Validity and Reliability of a Sensor Based Electronic Spinal Mobility Index for Axial Spondyloarthritis

Philip Gardiner, Dawn Small, Karla Munoz Esquivel, Joan Condell, Antonio Cuesta-Vargas, Jonathan Williams, Pedro M Machado, Juan L. Garrido-Castro

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OBJECTIVE: To evaluate the validity and reliability of inertial measurement unit (IMU) sensors in the assessment of spinal mobility in axial spondyloarthritis (axSpA).
METHODS: A repeated measures study design involving 40 participants with axSpA was used. Pairs of IMU sensors were used to measure the maximum range of movement at the cervical (Cx) and lumbar (Lu) spine. A composite IMU score was defined by combining the IMU measures. Conventional metrology and physical function assessment were performed. Validation was assessed considering the agreement of IMU measures with conventional metrology and correlation with physical function. Reliability was assessed using intra-class correlation coefficients (ICCs).
RESULTS: The composite IMU score correlated closely (r = 0.88) with the BASMI. Conventional Cx rotation and lateral flexion tests correlated closely with IMU equivalents (r = 0.85, 0.84). All IMU movement tests correlated strongly with BASFI, while this was true for only some of the BASMI tests. The reliability of both conventional and IMU tests (except for chest expansion) ranged from good to excellent. Test-retest ICCs for individual conventional tests varied between 0.57 and 0.91, in comparison to a range from 0.74 to 0.98 for each of the IMU tests. Each of the composite regional IMU scores had excellent test-retest reliability (ICCs=0.94-0.97), comparable to the reliability of the BASMI (ICC=0.96).
CONCLUSION: Cx and Lu spinal mobility measured using wearable IMU sensors is a valid and reliable assessment in multiple planes (including rotation), in patients with a wide range of axSpA severity.

Original languageEnglish
Article numberRHE-19-1951.R1
Pages (from-to)3415-3423
Number of pages9
Issue number11
Early online date28 Apr 2020
Publication statusPublished (in print/issue) - 1 Nov 2020

Bibliographical note

Funding Information:
The authors acknowledge the willing collaboration of all the patients who were partners in this research. They also acknowledge the hard work and expertise of Eithne Boyle, Ann-Marie Conlon and Stephanie Keys. P.M.M. is supported by the National Institute for Health Research (NIHR) University College London Hospitals (UCLH) Biomedical Research Centre (BRC). The views expressed are those of the authors and not necessarily those of the (UK) National Health Service (NHS), the NIHR or the (UK) Department of Health. Preliminary data included in this publication was published at the ACR Annual Meeting 2018. Funding: This work was supported by a project grant from the Foundation for Research in Rheumatology (FOREUM). The funders had no role in study design, data collection, analysis, decision to publish or preparation of the manuscript. Sensors were purchased from DorsaVi ltd. under a research agreement. DorsaVi had no input in the analysis or interpretation of data. Disclosure statement: P.V.G. reports honoraria from Celgene; consulting fees from Pfizer and Genomics Medicine Ireland; involvement in a clinical trial funded by Abbvie. P.M.M. reports honoraria/consulting fees from Abbvie, BMS, Celgene, Janssen, MSD, Novartis, Pfizer, Roche and UCB. The other authors have declared no conflicts of interest.

Publisher Copyright:
© The Author(s) 2020. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved. For permissions, please email:

Copyright 2020 Elsevier B.V., All rights reserved.


  • axial spondyloarthritis
  • inertial measurement unit
  • reliability
  • sensor
  • spinal mobility


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