Abstract
Introduction and Aims
The 21st Century has seen ceramic bearings become an increasingly popular choice in total hip arthroplasty due to their high wear resistance and inert wear debris without osteolysis promising a long term bearing solution. Early ceramic bearings were hindered by fracture but improved manufacturing processes and materials subsequently produced stronger ceramics. These third generation ceramics showed greatly reduced fracture rates but there is limited evidence in the literature reporting their long term survival and wear characteristics. The purpose of this study was to determine osteolysis and survival rates of Alumina ceramic bearings in cementless total hip arthroplasties with a minimum follow-up of 15 years.
Methods
We analyzed a series of 301 third-generation alumina-on-alumina cementless primary total hip replacements in 283 patients. The average age of the patients at the time of the arthroplasty was fifty-eight years, 51% were in women and 54% were right sided. All procedures were performed using the same surgical technique and the same implant at a single centre. Patients were followed up at six weeks, one, two, five, ten and 15 years. At 15 years postoperatively 46 patients (17%) had died of unrelated causes and 31 (10.2%) were lost to follow-up. Patients were assessed clinically and radiographically. Retrieved bearings were analyzed for wear.
Results
At the time of the latest follow-up the mean Harris Hip Score was 94 points and 97% of the patients scored an excellent or good result with less than 4% having moderate residual pain. Radiographically, all patients assessed had evidence of stable bony ingrowth. Minor osteolysis was seen adjacent to 4% of cups and in none of the stems. There were eleven revisions in all, four stem revisions due to periprosthetic fracture, one secondary to aseptic loosening and one to facilitate a femoral shortening osteotomy. One cup was revised for aseptic loosening and one cup was revised for soft tissue impingement. One cup underwent revision due to acetabular osteolysis due to metallosis with some ceramic wear caused by neck impingement. There were two revisions for ceramic fracture, one liner and one femoral head. Overall, the survival rate of the implants for any cause revision was 96% at 15 years, with. The rate of survival of both components, with revision because of aseptic loosening or osteolysis as the end point, was 99% at 15 years. Analysis of retrieved femoral heads identified a median wear rate of 0.2mm3/year.
Conclusion
Ceramic bearings were designed to overcome the problem of osteolysis due to wear from polyethylene bearings. This study has shown that Alumina bearings in cementless primary total hip arthroplasty have an excellent survival rate at 15 years with good function, low wear rate and no adverse radiographic changes typical of osteolysis. The fracture rate was low in our study. These findings strongly supporting the use of Ceramic as a bearing choice for the 21st Century.
