Variations of Marker Sets and Models for Standard Gait Analysis

Abstract

A variety of different approaches is used in 3D clinical gait analysis. This chapter provides an overview of common terms, different marker sets, underlying ana-tomical models, as well as a fundamental understanding of measurement tech-niques commonly used in clinical gait analysis and the consideration of possible errors associated with these different techniques. Besides the different marker 1 sets, two main approaches can be used to quantify marker-based joint angles: a prediction approach based on regression equations and a functional approach. The prediction approach uses anatomical assumptions and anthropometric refer-ence data to define the locations of joint centers/axes relative to specific anatom-ical landmarks. In the functional approach, joint centers are determined via optimization of marker movement. The accuracy of determining skeletal kine-matics is limited by ambiguity in landmark identification and soft-tissue artifacts. When the intersubject variability of control data becomes greater than the expected change due to pathology, the clinical usefulness of the data becomes doubtful. To allow a practical interpretation of a comparison of approaches, differences and the measurement error should be quantified in the unit of interest (i.e., degree or percent). The highest reliability indices occurred in the hip and knee in the sagittal plane, with lowest reliability and highest errors for hip and knee rotation in the transverse plane. In addition, knowledge about sources of errors should be known before the approach is applied in practice.