Non-invasive Assessment and Compensation of Soft-tissue Artefacts in Hip Joint Kinematics

Determination of the hip joint centre by functional methods suffers inaccuracy due to the soft tissue artefact; this is the relative motion between the markers and the underlying bone due to the muscle and skin deformation. To solve this issue, we present a non-invasive method to assess and reduce the effect of the soft tissue artefact using optical motion capture data and tissue thickness from ultrasound measurements during flexion, extension, and abduction of the hip joint. The marker displacements are dependent on the movement type, being relatively larger in abduction movement. The quantification of soft tissue artefacts is used as a basis for a correction procedure for hip joint centre and minimizing the soft tissue artefact effects. Results show that our method for soft tissue artefact assessment and minimization reduces the error in the functional hip joint centre approximately from 13-23mm to 7-14 mm.