title: Should we worry about periacetabular interference gaps in hip resurfacing?
abstract: BACKGROUND
  Press-fit acetabular component seating in hip resurfacing can be challenging as a strong interference fit is required. It has not been established whether reducing the acetabular underream minimizes incomplete component seating or leads to increased acetabular loosening.
  
  
  OBJECTIVE
  We examined (1) the incidence and natural history of postoperative interference gaps in hip resurfacing and (2) whether reduction of the acetabular underream from 2 mm to 1 mm reduces the incidence of periacetabular interference gaps.
  
  
  METHODS
  Of 327 Birmingham Hip™ Resurfacings (Smith & Nephew Inc, Memphis, TN, USA) performed by a single surgeon from 2005 to 2010, we evaluated 306 hips with a minimum 1-year radiographic followup. Postoperative periacetabular interference gaps were monitored for radiographic gap resolution at latest followup. The frequency of incomplete component seating was compared between acetabula prepared with 1- and 2-mm underream techniques. Minimum followup was 1 year (mean, 2.7 years; range, 1-6 years).
  
  
  RESULTS
  Fifty-one percent of the postoperative radiographs demonstrated the presence of a periacetabular interference gap. At latest followup, 96% of these gaps were no longer visible. We observed a reduction in the number of interference gaps identified when acetabular preparation changed from a 2-mm underream (63%) to a 1-mm underream (39%). There were no revisions due to acetabular failure.
  
  
  CONCLUSIONS
  Periacetabular interference gaps were common in this series but not associated with acetabular component failure. The use of a 1-mm underream is sufficient for adequate short-term press-fit fixation of the acetabular component in Birmingham Hip™ Resurfacing arthroplasty.
  
  
  METHODS
  Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Division of Orthopaedic Surgery, Department of Surgery, St Michael's Hospital, Room 800, 55 Queen Street East, Toronto, ON, M5C1R6, Canada.
authors.forename: Bruno
authors.initials: B
authors.lastname: Gomes
authors.forename: Michael
authors.initials: M
authors.lastname: Olsen
authors.forename: Michael
authors.initials: M
authors.lastname: Donnelly
authors.forename: Ashesh
authors.initials: A
authors.lastname: Kumar
authors.forename: Emil H
authors.initials: EH
authors.lastname: Schemitsch
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging / Q000601:surgery*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000000981:diagnostic imaging / Q000601:surgery*; D011859:Radiography; D016896:Treatment Outcome