title: Increased anteversion of press-fit femoral stems compared with anatomic femur.
abstract: BACKGROUND
  With contemporary canal-filling press-fit stems, there is no adjustability of stem position in the canal and therefore the canal anatomy determines stem version. Stem version will affect head/neck impingement, polyethylene wear from edge loading, and hip stability, but despite this, the postoperative version of a canal-filling press-fit stem is unclear.
  
  
  OBJECTIVE
  Is there a difference between the version of the nonoperated femur and the final version of a canal-filling press-fit femoral component? Could a difference create an alignment problem for the hip replacement?
  
  
  METHODS
  Sixty-four hips were studied with fluoroscopy and 46 nonarthritic and 41 arthritic hips were studied with MRI. A standardized fluoroscopic technique for determining preoperative and postoperative femoral version was developed with the patient supine on a fracture table undergoing supine total hip arthroplasty. To validate the methods, the results were compared with two selected series of axial MRI views of the hip comparing the version of the head with the version of the canal at the base of the neck.
  
  
  RESULTS
  For the operated hips, the mean anatomic hip version was less than the stem version: 18.9° versus 27.0°. The difference on average was 8.1° of increased anteversion (SD, 7.4°). Both MRI series showed the femoral neck was more anteverted on average than the femoral head, thereby explaining the operative findings.
  
  
  CONCLUSIONS
  With a canal-filling press-fit femoral component there is wide variation of postoperative component anteversion with most stems placed in increased anteversion compared with the anatomic head. The surgical technique may need to adjust for this if causing intraoperative impingement or instability.
authors.affiliation: Texas Health Presbyterian Hospital Plano, Plano, TX, USA. rhemerson@msn.com
authors.forename: Roger H
authors.initials: RH
authors.lastname: Emerson
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D005471:Fluoroscopy; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology / Q000601:surgery*; D006622:Hip Prosthesis; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D056888:Patient Positioning; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D016683:Supine Position; D013781:Texas; D016896:Treatment Outcome