Smartphone-based Measurement of Post-traumatic Elbow Range of Motion: Agreement with Goniometry and Clinical Assessment.

BACKGROUND: Elbow range of motion (ROM) is commonly assessed during initial evaluation and follow-up. While goniometry is considered the current gold standard, previous studies have raised concerns regarding its user dependence and measurement consistency. OBJECTIVES: To evaluate whether smartphone application-based elbow ROM measurements are comparable to visual estimation and goniometry in patients following elbow trauma. METHODS: We conducted a prospective cohort study of 18 patients with elbow injuries. Demographic and medical data were collected. Maximal flexion-extension active ROM was measured by goniometry, smartphone application, and visual estimation by orthopedic surgeons. Measurements were compared to determine agreement and accuracy among different modalities. RESULTS: Eighteen patients with elbow injuries were included. Inter-rater reliability was good to excellent across all rater groups (intraclass correlation coefficient 0.78-0.93). Using paired t-tests with Bonferroni correction, only one attending surgeon showed a significant underestimation of extension compared to goniometry (16.9° vs. 22.5°, P < 0.05). No significant differences were found for residents, other attendings, or smartphone measurements in either extension or flexion (P > 0.05). Bland-Altman analysis revealed modest mean bias within ± 6° for all methods, although limits of agreement were wide (up to ± 20-30°). Smartphone-based measurements demonstrated significantly higher and less variable Pearson correlation coefficients with goniometry compared to surgeon visual estimations (0.91-0.95 vs. 0.81-0.93, P < 0.05). CONCLUSIONS: Smartphone-based elbow ROM measurements were statistically comparable to goniometry and demonstrated superior correlation and accuracy relative to clinical visual assessments. These findings support the integration of smartphone tools in the clinical setting.