The influence of soft tissue artefacts on calculated foot kinematics

Soft tissue artefacts (STA) between markers and bones introduces errors in the calculation of foot kinematics. The aim of this study was to quantify STA of markers on the foot and their effect on the calculated foot kinematics according to the Oxford Foot Model (OFM) and Rizzoli Foot Model (RFM). Participants were placed on a loading device in a CT-scanner with an OFM and RFM marker set on their right foot. The foot was placed in different positions to quantify the movement of the markers with respect to the corresponding bones. The largest STA were present for the marker on the most proximal posterior aspect of the calcaneus during 40° plantar flexion. STA influenced the kinematics as calculated by OFM and RFM by introducing a clinically significant amount of error up to 4.5° on average, which suggests that some of the marker locations should be reconsidered.