% of the hips, avascular necrosis in 21.5% and congenital dysplasia in 16.1%. Data was gathered pre-, intra- and in varying intervals postoperatively. After an average follow up of 19.3 years all 57 surviving patients with 67 hip replacements were located, 51 of which could be examined. The outcome of all 13 revised patients as well as of all 23 deceased patients could be traced. There was no lost to follow-up. 77.6% of the hip replacements still had the initial combination of implants in place. At the latest follow-up evaluation the mean Harris hip score of the unrevised cases was 87.5 out of 100 points. 79.6% were graded as excellent or good, 10.2% as fair and 10.2% as poor. 91.8% of the cases reported having no or only mild pain not affecting daily activities, which correlated to the high grade of subjective satisfaction. No patient regretted having had the operation. The radiological evaluation of the unrevised cases showed acetabular osteolysis in 17.6% and femoral osteolysis in 34.8% mainly of the proximal region. Only one femoral and one acetabular component were suspected to be radiologically loose. In all other cases a stable fixation was assumed. The wear of the cup was 0.119 mm per year for the entire series. Increased wear rates could be associated with revision, acetabular or femoral osteolysis and metal heads in comparison to ceramic heads. A method of wear assessment particularly devised for this study could be perfectly associated with the EBRA method (R² = 0.86) and thus successfully used for the radiological examination. 14 acetabular components had to be revised after a mean interval of 12.3 years between the index operation and the revision. The revision was performed for aseptic loosening in 5 hips, because of wear and osteolysis in 7 hips and because of infection in 2 hips. 8 femoral components had to be revised after a mean interval of 7.2 years. The revision was performed for aseptic loosening in 4 hips, because of periprosthetic fracture in 2 hips and because of infection in 2 hips. The analysis of the revision reports proved an excellent bone stock with good re-operability. Survivorship analysis of the revision of the acetabular component because of aseptic loosening as the end point revealed a cumulative survival rate of 94.4% at 19.3 years and a total probability of revision of 82.7%. The corresponding results for the femoral components were 95.0%, respectively 90.4% and for the combination of both components 90.7% and 79.7%. The log-rank-test resulted in statistically significant higher survival rates for the group of patients older than 52 years compared to the younger group. Our follow-up study revealed high survival rates of the evaluated cementless system at 20 years and confirms the accuracy of the implants’ philosophy.