Gait analysis system for assessment of dynamic loading axis of the knee.
ABSTRACT The purpose of this study was (1) to demonstrate a computer-assisted gait analysis system that can visualize the locus of the dynamic loading axis on the proximal tibia joint surface, and (2) to assess the accuracy of this system in a patient with bilateral knee osteoarthritis (OA). This system uses force plate data, CT skeletal structure data and motion capture data obtained from an infrared position sensor. The relative positions between bones and markers were used to calculate skeletal model movement based on movement of the markers. The locus of the dynamic loading axis on the knee joint was defined as the point on the proximal tibia joint surface that intersected with the loading axis of the lower limb, which passed through the centre of the femoral head and the centroid of multiple points surrounded by the distal tibia joint surface contour. To assess the accuracy of this system, open MRI was used to evaluate positions of skin markers against bones in six healthy volunteers. The locus in a patient was affected by differences between the varus knee with medial compartment OA on the non-operative side and the knee treated with high tibial osteotomy (HTO) on the opposite side. At knee flexion angles of 0 degrees, 15 degrees and 30 degrees, the mean value of measurement error for point locations on the locus was within 5.6% of joint width in the lateral direction (JWLD) on the proximal tibia joint. This system can provide clinically useful information for evaluation of the dynamic loading axis on the knee joint surface.
SourceAvailable from: Min-Hyeok Kang[Show abstract] [Hide abstract]
ABSTRACT: Hamstring-stretching exercises are frequently used to change lumbar spine and hip movements in the clinic. However, little research into the effects of hamstring flexibility on lumbar spine and hip movements during lifting tasks has been reported. We investigated effects of hamstring-stretching exercises on the kinematics of the lumbar spine and hip during stoop lifting. We recruited 16 males with a reduced range of motion (ROM) in active knee extension (AKE). The angle of the lumbar spine and hip was measured during stoop lifting using a 3D motion-capture system. The ROM of AKE and the angle of the lumbar spine and hip during stoop lifting between pre- and post-stretching were analyzed using a paired t-test. We found that hamstring-stretching exercises increased the ROM of AKE significantly. After hamstring-stretching exercises, there was a significant increase in hip flexion and decreases in both lumbar flexion and the lumbar/hip flexion ratio during the preparation phase of stoop lifting. In the lifting phase, only the movement range of the hip was increased significantly. Hamstring-stretching exercises may be useful for decreasing lumbar flexion and increasing hip flexion in people who perform repetitive stoop lifting in the workplace or during daily activities.Journal of Back and Musculoskeletal Rehabilitation 01/2013; 26(3):329-36. DOI:10.3233/BMR-130388 · 1.04 Impact Factor
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ABSTRACT: This paper presents development of a wearable force sensor system for human dynamics analysis. Forces and moments are detected by combining responses from eight load cells fabricated on a parallel connection foundation. Finite element method was used for designing preliminary mechanical structures and simulating the mechanical stresses and strains in the load cells. Sensitivity of the load cells in the force sensor was increased by distributing strain gauges on the maximum strain positions. A smart electrical board consisting of signal conditioning circuits, A/D module and a micro-computer controller based communication module was built and integrated into the force sensor. The calibration experiments were performed using a force platform (EFP-S-2KNSA12) as a reference sensor, and in order to investigate interference errors of the sensor, preliminary characterization tests were implemented using a purposely developed characterization workstation. The sensor’s abilities to measure ground-reaction forces with high precision and low interference error were demonstrated.Measurement 07/2007; 40(6-40):644-653. DOI:10.1016/j.measurement.2006.08.008 · 1.53 Impact Factor
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ABSTRACT: Accurate localization of joint centers is essential in movement analysis. However, joint centers cannot be directly palpated and alternative methods must be used. To assess the relative merits of these methods, a medical image based reference should be used. The EOS(®) system, a new low dose bi-planar X-rays imaging technique may be considered. The aim of this study was to evaluate the accuracy of hip joint center (HJC) localization using the EOS(®) system. Seventeen healthy young adults participated in the study. Femoral heads and pelvic external markers were localized using the EOS(®) system and the HJCs were expressed in the movement analysis coordinate system. Results showed that external marker localization was reliable within 0.15mm for trained assessors. Mean accuracy for HJC localization was 2.9mm (SD: 1.3, max: 6.2). The EOS based method therefore appeared reliable and may be used for femoral head localization or as a reference to assess the accuracy of other methods for HJC localization.Gait & posture 09/2013; 39(1). DOI:10.1016/j.gaitpost.2013.08.020 · 2.30 Impact Factor