A Comparison of Elbow Range of Motion Measurements: Smartphone-Based Digital Photography Versus Goniometric Measurements

Abstract

Purpose: The purpose of this study was to validate elbow flexion and extension measured from smartphone photography obtained by participants and compared them with photographs obtained by surgeons and goniometric measurements.

Methods: We enrolled 32 participants with a total of 64 elbows, aged 25 to 68 years. Participants obtained smartphone photographs of full elbow flexion and extension. Then surgeons obtained the same photographs and goniometric measurement of elbow range of motion (ROM). We measured ROM from the photographs using Adobe Photoshop and calculated average ROM. Comparisons of manual goniometer versus digital measurements, participant versus surgeon photograph measurements, and interobserver measurements were statistically analyzed.

Results: Average ROM measured by manual goniometer and digital photographs was 0° to 129° (range, 0° to 140°) and 0° to 129° (range, 0° to 145°), respectively. The goniometer versus digital measurements interclass correlation was 0.828 (L) and 0.740 (R). Pearson coefficient was 0.845 (L) and 0.757 (R). Bland-Altman plots demonstrated that 30 of 32 digital measurements (L) and 31 of 32 measurements (R) were within the 95% confidence interval. Participant-obtained photographs compared with researcher's photographs interclass correlation was 0.955 (L) and 0.941 (R), with a Pearson coefficient of 0.962 (L) and 0.957 (R), respectively. Reviewing interobserver reliability, concordance coefficients were 0.793 (L) and 0.767 (R) and Pearson coefficients were 0.811 (L) and 0.780 (R). Bland-Altman plots demonstrated that 28 of 32 digital measurements (L) and 26 of 32 measurements (R) were within the 95% confidence interval.

Conclusions: Measuring elbow ROM using smartphone digital photography is valid and reliable. Participants were able to obtain accurate photographs and the measurements based on these photographs show no statistical difference from those taken by surgeons or goniometric measurement.

Clinical relevance: This study validates using smartphone photography for measuring elbow ROM by laymen in a remote setting.

Type of study/level of evidence: Diagnostic II.

Keywords: Digital photography; elbow range of motion; smartphone.