title: Novel alignment measurement technique for total knee arthroplasty using patient specific instrumentation.
abstract: BACKGROUND
  This study was designed to evaluate the true accuracy of patient specific instrumentation (PSI) for total knee arthroplasty (TKA) using a new 3D measurement method.
  
  
  METHODS
  Consecutive 21 patients (30 knees) who underwent TKA using computed tomography (CT)-based PSI were retrospectively evaluated. Mean patient age was 69.2 years (62 to 77). The postoperative three-dimensional (3D) CT image were superimposed onto the preoperative 3D CT plan and measured the absolute difference in the prosthetic alignment using six parameters: coronal, sagittal, and axial alignment of the femoral and tibial prostheses. Cases in which the difference in the prosthetic alignment was greater than 3° were considered outliers.
  
  
  RESULTS
  For the femoral prosthesis, mean absolute differences between the preoperative 3D CT plan and postoperative 3D CT image were not significantly different and the rates of outliers were 10.0, 33.3, 23.3% in the coronal, sagittal, and axial planes. For the tibial prosthesis, mean absolute differences were significantly larger in the axial plane than in the coronal and sagittal planes (p < 0.001) and the rates of outliers were 23.3, 36.7, 63.3% in the coronal, sagittal, and axial planes. The rates of outliers for the axial alignment of tibial prosthesis were significantly higher than for the other five planes (p = 0.006).
  
  
  CONCLUSIONS
  The rotation of the tibial prosthesis with CT-based PSI was less accurate in the axial plane than in the other five planes.
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Kazumasa
authors.initials: K
authors.lastname: Yamamura
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi Abeno-ku, Osaka, 545-8585, Japan. yminoda@msic.med.osaka-cu.ac.jp.
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Minoda
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Shigekazu
authors.initials: S
authors.lastname: Mizokawa
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Ohta
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Ryo
authors.initials: R
authors.lastname: Sugama
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Suguru
authors.initials: S
authors.lastname: Nakamura
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Ueyama
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods*; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery*; D011184:Postoperative Period; D012189:Retrospective Studies; D012399:Rotation; D025321:Surgery, Computer-Assisted / Q000379:methods; D013977:Tibia / Q000601:surgery; D014057:Tomography, X-Ray Computed
keywords: Computed tomography; Patient specific instrumentation; Three-dimensional evaluation; Total knee arthroplasty