INTERPRETATION There was a clinical ly relevant association between early migration of acetabular cups  and late revision due to loosening .
BACKGROUND AND PURPOSE The association between excessive early migration of acetabular cups  and late aseptic revision has been scantily reported .
We therefore performed 2 parallel systematic review s and meta-analyses to determine the association between early migration of acetabular cups  and late aseptic revision .
Survival of Hip Replacements: A Comparison of a Randomized Trial and a Registry
At the authors ' hospital , 410 primary total hip replacements were performed on 372 patients between September 1 , 1985 , and May 31 , 1989 . All hips were assigned r and omly to receive a Charnley prosthesis with an ogee flanged cup or a Spectron prosthesis with a metal backed cup .  Eleven-year survivor analysis , using revision as the end point definition of failure , revealed a survival rate of 93.2 % ± 5.8 % for the Charnley replacement and 95.9 % ± 3.0 % for the Spectron . If each component of the systems was analyzed ( concerning aseptic loosening ) , the ogee cup and the Spectron stem had 100 % survival . The survivorship for all 410 hips was 94.5 % ± 3.4 % . If the end point definition of failure was exp and ed to include patient dissatisfaction , the survival rate decreased to 86.3 % ± 4.9 % . These survival rates were compared with the rates obtained by the Swedish National Hip Registry . The national cohort included all patients in Sweden who were treated surgically with a Charnley ( 14,053 patients ) or Spectron ( metal backed cup ) prosthesis ( 726 patients ) between September 1 , 1985 , and May 31 , 1989 .  Eleven-year survivor analysis revealed a national survival rate of 92.1 % ± 0.7 % for the Charnley replacement and 88.6 % ± 6.1 % for the Spectron . The analyses from the Swedish Registry are based on more than 160,000 primary operations and 11,500 revisions . Despite the enormous amount of data , there are drawbacks , and registries never can replace the prospect i ve , r and omized trial . One reason is the Swedish National Registry is unable to discriminate between the individual cup and stem components when analyzing the cause of revision , and no clinical or radiographic information is collected . A potential drawback for the r and omized trial is performance bias because surgeons from specialized centers might perform better than the general orthopaedic surgeon
INTERPRETATION There was a clinical ly relevant association between early migration of acetabular cups  and late revision due to loosening .
BACKGROUND AND PURPOSE The association between excessive early migration of acetabular cups  and late aseptic revision has been scantily reported .
We therefore performed 2 parallel systematic review s and meta-analyses to determine the association between early migration of acetabular cups  and late aseptic revision .