title: Early proximal migration of cups is associated with late revision in THA: a systematic review and meta-analysis of 26 RSA studies and 49 survivalstudies.
abstract: OBJECTIVE
  The association between excessive early migration of acetabular cups and late aseptic revision has been scantily reported. We therefore performed 2 parallel systematic reviews and meta-analyses to determine the association between early migration of acetabular cups and late aseptic revision.
  
  
  METHODS
  One review covered early migration data from radiostereometric analysis (RSA) studies, while the other focused on revision rates for aseptic loosening from long-term survival studies. Thresholds for acceptable and unacceptable migration were classified according the Swedish Hip Arthroplasty Register and the Australian National Joint Replacement Registry: < 5% revision at 10 years.
  
  
  RESULTS
  Following an elaborate literature search, 26 studies (involving 700 cups) were included in the RSA review and 49 studies (involving 38,013 cups) were included in the survival review. For every mm increase in 2-year proximal migration, there was a 10% increase in revision rate, which remained after correction for age, sex, diagnosis, hospital type, continent, and study quality. Consequently, proximal migration of up to 0.2 mm was considered acceptable and proximal migration of 1.0 mm or more was considered unacceptable. Cups with proximal migration of between 0.2 and 1.0 mm were considered to be at risk of having revision rates higher than 5% at 10 years.
  
  
  CONCLUSIONS
  There was a clinically relevant association between early migration of acetabular cups and late revision due to loosening. The proposed migration thresholds can be implemented in a phased evidence-based introduction, since they allow early detection of high-risk cups while exposing a small number of patients.
authors.affiliation: Department of Orthopaedics, Bio-Imaging Group, Leiden University Medical Center, Leiden, the Netherlands. b.g.c.w.pijls@lumc.nl
authors.forename: Bart G
authors.initials: BG
authors.lastname: Pijls
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Nieuwenhuijse
authors.forename: Marta
authors.initials: M
authors.lastname: Fiocco
authors.forename: Josepha Wm
authors.initials: JW
authors.lastname: Plevier
authors.forename: Saskia
authors.initials: S
authors.lastname: Middeldorp
authors.forename: Rob Ghh
authors.initials: RG
authors.lastname: Nelissen
authors.forename: Edward R
authors.initials: ER
authors.lastname: Valstar
mesh_terms: D000367:Age Factors; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000379:methods*; D019317:Evidence-Based Medicine; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation / Q000379:methods / Q000706:statistics & numerical data; D018570:Risk Assessment; D012737:Sex Factors; D013997:Time Factors; D016896:Treatment Outcome