Conference Contribution Details
Mandatory Fields
Telfer, S., Morlan, G., Hyslop, E., Semple, R., Rafferty, D., Woodburn, J.
International Foot & Ankle Biomechanics Conference (iFAB)
A Novel Technique for Improving Marker Placement Accuracy - 3.10.8
Poster Presentation
Optional Fields
INTRODUCTION: Repeatability of marker placement has been acknowledged as a source of error affecting the reliability of multi-segment foot models [1]. A novel technique intended to reduce marker placement error is proposed and its effect on the reliability of intersegment kinematic data of the foot is investigated. METHODS: Reflective markers (7mm diameter with flat base (Qualysis AB, Gothenburg, Sweden) had1mm holes drilled centrally, perpendicular to their base. These markers were then threaded on to a 1mm diameter flexible polystyrene wire which was bent over at each end to prevent the markers falling off (Figure 1). When attaching the markers to the foot, a piece of transparent double sided tape was adhered over the pen marks on the subject’s foot. Then, the end of the plastic wire was placed on the target mark and the wire used to guide the marker down to the skin where it adhered to the tape. The technique was tested by comparing replacement accuracy and reliability for static and walking trials in eight subjects who twice had markers attached by a podiatrist using the standard approach (and blinded to the purpose of the trial), and twice by a researcher using the novel technique. RESULTS: The mean marker placement variability using the standard placement method was 1.4mm (SD 0.23). Using the novel device this error was reduced to 1.1mm (SD 0.28), a statistically significant improvement (p=0.03). In general, between test coefficient of multiple correlations (CMCs) tended to be greater and had lower ranges for trials using the novel technique (Figure 2). Overall these improvements were also shown to be significant (p=0.02). DISCUSSION: The novel technique is a simple and inexpensive tool for improving the consistency of skin mounted marker placement. Results suggest that reductions in the error related to marker placement tended to improve the overall reliability of multi-segment kinematic data from the foot model.
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