title: Validity and reliability of smartphone magnetometer-based goniometer evaluation of shoulder abduction--A pilot study.
abstract: BACKGROUND
  Goniometers are commonly used by physical therapists to measure range-of-motion (ROM) in the musculoskeletal system. These measurements are used to assist in diagnosis and to help monitor treatment efficacy. With newly emerging technologies, smartphone-based applications are being explored for measuring joint angles and movement.
  
  
  OBJECTIVE
  This pilot study investigates the intra- and inter-rater reliability as well as concurrent validity of a newly-developed smartphone magnetometer-based goniometer (MG) application for measuring passive shoulder abduction in both sitting and supine positions, and compare against the traditional universal goniometer (UG).
  
  
  METHODS
  This is a comparative study with repeated measurement design.
  
  
  METHODS
  Three physical therapists utilized both the smartphone MG and a traditional UG to measure various angles of passive shoulder abduction in a healthy subject, whose shoulder was positioned in eight different positions with pre-determined degree of abduction while seated or supine. Each therapist was blinded to the measured angles. Concordance correlation coefficients (CCCs), Bland-Altman plotting methods, and Analysis of Variance (ANOVA) were used for statistical analyses.
  
  
  RESULTS
  Both traditional UG and smartphone MG were reliable in repeated measures of standardized joint angle positions (average CCC > 0.997) with similar variability in both measurement tools (standard deviation (SD) ± 4°). Agreement between the UG and MG measurements was greater than 0.99 in all positions.
  
  
  CONCLUSIONS
  Our results show that the smartphone MG has equivalent reliability compared to the traditional UG when measuring passive shoulder abduction ROM. With concordant measures and comparable reliability to the UG, the newly developed MG application shows potential as a useful tool to assess joint angles.
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of California at Davis School of Medicine and Medical Center, 4860 Y Street, Suite 3850, Sacramento, CA 95817, USA. Electronic address: linda.johnson@ucdmc.ucdavis.edu.
authors.forename: Linda B
authors.initials: LB
authors.lastname: Johnson
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of California at Davis School of Medicine and Medical Center, 4860 Y Street, Suite 3850, Sacramento, CA 95817, USA. Electronic address: sean.sumner@ucdmc.ucdavis.edu.
authors.forename: Sean
authors.initials: S
authors.lastname: Sumner
authors.affiliation: Children's National Medical Center, 111 Michigan Avenue NW, DC 20011, USA. Electronic address: Tina.duong@me.com.
authors.forename: Tina
authors.initials: T
authors.lastname: Duong
authors.affiliation: Department of Electrical Engineering and Computer Science, University of California at Berkeley College of Engineering, 752 Sutardja Dai Hall, Berkeley, CA 94720-1764, USA. Electronic address: posu.yan@gmail.com.
authors.forename: Posu
authors.initials: P
authors.lastname: Yan
authors.affiliation: Department of Electrical Engineering and Computer Science, University of California at Berkeley College of Engineering, 752 Sutardja Dai Hall, Berkeley, CA 94720-1764, USA. Electronic address: bajcsy@eecs.berkeley.edu.
authors.forename: Ruzena
authors.initials: R
authors.lastname: Bajcsy
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of California at Davis School of Medicine and Medical Center, 4860 Y Street, Suite 3850, Sacramento, CA 95817, USA. Electronic address: tabresch@gmail.com.
authors.forename: R Ted
authors.initials: RT
authors.lastname: Abresch
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of California at Davis School of Medicine and Medical Center, 4860 Y Street, Suite 3850, Sacramento, CA 95817, USA. Electronic address: evan.debie@ucdmc.ucdavis.edu.
authors.forename: Evan
authors.initials: E
authors.lastname: de Bie
authors.affiliation: Department of Physical Medicine and Rehabilitation, University of California at Davis School of Medicine and Medical Center, 4860 Y Street, Suite 3850, Sacramento, CA 95817, USA. Electronic address: jay.han@ucdmc.ucdavis.edu.
authors.forename: Jay J
authors.initials: JJ
authors.lastname: Han
mesh_terms: D053587:Arthrometry, Articular / Q000295:instrumentation*; D015331:Cohort Studies; D016001:Confidence Intervals; D004867:Equipment Design; D006801:Humans; D008297:Male; D015588:Observer Variation; D056888:Patient Positioning / Q000379:methods; D010865:Pilot Projects; D016059:Range of Motion, Articular / Q000502:physiology*; D015203:Reproducibility of Results; D012785:Shoulder Joint / Q000502:physiology*; D000068997:Smartphone / Q000706:statistics & numerical data*; D016683:Supine Position
keywords: Goniometry; Reliability; Smartphone; Validity