title: External rotation of the femoral component decreases patellofemoral contact stress in total knee arthroplasty.
abstract: OBJECTIVE
  The purpose of this study was to investigate the relationship between patellofemoral (PF) contact stress in vivo and the alignment of the femoral component in patients after total knee arthroplasty (TKA).
  
  
  METHODS
  Thirty knees with medial compartment osteoarthritis that underwent mobile-bearing TKA with modified gap technique were evaluated. Surgery was performed using a subvastus approach to eliminate the effect of the approach to muscle balance, with a computed tomography-based navigation system (Vector Vision 1.61; Brain Lab, Heimstetten, Germany). PF contact stress was measured by a Flexiforce pressure sensor (Nitta Co., Ltd., Osaka, Japan) intraoperatively, and the results were compared with the alignment of the femoral component after TKA.
  
  
  RESULTS
  The PF contact stress was not correlated with sagittal and coronal alignment of the femoral component and patellar tracking, whereas rotational alignment of the femoral component was negatively correlated with PF contact stress (r = -0.718, p < 0.01).
  
  
  CONCLUSIONS
  Regarding the alignment of the femoral component, only the rotational alignment of the femoral component was correlated with PF contact stress. PF contact stress decreased more as the femoral component rotated more externally.
  
  
  METHODS
  Case control study, Level III.
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido University Graduate School of Medicine, North 15 West 7, Kita-Ku, Sapporo, 060-8638, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Terashima
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido University Graduate School of Medicine, North 15 West 7, Kita-Ku, Sapporo, 060-8638, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Onodera
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido University Graduate School of Medicine, North 15 West 7, Kita-Ku, Sapporo, 060-8638, Japan.
authors.forename: Naohiro
authors.initials: N
authors.lastname: Sawaguchi
authors.affiliation: Department of Orthopaedic Surgery, Hokkaido University Graduate School of Medicine, North 15 West 7, Kita-Ku, Sapporo, 060-8638, Japan.
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Kasahara
authors.affiliation: Department of Orthopedic Surgery, International University of Health and Welfare Hospital, 537-8, Iguchi, Nasushiobara, 329-2763, Japan. tkmajima@iuhw.ac.jp.
authors.forename: Tokifumi
authors.initials: T
authors.lastname: Majima
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D017755:Prosthesis Fitting; D012399:Rotation; D013314:Stress, Mechanical
keywords: Patellofemoral contact stress; Patellofemoral joint; Rotational alignment of the femoral component; Total knee arthroplasty