Malcolm Forward

Test-retest reliability of three dimensional gait analysis: Including a novel approach to visualising agreement of gait cycle waveforms with Bland and Altman plots

BACKGROUND/AIM Estimating the measurement error (reliability) of three dimensional gait analysis (3DGA) is crucial to interpretation of gait data. The purpose of this study was to investigate the intra-rater reliability of 3DGA and apply a novel method of visualising reliability of gait cycle waveforms. METHODS A test re-test design was employed. A convenience sample of 30 healthy adults (18F; 12 M: mean age 30 ± 6.8 years) participated. Subjects walked along a 10 m walkway at their preferred gait speed and 3DGA data were collected using a VICON(®) 3DGA system. Testing was performed by the same investigator on two separate days within two weeks. Data from 10 trials were averaged and analysed. ANALYSIS The intraclass correlation coefficient (ICC), the standard error of measurement (SEM), minimal detectable change (MDC) and limits of agreement were calculated for kinetic and kinematic data. Bland and Altman plots were applied to gait cycle waveforms. RESULTS Spatio-temporal parameters such as cadence, step length, velocity, step time and step width were highly repeatable generating ICCs of 0.90 and above and low SEM/MDC. Range of joint movement across the gait cycle was generally more reliable than either minimum or maximum values and higher ICCs were obtained for movement in the sagittal plane. For kinematic data the standard error of measurement was low (≤ 5) for the majority of parameters. Transverse plane measurements showed poor reliability with lowest ICCs. ICCs for kinetic data ranged from 0.51 to 0.81. CONCLUSIONS Reliability of 3DGA has been estimated for our gait laboratory. Bland and Altman plots of gait cycle waveforms provide a useful addition to reliability analysis.

The Effect of Simulating Weight Gain on the Energy Cost of Walking in Unimpaired Children and Children With Cerebral Palsy

OBJECTIVE To examine the effect of simulating weight gain on the energy cost of walking in children with cerebral palsy (CP) compared with unimpaired children. DESIGN Repeated measures, matched subjects, controlled. SETTING University hospital clinical gait and movement analysis laboratory. PARTICIPANTS Children (n=42) with CP and unimpaired children (n=42). INTERVENTIONS Addition of 10% of body mass in weight belt. MAIN OUTCOME MEASURES Energy cost of walking parameters consisting of walking speed, Physiological Cost Index, Total Heart Beat Index, oxygen uptake (VO2), gross oxygen cost, nondimensional net oxygen cost, and net oxygen cost with speed normalized to height were measured by using a breath-by-breath gas analysis system (K4b2) and a light beam timing gate system arranged around a figure 8 track. Two walking trials were performed in random order, with and the other without wearing a weighted belt. RESULTS Children with CP and their unimpaired counterparts responded in fundamentally different ways to weight gain. The unimpaired population maintained speed and VO2 but the children with CP trended toward a drop in their speed and an increase in their VO2. The oxygen consumption of children with CP showed a greater dependence on mass than the unimpaired group (P=.043). CONCLUSIONS An increase of a relatively small percentage in body mass began to significantly impact the energy cost of walking in children with CP. This result highlights the need for weight control to sustain the level of functional walking in these children.

Energy cost of walking: Solving the paradox of steady state in the presence of variable walking speed

Measurement of the energy cost of walking in children with cerebral palsy is used for baseline and outcome assessment. However, such testing relies on the establishment of steady state that is deemed present when oxygen consumption is stable. This is often assumed when walking speed is constant but in practice, speed can and does vary naturally. Whilst constant speed is achievable on a treadmill, this is often impractical clinically, thus rendering an energy cost test to an element of subjectivity. This paper attempts to address this issue by presenting a new method for calculating energy cost of walking that automatically applies a mathematically defined threshold for steady state within a (non-treadmill) walking trial and then strips out all of the non-steady state events within that trial. The method is compared with a generic approach that does not remove non-steady state data but rather uses an average value over a complete walking trial as is often used in the clinical environment. Both methods were applied to the calculation of several energy cost of walking parameters of self-selected walking speed in a cohort of unimpaired subjects and children with cerebral palsy. The results revealed that both methods were strongly correlated for each parameter but showed systematic significant differences. It is suggested that these differences are introduced by the rejection of non-steady state data that would otherwise have incorrectly been incorporated into the calculation of the energy cost of walking indices during self-selected walking with its inherent speed variation.

