veículo de difusão de informações em análise de marcha, reabilitação e biomecânica, captura de movimento para produções industriais
clinical gait analysis, rehabilitation and biomechanics, industrial "motion capture" (MoCap)

Measurement of errors in quantitative gait data:
Errors, Reliability and Repeatability

  • Analysis of measurement performance in optical motion capturing
  • Validity and reliability as scientific quality criteria have to be considered when using motion capture systems for research purposes. System characteristics such as accuracy and precision are often not addressed in scientific reports of human motion analysis studies, even though literature and standards recommend individual laboratory setup evaluation. One reason could be due to the lack of a simple and practical method to evaluate system performance. We developed a protocol for practical laboratory setup evaluation in context of usability in human movement analysis.
  • Assessment of the kinematic variability among 12 motion analysis laboratories
  • Variability of kinematic measurements among sites participating in a collaborative research investigation is a primary factor in determining number of subjects, level of detectable difference and statistical power of a multi-site research study. In this study, one subject was evaluated by 24 examiners at 12 motion analysis laboratories and the observed variability of nine kinematic parameters are reported.
  • Effects of hip joint centre mislocation on gait kinematics
  • Effects of hip joint centre mislocation on gait kinematics of children with cerebral palsy calculated using patient-specific direct and inverse kinematic models

    Joint kinematics can be calculated by Direct Kinematics (DK), which is used in most clinical gait laboratories, or Inverse Kinematics (IK), which is mainly used for musculoskeletal research. In both approaches, joint centre locations are required to compute joint angles. The hip joint centre (HJC) in DK models can be estimated using predictive or functional methods, while in IK models can be obtained by scaling generic models. The aim of the current study was to systematically investigate the impact of HJC location errors on lower limb joint kinematics of a clinical population using DK and IK approaches.

  • Measurement and management of errors in quantitative gait data
  • Gait analysis is a valuable tool in the evaluation of children and adults with movement disorders. The data produced from gait analysis, however, is not necessarily free of errors. The purpose of this study was two-fold: (i) to estimate the errors associated with quantitative gait data; and (ii) to propose a method for incorporating the knowledge of these errors into the clinical interpretation process.

  • Measurement of the screw-home motion of the knee is sensitive to errors in axis alignment (summary)
  • Several authors have reported on the "screwhome" motion of the knee joint (external rotation of the tibia with respect to the femur during extension) with varying results (Kurosawa et al., 1985; Lafortune et al., 1992). These discrepancies in measurements of axial knee rotation may be due to errors caused by kinematic "crosstalk". Such errors arise when the chosen knee joint coordinate system is not aligned with anatomical axes (e.g., when the flexion-extension axis is not aligned in the mediolateral direction).

    The purpose of the present study is to investigate the possibility that screw-home motion of the knee is a manifestation of kinematic crosstalk. It may be that external rotation of the tibia does not accompany knee extension but rather is knee extension that appears as rotation about a different axis. We hypothesize that small misalignments of the knee joint coordinate system may result in knee extension being misinterpreted as external rotation of a magnitude consistent with reports of measured screw-home motion. Specifically, we will test (1) whether a screw-home motion can be measured where none exists, and (2) whether kinematic crosstalk can hide a screw-home motion that is known to occur.

  • Measurement of the screw-home motion of the knee is sensitive to errors in axis alignment (paper)
  • Measurements of joint angles during motion analysis are subject to error caused by kinematic crosstalk, that is, one joint rotation (e.g., flexion) being interpreted as another (e.g., abduction).Kinematic crosstalk results from the chosen joint coordinate system being misaligned with the axes about which rotations are assumed to occur.The aim of this paper is to demonstrate that measurement of the so-called "screw-home" a motion of the human knee, in which axial rotation and extension are coupled, is especially prone to errors due to crosstalk.

