title: Development of a cost effective three-dimensional posture analysis tool: validity and reliability.
abstract: BACKGROUND
  The lack of clear understanding of the association between sitting posture and adolescent musculoskeletal pain, might reflect invalid and/or unreliable posture measurement instruments. The psychometric properties of any new measurement instrument should be demonstrated prior to use for research or clinical purposes. This paper describes psychometric testing of a new three-dimensional (3D), portable, non-invasive posture analysis tool (3D-PAT), from sequential studies using a mannequin and high school students.
  
  
  METHODS
  The first study compared the 3D-(X-, Y- and Z-) coordinates of reflective markers placed on a mannequin using the 3D-PAT, and the Vicon motion analysis system. This study also tested the reliability of taking repeated measures of the 3D-coordinates of the reflective markers. The second study determined the concurrent validity and test-retest reliability of the 3D-PAT measurements of nine sitting postural angles of high school students undertaking a standard computing task. In both studies, concordance correlation coefficients and Intraclass correlation coefficients described test-retest reliability, whilst Pearson product moment correlation coefficients and Bland-Altman plots demonstrated concurrent validity.
  
  
  RESULTS
  The 3D-PAT provides reliable and valid 3D measurements of five of the nine postural angles i.e. head flexion, neck flexion, cranio-cervical angle, trunk flexion and head lateral bending in adolescents undertaking a standard task.
  
  
  CONCLUSIONS
  The 3D-PAT is appropriate for research and clinical settings to measure five upper quadrant postural angles in three dimensions. As a measurement instrument it can provide further understanding of the relationship between sitting posture, changes to sitting posture and adolescent musculoskeletal pain.
authors.affiliation: Division of Physiotherapy, Department of Interdisciplinary Health Sciences, Faculty of Medicine and Health Sciences, Stellenbosch University, PO Box 19063, Tygerberg 7505, South Africa. ybrink@sun.ac.za.
authors.forename: Yolandi
authors.initials: Y
authors.lastname: Brink
authors.forename: Quinette
authors.initials: Q
authors.lastname: Louw
authors.forename: Karen
authors.initials: K
authors.lastname: Grimmer
authors.forename: Kristiaan
authors.initials: K
authors.lastname: Schreve
authors.forename: Gareth
authors.initials: G
authors.lastname: van der Westhuizen
authors.forename: Esmè
authors.initials: E
authors.lastname: Jordaan
mesh_terms: D000293:Adolescent; D003362:Cost-Benefit Analysis / Q000191:economics / Q000639:trends; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000191:economics* / Q000592:standards* / Q000639:trends; D008297:Male; D008953:Models, Anatomic; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology