title: Do monoblock cups improve survivorship, decrease wear, or reduce osteolysis in uncemented total hip arthroplasty?
abstract: BACKGROUND
  Monoblock acetabular components used in uncemented total hip arthroplasty (THA) have certain mechanical characteristics that potentially reduce acetabular osteolysis and polyethylene wear. However, the degree to which they achieve this goal is not well documented.
  
  
  OBJECTIVE
  The purpose of this study was to use a systematic review of controlled trials to test the hypothesis that monoblock cups have superior (1) polyethylene wear rate; (2) frequency of cup migration; (3) frequency of acetabular osteolysis; and (4) frequency of aseptic loosening compared with modular components used in uncemented THA.
  
  
  METHODS
  A systematic search was conducted in the Medline, Embase, and Cochrane electronic databases to assemble all controlled trials comparing monoblock with modular uncemented acetabular components in primary THA. Included studies were considered "best evidence" if the quality score was either ≥ 50% on the Cochrane Back Review Group checklist or ≥ 75% the Newcastle-Ottawa quality assessment scale. A total of seven publications met our inclusion criteria.
  
  
  RESULTS
  Best evidence analysis showed no difference in polyethylene wear rate, the frequency of cup migration, and aseptic loosening between monoblock and modular acetabular components. No convincing evidence was found for the claim that lower frequencies of acetabular osteolysis are observed with the use of monoblock cups compared with modular uncemented cups.
  
  
  CONCLUSIONS
  The purported benefits of monoblock cups were not substantiated by this systematic review of controlled studies in that polyethylene wear rates and frequencies of cup failure and acetabular osteolysis were similar to those observed with modular implants. Other factors should therefore drive implant selection in cementless THA.
authors.affiliation: Clinical Orthopedic Research Center-midden Nederland (CORC-mN), Department of Orthopaedics, Diakonessenhuis Hospital, PO Box 80250, 3508 TG, Utrecht, The Netherlands, jhalma@diakhuis.nl.
authors.forename: Jelle J
authors.initials: JJ
authors.lastname: Halma
authors.forename: H Charles
authors.initials: HC
authors.lastname: Vogely
authors.forename: Wouter J
authors.initials: WJ
authors.lastname: Dhert
authors.forename: Steven M
authors.initials: SM
authors.lastname: Van Gaalen
authors.forename: Arthur
authors.initials: A
authors.lastname: de Gast
mesh_terms: D000077:Acetabulum / Q000503:physiopathology / Q000601:surgery*; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D019985:Benchmarking; D019317:Evidence-Based Medicine; D005548:Foreign-Body Migration / Q000209:etiology / Q000517:prevention & control*; D006621:Hip Joint / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D010014:Osteolysis / Q000209:etiology / Q000517:prevention & control*; D020959:Polyethylene; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013314:Stress, Mechanical; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D020959:Polyethylene
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