title: Is computed tomography an accurate and reliable method for measuring total knee arthroplasty component rotation?
abstract: OBJECTIVE
  Computed tomography (CT) is widely used to assess component rotation in patients with poor results after total knee arthroplasty (TKA). The purpose of this study was to simultaneously determine the accuracy and reliability of CT in measuring TKA component rotation.
  
  
  METHODS
  TKA components were implanted in dry-bone models and assigned to two groups. The first group (n = 7) had variable femoral component rotations, and the second group (n = 6) had variable tibial tray rotations. CT images were then used to assess component rotation. Accuracy of CT rotational assessment was determined by mean difference, in degrees, between implanted component rotation and CT-measured rotation. Intraclass correlation coefficient (ICC) was applied to determine intra-observer and inter-observer reliability.
  
  
  RESULTS
  Femoral component accuracy showed a mean difference of 2.5° and the tibial tray a mean difference of 3.2°. There was good intra- and inter-observer reliability for both components, with a femoral ICC of 0.8 and 0.76, and tibial ICC of 0.68 and 0.65, respectively.
  
  
  CONCLUSIONS
  CT rotational assessment accuracy can differ from true component rotation by approximately 3° for each component. It does, however, have good inter- and intra-observer reliability.
authors.affiliation: Knee Surgery Unit, Hospital Militar de Santiago, Av. Alcalde Fernando Castillo Velasco 9100, Santiago, Chile.|Knee Surgery Unit, Clínica Dávila, Avenida Recoleta 464, Santiago, Chile.|Department of Orthopedics, School of Medicine, Universidad de los Andes, Mons. Álvaro del Portillo, 12.455, Santiago, Chile.
authors.forename: José
authors.initials: J
authors.lastname: Figueroa
authors.affiliation: Department of Orthopedics, School of Medicine, Universidad de los Andes, Mons. Álvaro del Portillo, 12.455, Santiago, Chile. jpguarachi@gmail.com.
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Guarachi
authors.affiliation: Department of Orthopedics, School of Medicine, Universidad de los Andes, Mons. Álvaro del Portillo, 12.455, Santiago, Chile.|Knee Surgery Unit, Clínica Meds, Las Condes, 13.451, Santiago, Chile.|Knee Surgery Unit, Clínica Universidad de los Andes, Santiago, Chile.
authors.forename: José
authors.initials: J
authors.lastname: Matas
authors.affiliation: Department of Orthopaedic Surgery St George's Hospital, Blackshaw Road, Tooting, London, SW17 0QT, UK.
authors.forename: Magnus
authors.initials: M
authors.lastname: Arnander
authors.affiliation: Knee Surgery Unit, Hospital Militar de Santiago, Av. Alcalde Fernando Castillo Velasco 9100, Santiago, Chile.|Department of Orthopedics, School of Medicine, Universidad de los Andes, Mons. Álvaro del Portillo, 12.455, Santiago, Chile.|Knee Surgery Unit, Clínica Universidad de los Andes, Santiago, Chile.
authors.forename: Mario
authors.initials: M
authors.lastname: Orrego
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012399:Rotation; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Accuracy; Computed tomography; Malrotation; Reliability; Rotation; Total knee arthroplasty