The validity and reliability of DrGoniometer, a smartphone application, for measuring forearm supination

Study Design: Clinical measurement (reliability and validity) study. Introduction: Forearm supination is important in many daily activities and is thus measured by therapists and researchers usually with a universal goniometer. DrGoniometer, a SmartPhone application, has been validated for other joint angles in the body. Purpose of the Study: To establish the reliability and validity of DrGoniometer (CDM S.r.L, Cagliari, Italy) for measuring forearm supination in healthy populations and those with forearm fractures. Methods: Participants had sustained a distal radius fracture that was treated non-surgically. Forearm supination of the participant’s fractured (n = 30) and healthy forearm (n = 30) was measured using DrGoniometer and the universal goniometer by two assessors. The assessors were blinded to each other’s measurements and their own previous measurements. Reliability was established by calculating Intra-class Correlation Coefficients, standard error of measurement and minimal detectable change. The validity of DrGoniometer was established against the universal goniometer using Pearson’s correlation co-efficient. Results: Intra-rater reliability of both DrGoniometer and the universal goniometer was high for both fractured and healthy forearms (ICCs ranged from 0.74-0.88). Inter-rater reliability of both DrGoniometer and the universal goniometer was also high in the fractured forearm group (0.76 and 0.72 respectively), but low in the healthy forearm group (0.34 and 0.42 respectively). Correlation between the tools was excellent across the fractured and healthy forearm groups (0.94 and 0.93 respectively). Discussion: Both goniometers demonstrated good-to-excellent intrarater and iner-rater reliability except in the healthy forearm group where both goniometers demonstrated poor inter-rater reliability which could be due to assessor instructions. The speed the photo can be taken and the digital record obtained are valuable aspects of DrGoniometer. Conclusion: DrGoniometer is a valid, alternate tool for measuring forearm supination.