Validation of an innovative method of shoulder range-of-motion measurement using a smartphone clinometer application.

Background: An accurate and reliable measurement of shoulder range of motion (ROM) is important in the evaluation of the shoulder. A smartphone digital clinometer application is a potentially simpler method for measuring shoulder ROM. The goal of this study was to establish the reliability and validity of shoulder ROM measurements among varying health care providers using a smartphone clinometer application in healthy and symptomatic adults.

Methods: An attending surgeon, fellow, resident, physician assistant, and student served as examiners. Bilateral shoulders of 24 healthy subjects were included. Fifteen postoperative patients served as the symptomatic cohort. Examiners measured ROM of each shoulder, first using visual estimation and then using a goniometer and smartphone clinometer in a randomized fashion.

Results: The interobserver reliability among examiners showed significant correlation, with average intraclass correlation coefficient [ICC(2,1)] values of 0.61 (estimation), 0.69 (goniometer), and 0.80 (smartphone). All 5 examiners had substantial agreement with the gold standard in healthy subjects, with average ICC(2,1) values ranging from 0.62 to 0.79. The interobserver reliability in symptomatic patients showed significant correlation, with average ICC(2,1) values of 0.72 (estimation), 0.79 (goniometer), and 0.89 (smartphone). Examiners had excellent agreement with the gold standard in symptomatic patients, with an average ICC(2,1) value of 0.98.

Conclusion: The smartphone clinometer has excellent agreement with a goniometer-based gold standard for measurement of shoulder ROM in both healthy and symptomatic subjects. There is good correlation among different skill levels of providers for measurements obtained using the smartphone. A smartphone-based clinometer is a good resource for shoulder ROM measurement in both healthy subjects and symptomatic patients.