Ambulatory system for the quantitative and qualitative analysis of gait and posture in chronic pain patients treated with spinal cord stimulation

The physical activity in normal daily life is determined to a large extent by the functional ability of a subject. As a result, the measurement of the physical activity that a subject performs spontaneously could be a useful and objective measurement of disability, particularly in patients with disease-related functional impairment. The aim of this study is to provide an accurate method for the measurement and analysis of the physical activity under normal life conditions. Using three kinematical sensors strapped to the body, both the posture and the gait parameters can be assessed qualitatively and quantitatively. A detailed description of the algorithms used to analyse both the posture and the gait are presented in this paper. Two methods, based on different sensor configurations and signal processing, are proposed for the detection of sitting and standing postures (Methods P1 and P2). Two other methods are used for the quantitative assessment of walking (Methods W1 and W2). The performance of the algorithms (expressed in terms of sensitivity, specificity and error) is based on the comparison of data recorded simultaneously by a non-interfering observer (reference data) with the data provided by the recording system (21 patients, 61 h). Sensitivity and specificity are respectively 98.2% and 98.8% (P1), 97.8% and 98.1% (P2) for sitting; 98.0% and 98.5% (P1), 97.4% and 97.8% (P2) for standing; 97.1% and 97.9% (W1), 92.4% and 94.9% (W2) for walking; and finally, 99.2% and 98.6% for lying. Overall detection errors (as a percent of range) are as follows: 1.15% (P1) and 1.20% (P2) for sitting, 1.36% (P1) and 1.40% (P2) for standing, 1.20% (W1) and 1.60% (W2) for walking and 0.40% for lying. The error for the estimated walking distance and the speed is 6.8% and 9.6%, respectively. We conclude that both methods can be used for the accurate measurement of the basic physical activity in normal daily life. Measurements performed before and after the delivery of a treatment can therefore provide information of unprecedented accuracy and objectivity on the ability of a procedure, in this case spinal cord stimulation, to restore functional capabilities. (C) 2003 Elsevier B.V. All rights reserved.

Analysis of gait and coordination for arthroplasty outcome evaluation using body-fixed sensors

Hooman Dejnabadi

The importance of evaluation of an orthopedic operation such as hip or knee arthroplasty has long been recognized. Many definitions of outcome and scoring questionnaires have been used in the past to assess the outcome of joint replacement. However, these assessments are subjective and not accurate enough. In addition, orthopedic surgeons require now more subtle comparisons between potentially efficacious treatments (e.g. two types of prostheses). Therefore, the use of objective instruments that have a better sensitivity and specificity than traditional scoring systems is needed. Gait analysis is one of the most currently used instrumented techniques in this respect. However, a gait analysis system is accessible only in a few specialized laboratories, as it is complex, expensive, need a lot of room space and fixed devices, and not convenient for the patient. In this thesis, we proposed an ambulatory system based on kinematic sensors attached on the lower limbs to overcome the limitations of the previously mentioned techniques. Technically the device is portable, easily mountable, non-invasive, and capable of continuously recording data in long term without hindrance to natural gait. The goal was to provide gait parameters as a new objective method to assess Total Knee Replacement (TKR). New solutions to fusing the data of accelerometers and gyroscopes were proposed to accurately measure lower limbs orientations and joint angles. The methods propose a minimal sensor configuration with one sensor module mounted on each segment. The models consider anatomical aspects and biomechanical constraints. In the proposed techniques, the angles are found without the need for integration, so absolute angles can be obtained which are free from any source of drift. These data were then used to develop a gait analysis system providing spatio-temporal parameters, kinematic curves, and a visualization tool to animate the motion data as synthetic skeletons performing the same actions as the subjects. Moreover, a new algorithm was proposed for assessing and quantification of inter-joint coordination during gait. The coordination model captures the whole dynamics of the lower limbs movements and shows the kinematic synergies at various walking speeds. The model imposes a relationship among lower limb joint angles (hips and knees) to parameterize the dynamics of locomotion for each individual. It provides a coordination score at various walking speeds which is ranged between 0 and 10. An integration of different analysis tools such as Harmonic Analysis, Principal Component Analysis, and Artificial Neural Network helped overcome high-dimensionality, temporal dependence, and non-linear relationships of the gait patterns. In order to show the effectiveness of the proposed methods in outcome evaluation, we have considered a clinical study where the outcomes of two types of knee prostheses were compared. We conducted a randomized controlled study, including 54 patients, to assess TKR outcome between patients with fixed bearing and mobile bearing tibial plates of implants. The patients were tested preoperatively and postoperatively at 6 weeks, 3 months, 6 months, and 1 year. Various statistical analyses were done to compare the outcomes of the two groups. Finally, we provided objective criteria, using ambulatory gait analysis, for assessing functional recovery following TKR procedure. We showed significant difference between the two groups where the standard clinical evaluation was unable to detect such a difference.

EPFL2006

Gait Features Assessment in Hip Osteoarthritis and Total Hip Replaced Patients Based on an ambulatory System (Physilog)

Kamiar Aminian, Hooman Dejnabadi, Bijan Najafi, Philippe Robert

Osteoarthritis is the most frequent joint pathology throughout the world. Obtaining objective, dynamic and quantified data allowing the evaluation of patients’ progress before and after hip arthroplasty is crucial. Gait analysis can be used for evaluating improvement in such patients, since walking is the principal human physical activity. Comprehensive gait analysis usually includes kinematics, kinetics, and electromyography. A complex instrumentation is thus required that only can be installed in a dedicated laboratory. These techniques are valuable to support clinical decisions and to evaluate the results. However, in several instances, a simplified analysis, concentrated on few selected gait parameters, can be valuable as well. Recently, we have proposed a new ambulatory system for gait analysis (Physilog) and validated its performances for normal and abnormal walking (Aminian et al., 2002). The aim of this study is to show the efficacy of Physilog system for clinical gait analysis in orthopaedics

2002

Is Dual task testing more sensitive to detect gait improvement after a balance training program?

Kamiar Aminian, Bijan Najafi

There is a growing interest in the role played by attention and cognitive processing in the control of posture and gait, investigated by means of dual task methodology. The rationale for dual task testing is to assess whether the simultaneous performance of two (or more) attention- demanding tasks exceed the central information-processing capacity. Recently, we proposed a new ambulatory system for gait analysis (Physilog®) and validated its performances in studying normal and abnormal walking [1]. This system measures temporal and spatial parameters of gait during long period of walking and therefore provides stride-to- stride variability of these parameters. In this pilot study, we used the Physilog® system to assess, under both single and dual task conditions, gait changes in 6 elderly subjects after a ten- weeks balance training program. Our objective was to determine whether dual task testing would be more sensitive than single task testing in detecting gait improvement in these elderly persons

2003

Analysis of gait and coordination for arthroplasty outcome evaluation using body-fixed sensors

Hooman Dejnabadi

EPFL2006