Seonhong Hwang

Comparison of Lumbopelvic Rhythm and Flexion-Relaxation Response Between 2 Different Low Back Pain Subtypes

Study Design. A cross-sectional study to compare the kinematics and muscle activities during trunk flexion and return task in people with and without low back pain (LBP). Objective. To characterize the lumbopelvic rhythms during trunk flexion and return task in a group of healthy persons and 2 different subgroups of patients with LBP, identifying the flexion-relaxation (FR) responses in each group. Summary of Background Data. The lumbopelvic rhythm is the coordinated movement of the lumbar spine and hip during trunk flexion and return and is a clinical sign of LBP. However, the reported patterns of lumbopelvic rhythm in patients with LBP are inconsistent, possibly because previous studies have examined a heterogeneous group of patients with LBP. To clarify the lumbopelvic rhythm patterns, it is necessary to study more homogeneous subgroups of patients with LBP. Methods. The study involved the following subjects: control group of healthy subjects (N = 16); lumbar flexion with rotation syndrome (LFRS) LBP subgroup (N = 17); and lumbar extension with rotation syndrome (LERS) LBP subgroup (N = 14). The kinematic parameters during the trunk flexion and return task were recorded using a 3-dimensional motion capture system, and the FR ratio of the erector spinae muscle was measured. Results. The flexion angle of the lumbar spine was larger in the LFRS subgroup than in the control group and the LERS LBP subgroup, and the hip flexion angle was larger in the LERS LBP subgroup than in the control group and LFRS subgroup. The FR response of the erector spinae muscle disappeared in the LFRS and LERS LBP subgroups. Conclusion. These results show that the lumbopelvic rhythms are different among healthy subjects and patients assigned to 2 specific LBP subgroups. These results provide information on the FR response of the erector spinae muscle. Level of Evidence: N/A

Feasibility study of using a Microsoft Kinect for virtual coaching of wheelchair transfer techniques.

Abstract The purpose of this study was to test the concurrent validity and test-retest reliability of the Kinect skeleton tracking algorithm for measurement of trunk, shoulder, and elbow joint angle measurement during a wheelchair transfer task. Eight wheelchair users were recruited for this study. Joint positions were recorded simultaneously by the Kinect and Vicon motion capture systems while subjects transferred from their wheelchairs to a level bench. Shoulder, elbow, and trunk angles recorded with the Kinect system followed a similar trajectory as the angles recorded with the Vicon system with correlation coefficients that are larger than 0.71 on both sides (leading arm and trailing arm). The root mean square errors (RMSEs) ranged from 5.18 to 22.46 for the shoulder, elbow, and trunk angles. The 95% limits of agreement (LOA) for the discrepancy between the two systems exceeded the clinical significant level of 5°. For the trunk, shoulder, and elbow angles, the Kinect had very good relative reliability for the measurement of sagittal, frontal and horizontal trunk angles, as indicated by the high intraclass correlation coefficient (ICC) values (>0.90). Small standard error of the measure (SEM) values, indicating good absolute reliability, were observed for all joints except for the leading arm’s shoulder joint. Relatively large minimal detectable changes (MDCs) were observed in all joint angles. The Kinect motion tracking has promising performance levels for some upper limb joints. However, more accurate measurement of the joint angles may be required. Therefore, understanding the limitations in precision and accuracy of Kinect is imperative before utilization of Kinect.

Torque and power outputs on skilled and unskilled users during manual wheelchair propulsion

Manual wheelchair users are at a high risk of pain and injuries to the upper extremities due to mechanical inefficiency of wheelchair propulsion motion. The kinetic analysis of the upper extremities during manual wheelchair propulsion in various conditions needed to be investigated. We developed and calibrated a wheelchair dynamometer for measuring kinetic parameters during propulsion. We utilized the dynamometer to investigate and compare the propulsion torque and power values of skilled and unskilled users under four different conditions. Skilled manual wheelchair users generated lower torques with more power than unskilled users and reacted alertly and sensitively to changing conditions. We expect that these basic methods and results may help to quantitatively evaluate the mechanical efficiency of manual wheelchair propulsion.

Changes of gait characteristics in a child with femoral nerve injury: a 16-month follow-up case study

Abstract An 11-year-old child was able to walk independently even though he had injured his femoral nerve severely due to a penetrating wound in the medial thigh. In this study, gait analysis was conducted five times totally for 16 months to observe the characteristics of the gait parameters, which enabled him to walk independently. The cadence, walking speed, stride length, step length, stride time, step time, double limb support, and single limb support all improved after the third test (GA3). Insufficient knee flexion during the stance phase, that was the main problem of the subject, improved from 0.96° to the normal level of 17.01°. Although hip extension was also insufficient at the first test it subsequently improved and reached the normal range at the GA5. The peaks of the ground reaction force curve were low at the initial tests. However, these eventually improved and reached the reference values. The knee extensor moment during the stance phase increased markedly at the last test. Although the child lost his femoral nerve function, he was able to walk independently by compensating for the major function of the rectus femoris. In order to facilitate shock-absorption and move the feet forward, he reduced both gait speed and stride length, respectively. The results of this study are expected to provide insight into how clinicians set up their therapy goals, while considering compensations and changes over time.

