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. 2025 Jun 18;25(12):3818.
doi: 10.3390/s25123818.

The Reliability and Validity of an Instrumented Device for Tracking the Shoulder Range of Motion

Rachel E Roos  1 , Jennifer Lambiase  2 , Michelle Riffitts  1 , Leslie Scholle  1 , Simran Kulkarni  1 , Connor L Luck  3 , Dharma Parmanto  4 , Vayu Putraadinatha  4 , Made D Yoga  4 , Stephany N Lang  2 , Erica Tatko  2 , Jim Grant  2 , Jennifer I Oakley  3 , Ashley Disantis  5 , Andi Saptono  4 , Bambang Parmanto  4 , Adam Popchak  6 , Michael P McClincy  3 , Kevin M Bell  1
Affiliations

The Reliability and Validity of an Instrumented Device for Tracking the Shoulder Range of Motion

Rachel E Roos et al. Sensors (Basel). .

Abstract

Rotator cuff tears are common in individuals over 40, and physical therapy is often prescribed post-surgery. However, access can be limited by cost, convenience, and insurance coverage. CuffLink is a telehealth rehabilitation system that integrates the Strengthening and Stabilization System mechanical exerciser with the interACTION mobile health platform. The system includes a triple-axis accelerometer (LSM6DSOX + LIS3MDL FeatherWing), a rotary encoder, a VL530X time-of-flight sensor, and two wearable BioMech Health IMUs to capture upper-limb motion. CuffLink is designed to facilitate controlled, home-based exercise while enabling clinicians to remotely monitor joint function. Concurrent validity and test-retest reliability were used to assess device accuracy and repeatability. The results showed moderate to good validity for shoulder rotation (ICC = 0.81), device rotation (ICC = 0.94), and linear tracking (from zero: ICC = 0.75 and RMSE = 2.41; from start: ICC = 0.88 and RMSE = 2.02) and good reliability (e.g., RMSEs as low as 1.66 cm), with greater consistency in linear tracking compared to angular measures. Shoulder rotation and abduction exhibited higher variability in both validity and reliability measures. Future improvements will focus on manufacturability, signal stability, and force sensing. CuffLink supports accessible, data-driven rehabilitation and holds promise for advancing digital health in orthopedic recovery.

Keywords: inertial measurement unit; reliability; rotator cuff repair; validity.

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Conflict of interest statement

Jim Grant is a co-inventor of the intellectual property (IP) associated with the Strengthening and Stabilization System, which was being adapted for the CuffLink project within this study. He is also the President of ēlizur. ēlizur has licensed interACTION, a system developed by the University of Pittsburgh’s Health and Rehabilitation Informatics (HARI) Lab, for use in this study. The interACTION platform was also being adapted for the CuffLink project. Additionally, Stephany N. Lang and Erica Tatko are currently employed, and Jennifer Lambiase was formerly employed by ēlizur. The remaining authors declare no competing interests.

Figures

Figure 1
Figure 1
(A) The top left image is a frontal view of Vicon sensors placed on the chest and right arm. (B) The top right image is a posterior view of Vicon sensors placed on the back/right shoulder. (C) The bottom left image is a sagittal view of Vicon sensors placed on the arm. (D) The bottom right image is an illustration of the placement of the BioMech IMU sensors on the upper arm and wrist.
Figure 1
Figure 1
(A) The top left image is a frontal view of Vicon sensors placed on the chest and right arm. (B) The top right image is a posterior view of Vicon sensors placed on the back/right shoulder. (C) The bottom left image is a sagittal view of Vicon sensors placed on the arm. (D) The bottom right image is an illustration of the placement of the BioMech IMU sensors on the upper arm and wrist.
Figure 2
Figure 2
The participant completed internal rotation passive range of motion with Vicon sensors placed on the left side and BioMech sensors placed on the left wrist and above the elbow.
Figure 3
Figure 3
Participant performing forward elevation PROM while being verbally guided by a virtual clinical specialist.
Figure 4
Figure 4
Bland–Altman plots to assess concurrent validity for BioMech (body) compared to Vicon during IR/ER, forward elevation, and abduction and for CuffLink (device) compared to Vicon during IR/ER, protraction/retraction, and combined forward elevation and abduction.
Figure 5
Figure 5
Bland–Altman plots to assess test–retest reliability for the shoulder (BioMech) during IR/ER, flexion/extension, forward elevation, and abduction and for the device (CuffLink) during IR/ER, protraction/retraction, and combined forward elevation and abduction.
See this image and copyright information in PMC

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