Using a smartphone goniometer to measure active thoracolumbar spine range of motion of lateral flexion and rotation among people with non-specific low back pain: a reliability and validity study

Aims/Background Thoracolumbar rotation and lateral flexion movement are essential in performing coordinated and smooth trunk movements. The smartphone goniometer measures range of motion, and it is easier and cheaper to use than a traditional goniometer. The aim of this study was to investigate the reliability of smartphone goniometer in measuring thoracolumbar spine active range of motion among people with non-specific low back pain. Methods In this randomised double-blind reliability and validity study, 64 participants with non-specific low back pain were recruited. Two independent blinded examiners performed range of motion measurements using both a universal goniometer and a smartphone goniometer application. Each participant performed lateral flexion to both sides and rotation to both sides. Three sets of movements were measured using a universal goniometer and three sets of movements were measured using a smart phone goniometer. Measurements were taken 2 hours apart and 48 hours later. Independent blinded recorders recorded the results. Pearson correlation coefficients were used to identify significant associations between the two instruments. Results Both the universal goniometer and smartphone-based goniometer were found to have good to excellent intrarater reliability (ranging from 0.71 to 0.83). The inter-rater reliability for both instruments also ranged from good to excellent (0.63–0.80). Bland Altman plots showed that there were no differences between the measurement values for both instruments. Conclusions The smartphone-based goniometer is a valid and reliable tool for measuring thoracolumbar lateral flexion and rotation. Implications for practice The smartphone goniometer application is available free and bee used by both clinicians and patients easily with no need for intensive training, besides this study can provide enough information about the reliability of smartphone range of motion measurement applications. There is a high need to establish enough information about its reliability and validity and the contributing errors in the different techniques, which may be helpful for the clinician while assessing range of motion.