title: Role of endocortical contouring methods on precision of HR-pQCT-derived cortical micro-architecture in postmenopausal women and young adults.
abstract: Precision errors of cortical bone micro-architecture from high-resolution peripheral quantitative computed tomography (pQCT) ranged from 1 to 16 % and did not differ between automatic or manually modified endocortical contour methods in postmenopausal women or young adults. In postmenopausal women, manually modified contours led to generally higher cortical bone properties when compared to the automated method.
  
  
  BACKGROUND
  First, the objective of the study was to define in vivo precision errors (coefficient of variation root mean square (CV%RMS)) and least significant change (LSC) for cortical bone micro-architecture using two endocortical contouring methods: automatic (AUTO) and manually modified (MOD) in two groups (postmenopausal women and young adults) from high-resolution pQCT (HR-pQCT) scans. Second, it was to compare precision errors and bone outcomes obtained with both methods within and between groups.
  
  
  METHODS
  Using HR-pQCT, we scanned twice the distal radius and tibia of 34 postmenopausal women (mean age ± SD 74 ± 7 years) and 30 young adults (27 ± 9 years). Cortical micro-architecture was determined using AUTO and MOD contour methods. CV%RMS and LSC were calculated. Repeated measures and multivariate ANOVA were used to compare mean CV% and bone outcomes between the methods within and between the groups. Significance was accepted at P < 0.05.
  
  
  RESULTS
  CV%RMS ranged from 0.9 to 16.3 %. Within-group precision did not differ between evaluation methods. Compared to young adults, postmenopausal women had better precision for radial cortical porosity (precision difference 9.3 %) and pore volume (7.5 %) with MOD. Young adults had better precision for cortical thickness (0.8 %, MOD) and tibial cortical density (0.2 %, AUTO). In postmenopausal women, MOD resulted in 0.2-54 % higher values for most cortical outcomes, as well as 6-8 % lower radial and tibial cortical BMD and 2 % lower tibial cortical thickness.
  
  
  CONCLUSIONS
  Results suggest that AUTO and MOD endocortical contour methods provide comparable repeatability. In postmenopausal women, manual modification of endocortical contours led to generally higher cortical bone properties when compared to the automated method, while no between-method differences were observed in young adults.
authors.affiliation: College of Kinesiology, University of Saskatchewan, 87 Campus Drive, Saskatoon, SK, S7N 5B2, Canada. chantal.kawalilak@usask.ca.
authors.forename: C E
authors.initials: CE
authors.lastname: Kawalilak
authors.affiliation: Department of Mechanical Engineering, College of Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9, Canada. jd.johnston@usask.ca.
authors.forename: J D
authors.initials: JD
authors.lastname: Johnston
authors.affiliation: Department of Anatomy and Cell Biology, College of Medicine, University of Saskatchewan, 107 Wiggins Road, Saskatoon, SK, S7N 5E5, Canada. dml.cooper@usask.ca.
authors.forename: D M L
authors.initials: DM
authors.lastname: Cooper
authors.affiliation: Director of the Saskatoon CaMos Centre; College of Medicine, University of Saskatchewan, 39 23rd St E Suite 103, Saskatoon, SK, S7K 0H6, Canada. wpolszynski@sasktel.net.
authors.forename: W P
authors.initials: WP
authors.lastname: Olszynski
authors.affiliation: College of Kinesiology, University of Saskatchewan, 87 Campus Drive, Saskatoon, SK, S7N 5B2, Canada. saija.kontulainen@usask.ca.
authors.forename: S A
authors.initials: SA
authors.lastname: Kontulainen
mesh_terms: D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology; D015519:Bone Density / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015663:Osteoporosis, Postmenopausal / Q000000981:diagnostic imaging* / Q000503:physiopathology; D016062:Porosity; D017698:Postmenopause / Q000502:physiology; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods; D011884:Radius / Q000000981:diagnostic imaging / Q000502:physiology; D015203:Reproducibility of Results; D013977:Tibia / Q000000981:diagnostic imaging / Q000502:physiology; D014057:Tomography, X-Ray Computed / Q000379:methods; D055815:Young Adult
keywords: Contour method comparison; Cortical micro-architecture; HR-pQCT; Least significant change; Reproducibility