Reliability of Smartphone Goniometry in Measuring Range of Motion of Proximal Interphalangeal Joints of Hand

Background: Smartphone app-based goniometers (SG) have been used as an alternative to the universal goniometer in finding the range of motion (ROM) of joints.There is enough evidence suggesting the reliability of smartphone goniometers in measuring the range of shoulder, elbow, knee, and ankle joint movements.The reliability of SG in measuring the ROM of small joints of the hand is unclear.This study tests the reliability of SG in measuring ROM of proximal interphalangeal (PIP) joints of the hand compared with universal goniometry.Objective: To test the reliability of smartphone-based goniometry in measuring ROM of PIP joints of the hand compared with universal goniometer.Methods: In this study, nine healthy volunteers (6 males, 3 females) were selected.ROM of PIP joints (index, middle, ring, and little finger) at random angles was measured with universal goniometer by an experienced hand therapist, after which the goniometer was removed and the finger photographed in the same position.Then the angles were measured by SG by five orthopedic residents.Intraclass coefficient and standard error of measurement (SEM) were used to calculate the reliability of SG.Results: There were 72 measurable datasets.SG showed excellent relative and absolute reliability in measuring ROM of PIP joints with ICC >0.85 and SEM of 1.17.Conclusion: SG is reliable in measuring the ROM of PIP joints of the hand compared with universal goniometry.Level of evidence: II.