title: Stem diameter and rotational stability in revision total hip arthroplasty: a biomechanical analysis.
abstract: BACKGROUND
  Proximal femoral bone loss during revision hip arthroplasty often requires bypassing the deficient metaphyseal bone to obtain distal fixation. The purpose of this study was to determine the effect of stem diameter and length of diaphyseal contact in achieving rotational stability in revision total hip arthroplasty.
  
  
  METHODS
  Twenty-four cadaveric femoral specimens were implanted with a fully porous-coated stem. Two different diameters were tested and the stems were implanted at multiple contact lengths without proximal bone support. Each specimen underwent torsional testing to failure and rotational micromotion was measured at the implant-bone interface.
  
  
  RESULTS
  The larger stem diameter demonstrated a greater torsional stability for a given length of cortical contact (p <or= 0.05). Decreasing length of diaphyseal contact length was associated with less torsional stability. Torsional resistance was inconsistent at 2 cm of depth.
  
  
  CONCLUSIONS
  Larger stem diameters frequently used in revisions may be associated with less diaphyseal contact length to achieve equivalent rotational stability compared to smaller diameter stems. Furthermore, a minimum of 3 cm or 4 cm of diaphyseal contact with a porous-coated stem should be achieved in proximal femoral bone deficiency and will likely be dependent on the stem diameter utilized at the time of surgery.
authors.affiliation: Joint Replacement Surgeons of Indiana Research Foundation, St. Vincent Center for Joint Replacement, Indianapolis, IN, USA. rm_meneghini@yahoo.com
authors.forename: R Michael
authors.initials: RM
authors.lastname: Meneghini
authors.forename: Nadim J
authors.initials: NJ
authors.lastname: Hallab
authors.forename: Richard A
authors.initials: RA
authors.lastname: Berger
authors.forename: Joshua J
authors.initials: JJ
authors.lastname: Jacobs
authors.forename: Wayne G
authors.initials: WG
authors.lastname: Paprosky
authors.forename: Aaron G
authors.initials: AG
authors.lastname: Rosenberg