title: How to improve femoral component rotational alignment in computer-assisted TKA.
abstract: OBJECTIVE
  Although several anatomical landmarks have been proposed to obtain adequate femoral component alignment in total knee arthroplasty (TKA), there is still no consensus regarding the best way to correctly position the prosthetic component on the horizontal plane. A previous computed tomography (CT)-based study has demonstrated anatomical transepicondylar axis (aTEA) to be externally rotated relative to surgical transepicondylar axis (sTEA) of approximately 4.5°. In this study, it is described a new methodological approach to femoral component rotational positioning through the use of previously reported CT scan information and navigation.
  
  
  METHODS
  Eight consecutive patients scheduled for navigated TKA were selected. Rotational placement of the femoral component was performed using navigation system. The femoral component was implanted setting 4.5° of internal rotation relative to the aTEA. Within 1 week from surgery, all patients underwent a CT scan, and the posterior condylar angle (PCA) was measured. A PCA of 0.0°, meaning component placement parallel to sTEA, was set as femoral rotational alignment target. Clinical evaluation was performed at a mean 14.3 months of follow-up with KOOS questionnaire.
  
  
  RESULTS
  The mean PCA measured on post-operative CT images was 0.4° (SD 1.3°), meaning that the femoral component was averagely implanted with 0.4° of internal rotation relative to the sTEA. Seven out of eight cases (87.5 %) resulted to have within 1° deviation from the rotational alignment target. All patients but one reported good clinical results.
  
  
  CONCLUSIONS
  Relevant finding of the present study was that the use of navigation and aTEA as a reference demonstrated to be accurate to set up femoral component rotational positioning on the horizontal plane in TKA. Further study should be performed to confirm this conclusion.
authors.affiliation: Department of Orthopaedic Surgery, Azienda Ospedaliero-Universitaria Policlinico di Modena, University of Modena and Reggio Emilia, via del Pozzo 71, 41124, Modena, Italy, francesco.zambianchi@gmail.com.
authors.forename: F
authors.initials: F
authors.lastname: Zambianchi
authors.forename: T
authors.initials: T
authors.lastname: Luyckx
authors.forename: J
authors.initials: J
authors.lastname: Victor
authors.forename: V
authors.initials: V
authors.lastname: Digennaro
authors.forename: A
authors.initials: A
authors.lastname: Giorgini
authors.forename: F
authors.initials: F
authors.lastname: Catani
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D056888:Patient Positioning; D012399:Rotation; D025321:Surgery, Computer-Assisted; D014057:Tomography, X-Ray Computed