Second-Generation MoM Hips Serve Patients Well

Patients who underwent total hip arthroplasty with second-generation metal-on-metal bearings had results similar to patients who received other hard-on-hard bearings at the 17-year follow-up.

“The clinical and radiographic results of our study, which to our knowledge, represent the longest duration of follow-up for a series of cementless total hip arthroplasties with use of a 28-mm metal-on-metal bearing, continue to be comparable with the results observed for other hard-on-hard bearings,” the authors wrote in the abstract.

In the retrospective study, the researchers followed up on clinical and radiographic results of 49 patients who underwent total hip arthroplasty with second-generation 28-mm metal-on-metal bearings between 1992 and 1994. The average follow-up was 17.9 years and the mean age was 70.9 years.

The implant had a titanium-aluminum-niobium alloy stem (Zweymüller, Alloclassic, Zimmer, Winterthur, Switzerland), conical screw cup made of titanium (CSF, Zimmer), a polyethylene liner and an articulating surface and ball made of cobalt-based Co-28Cr-6Mo alloy (Metasul, Zimmer).

Surgeons revised three cups and one stem for aseptic loosening and focal osteolysis. The mean Harris Hip Score was 88.8 points and University of California Los Angeles Activity score was 6.7 points. At 18.8 years, implant survival was 93 percent. The average serum cobalt concentration was 0.70 µg/L.

“These results were superior to those of certain bearings like polyethylene-on-ceramic and even comparable with those of other hard-on-hard bearings,” the authors wrote.