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 .
Comparison of total hip replacement with and without cement in patients younger than 50 years of age: the results at 18 years.
There have been comparatively few studies of the incidence of osteolysis and the survival of hybrid and cementless total hip replacements ( THRs ) in patients younger than 50 years of age . We prospect ively review ed 78 patients ( 109 hips ) with a hybrid THR having a mean age of 43.4 years ( 21 to 50 ) and 79 patients ( 110 hips ) with a cementless THR with a mean age of 46.8 years ( 21 to 49 ) . The patients were evaluated clinical ly using the Harris hip score , the Western Ontario and McMaster Universities ( WOMAC ) osteoarthritis score and the University of California , Los Angeles ( UCLA ) activity score .  Radiographs and CT scans were assessed for loosening and osteolysis . The mean follow-up was for 18.4 years ( 16 to 19 ) in both groups . The mean post-operative Harris hip scores ( 91 points versus 90 points ) , the mean WOMAC scores ( 11 points versus 13 points ) and UCLA activity scores ( 6.9 points versus 7.1 points ) were similar in both groups . The revision rates of the acetabular component ( 13 % versus 16 % ) and the femoral component ( 3 % versus 4 % ) , and the survival of the acetabular component ( 87 % versus 84 % ) and the femoral component ( 97 % versus 96 % ) were similar in both groups . Although the long-term fixation of the acetabular metallic shell and the cemented and cementless femoral components was outst and ing , wear and peri-acetabular osteolysis constitute the major challenges of THR in young patients
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 .