Accuracy and reliability of skin-markers based measures of the medial longitudinal arch of the foot

The foot medial-longitudinal arch (MLA) is perhaps the most important feature characterizing foot morphology. Current MLA models based on skin-markers for motion analysis allow non-invasive assessment of foot arch shape and deformation, but little is known on their anatomical accuracy and repeatability. The aim of this study was to propose novel MLA measures based on skin-markers and assess their accuracy and repeatability with respect to current clinical definitions. Accuracy was tested by comparing double-leg standing static MLA angles with radiographic-based measurements. Repeatability was assessed in multiple walking and running trials in two volunteers. The average error with respect to radiographic measurements ranged 3.3 – 23.8 deg across all MLA definitions. The inter-session variability was between 2.9 – 7.7 deg, and the inter-examiner between 3.7 – 9.3 deg across all MLA definitions in walking and running.