# Reliability and Validity of the Single-Camera Markerless Motion Capture System for Measuring Shoulder Range of Motion in Healthy Individuals and Patients with Adhesive Capsulitis: A Single-Center Study

## TL;DR

A new camera-based system called iBalance accurately measures shoulder movement and could replace traditional tools in clinics.

## Contribution

iBalance is a reliable and valid single-camera markerless system for measuring shoulder range of motion in clinical settings.

## Key findings

- iBalance showed excellent reliability for measuring shoulder flexion, abduction, and passive abduction.
- The system demonstrated strong validity when compared to goniometers for key shoulder movements.
- Patients with adhesive capsulitis showed greater variability in measurements than healthy individuals.

## Abstract

What are the main findings?
iBalance, a single-camera markerless motion capture system for measuring shoulder range of motion, demonstrated excellent inter- and intra-rater reliability for flexion, abduction, and passive abduction, along with strong validity compared to the goniometer for these movements.Patients with adhesive capsulitis exhibited greater variability than healthy individuals.

iBalance, a single-camera markerless motion capture system for measuring shoulder range of motion, demonstrated excellent inter- and intra-rater reliability for flexion, abduction, and passive abduction, along with strong validity compared to the goniometer for these movements.

Patients with adhesive capsulitis exhibited greater variability than healthy individuals.

What is the implication of the main finding?
The iBalance system has the potential to serve as a clinical alternative to goniometers.Its ability to capture dynamic range of motion and compensatory movements offers significant advantages for diagnosing and managing musculoskeletal disorders.

The iBalance system has the potential to serve as a clinical alternative to goniometers.

Its ability to capture dynamic range of motion and compensatory movements offers significant advantages for diagnosing and managing musculoskeletal disorders.

Assessing shoulder joint range of motion (ROM) is essential for diagnosing musculoskeletal disorders and optimizing treatments. This single-center pilot study evaluated the reliability and validity of iBalance, a single-camera markerless motion capture system, for measuring shoulder ROM. Forty participants (30 healthy individuals and 10 patients with adhesive capsulitis) underwent measurements of seven shoulder joint movements. Each movement was assessed three times by two raters using both iBalance and a goniometer, with measurements repeated after 1 week. The iBalance demonstrated excellent inter- and intra-rater reliability for flexion (ICC = 0.93 [0.91–0.95], 0.91 [0.88–0.94]), abduction (ICC = 0.97 [0.95–0.98], 0.93 [0.91–0.95]), and passive abduction (ICC = 0.97 [0.96–0.98], 0.98 [0.97–0.98]). The system also showed strong validity compared to the goniometer for flexion (ICC = 0.85 [0.68–0.92]), abduction (ICC = 0.95 [0.94–0.96]), and passive abduction (ICC = 0.97 [0.96–0.98]). Bland–Altman plots showed high consistency between the two devices for flexion, abduction, and passive abduction, with most data points falling within the limits of agreement. Patients with adhesive capsulitis exhibited greater variability than healthy individuals. No adverse events were reported, supporting the safety of the system. This study highlights the potential of a single-camera markerless motion capture system for diagnosing and treating shoulder joint disorders. The iBalance showed clinical applicability for measuring flexion, abduction, and passive abduction. Future enhancements to the algorithm and the incorporation of advanced metrics could improve its performance, facilitating broader clinical applications for diagnosing complex shoulder conditions.