Cockcroft John, Louw Quinette, Baker Richard
a Department of Mechanical and Mechatronic Engineering , Stellenbosch University , Stellenbosch , South Africa.
b Division of Physiotherapy , Stellenbosch University , Stellenbosch , South Africa.
Comput Methods Biomech Biomed Engin. 2016 Nov;19(14):1497-504. doi: 10.1080/10255842.2016.1157865. Epub 2016 Mar 1.
A primary source of measurement error in gait analysis is soft-tissue artefact. Hip and knee angle measurements, regularly used in clinical decision-making, are particularly prone to pervasive soft tissue on the femur. However, despite several studies of thigh marker artefact it remains unclear how lateral thigh marker height affects results using variants of the Conventional Gait Model. We compared Vicon Plug-in Gait hip and knee angle estimates during gait using a proximal and distal thigh marker placement for ten healthy subjects. Knee axes were estimated by optimizing thigh rotation offsets to minimize knee varus-valgus range during gait. Relative to the distal marker, the proximal marker produced 37% less varus-valgus range and 50% less hip rotation range (p < 0.001), suggesting that it produced less soft-tissue artefact in knee axis estimates. The thigh markers also produced different secondary effects on the knee centre estimate. Using whole gait cycle optimization, the distal marker showed greater minimum and maximum knee flexion (by 6° and 2° respectively) resulting in a 4° reduction in range. Mid-stance optimization reduced distal marker knee flexion by 5° throughout, but proximal marker results were negligibly affected. Based on an analysis of the Plug-in Gait knee axis definition, we show that the proximal marker reduced sensitivity to soft-tissue artefact by decreasing collinearity between the points defining the femoral frontal plane and reducing anteroposterior movement between the knee and thigh markers. This study suggests that a proximal thigh marker may be preferable when performing gait analysis using the Plug-in Gait model.
步态分析中测量误差的一个主要来源是软组织伪影。临床决策中常用的髋部和膝部角度测量，特别容易受到股骨上广泛软组织的影响。然而，尽管对大腿标记伪影进行了多项研究，但尚不清楚大腿外侧标记高度如何影响使用传统步态模型变体的结果。我们比较了10名健康受试者在步态过程中使用近端和远端大腿标记放置时Vicon插件式步态髋部和膝部角度的估计值。通过优化大腿旋转偏移来估计膝轴，以最小化步态过程中的膝内翻-外翻范围。相对于远端标记，近端标记产生的内翻-外翻范围减少了37%，髋部旋转范围减少了50%（p<0.001），这表明它在膝轴估计中产生的软组织伪影较少。大腿标记对膝关节中心估计也产生了不同的次要影响。使用整个步态周期优化，远端标记显示出更大的最小和最大膝关节屈曲（分别增加6°和2°），导致范围减少4°。站立中期优化使远端标记的膝关节屈曲在整个过程中减少了5°，但近端标记的结果受影响可忽略不计。基于对插件式步态膝轴定义的分析，我们表明近端标记通过减少定义股前平面的点之间的共线性以及减少膝关节和大腿标记之间的前后移动，降低了对软组织伪影的敏感性。这项研究表明，在使用插件式步态模型进行步态分析时，近端大腿标记可能更可取。
