The Reliability and Concurrent Validity of Digital Inclinometer, Smartphone Applications, and the Cervical Range of Motion Device for Measuring the Cervical Range of Motion

Objectives: Changes in the Range of Motion (ROM) are essential criteria in determining the severity of spinal disorders and could be effective in predicting pain progression. Instruments to measure the ROM are costly and unavailable in most therapy settings. While there is a tendency in therapists to use their smartphones instead, there is no report to measure the suitability of smartphones to be employed for this purpose. The current study aimed to compare the inter- and intra-rater reliability and concurrent validity of a Cervical Range of Motion (CROM) device (as a gold standard), a digital inclinometer, and smartphones in measuring the CROM in asymptomatic adults. Methods: Twenty-four healthy subjects (11 women, 13 men) aged 22 to 45 years were recruited for this study. Neck movements were assessed per study subject using CROM device, dual digital inclinometer, as well as IOS (for iPhone), and Android applications. Despite the popularity of using smartphone applications, there was no study comparing such applications. Results: The dual inclinometer and iPhone clinometer and compass applications presented acceptable absolute and relative reliability (ICC=0.662-0.913) and (ICC=0.753-0.887), respectively for neck movements in all planes. The reliability of the Android clinometer application in the sagittal and frontal planes was also acceptable (ICC=0.76-0.937); however, the Android compass application used in the horizontal plane indicated the least intraclass correlation coefficient (ICC: 0.202-0.433) in this area. Discussion: All the tested tools differed from the gold standard depending on the direction of movement, confirmed i.e.  approved by the Bland-Altman. The dual digital inclinometer presented moderate to high agreement to the CROM device for all motions, except for rotation. The iPhone applications had high to a very high agreement, and the Android application revealed poor to a moderate agreement. These discrepancies should be considered in employing smartphones for diagnosing a cervical disorder and determining a therapeutic plan. However, as phone applications indicated desirable reproducibility, these tools could be used for the follow-up and monitoring of changes in the CROM.