P.W. Knapp et al. found in a study that – Digital app measurements were comparable to measurements made by either a surgeon or physical therapist with a manual goniometer in the clinical setting and may be beneficial for measuring and monitoring patients’ range of motion remotely.

Digital technology has emerged as a useful tool for preoperative and postoperative patient engagement and for remote patient monitoring. Smartphones are equipped with motion-sensing technology, and apps can be designed which use these features to create a simple method for measuring range of motion.

The authors conducted a study to determine the accuracy of digital technology in assessing knee range of motion using a smartphone app, compared to traditional goniometric measurements in an office setting.

Fifty-three (53) patients in a clinical practice were enrolled for the study.

Patients were included regardless of the reason for clinical visit; they did not need to be surgical patients as the goal of the study was to determine the correlation between manual goniometric and digital measurements.

Patients were excluded if there was a history of acute traumatic injury to the knee limiting ROM.

In addition to ROM, patient height, weight, and body mass index (BMI) were also recorded. BMI measurements were included to address clinical concerns with accuracy associated with patients’ body habitus.

The App vocalizes instructions to the patient or provider on the proper technique. The protocol involves placing the phone on the anterior thigh and, when instructed, sliding the phone down to the mid tibia region. The App then calculates and states the calculated ROM. Patients were then immediately brought to the hospital for readings with a manual goniometer by surgeon & physical therapist.

Three separate measurements were taken during the patient encounter: (1) the surgeon, (2) the app, and (3) the physical therapist.

Intraclass correlations were computed to assess the agreement between (1) the surgeon and app and (2) that between the physical therapist and surgeon.

The observations of the study were –1.When measuring flexion, the correlation between either the surgeon or therapist with the app was good, whereas the comparison between the surgeon and therapist was moderate.

2.All extension measurement comparisons, between the app, surgeon, and therapist, showed moderate correlation.

3.Limits of agreements showed that 80% of the difference between surgeon and app is within 10 degrees for extension and 11 degrees for flexion.

4.Body mass index did not affect the accuracy of the measurements.

The authors concluded that – Newer technology that allows for remote patient monitoring continues to provide appealing applications for surgeons and patients. They demonstrated that the studied digital application measuring remote knee ROM was comparable to manual measurements made by either a surgeon and/or PT. Further investigation is necessary to track long-term outcomes and appropriate utilization of this technology in a clinical setting.

Further reading:

Comparison of a Smartphone App to Manual Knee Range of Motion Measurements

Paul W. Knapp, Robert A. Keller, Kathryn A. Mabee, Jing Shi, Raji Pillai, Nicholas B. Frisch.

Arthroplasty Today 15 (2022) 43-46


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