title: Rotational limb alignment changes following total knee arthroplasty.
abstract: OBJECTIVE
  The aim of the present study was to assess the changes in rotational alignment introduced by total knee arthroplasty (TKA) and the reproducibility of pre- and postoperative CT measurements of rotational limb alignment.
  
  
  METHODS
  For this purpose we analyzed data from 196 consecutive cruciate-retaining, fixed bearing Columbus TKA procedures. Both pre- and postoperative scans torsion difference CT scans were available for measurements in 89 cases. Using these CT scans the neck-malleolar angle (NMA), the femoral posterior condylar angle (fPCA), the tibial posterior condylar axis (tPCA) and the tibial torsion angle (TTA) were independently assessed by three raters. CT scans were re-evaluated 8 weeks later by the most experienced rater for assessment of intraobserver agreement.
  
  
  RESULTS
  Measurements of all angles were prone to high standard deviations reflecting interindividual variability. Mean fPCA changed from 1.3° to 2.7° internal rotation preoperatively to 0.1°-1.9° internal rotation postoperatively. Based on a relative external rotation of the tibial base plate as compared to the preoperative situation, we found a relative internal rotation of the postoperative NMA and tibial torsion of 3°-5.4° and 6°-7.5°, respectively. Intra- and interobserver agreement was strong for all angles assessed (ICCs 0.7-1.0) except for fPCA (ICC 0.2-0.6). However, mean absolute measurement differences for fPCA were clinically acceptable (1.2°-2.6°).
  
  
  CONCLUSIONS
  Reproducibility of CT rotational limb alignment measurements was found to be clinically acceptable. Rotational alignment of the femoral and even more so of the tibial component will ultimately affect the rotational alignment of the entire limb-at least when fixed bearings are used.
  
  
  METHODS
  Diagnostic study, Level III.
authors.affiliation: Department for Orthopedic and Trauma Surgery, Freiburg University Medical Center, Hugstetterstr. 55, 79106, Freiburg, Germany, oliver.hauschild@uniklinik-freiburg.de.
authors.forename: Oliver
authors.initials: O
authors.lastname: Hauschild
authors.forename: Matthias
authors.initials: M
authors.lastname: Muenzberg
authors.forename: Dagmar
authors.initials: D
authors.lastname: Knothe
authors.forename: Lukas
authors.initials: L
authors.lastname: Konstantinidis
authors.forename: Peter
authors.initials: P
authors.lastname: Helwig
authors.forename: Norbert P
authors.initials: NP
authors.lastname: Sudkamp
authors.forename: Friedrich W
authors.initials: FW
authors.lastname: Thielemann
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods; D060750:Bone Anteversion / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D017760:Bone Malalignment / Q000000981:diagnostic imaging / Q000209:etiology / Q000517:prevention & control; D060751:Bone Retroversion / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D015588:Observer Variation; D020370:Osteoarthritis, Knee / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D011182:Postoperative Care; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000517:prevention & control; D011300:Preoperative Care; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012399:Rotation; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome