title: Influence of coronal bowing on the lower alignment and the positioning of component in navigation and conventional total knee arthroplasty.
abstract: Coronal alignment is an important factor for the function and longevity of total knee arthroplasty (TKA). Coronal bowing of the lower extremity is common among Asians and it may pose a risk for malalignment of the lower leg and malposition of component.
  
  
  
  We hypothesized that coronal bowing itself has a risk for malalignment of the lower leg and malposition of femoral/tibial components and that navigation TKA is beneficial for patients with coronal bowing. We investigated the incidence of femoral/tibial bowing in patients treated with TKA and compared the radiographic parameters between the navigation group and the conventional group. Additionally, the influence of coronal bowing on these radiographic parameters was investigated.
  
  
  
  We enrolled 35 patients with knee osteoarthritis and 70 bilateral simultaneous TKAs. The patients underwent TKA with the use of a computer tomography-free navigation in one knee and conventional TKA in the contralateral knee. Preoperative coronal bowing were measured, and the subjects were divided into 2 subgroups, i.e. the bowing group and the non-bowing group. Lateral bowing was expressed as plus (+) and medial bowing was expressed as minus (-). Various radiographic parameters, including coronal bowing, lower leg alignment, component position, and outliers were compared between the navigation group and the conventional group.
  
  
  
  Femoral bowing varied from -7.4° to 10.9° with an average of 3.0°. Tibial bowing varied from -4.1° to 4.6° with an average of 0.4°. The femoral component was placed more properly in the navigation group. Number of outlier regarding to the coronal femoral component angle to the femoral mechanical axis was 14 cases (37.8%) in the bowing group and 6 cases (18.2%) in the non-bowing group (P=0.04).
  
  
  
  In conclusion, coronal femoral bowing has an important effect on femoral bone cut in TKA. The navigated TKA was more consistent than conventional TKA in aiding proper alignments of femoral component.
  
  
  
  Level II, comparative prospective study.
authors.affiliation: Department of orthopaedic surgery, Yokohama city university, school of medicine, 3-9, Fukuura, Kanazawa, Yokohama, Kanagawa 236-0004, Japan. Electronic address: hi-deo@live.jp.
authors.forename: H
authors.initials: H
authors.lastname: Kobayashi
authors.affiliation: Department of orthopaedic surgery, Yokohama city university, school of medicine, 3-9, Fukuura, Kanazawa, Yokohama, Kanagawa 236-0004, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Akamatsu
authors.affiliation: Department of orthopaedic surgery, Yokohama city university, school of medicine, 3-9, Fukuura, Kanazawa, Yokohama, Kanagawa 236-0004, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kumagai
authors.affiliation: Department of orthopaedic surgery, Yokohama city university, school of medicine, 3-9, Fukuura, Kanazawa, Yokohama, Kanagawa 236-0004, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Kusayama
authors.affiliation: Department of orthopaedic surgery, Yokohama city university, school of medicine, 3-9, Fukuura, Kanazawa, Yokohama, Kanagawa 236-0004, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Aratake
authors.affiliation: Department of orthopaedic surgery, Yokohama city university, school of medicine, 3-9, Fukuura, Kanazawa, Yokohama, Kanagawa 236-0004, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Saito
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D044466:Asian People; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D056305:Genu Varum / Q000150:complications / Q000000981:diagnostic imaging*; D006801:Humans; D007564:Japan; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000601:surgery*; D056888:Patient Positioning; D011446:Prospective Studies; D011859:Radiography; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery; D014057:Tomography, X-Ray Computed
keywords: Alignment; Coronal bowing; Navigation; Total knee arthroplasty (TKA)