Introduction

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.

中文翻译：

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三维步态分析中脚跟标记的可靠性测试

介绍

在三维步态分析中，解剖轴由标记放置定义，因此对标记放置敏感。先前对牛津脚模型（OFM）的分析表明，后脚的轴对脚后跟标记的放置最敏感。由于其他多段脚模型也使用类似的标记，因此找到尽可能准确地放置它的方法很重要。

这项初步研究的目的是针对眼球标记物放置位置测试两种不同的“夹具”（解剖学对准设备），以提高脚跟标记物放置位置的可靠性以及使用OFM计算后足角度的可靠性。

方法

使用三维打印设计了两个夹具：比率卡尺和脚跟模具。收集了十个健康成年人的OFM运动学信息。测试者内部和测试者间后脚标记物放置的重复性使用经验丰富和经验不足的步态分析人员对5个临床相关变量进行评估。

结果

对于5个变量中的3个，所有标记放置方法的测试者内部和测试者内部变异性都低于2度。对于所有5个变量，经验丰富的步态分析者和没有经验的步态分析者，比率卡尺的测试者内部变异性最低。但是，对于测试者间的可变性，比率卡尺仅低于5个变量中的2个的眼球方法。对于5个变量中的3个，霉菌产生的结果最差，并且在评估平均后足旋转度时，特别容易产生变异性，从而使该方法总体上最不可靠。

结论

使用比率卡尺可以改善测试者内部的可变性，但似乎并不优于测试者之间可变性的标记放置眼球方法。不建议使用脚跟模具。