Conclusions Revisions and reoperations are more frequent and occur earlier with metal-on-metal hip resurfacing , except when discontinued devices are removed from the analyses .
Background Metal-on-metal hip resurfacing was developed for younger , active patients as an alternative to THA , but it remains controversial .
Study heterogeneity , inconsistent outcome definitions , and unst and ardized outcome measures challenge our ability to compare arthroplasty outcomes studies .
Questions / purpose sWe asked how early revisions or reoperations ( within 5 years of surgery ) and overall revisions , adverse events , and postoperative component malalignment compare among studies of metal-on-metal hip resurfacing with THA  among patients with hip osteoarthritis .
Secondarily , we compared the revision frequency identified in the systematic review with revisions reported in four major joint replacement registries .
Cobalt and chromium levels in blood and urine following hip resurfacing arthroplasty with the Conserve Plus implant.
BACKGROUND The purpose of the present study was to determine cobalt and chromium ion levels in the blood and urine of patients in whom a modern-generation metal-on-metal hip resurfacing device had been implanted . METHODS A total of ninety-seven patients with a Conserve Plus metal-on-metal hip resurfacing implant  were followed prospect ively for two years . Cobalt and chromium levels in erythrocytes , serum , and urine were measured preoperatively as well as three , six , twelve , and twenty-four months postoperatively . RESULTS The median serum cobalt and chromium ion levels were 1.04 μg/L ( range , 0.31 to 7.42 μg/L ) and 2.00 μg/L ( range , 0.28 to 10.49 μg/L ) , respectively , at one year after surgery and 1.08 μg/L ( range , 0.44 to 7.13 μg/L ) and 1.64 μg/L ( range , 0.47 to 10.95 μg/L ) , respectively , at two years after surgery . The corresponding mean levels ( and st and ard deviations ) of serum cobalt and chromium were 1.68 ± 1.66 μg/L and 2.70 ± 2.22 μg/L , respectively , at one year after surgery and 1.79 ± 1.66 μg/L and 2.70 ± 2.37 μg/L , respectively , at two years after surgery . CONCLUSIONS These levels compare favorably with other published ion results for metal-on-metal hip resurfacing and replacement implants . No pseudotumors or other adverse soft-tissue reactions were encountered in our study population . Further research is needed to determine the clinical importance of increased cobalt and chromium ion levels in serum and urine following metal-on-metal hip resurfacing
Conclusions Revisions and reoperations are more frequent and occur earlier with metal-on-metal hip resurfacing , except when discontinued devices are removed from the analyses .
Background Metal-on-metal hip resurfacing was developed for younger , active patients as an alternative to THA , but it remains controversial .
Study heterogeneity , inconsistent outcome definitions , and unst and ardized outcome measures challenge our ability to compare arthroplasty outcomes studies .
Questions / purpose sWe asked how early revisions or reoperations ( within 5 years of surgery ) and overall revisions , adverse events , and postoperative component malalignment compare among studies of metal-on-metal hip resurfacing with THA  among patients with hip osteoarthritis .
Secondarily , we compared the revision frequency identified in the systematic review with revisions reported in four major joint replacement registries .