[Clinical efficacy and serum cobalt, chromium metal ion concentrations after total hip arthroplasty with three different hard-on-hard bearings].

OBJECTIVE: To compare the clinical efficacy and serum concentrations of cobalt, chromium metal ion in three different hard-on-hard bearings after total hip arthroplasty at 2-years postoperatively. METHODS: Ninety (90) THA patients were divided into ceramic-on-ceramic (COC), ceramic-on-metal (COM), metal-on-metal (MOM) group (n = 30 in each group). At preoperative and 3, 6, 12, 24 months postoperative 5 time points, serum concentrations of cobalt and chromium metal ion were measured, Harris hip score was evaluated, X-rays and color doppler ultrasound examination of the ipsilateral hip also were observed. RESULTS: The excellent rates of Harris hip score were 100% in three groups. Continuous X-rays showed no radiolucent line around the acetabular component, no osteolysis, and no inflammatory pseudotumor. After the THA operation, the metal ion levels in COM and MOM groups increased rapidly, and stabilized at 12 months, then showed a downward trend, but the chromium ion level of MOM continued to rise at 24 months, with a significant difference when compared with that at 12 months (an increase of 0.48 microg/L, P = 0.021). The serum concentrations of metal ion in COC group were relatively constant at all time points, and the cobalt, chromium ion levels of MOM group were significantly higher than those of COC and COM group. CONCLUSION: The postoperative functional recovery of the three hard-on-hard bearings all were good, and no inflammatory pseudotumor and osteolysis were found. The serum levels of cobalt, chromium ion of COM were lower than those of MOM, but higher than those of COC.