Range of Motion Measurements of the Fingers Via Smartphone Photography.

Background: Range of motion (ROM) measurements of the fingers are frequently obtained during hand physical examinations. While traditionally measured by manual goniometry, smartphone photography introduces an alternative method of ROM measurement that also has potential telemedicine applications. The purpose of this study was to evaluate the reliability of smartphone photography measurements as an alternative to traditional goniometry, using the patient with Dupuytren disease as a model.
Methods: Patients with a confirmed Dupuytren contracture were prospectively enrolled in this study. Range of motion measurements of the affected joints were obtained prior to any invasive treatments. Two sets of photographs were taken by both a clinical staff member and a nonclinical individual unaffiliated with the study. Both sets of photos were analyzed for degree of contracture via software analysis and compared against traditional goniometer measurements.
Results: The study prospectively enrolled 50 consecutive patients with Dupuytren disease, comprising 123 affected joints. The mean contractures of all affected joints as measured by manual goniometry, trained photograph goniometry, and untrained photograph goniometry were 38.5, 35.3, and 35.5, respectively. The mean difference in contracture measurement was 3.2° between manual and trained photograph goniometry and 3.0° between manual and untrained photograph goniometry. There was no statistically significant difference between trained and untrained photo set measurements. Photograph measurements between separate raters demonstrated high consistency (intraclass correlation coefficient = 0.92). Conclusions: Smartphone photography provides contracture measurements equivalent to the accepted error of a finger goniometer (3.2° compared with 5°). The accuracy of smartphone photography in measuring contractures offers potential telemedicine applications for both clinical and research needs.