Validation of joint angle measurements: Comparison of a novel low cost marker-less system with an industry standard marker-based system.

Purpose: Biomechanical analysis is a powerful tool in the evaluation of movement dysfunction in orthopaedic and neurologic populations. Three-dimensional (3D) motion capture systems are widely used accurate systems, but are costly and not available in many clinical settings. This study compared joint angles measured in functional tests using the novel low-cost Microsoft Kinect Perfect Phorm system with the established marker based Nexus VICON system. A series of specified functional tests are performed in unimpaired participants, with the aim to examine the relative accuracy of the Kinect Perfect Phorm system and the correlation between the two systems.

Primary Objectives:  Measurements using the new system (Kinect) will be compared to those using the Nexus Vicon as the “gold standard” measurement, in order to examine whether the Kinect system makes valid measurements.

Results: This study compared joint angles measured in functional tests using the novel low-cost Microsoft Kinect Perfect Phorm system with the established marker-based Nexus VICON system. When measuring right and left knee flexion, the average difference between the VICON and Kinect Perfect Phorm measurement was 13.2%, with a SD of 19.6. Both overestimation and underestimation of the joint angle was recorded in different participants. Although the average percentage difference during hip abduction tests was lower at -3.9%, the range of error was far greater (SD = 75). From this, it can be concluded that the level of accuracy presented in the new low-cost Kinect Perfect Phorm system is not yet suitable for clinical assessments. However, for general tests of performance, and for tracking cases where absolute accuracy is less critical, future versions of this software may have a place.

The full report of this study can be accessed here.

Validation of joint angle measurements