In a randomized study of 60 patients allergic reactions are evaluated in three joint prosthesis groups, a resurfacing arthroplasty (ReCap), a non-cemented, large metal-on-metal head (Bimetric Magnum) and a non-cemented, alumina ceramic-on-ceramic bearing in a titanium shell (Bimetric C2a). The inclusion criteria were osteoarthritis, ASA I–II, MRI-scan without caput necrosis, DXA-scan without osteoporosis. The exclusion criteria were short neck (<2cm.), large cysts (>1cm.), medical treatment affecting the bone metabolism, severe deformity of the femoral head, impaired kidney function and inability to co-operate. Blood samples were drawn prior to and 6 weeks, 6 months, 1 year, and 3 years after surgery; two tubes from which plasma was prepared, and two tubes for serum. From the last included 20 patients in each group was also taken blood one and three years after surgery for an in vitro lymphocyte assay for scoring of possible hypersensitivity to prosthesis metals. The isolated lymphocytes were subjected to measurement of proliferation and expression of CD69 by flow cytometry and measurement of the Migration Inhibitory Factor (MIF) by ELISA. Plasma concentrations of the cytokines IL-1, IL-4, IL-6, IL-8, IL-12p70, IL-15, interferon-and osteoprotegerin were determined by multiplex-immunoassay. Serum concentrations of chromium and cobalt were determined by graphite furnace atomic absorption spectrometry. The serum concentrations of chromium and cobalt were lowest in patients with the C2a implant and highest with Magnum, some of these differences were significant at 6 weeks, 6 months, and 1 year after surgery. No patient had a very high serum metal concentration. The values of the variables measured in the in vitro lymphocyte assay mainly changed in the expected direction depending on the concentration of the same metal in the serum sample drawn at the same time, but no significant correlation was seen. One patient had uncertain symptoms of metal hypersensitivity and relatively high serum metal concentrations 3 years after arthroplasty with a Magnum prosthesis and was assessed extraordinarily, and elicited the marginally highest MIF responses in the lymphocyte assay. A strong correlation was found between the plasma concentrations of most cytokines, but the cytokine concentrations were not correlated to contemporary metal concentrations

Introduction. Metal-on-metal (MoM) articulations in total hip replacement (THR) have become an attractive option for young, active patients. Short-term reports have demonstrated elevated systemic metal ion levels in the blood and urine. Disseminated concentrations of cobalt and chromium have raised concern regarding cellular toxicity, chromosomal damage and adverse local soft tissue reactions. Long-term studies are required to support the increased use of MoM bearings in younger patients given their potential deleterious effects. The purpose of the current study was to report the 7–13 year clinical, radiographic, and metal ion results in patients following MoM THR. Methods. We prospectively followed 165 patients (196 hips) after second-generation MoM THR between July 1997 and November 2003. Functional outcome was measured using the Harris Hip Score (HHS) and the University of California Los Angeles (UCLA) Activity Score. Radiographic analysis was performed using Einzel-Bild-Roentgen-Analyse (EBRA) by two of the authors blinded to the study. Cobalt and chromium metal ions were measured from whole blood and analyzed using inductively coupled plasma-mass spectrometry. Results. 163 prostheses were analyzed. The mean age at surgery was 50.8 years (range, 17 to 66). There were 80 females and 83 males. The mean follow-up was 8.87 years (range, 7–13 years). Four hips (2.5%) were revised: 2 for infection at 0.2 and 7 years; 1 for a loose stem at 1.3 years; and 1 for a loose cup at 9 years. One patient received wound debridement for a superficial infection and did not have any components revised. The mean HHS and UCLA scores at the last follow-up were 91 and 6.8, respectively. The mean acetabular inclination and anteversion was 40 degrees (range, 24 to 57), and 19 degrees (range, 3 to 39), respectively. Median cobalt levels peaked at a value of 2.87 μg/L at 4 years (p<0.0001 vs. pre-operative) and subsequently decreased to 2.0 μg/L after 9 years (p=0.002 vs. 4-years). Median chromium levels maximally increased up to 0.75 μg/L after 5 years (p<0.0001 vs. pre-operative) and tended to decrease thereafter to values of 0.56 μg/L after 7 years. The Kaplan-Meier survivorship was 91.3% for revision for all causes, and 97.5% when excluding the hips revised for a manufacturer's defect at a mean of 8.87 years (range, 7–13 years). Conclusion. The present 7–13 years follow-up study of MoM THRs indicates that the clinical and radiological results are satisfactory with low revision rates. Furthermore, our study demonstrates the trend of metal ion levels in whole blood over a long-term. Both cobalt and chromium ion levels peaked at 4 and 5 years, respectively, and gradually decreased thereafter