Reliability testing of the heel marker in three-dimensional gait analysis

Abstract

In three-dimensional gait analysis, anatomical axes are defined by and therefore sensitive to marker placement. Previous analysis of the Oxford Foot Model (OFM) has suggested that the axes of the hindfoot are most sensitive to marker placement on the posterior aspect of the heel. Since other multi-segment foot models also use a similar marker, it is important to find methods to place this as accurately as possible. The aim of this pilot study was to test two different 'jigs' (anatomical alignment devices) against eyeball marker placement to improve reliability of heel marker placement and calculation of hindfoot angles using the OFM. Methods: Two jigs were designed using three-dimensional printing: a ratio caliper and heel mould. OFM kinematics were collected for ten healthy adults; intra-tester and inter-tester repeatability of hindfoot marker placement were assessed using both an experienced and inexperienced gait analyst for 5 clinically relevant variables. Results: For 3 out of 5 variables the intra-tester and inter-tester variability was below 2 degrees for all methods of marker placement. The ratio caliper had the lowest intra-tester variability for the experienced gait analyst in all 5 variables and for the inexperienced gait analyst in 4 out of 5 variables. However for inter-tester variability, the ratio caliper was only lower than the eyeball method in 2 out of the 5 variables. The mould produced the worst results for 3 of the 5 variables, and was particularly prone to variability when assessing average hindfoot rotation, making it the least reliable method overall. Conclusions: The use of the ratio caliper may improve intra-tester variability, but does not seem superior to the eyeball method of marker placement for inter-tester variability. The use of a heel mould is discouraged.

The Amsterdam Foot Model: a clinically informed multi‐segment foot model developed to minimize measurement errors in foot kinematics

“…This high sensitivity was acceptable as the clinical expert panel considered the varus‐valgus angle of the hindfoot as a clinically relevant outcome measure, which can best be described by directly using two markers at the posterior aspect of the calcaneus. Nevertheless, high sensitivity shows the importance of placing these markers as accurately as possible, for example by drawing a line at the back of the calcaneus before placing the markers or using devices that improve the marker placement consistency [56, 57]. The fact that AFM is more robust to marker misplacements potentially improves its repeatability compared to other MFMs, although that obviously also depends on the marker placement accuracy.…”

Marker placement sensitivity in the Oxford and rizzoli foot models in adults and children

“…As some errors due to inconsistent marker misplacement were found to be substantial and clinically relevant, it is important to reduce those errors. Multiple devices have been developed that improve marker placement consistency (Deschamps et al, 2014;Kalkum et al, 2016;McCahill et al, 2021;Simon et al, 2006;Telfer et al, 2010). Some are used for all markers on the foot (Kalkum et al, 2016;Telfer et al, 2010), while others focus on the heel marker (McCahill et al, 2021) or the medial and lateral makers on the calcaneus (Deschamps et al, 2014;Simon et al, 2006).…”

“…Multiple devices have been developed that improve marker placement consistency (Deschamps et al, 2014;Kalkum et al, 2016;McCahill et al, 2021;Simon et al, 2006;Telfer et al, 2010). Some are used for all markers on the foot (Kalkum et al, 2016;Telfer et al, 2010), while others focus on the heel marker (McCahill et al, 2021) or the medial and lateral makers on the calcaneus (Deschamps et al, 2014;Simon et al, 2006). The latter is remarkable, because our results and those of others (Carty et al, 2015;Paik et al, 2014) show that errors in the hindfoot segment orientation are mainly caused by inconsistent marker misplacement of the markers at the posterior aspect of the calcaneus and not on the ones on the medial and lateral sides.…”