title: The effect of femoral component rotation on the five-year outcome of cemented mobile bearing total knee arthroplasty.
abstract: OBJECTIVE
  Performing total knee replacement, accurate alignment and neutral rotation of the femoral component are widely believed to be crucial for the ultimate success. Contrary to absolute bone referenced alignment, using a ligament balancing technique does not automatically rotate the femoral component parallel to the transepicondylar axis. In this context we established the hypothesis that rotational alignment of the femoral component parallel to the transepicondylar axis (0° ± 3°) results in better outcome than alignment outside of this range.
  
  
  METHODS
  We analysed 204 primary cemented mobile bearing total knee replacements five years postoperatively. Femoral component rotation was measured on axial radiographs using the condylar twist angle (CTA). Knee society score, range of motion as well as subjective rating documented outcome.
  
  
  RESULTS
  In 96 knees the femoral component rotation was within the range 0 ± 3° (neutral rotation group), and in 108 knees the five-year postoperative rotational alignment of the femoral component was outside of this range (outlier group). Postoperative CTA showed a mean of 2.8° (±3.4°) internal rotation (IR) with a range between 6° external rotation (ER) and 15° IR (CI 95). No difference with regard to subjective and objective outcome could be detected.
  
  
  CONCLUSIONS
  The present work shows that there is a large given natural variability in optimal rotational orientation, in this study between 6° ER and 15° IR, with numerous co-factors determining correct positioning of the femoral component. Further studies substantiating pre- and postoperative determinants are required to complete the understanding of resulting biomechanics in primary TKA.
authors.affiliation: DAL/Service d'Orthopédie et Traumatologie, CHUV Lausanne, Lausanne, Switzerland. anna_rienmueller@live.com
authors.forename: Anna
authors.initials: A
authors.lastname: Rienmüller
authors.forename: Thomas
authors.initials: T
authors.lastname: Guggi
authors.forename: Gerald
authors.initials: G
authors.lastname: Gruber
authors.forename: Stefan
authors.initials: S
authors.lastname: Preiss
authors.forename: Tomas
authors.initials: T
authors.lastname: Drobny
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001172:Arthritis, Rheumatoid / Q000503:physiopathology / Q000601:surgery; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D001843:Bone Cements; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000517:prevention & control*; D002484:Cementation; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007593:Joint Instability / Q000209:etiology / Q000517:prevention & control*; D007718:Knee Injuries / Q000503:physiopathology / Q000601:surgery; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000503:physiopathology / Q000601:surgery; D010149:Postoperative Pain; D011183:Postoperative Complications; D011474:Prosthesis Design; D011859:Radiography; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012399:Rotation; D016896:Treatment Outcome
chemical_list: D001843:Bone Cements