  • Quantitative comparison of five current protocols in gait analysis
  • Data collection and reduction procedures, coherently structured in protocols, are necessary in gait analysis to make kinematic and kinetic measurements clinically comprehensible. The current protocols differ considerably for the marker-set and for the biomechanical model implemented. Nevertheless, conventional gait variables are compared without full awareness of these differences.
    A comparison was made of five worldwide representative protocols by analysing kinematics and kinetics of the trunk, pelvis and lower limbs exactly over the same gait cycles. A single comprehensive arrangement of markers was defined by merging the corresponding five marker-sets. This resulted in 60 markers to be positioned either on the skin or on wands, and in 16 anatomical landmark calibrations to be performed with an instrumented pointer. Two healthy subjects and one patient who had a special two degrees of freedom knee prosthesis implanted were analysed. Data from up-right posture and at least three gait repetitions were collected. Five corresponding experts participated in the data collection and analysed independently the data according to their own procedures.
  • Quantifying sources of variability in gait analysis
  • Measurements from gait analysis are affected by many sources of variability. Schwartz et al. illustrated an experimental design and methods to estimate these variance components. However, the derivation contains errors which could severely bias the estimation of some components. Therefore, in this paper, we presented correction to this method using ANOVA and Likelihood methods.
  • Reliability of four models for clinical gait analysis
  • Three-dimensional gait analysis (3DGA) has become a common clinical tool for treatment planning in children with cerebral palsy (CP). Many clinical gait laboratories use the conventional gait analysis model (e.g. Plug-in-Gait model), which uses Direct Kinematics (DK) for joint kinematic calculations, whereas, musculoskeletal models, mainly used for research, use Inverse Kinematics (IK). Musculoskeletal IK models have the advantage of enabling additional analyses which might improve the clinical decision-making in children with CP. Before any new model can be used in a clinical setting, its reliability has to be evaluated and compared to a commonly used clinical gait model (e.g. Plug-in-Gait model) which was the purpose of this study. Two testers performed 3DGA in eleven CP and seven typically developing participants on two occasions. Intra- and inter-tester standard deviations (SD) and standard error of measurement (SEM) were used to compare the reliability of two DK models (Plug-in-Gait and a six degrees-of-freedom model solved using Vicon software) and two IK models (two modifications of 'gait2392' solved using OpenSim). All models showed good reliability (mean SEM of 3.0° over all analysed models and joint angles).
  • Repeatability of gait data using a functional hip joint centre and a mean helical knee axis
  • The purpose of this paper was to compare the repeatability of gait data obtained from two models, one based on ALs (AL model), and the other incorporating a functional method to define hip joint centres and a mean helical axis to define knee joint flexion/extension axes (FUN model).
  • Statisticians issue warning on P values
  • Misuse of the P value — a common test for judging the strength of scientific evidence — is contributing to the number of research findings that cannot be reproduced, the American Statistical Association (ASA) warned on 8 March. The group has taken the unusual step of issuing principles to guide use of the P value, which it says cannot determine whether a hypothesis is true or whether results are important.
  • The clinical impact of hip joint centre regression equation error
  • The clinical impact of hip joint centre regression equation error on kinematics and kinetics during paediatric gait

    Regression equations based on pelvic anatomy are routinely used to estimate the hip joint centre during gait analysis. While the associated errors have been well documented, the clinical significance of these errors has not been reported. This study investigated the clinical agreement of three commonly used regression equation sets (Bell et al., Davis et al. and Orthotrak software) against the equations of Harrington et al.

  • The reliability of three-dimensional kinematic gait measurements: A systematic review
  • Three-dimensional kinematic measures of gait are routinely used in clinical gait analysis and provide a key outcome measure for gait research and clinical practice. This systematic review identifies and evaluates current evidence for the inter-session and inter-assessor reliability of threedimensional kinematic gait analysis (3DGA) data.
  • Validation of hip joint center localization methods during gait analysis
  • Validation of hip joint center localization methods during gait analysis using 3D EOS imaging in typically developing and cerebral palsy children

    Localization of the hip joint center (HJC) is essential in computation of gait data. EOS low dose biplanar X-rays have been shown to be a good reference in evaluating various methods of HJC localization in adults. The aim is to evaluate predictive and functional techniques for HJC localization in typically developing (TD) and cerebral palsy (CP) children, using EOS as an image based reference.

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