Concurrent Validity Study of 3D Motion Measurement Systems: VICON vs. Xsens

As the Inertial Measurement System (IMS) being a potential alternative to the Optoelectronic Measurement System (OMS) in terms of capturing comprehensive and objective musculoskeletal data, they need to be verified concurrently with the OMS before we start using the IMS in clinical motion analysis. To achieve this, a concurrent validity experiment of the Xsens system (IMS) in comparison to the Vicon system (OMS) was conducted for both upper and lower extremity movements during walk, squat, and lateral lunge (left and right) to quantify the degree of similarity of kinematic data between the two systems by direct comparison, root mean square difference (RMSD) and Bland Altman (BA) analysis between the Vicon system and the Xsens system. Ten healthy adults (four females and six males; 24.9 ± 1.6 yrs.; 76.3 ± 19.9 kg; 176.9 ± 10.2 cm) gave consents and participated in the study. Both the Vicon markers and the Xsens sensors were placed concurrently to measure angular displacements of both upper and lower extremities for all the movements. In gait, the RMSD value for the lower extremity ranged from 2 to 15 degrees in the sagittal plane, 0.5 to 15 degrees in the frontal plane and 3 to 28 degrees in the transverse plane. In squat, the RMSD values varied from 1 to 14 degrees, 1 to 18 degrees and 2 to 42 degrees for the sagittal plane, the frontal plane, and the transverse plane respectively. In lunge, these values ranged from 1 to 19 degrees for the sagittal plane, 1 to 22 degrees for the frontal plane and 2 to 38 degrees for the transverse plane. The mean RMSD value suggested that the Xsens could produce clinically meaning full data (within the 5 degrees limit) compared to the Vicon data only in the sagittal plane for the lower extremity joints throughout all the movements. The BA analysis indicated that the Xsens could not replace the Vicon in clinical motion analysis. However, the Xsens could be utilized with caution to measure the change in large motion or gait abnormalities in settings where OMS was not practical or accessible