title: Development and validation of a digital head posture measuring system.
abstract: OBJECTIVE
  To report the accuracy and repeatability of a new digital head posture measuring system.
  
  
  METHODS
  Prospective study, clinical laboratory investigation.
  
  
  METHODS
  The digital head posture measuring system consists of a head-mounted motion tracker, a standard personal computer, and customized software to sample and display 3-dimensional (3D) head posture in real-time. Using a mechanical head posture measuring device as a reference, 3D head positions of an artificial head and 12 human subjects were recorded with the digital head posture device. Accuracy of the digital device outputs, relationship between digital outputs and actual head rotations, and repeatability of the tests were analyzed.
  
  
  RESULTS
  The digital head posture device showed consistent outcomes when compared to the mechanical one. The digital outputs of 3D rotations are very close to actual artificial head and human head rotations. The correlation coefficients of the linear relationship between the digital outputs and actual head movements were greater than 0.99. Repeatability tests for the artificial head and human subjects for all 3D rotations had 95% limits of agreement angles less than +/-6 degrees and +/-8 degrees, respectively.
  
  
  CONCLUSIONS
  The digital head posture device is an acceptable device with high accuracy, repeatability, and validity in measuring head posture in 3 dimensions.
authors.affiliation: Department of Ophthalmology, Ocular Motor Neurophysiology Laboratory, The UPMC Eye Center, The Children's Hospital of Pittsburgh and University of Pittsburgh, Pittsburgh, Pennsylvania 15213, USA.
authors.forename: Eric S
authors.initials: ES
authors.lastname: Hald
authors.forename: Richard W
authors.initials: RW
authors.lastname: Hertle
authors.forename: Dongsheng
authors.initials: D
authors.lastname: Yang
mesh_terms: D000328:Adult; D003936:Diagnosis, Computer-Assisted / Q000295:instrumentation*; D005260:Female; D006257:Head / Q000502:physiology*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation*; D008297:Male; D008348:Manikins; D008875:Middle Aged; D009068:Movement / Q000502:physiology; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012399:Rotation