Validity and Reliability of an Apple ® Device Application Compared to a Standard Goniometer and a Known Angle When Measuring Shoulder Abduction

PURPOSE: Goniometers are commonly used to measure joint range of motion (ROM) and are considered the current gold standard. With the increase in use and capabilities of mobile devices, numerous medical applications (apps) have been developed, including apps to measure joint ROM. If proven valid, apps designed to measure joint ROM may provide an alternative to goniometric measurements with the potential to improve traditional goniometer use. Previous studies have explored the validity and reliability of a photo-based app, DrGoniometer (DrG), when measuring ROM of hinge joints compared with standard goniometric measurements, with positive results (Ferriero et al., 2013). The purpose of this research is to determine the validity and reliability of the DrG app when measuring a multiaxial joint, the shoulder, and when compared with standard goniometric measurements and a known angle.

DESIGN AND METHOD: This study used a quasi-experimental design. There were 70 participants. Participants were volunteers and average college students with no experience in goniometry. There were male and female participants, all over age 18. The study was approved by the institutional review board, and consent forms were signed by all participants. A custom-made device was used to place each participant in the same amount of shoulder abduction, and the device was later measured using a protractor to determine a known angle. The DrG app was used on an Apple iPad^® to take photos of each participant. An experienced clinician then used a standard goniometer to measure each participant.

To determine interrater reliability, the DrG app photos were used by three different researchers to measure the angles for each participant using the app’s virtual goniometer. One of the researchers repeated the DrG app measurements to determine intrarater reliability. The data were analyzed using IBM SPSS Statistics. Intraclass correlation coefficients (ICCs) were used to analyze reliability. Pearson correlation was used to determine concurrent validity of the app with the goniometer, and t tests were used to compare the app and goniometer with the known angle.

RESULTS: The results of this study show that when used to measure shoulder abduction, the DrG app has strong intrarater (ICC = .847) and interrater reliability (ICC = .885). The correlation between the app and goniometer was fair (r = .669, p < .001). However, the app’s mean (44.2° ± 3.92) was significantly less (p < .001) than the mean for the goniometric measurements (47.8° ± 3.72), and both the app and goniometer results were significantly less than the known angle of 55° (p < .001). Similar results for reliability and concurrent validity were reported in a study comparing measurements using the DrG app and a goniometer, when measuring the first MTP joint of the foot (Otter et al., 2015).

CONCLUSION: The results of this study suggest that the DrG app may be a suitable alternative to standard goniometer measurements, at least in terms of reliability. However, more work needs to be done to prove the app is valid when measuring multiaxial joints. Other types of body joints would need to be assessed to determine if the app sufficiently measures these as well. Despite advantages sustained by the use of mobile devices (e.g., increased accessibility), there is a growing need to validate medical apps, as supported in a review of smartphone use in medicine (Ozdalga, Ozdalga, & Ahuja, 2012). The results of this study affirm the importance of validating apps used for clinical purposes. Emphasizing this type of research is an essential reminder for clinicians to be cognizant of the fact that, although there are apps with considerable potential, many have not been validated.

References

Ferriero, G., Vercelli, S., Sartorio, F., Muñoz Lasa, S., Ilieva, E., Brigatti, E., . . . Foti, C. (2013). Reliability of a smartphone-based goniometer for knee joint goniometry. International Journal of Rehabilitation Research, 36, 146–151. https://doi.org/10.1097/MRR.0b013e32835b8269

Otter, S., Agalliu, B., Baer, N., Hales, G., Harvey, K., James, K., . . . Wong, D. (2015). The reliability of a smartphone goniometer application compared with a traditional goniometer for measuring first metatarsophalangeal joint dorsiflexion. Journal of Foot and Ankle Research, 8, 30. https://doi.org/10.1186/s13047-015-0088-3

Ozdalga, E., Ozdalga, A., & Ahuja, N. (2012). The smartphone in medicine: A review of current and potential use among physicians and students. Journal of Medical Internet Research, 14(5), e128. https://doi.org/10.2196/jmir.1994