Background: We previously reported the outcomes of a case-control study, at a minimum of five years of follow-up, comparing metal-on-metal and ceramic-on-polyethylene bearings for cementless primary hip arthroplasty in active patients below the age of fifty years. This report is an update on these groups after a minimum duration of follow-up of twelve years.
Methods: Thirty-nine metal-on-metal cementless hip replacements with a 28-mm-diameter Metasul articulation were compared with a control group that included thirty-nine cementless ceramic-on-polyethylene hip replacements performed with a 28-mm-diameter head. The Metasul group included thirty patients with a mean age of forty years (range, twenty-three to forty-nine years), and the control group included thirty-two patients with a mean age of forty-one years (range, fifteen to forty-nine years). The groups were matched for age, activity level, preoperative Harris hip score, acetabular cup diameter, and indication for hip arthroplasty. All patients had a high level of activity, with 82% rated as grade IV or V according to the Devane scale.
Results: After a mean duration of follow-up of thirteen years (twelve to fourteen years), only one hip (3%) had asymptomatic acetabular osteolysis and no hip (0%) had been revised in the metal-on-metal group, whereas eighteen hips (46%) had osteolysis and eleven hips (28%) had been revised because of wear or osteolysis in the ceramic-on-polyethylene group (p < 0.003). In the metal-on-metal group, the median Co concentration in the whole blood was 0.95 μg/L (0.4 to 4.8 μg/L) and the median Cr concentration was 1.2 μg/L (0.1 to 5.6 μg/L). The twelve-year survival rate (with reoperation for any reason as the end point) was 100% in the metal-on-metal group and 70% (95% confidence interval, 63% to 77%) in the ceramic-on-polyethylene group (p = 0.003).
Conclusions: After twelve to fourteen years of follow-up, metal-on-metal implants demonstrated better radiographic and survival results than ceramic-on-polyethylene implants in young, very active patients. Current wrought metal-on-metal implants with a 28-mm-diameter head and high carbide concentration did not produce the high rates of osteolysis and allergic reactions that may be observed with cast low-carbide metal-on-metal bearings after a shorter duration of follow-up.
Level of Evidence: Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.