title: Sagittal cutting error changes femoral anteroposterior sizing in total knee arthroplasty.
abstract: BACKGROUND
  Prosthetic alignment and size are important factors in achieving a long-term survival in TKA. Although two-dimensional and three-dimensional (3-D) planning for component sizing has been introduced, it sometimes is difficult to cut the bones accurately according to preoperative planning. It is unclear whether changing sagittal alignment of the distal femur affects the AP dimension and sizing of the prepared bone.
  
  
  OBJECTIVE
  We therefore determined whether the AP dimension of the prepared distal femur increases if the distal femur is cut in extension and decreases if it is cut in flexion.
  
  
  METHODS
  One hundred knees were evaluated using 3-D imaging software. The AP dimension of the cutting surface was measured when the femoral component was aligned perpendicular to the anatomic axis. The measurement was repeated when the distal bone cut was planned in flexed positions of 3° and 5° and extended positions of 3° and 5°.
  
  
  RESULTS
  The AP dimension of the prepared femur was increased by 2 and 3 mm with 3° and 5° extension, respectively. The AP dimension of the prepared femur was decreased by 2 and 3 mm with 3° and 5° flexion, respectively.
  
  
  CONCLUSIONS
  Our data suggest upsizing or downsizing of the femoral component can occur if the femoral osteotomy is performed in at least 3° extension or flexion.
  
  
  METHODS
  Level II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakahara
authors.forename: Shuichi
authors.initials: S
authors.lastname: Matsuda
authors.forename: Ken
authors.initials: K
authors.lastname: Okazaki
authors.forename: Yasutaka
authors.initials: Y
authors.lastname: Tashiro
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Iwamoto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D010027:Osteotomy; D011474:Prosthesis Design; D011857:Radiographic Image Interpretation, Computer-Assisted; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted; D016896:Treatment Outcome