title: Change in tibiofemoral rotational alignment during total knee arthroplasty.
abstract: BACKGROUND
  Rotational mismatch between femoral and tibial components has been recognized as a risk factor of unsuccessful total knee arthroplasty (TKA), but a main cause of rotational mismatch is uncertain. This study aims to evaluate rotational alignment of the knee by measuring both component rotation and version of the knee in TKA.
  
  
  METHODS
  Fifty-one TKAs (mean age 73.7 years) were included in this study. The three dimensional, weight-bearing knee alignment was measured before and after TKA. A transepicondylar axis was referenced to femoral component rotation, and an anteroposterior axis of the tibia (middle of posterior cruciate ligament attachment to medial border of patella tendon attachment) was referenced to tibial component rotation. Knee rotational angle was defined as the angle between these two axes.
  
  
  RESULTS
  The mean preoperative knee rotation angle of 9.7° (±8.5°) internal rotation was significantly reduced to 1.8° (±7.3°) external rotation after TKA. Twenty-one of 51 knees (41%) exhibited rotational mismatch (>10°) preoperatively, and this number was reduced to eight knees (16%) post-TKA. The femoral component was rotationally aligned within 5° of neutral in all knees, while rotational alignment of the tibial component showed a high degree of variability (range 20.7° internal rotation to 17.2° external rotation).
  
  
  CONCLUSIONS
  Rotational malposition of the tibial component was considered to be a main factor of rotational mismatch of the knee after TKA.
authors.affiliation: Division of Orthopaedic Surgery, Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medicine and Dental Sciences, Niigata, Japan, wwsatoshiww@gmail.com.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Watanabe
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
authors.forename: Go
authors.initials: G
authors.lastname: Omori
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Koga
authors.forename: Naoto
authors.initials: N
authors.lastname: Endo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D005269:Femur; D006801:Humans; D007719:Knee Joint / Q000502:physiology* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D013977:Tibia