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 .
Primary Total Hip Arthroplasty with a Porous-Coated Acetabular Component. Seven-to-Ten-Year Results*
One hundred and eighty-four patients who had been managed , between 1984 and 1985 , with a total of 204 consecutive primary total hip arthroplasties with insertion of a Harris-Galante type-I acetabular component without cement were prospect ively studied . There were eighty-two men ( 45 per cent ) and 102 women ( 55 per cent ) . The mean age at the time of the operation was fifty-two years ( range , twenty to eighty-four years ) . One hundred and fifty-seven patients ( 173 hips ) were available for clinical review at a mean of 104 months ( range , seventy-eight to 126 months ) . At this time , the mean preoperative Harris hip score of 52 points ( range , 12 to 79 points ) had improved to a mean of 90 points ( range , 44 to 100 points ) . Two patients ( two hips ) had had an exchange of an excessively worn polyethylene liner . One patient ( one hip ) had had débridement and grafting of an area of massive retroacetabular osteolysis . Two stable acetabular components ( 1 per cent ) had been revised at the time of femoral revision . None of the cups had been revised because of aseptic loosening . Radiographic examination of 150 patients ( 165 hips ) at a mean of 104 months ( range , seventy-eight to 126 months ) revealed that 156 cups ( 95 per cent ) were stable . Eight cups ( 5 per cent ) were considered to be possibly unstable , with a radiolucent line between the prosthesis and the bone that was one millimeter wide or less in at least four of five zones ; two of the eight had a complete radiolucent line in all zones . One component , which had been implanted with a bulk allograft from a femoral head , migrated more than two millimeters in the first two years and then stabilized without complication . Osteolysis was seen in seven acetabula ( 4 per cent ) and was limited to the periphery of the cup in six . Survivorship analysis at ten years revealed that the acetabular component had a 99 per cent chance of survival ( 95 per cent confidence interval , 0.98 to 1.0 ) with revision or aseptic loosening as the end point and a 97 per cent chance of survival ( 95 per cent confidence interval , 0.95 to 1.0 ) with revision , aseptic loosening , or reoperation because of a problem related to the acetabular component as the end point
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 .