Measurement properties of smartphone applications for the measurement of neck range of motion: a systematic review and meta analyses

Background
Smartphone applications offer an accessible and practical option to measure neck range of motion (ROM) and are becoming more commonly used in clinical practice. We assessed the validity, reliability, and responsiveness of smartphone applications (apps) to measure neck ROM in people with and without neck pain.

Methods
A comprehensive electronic search strategy of the main electronic databases was conducted from inception until June 2021. The identified studies investigated apps which measured neck ROM, and evaluated their validity, reliability, or responsiveness, in adult participants with neck pain or asymptomatic individuals. Two independent reviewers determined eligibility and risk of bias following COSMIN guidelines. The quality of evidence was assessed according to the GRADE approach.

Results
Eleven studies, with a total of 376 participants were included. Three types of apps were identified: clinometer apps, compass apps, and other apps of ‘adequate’ to ‘doubtful’ risk of bias. A meta-analysis revealed ‘good’ to ‘excellent’ intra-rater and inter-rater reliability across the three types of apps. The overall validity was rated from ‘moderate’ to ‘very high’ across all apps. The level of evidence was rated as ‘low’ to ‘very low’.

Conclusion
Smartphone applications showed sufficient intra-rater reliability, inter-rater reliability, and validity to measure neck ROM in people with and without neck pain. However, the quality of evidence and the confidence in the findings are low. High-quality research with large sample sizes is needed to further provide evidence to support the measurement properties of smartphone applications for the assessment of neck ROM.

Study registration
Following indications of Prisma-P guidelines, this protocol was registered in PROSPERO on 1/05/2021 with the number CRD42021239501.