The clinical relevance of selecting resting data at different points in an energy cost of walking test in cerebral palsy

Aim  Energy cost of walking (ECOW) is defined as ‘walking oxygen consumption minus resting oxygen consumption divided by speed’, where ‘resting’ data can be obtained either at the start or cessation of a test. This study aimed to ascertain when resting data should be taken during an ECOW test in children with cerebral palsy (CP).

Development and clinical evaluation of laser-sintered ankle foot orthoses

ABSTRACT Ankle foot orthoses (AFOs) are traditionally manufactured using vacuum thermoforming as shaping technology. Additive manufacturing has the potential to disruptively change the way these orthopaedic devices are produced. In this study, AFOs are developed which are virtually designed and produced with laser sintering as shaping technology. The mechanical and clinical performances of these laser-sintered AFOs are compared with traditionally manufactured AFO by asking seven patients (both children and adults) to walk with each type of AFO.

A novel experimental setup for evaluating the stiffness of ankle foot orthoses

ObjectiveThe purpose of this study was the construction of a new semi-automated experimental setup for the evaluation of the stiffness of ankle foot orthoses (AFOs) around an axis aligned to the anatomical ankle joint during the second rocker of the gait. The setup, developed in close collaboration with the orthopedic device company V!GO NV (Wetteren, Belgium), allows measurement of plantarflexion and dorsiflexion in the sagittal plane for a maximal range of motion of 50° (− 25° plantarflexion up to 25° dorsiflexion) in a non-destructive way.ResultsThe mechanical properties of four 3D printed AFOs are investigated, based on the ranges of motion derived from the gait assessment of the patients when they walked with their AFO. The reliability of the stiffness measures was studied by the evaluation of the test–retest repeatability and the intra-tester and inter-tester variability. These studies revealed that the ankle stiffness can be measured with high reliability (ICC = 0.94–1.00). The obtained outcomes indicate that the experimental setup could be applied to measure the ankle stiffness of any topology of AFOs and, in the future, help finding the correlation with the information coming from the gait assessment of the patients.

Efectos de la variación muscular en la prueba neurodinámica del nervio mediano en una población sana con arco axilar de Langer

Objetivo La prueba neurodinamica del nervio mediano (PNES1, prueba neurodinamica 1 de la extremidad superior, o ULNT1 en ingles) se utiliza con frecuencia para evaluar la mecanica y la fisiologia del plexo braquial y del nervio mediano. El presente estudio investiga las PNES1 positivas en una poblacion sana con arco axilar de Langer (AAL) y analiza si el AAL afecta al arco de movimiento durante la extension de codo (AM-EC) durante la PNES1. Material y metodos De los 640 voluntarios examinados, finalmente se incluyeron 26 lados con AAL. La realizacion de un cuestionario clinico adicional revelo “sintomas menores” en algunos sujetos. Estos sintomas menores no se consideraron un trastorno porque no suponian un obstaculo para la realizacion de las actividades diarias y los sujetos no solicitaron atencion medica. Este estudio investiga si la PNES1 puede producir o reproducir sintomas menores o respuestas anormales en sujetos con AAL. Se comparo el AM-EC del lado izquierdo y derecho de los sujetos. Por otra parte, se comparo el angulo de sustraccion, que es el efecto de colocar la columna cervical en flexion lateral contralateral, entre los lados con AAL y los controles. Resultados Los lados con arco axilar de Langer mostraron un aumento significativo en la aparicion de sintomas menores y PNES1 positivas, pero no se observo efecto alguno en el AM-EC. Conclusiones Estos hallazgos indican que el AAL puede afectar de forma transitoria al haz neurovascular axilar. La falta de efectos sobre los AM-EC puede ser consecuencia del origen vascular de los sintomas menores o de una respuesta del nervio cubital/cordon medial a la PNES1.