title: Test-retest reliability of tibiofemoral joint space width measurements made using a low-dose standing CT scanner.
abstract: OBJECTIVE
  To determine the test-retest reliability of knee joint space width (JSW) measurements made using standing CT (SCT) imaging.
  
  
  METHODS
  This prospective two-visit study included 50 knees from 30 subjects (66% female; mean ± SD age 58.2 ± 11.3 years; BMI 29.1 ± 5.6 kg/m2; 38% KL grade 0-1). Tibiofemoral geometry was obtained from bilateral, approximately 20° fixed-flexed SCT images acquired at visits 2 weeks apart. For each compartment, the total joint area was defined as the area with a JSW <10 mm. The summary measurements of interest were the percentage of the total joint area with a JSW less than 0.5-mm thresholds between 2.0 and 5.0 mm in each tibiofemoral compartment. Test-retest reliability of the summary JSW measurements was assessed by intraclass correlation coefficients (ICC 2,1) for the percentage area engaged at each threshold of JSW and root-mean-square errors (RMSE) were calculated to assess reproducibility.
  
  
  RESULTS
  The ICCs were excellent for each threshold assessed, ranging from 0.95 to 0.97 for the lateral and 0.90 to 0.97 for the medial compartment. RMSE ranged from 1.1 to 7.2% for the lateral and from 3.1 to 9.1% for the medial compartment, with better reproducibility at smaller JSW thresholds.
  
  
  CONCLUSIONS
  The knee joint positioning protocol used demonstrated high day-to-day reliability for SCT 3D tibiofemoral JSW summary measurements repeated 2 weeks apart. Low-dose SCT provides a great deal of information about the joint while maintaining high reliability, making it a suitable alternative to plain radiographs for evaluating JSW in people with knee OA.
authors.affiliation: Department of Rehabilitation Medicine, University of Kansas Medical Center, 3901 Rainbow Boulevard, Mailstop 1046, Kansas City, KS, 66160, USA. segal-research@kumc.edu.|The University of Iowa, Iowa City, IA, USA. segal-research@kumc.edu.
authors.forename: Neil A
authors.initials: NA
authors.lastname: Segal
authors.affiliation: The University of Iowa, Iowa City, IA, USA.
authors.forename: John
authors.initials: J
authors.lastname: Bergin
authors.affiliation: The University of Iowa, Iowa City, IA, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kern
authors.affiliation: The University of Iowa, Iowa City, IA, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Findlay
authors.affiliation: Department of Orthopaedics and Rehabilitation, The University of Iowa, Iowa City, IA, USA.
authors.forename: Donald D
authors.initials: DD
authors.lastname: Anderson
mesh_terms: D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging*; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted; D015203:Reproducibility of Results; D013977:Tibia / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed / Q000295:instrumentation*
keywords: Computed tomography; Imaging; Knee osteoarthritis; Reliability