Gait Analysis of a Pediatric-Patient with Femoral Nerve Injury : A Case Study

The femoral nerve innervates the quadriceps muscles and its dermatome supplies anteromedial thigh and medial foot. Paralysis of the quadriceps muscles due to the injury of the femoral nerve results in disability of the knee joint extension and loss of sensory of the thigh. A child could walk independently even though he had injured his femoral nerve severely due to the penetrating wound in the medial thigh. We measured and analyzed his gait performance in order to find the mechanisms that enabled him to walk independently. The child was eleven-year-old boy and he could not extend his knee voluntarily at all during a month after the injury. His gait analysis was performed five times (GA1~GA5) for sixteen months. His temporal-spatial parameters were not significantly different after the GA2 or GA3 test, and significant asymmetry was not observed except the single support time in GA1 results. The Lower limb joint angles in affected side had large differences in GA1 compared with the normal normative patterns. There were little knee joint flexion and extension motion during the stance phase in GA1 The maximum ankle plantar/dorsi flexion angles and the maximum knee extension angles were different from the normal values in the sound side. Asymmetries of the joint angles were analyzed by using the peak values. Significant asymmetries were found in GA1with seven parameters (ankle: peak planter flexion angle in stance phase, range of motion; ROM, knee: peak flexion angles during both stance and swing phase, ROM, hip: peak extension angle, ROM) while only two parameters (maximum hip extension angle and ROM of hip joint) had significant differences in GA5. The mid-stance valleys were not observed in both right and left sides of vertical ground reaction force (GRF) in the GA1, GA2. The loading response peak was far larger than the terminal stance peak of vertical ground reaction curve in the affected side of the GA3, GA4, GA5. The measured joint moment curves of the GA1, GA2, GA3 had large deviations and all of kinetic results had differences with the normal patterns. EMG signals described an absence of the rectus femoris muscle activity in the GA1 and GA2 (affected side). The EMG signals were detected in the GA3 and GA4 but their patterns were not normal yet, then their normal patterns were detected in the GA5. Through these following gait analysis of a child who had selective injuries on the knee extensor muscles, we could verify the actual functions of the knee extensor muscles during gait, and we also could observe his recovery and asymmetry with quantitative data during his rehabilitation.

Joint Kinetics and Lumbar Curvatures during Symmetric Lifting: Squat and Stoop

In this study, joint moments, joint powers, and lumbar lordosis were investigated for two different symmetrical lifting techniques using the three- dimensional motion analysis: squat and stoop. Twentynine male volunteers lifted boxes weighing 5, 10 and 15 kg by both squat and stoop lifting techniques. There were no significant differences in maximum lumbar joint moments between two techniques. Ankle, hip and lumbar joints generated power and only knee joint absorbed power in squat lifting, Ankle, knee joints absorbed power and hip, lumbar joints generated power in stoop lifting. At the time of lordotic curvature appearance in squat lifting, strong correlations were found in all three lower extremity joint moments with the lumbar joint. Differently, in stoop lifting, strong correlations existed in hip moment with the lumbar joint. Lordotic angle difference between fluoroscopic images and markers were 6.47plusmn1.02%, 13.01plusmn2.66 degree, and 26.43plusmn5.14 degree by three different calculation methods. In conclusion, considering the correlation with the lumbar joint, the current results suggested that lower limbs contribute to minimize mechanical loading on the waist by the change of lordotic curvature in the lumbar spine for the safe lifting.

Lower extremity joint moments during symmetric lifting: squat vs stoop

In this study, we analyzed joint moments during the symmetrical lifting in two different postures, using the three-dimensional motion analysis. Boxes weighing 5, 10 and 15kg were lifted by both squat and stoop techniques. The ankle moment in stoop was always larger than that in squat and the support moment was the largest at the end of the lifting in both techniques. The knee flexion moment played an important role in stoop lifting to support the lower limbs. In the end stage of the lifting, the hip joint showed less contributions on the support moment in both lifting techniques. However, the maximum hip extension moment in stoop lifting was larger than that in squat. In addition, the maximum waist moment in squat was larger than in stoop. Therefore, these results could support the previous research that the squat lifting was not the best strategy with no harm to the waist. It is expected that these results could provide a basic information to analyze and propose an efficient lifting strategy.