A randomised, controlled clinical study on total hip arthroplasty using 4 different bearings: results after 10 years.

PURPOSE: To compare 4 different bearings in total hip arthroplasty (THA) in a randomised controlled clinical study on clinical performance. METHODS: 393 patients with osteoarthritis of the hip or avascular necrosis were included and allocated to 1 of the head-and-cup couples zirconia-on-polyethylene (group A), metal-on-metal (group B), zirconia-on-polyethylene with the liner moulded into the shell (group C), or alumina-on-alumina (group D). In the individual case the surgeon could choose other implants if indicated. RESULTS: 299 patients were operated with the allocated prosthesis. The estimated cumulated prosthesis survival percentages and 95% confidence interval after 10 years were: group A 84.6 (75.8-93.4); group B 95.0 (89.5-100); group C 93.2 (86.7-99.7); group D 66.1 (54.5-77.7). The patients' physical function was significantly improved and remained equally good in all 4 groups, however slightly declining with ageing. The luxation rate was initially high, and equal between the groups, but was reduced by improving the surgical procedure introducing capsule repair by reinsertion of the short external hip rotators. CONCLUSIONS: The metal-on-metal or zirconia-on-polyethylene prostheses had high 10-year survival percentages. The longevity of these bearing couples by themselves was not related to the combination of materials. The zirconia-on-polyethylene prosthesis with the liner mounted peroperatively possibly exhibited cases of backside wear which the corresponding bearing couple with moulded polyethylene (Asian) did not. The alumina-on-alumina bearing performed poorly - it was redesigned after our study initiation and later withdrawn from the market.

Clinical Performance of the ASR and ReCap Resurfacing Implants­7 Years Follow-Up.

We perform a non-randomized, consecutive pilot study on the ASR and ReCap resurfacing hip implants and have completed 7 years follow-up. Forty-six non-osteoporotic patients with hip osteoarthritis and anatomical conditions suitable for resurfacing were divided into 2 equal groups and operated sequentially, starting with the ASR implants. Sixteen patients operated with ASR and 19 patients with ReCap have been followed-up. There were no significant differences between the two groups preoperatively as to physical function, pain, or femoral BMD. The serum concentrations of cobalt and chromium were higher in the ASR group from 1/2 to 7 years postoperatively. Five of 16 ASR implants have been revised, and none of the ReCap implants. BMD below the femoral component increased in both groups.