<p>Understanding the effect of individual marker misplacements is important to improve the repeatability and aid to the interpretation of multi-segment foot models like the Oxford and Rizzoli Foot Models (OFM, RFM). Therefore, this study aimed to quantify the effect of controlled anatomical marker misplacement on multi-segment foot kinematics (i.e. marker placement sensitivity) as calculated by OFM and RFM in a range of foot sizes. Ten healthy adults and nine children were included. A combined OFM and RFM marker set was placed on their right foot and a static standing trial was collected. Each marker was replaced ± 10 mm in steps of 1 mm over the three axes of a foot coordinate system. For each replacement the change in segment orientation (tibia, hindfoot, midfoot, forefoot) was calculated with respect to the reference pose in which no markers were replaced. A linear fit was made to calculate the sensitivity of segment orientation to marker misplacement in °/mm. Additionally, the effect of foot size on the sensitivity was determined using linear regressions. For every foot segment of both models, at least one marker had a sensitivity ≥ 1.0°/mm. Highest values were found for the markers at the posterior aspect of the calcaneus in OFM (1.5°/mm) and the basis of the second metatarsal in RFM (1.4°/mm). Foot size had a small effect on 40% of the sensitivity values. This study identified markers of which consistent placement is critical to prevent clinically relevant errors (&gt;5°). For more repeatable multi-segment models, the role of these markers within the models’ definitions needs to be reconsidered.</p>

doi.org/10.1016/j.jbiomech.2021.110629, hdl.handle.net/1765/135922
Journal of Biomechanics
Erasmus MC: University Medical Center Rotterdam

Wouter Schallig, Josien C. van den Noort, Mario Maas, J. (Jaap) Harlaar, & Marjolein M. van der Krogt. (2021). Marker placement sensitivity of the Oxford and Rizzoli foot models in adults and children. Journal of Biomechanics, 126. doi:10.1016/j.jbiomech.2021.110629