title: The position and orientation of total knee replacement components: a comparison of conventional radiographs, transverse 2D-CT slices and 3D-CT reconstruction.
abstract: We studied the intra- and interobserver reliability of measurements of the position of the components after total knee replacement (TKR) using a combination of radiographs and axial two-dimensional (2D) and three-dimensional (3D) reconstructed CT images to identify which method is best for this purpose. A total of 30 knees after primary TKR were assessed by two independent observers (an orthopaedic surgeon and a radiologist) using radiographs and CT scans. Plain radiographs were highly reliable at measuring the tibial slope, but showed wide variability for all other measurements; 2D-CT also showed wide variability. 3D-CT was highly reliable, even when measuring rotation of the femoral components, and significantly better than 2D-CT. Interobserver variability in the measurements on radiographs were good (intraclass correlation coefficient (ICC) 0.65 to 0.82), but rotational measurements on 2D-CT were poor (ICC 0.29). On 3D-CT they were near perfect (ICC 0.89 to 0.99), and significantly more reliable than 2D-CT (p < 0.001). 3D-reconstructed images are sufficiently reliable to enable reporting of the position and orientation of the components. Rotational measurements in particular should be performed on 3D-reconstructed CT images. When faced with a poorly functioning TKR with concerns over component positioning, we recommend 3D-CT as the investigation of choice.
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Kantonsspital Bruderholz, CH-4101 Bruderholz, Switzerland. michael.hirschmann@ksbh.ch
authors.forename: M T
authors.initials: MT
authors.lastname: Hirschmann
authors.forename: P
authors.initials: P
authors.lastname: Konala
authors.forename: F
authors.initials: F
authors.lastname: Amsler
authors.forename: F
authors.initials: F
authors.lastname: Iranpour
authors.forename: N F
authors.initials: NF
authors.lastname: Friederich
authors.forename: J P
authors.initials: JP
authors.lastname: Cobb
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D007720:Knee Prosthesis; D008875:Middle Aged; D015588:Observer Variation; D009949:Orientation; D011182:Postoperative Care / Q000379:methods; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods