Enrique Medina Ripoll, Juan López Pascual, Francisco Parra González, Mª Francisca Peydro de Moya, Cristina Herrera Ligero, Javier Andrade Celdrán, Ignacio Bermejo Bosch (*)
Instituto de Biomecánica (IBV). Universitat Politècnica de València. Edificio 9C. Camino de Vera s/n (E-46022) Valencia. Spain
(*) IBV’s Healhcare Technology Group, CIBER IN BIOENGINEERING, BIOMATERIALS AND NANOMEDICINE (CIBER-BBN)
A comprehensive analysis of human gait requires expensive instrumentation protocols and highly qualified staff, which limits the use of this biomechanical assessment technique. In view of this reality, Instituto de Biomecánica has developed the NedAMHplus/IBV application based on kinematic, dynamic and electromyographic measurements. NedAMHplus/IBV offers easy-to-interpret information for clinical decision making using a fast and simple protocol. The studies performed concluded that the results of NedAMHplus/IBV are reproducible and valid for gait assessment.
The analysis of human gait refers to the measurement of the movement patterns that occur when walking and the interpretation of the data obtained. The objectives of gait analysis are to analyze dynamic gait disorders, to help in rehabilitation treatment planning, to provide information for making decisions on the treatment, to assess the return to work of patients, etc. [1-2]
This type of analysis includes information on joint mobility (kinematic), the forces exerted during the stance phase (dynamic), and muscular behavior (surface electromyography). The main drawback of a comprehensive human gait analysis is that it requires very expensive instrumentation protocols and highly qualified staff to correctly apply it and interpret the results. For this reason, comprehensive human gait analyses are performed almost exclusively on very complex patients, such as those who show neurological pathologies.
For all these reasons, Instituto de Biomecánica (IBV) decided to conduct a research project to develop a simple and valid method for the clinical assessment of gait that could provide kinematic, dynamic and electromyographic information. The result of this research is the NedAMHplus/IBV application.
OBJECTIVES OF NedAMHplus/IBV
The objective of NedAMHplus/IBV is to provide a simple, objective and reliable method for assessing human gait which allows the user to make decisions about the follow-up, treatment and return to work or discharge of patients.
DESCRIPTION OF NedAMHplus/IBV
NedAMHplus/IBV is a system for the biomechanical assessment of human gait that generates reliable and objective information to determine the functionality of the patient. NedAMHplus/IBV provides a quantitative and objective assessment of the overall functionality of the subject, both from a dynamic and kinematic point of view. To do this, the system generates assessment indices to evaluate the degree of functional limitation. Likewise, NedAMHplus/IBV can record surface electromyography to complement the kinematic and dynamic assessment of human gait.
The most relevant aspects of the NedAMHplus/IBV application are described below:
NedAMHplus/IBV combines a force platform, a photogrammetry system and, optionally, a surface electromyography system to obtain the dynamic, physiological and kinematic information of gait movements.
The marker model developed is based on the Plug in Gait standard model (Figure 1) and meets the following design criteria:
♦ Small number of markers (n=10)
♦ Simple instrumentation of the patient
♦ To provide relevant information
The recommended instrumentation for the electromyographic analysis consists of 8 electrodes and is based on the one proposed by SENIAM ; however, the healthcare professional may decide to use other protocols.
Figure 1. Example of instrumentation with the NedAMHplus/IBV marker model and detail of markers arrangement.
In order to ensure the reproducibility of the measurements and minimize the variability generated by both the evaluator and the patient, special attention has been paid to the definition of a controlled measurement protocol. The aspects considered include patient instrumentation, recording of the reference position, control of gait speed, and instructions to perform the tests.
♦ NedAMHplus/IBV obtains the main parameters of human gait, which were determined during the study. After various statistical analyses, the parameters that make it possible to significantly differentiate the behavior among subjects were selected. These selected parameters include:
♦ Neutral posture. Angles of the hip, knee and ankle, and progression of the patient’s foot in the standing position.
♦ Dynamics. Reaction forces during support while walking. The forces are represented, together with the corresponding normalcy band, with respect to the group of healthy subjects.
♦ Kinematics. Angles of the hip, knee and ankle, in the sagittal plane during gait cycle. These angles are represented together with the corresponding normalcy bands.
♦ Spatio-temporal. Main spatio-temporal parameters: speed, cadence, length and width of the step, among others. 
♦ Morphology. Assessment of the similarity of the movement and force curves with respect to the reference curve of gait speed, age and gender of the patient. This index is calculated from the Gait Variable Score (GVS) index. 
♦ Symmetry. Assessment of the similarity between the parameters and curves obtained for the right leg compared to those obtained for the left leg.
Besides, the application provides the result curves of the kinematic, dynamic and electromyography information compared with databases to facilitate their interpretation.
Finally, classification algorithms were generated from a database of both healthy and pathological subjects in order to facilitate the interpretation of the NedAMHplus/IBV results. Thus, the following global results are automatically shown:
♦ Index of Dynamic Assessment. This index makes it possible to determine quickly and objectively whether the patient shows an alteration of the reaction forces during gait.
♦ Index of Kinematic Assessment. Analogously, this index allows us to determine if the patient shows any alterations in the movement pattern during gait.
Software application and reports
The computer application NedAMHplus/IBV was developed to facilitate the work of professionals and to guarantee the correct application of the methodology and interpretation of results.
Figure 2. Screen of the NedAMHplus/IBV software showing kinematic and dynamic information
In order to achieve this goal, the software guides the user throughout the whole process and automatically provides the results of the assessment in real time (Figure 2 and Figure 3). Additionally, once the assessment is completed, the application can generate automatic reports both in Word and PDF format to speed up the work of the healthcare professional.
Figure 3. Screen of the NedAMHplus/IBV software showing electromyographic information.
VALIDATION OF THE NedAMHplus/IBV SYSTEM
In order to verify the repeatability of the system in the measurement of human gait variables, a reliability study was performed. The test sample consisted of 15 healthy subjects. Each subject was assessed by two different evaluators in two different sessions.
For each parameter, the standard error of the mean (SEM) and the minimum detectable change (MDC) were calculated. Table 1 shows the results of the SEM with respect to the average value of the parameter studied.
Moreover, the reproducibility of the curves obtained by the NedAMHplus/IBV system was studied. To this end, the methodology proposed by Kadaba et al. was used.  The results show very good reproducibility in all cases (CMC > 0.85) (Table 2). 
BENEFITS OF NedAMHplus/IBV
♦ Clinical usefulness and scientific validity. NedAMHplus/IBV provides information necessary to perform a comprehensive analysis of human gait. In addition, the studies conducted demonstrated the reliability and validity of NedAMHplus/IBV to assess human gait.
♦ Fast. It takes between 25 and 30 minutes to perform a comprehensive human gait assessment test and obtain an automatic report using the NedAMHplus/IBV application. The reports are specially designed to allow professionals to dedicate time to what really matters: their patients.
♦ Simplicity. Training for professionals, software and assessment indices make it easy to use the NedAMHplus/IBV application and to interpret the information it provides.
♦ Cost-effectiveness. The use of a model of markers specially designed to be used in the clinical setting reduces the patient's instrumentation time, which leaves more time for the examination, and for taking and analyzing the measurements.
We thank IBERMUTUA, UMIVALE and MAZ for their collaboration in the development and validation of this research project.
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