The smartphone inclinometer: A new tool to determine elbow range of motion?

BACKGROUND: There are easily accessible tools on smartphones (APP) for measuring elbow range of motion (ROM). The purpose of this study is to evaluate the validity of a particular APP in determining elbow ROM in comparison with the commonly used goniometer (GON), surgeon estimation of range (EST) and measurement on X-ray (XR).

METHODS: The study included 20 patients (40 elbows). Flexion, extension, pronation and supination were measured using three different methods: EST, GON and APP. Radiographic measurements were taken using the average humeral diaphysis axis and dorsal midthird of ulna in flexion and extension.

RESULTS: The accuracy of the three different methods has been compared to GON using statistical analysis (ANOVA and paired samples test). There was no statistically significant difference for XR flexion measurement (mean of 2.8° ± 1.5°). The APP overestimated flexion (mean of 6.4° ± 1.0°), and EST underestimated it (mean of - 7.9° ± 1.1°). For extension, the mean difference was 2.8° ± 0.7° for EST and - 26.8° ± 3.1° for XR. The APP method did not significantly differ from GON. Supination accuracy was greater with EST (2.7° ± 1.7°) than with APP (5.9° ± 1.9°). There was no difference for pronation measurement with both EST and APP.

CONCLUSIONS: This study is the first comparing four measurement techniques of elbow ROM. Our results showed that EST was only accurate for forearm rotation. The XR scored the best for flexion but is less reliable for extension. Surprisingly, compared to GON, APP did not correlate as we expected for flexion and supination, but the other methods were also inaccurate. We found APP to be very useful to measure complete arc of motion (difference between maximal flexion and maximal extension).

LEVEL OF EVIDENCE: III, Retrospective review of a prospective cohort of elbow fracture patients: Diagnostic Study.