title: Risk of dislocation using large- vs. small-diameter femoral heads in total hip arthroplasty.
abstract: BACKGROUND
  Dislocation remains a difficult problem in total hip arthroplasty. Large-diameter femoral heads may lower the incidence of dislocation by enhancing the jump distance and decreasing impingement, but their performance against small-diameter heads has not been assessed. This study compared the mid-term radiographic and functional outcomes of two matched cohorts of patients undergoing total hip arthroplasty who had a high pre-operative risk for dislocation and who received either small-diameter (26- or 28-millimeters) or large-diameter (≥36-millimeters) femoral heads.
  
  
  METHODS
  All patients who received large-diameter heads (≥36-millimeter) between 2002 and 2005, and who had pre-operative risk factors for dislocation, were identified in the institution's joint registry. Forty-one patients (52 hips) who received large-diameter heads were identified, and these patients were matched to 48 patients (52 hips) in the registry who received small-diameter femoral heads.
  
  
  RESULTS
  At mean final follow-up of 62 months (range, 49 to 101 months), both groups achieved excellent functional outcomes as measured by Harris Hip scores, with slightly better final scores in the large-diameter group (90 vs. 83 points). No patient showed any radiographic signs of loosening. No patient dislocated in the large-diameter femoral head group; the smaller-diameter group had a greater rate of dislocation (3.8%, 2 out of 52).
  
  
  CONCLUSIONS
  Large-diameter femoral head articulations may reduce dislocation rates in patients who have a high pre-operative risk for dislocation while providing the same functional improvements and safety as small-diameter bearings.
authors.affiliation: Department of Orthopaedic Surgery, Wake Forest School of Medicine,Medical Center Boulevard, Winston-Salem, NC 27157-1070, USA.
authors.forename: Johannes F
authors.initials: JF
authors.lastname: Plate
authors.forename: Thorsten M
authors.initials: TM
authors.lastname: Seyler
authors.forename: D Alex
authors.initials: DA
authors.lastname: Stroh
authors.forename: Kimona
authors.initials: K
authors.lastname: Issa
authors.forename: Michael
authors.initials: M
authors.lastname: Akbar
authors.forename: Michael A
authors.initials: MA
authors.lastname: Mont
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D005260:Female; D006617:Hip Dislocation; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors