Brace for it: assessing lumbar spinal loads for a braced arm-to-thigh lifting and bending technique using a musculoskeletal modelling approach

Manual material handling activities that involve forward bending and lifting have been identified as risk factors for the development of low back pain, due to the spinal loads and postures experienced during these tasks. Several activities of daily living, such as lifting light-to-moderate objects, gardening, and cleaning, require forward bending and lifting. Many of these tasks can be performed with one hand, therefore allowing for trunk support by placing the free hand on the ipsilateral thigh. This “braced arm-to-thigh technique” (BATT) could especially benefit individuals with low back pain (LBP). However, the BATT has not been evaluated biomechanically in this specific population, and has not been evaluated when applied to tasks other than lifting. The overall goal of this thesis was to evaluate the effect of a bracing force, applied by the hand on the ipsilateral thigh, on lumbar spine loading and trunk kinematics for symmetrical and asymmetrical bending and lifting tasks, using a newly developed and validated full-body musculoskeletal model with a detailed lumbar spine. In Study 1 (Chapter 4), an OpenSim full-body model was developed and validated by adapting an existing OpenSim jogging model to be suitable for lifting motions. Muscle activations predicted by the resulting Lifting Full-Body (LFB) model were directly compared to muscle activations measured with electromyography (EMG), during various lifting tasks. Good agreement, both with respect to pattern and timing, was observed for the back musculature. Comparison between model estimates of intradiscal pressures (IDP) and in vivo IDP measurements also showed strong agreement. The spinal loads estimated by the model matched the trends reported for vertebral body replacement (VBR) measurements in older individuals for similar lifting tasks. This study demonstrated that the LFB model is suitable to evaluate changes in lumbar loading during symmetrical and asymmetrical lifting. In Study 2 (Chapter 5), trunk kinematics and L4/L5 spine loading for the BATT were compared to those of three common unsupported two-handed and one-handed lifting techniques for two loading conditions (2 kg and 10 kg), in 20 healthy participants (30-70 years old) matched in age and gender to 18 participants. The thigh bracing force, measured by a load cell secured to the thigh with a custom apparatus, significantly reduced L4/L5 extension moments, compressive and antero-posterior (AP) shear forces, compared to unsupported lifting techniques. However, the BATT technique also increased asymmetrical L4/L5 moments and trunk angles. In Study 3 (Chapter 6), the BATT was adapted to three activities of daily living (ADLs) to understand the effect of thigh bracing on lumbar loading and spine kinematics in tasks other than lifting. These three tasks, namely weeding (gardening), reaching for objects in low cupboards, and car egress, were simulated in the laboratory, using custom apparatus, by ten healthy young males. The BATT reduced L4/L5 extension moments, compressive and AP shear forces compared to self-selected techniques. This thesis presents the first validated full-body OpenSim model suited to estimating lumbar spine loading in symmetrical and asymmetrical lifting tasks, with or without external loads. Using this LFB model, it was demonstrated that the BATT reduces lumbar extension moments, compression and AP shear forces for lifting tasks and other ADLs, compared to unsupported techniques, for healthy and LBP populations.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 201

Chronic non-specific low back pain - sub-groups or a single mechanism?

Copyright 2008 Wand and O'Connell; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Background: Low back pain is a substantial health problem and has subsequently attracted a considerable amount of research. Clinical trials evaluating the efficacy of a variety of interventions for chronic non-specific low back pain indicate limited effectiveness for most commonly applied interventions and approaches. Discussion: Many clinicians challenge the results of clinical trials as they feel that this lack of effectiveness is at odds with their clinical experience of managing patients with back pain. A common explanation for this discrepancy is the perceived heterogeneity of patients with chronic non-specific low back pain. It is felt that the effects of treatment may be diluted by the application of a single intervention to a complex, heterogeneous group with diverse treatment needs. This argument presupposes that current treatment is effective when applied to the correct patient. An alternative perspective is that the clinical trials are correct and current treatments have limited efficacy. Preoccupation with sub-grouping may stifle engagement with this view and it is important that the sub-grouping paradigm is closely examined. This paper argues that there are numerous problems with the sub-grouping approach and that it may not be an important reason for the disappointing results of clinical trials. We propose instead that current treatment may be ineffective because it has been misdirected. Recent evidence that demonstrates changes within the brain in chronic low back pain sufferers raises the possibility that persistent back pain may be a problem of cortical reorganisation and degeneration. This perspective offers interesting insights into the chronic low back pain experience and suggests alternative models of intervention. Summary: The disappointing results of clinical research are commonly explained by the failure of researchers to adequately attend to sub-grouping of the chronic non-specific low back pain population. Alternatively, current approaches may be ineffective and clinicians and researchers may need to radically rethink the nature of the problem and how it should best be managed

Combined musculoskeletal and finite element modelling of the lumbar spine and lower limbs

Bone health deterioration is a major public health issue increasing the risk of fragility fracture with a substantial associated psychosocioeconomic impact. In the lumbar spine, physical deconditioning associated with ageing and chronic pain is a potential promoter of bone structural degradation. General guidelines for the limitation of bone loss and the management of pain have been issued, prescribing a healthy lifestyle and a minimum level of physical activity. However, there is no specific recommendation regarding targeted activities that can effectively maintain lumbar spine bone health in populations at risk. The aim of this thesis was to develop a new predictive computational modelling framework for the study of bone structural adaptation to healthy and pathological conditions in the lumbar spine. The approach is based on the combination of a musculoskeletal model of the lumbar spine and lower limbs with structural finite element models of the lumbar vertebrae. These models are built with bone and muscle geometries derived from healthy individuals. Based on daily living activities, musculoskeletal simulations provide physiological loading conditions to the finite element models. Cortical and trabecular bone are modelled with shell and truss elements whose thicknesses and radii are adapted to withstand the physiological mechanical environment using a strain driven optimisation algorithm. This modelling framework allows to generate healthy bone architecture when a loading envelope representative of a healthy lifestyle is applied to the vertebrae, and identify influential activities. Prediction of bone remodelling under altered loading scenarios characteristic of lumbar pathologies can also be achieved. The modelling approach developed in this thesis is a powerful tool for the investigation of bone remodelling in the lumbar spine. Preliminary results indicate that locomotion activities are insufficient to maintain lumbar spine bone health. Specific recommendations to limit the effect of physical deconditioning related to muscle weakening back pain are suggested. The approach is also promising for the investigation of other lumbar pathologies such as age related osteoporosis and scoliosis.Open Acces

AN EMG OPTIMIZATION MODEL OF THE KINETIC DEMANDS ON THE LOWER BACK DURING ASYMMETRICAL GAIT AND LOAD CARRIAGE

Gait asymmetries are associated with a high incidence of lower back pain (LBP). Although there are several causes of gait asymmetry (i.e. amputation, injury, or deformities), lower back kinetic demands have not been quantified and suitably compared due to experimental limitations in these clinical populations. Further, the impact of gait asymmetry on lower back demands during carrying tasks has not been established. This dissertation addressed these issues by artificially and safely inducing gait asymmetry in healthy able-bodied participants during walking and carrying tasks. LBP risk was assessed by L5/S1 vertebral joint force levels estimated with an OpenSim musculoskeletal model of the lower back adapted to incorporate participant-specific responses using an EMG optimization approach. The model was evaluated systematically for force estimate efficacy and sensitivity to input parameters prior to gait asymmetry assessments. Twelve participants performed walking and carrying tasks on a treadmill at individually scaled speeds while kinematics, external kinetics, and muscle activities (EMG) were recorded. Walking conditions consisted of unperturbed symmetrical gait, and asymmetrical gait induced by perturbing the right leg with a 2.54 cm shoe leveler, ~1 kg ankle weight, combined weight and shoe leveler, or a clinical walking boot that restricted ankle joint motion and added mass. Load carrying was performed while holding 7.5% and 15% bodyweight dumbbells in one or two hands during symmetric gait and asymmetric gait induced by the walking boot. The perturbations were successful in producing different degrees of gait asymmetry. However, L5/S1 joint forces were not significantly different between conditions despite unique spatiotemporal asymmetries. This indicates that LBP in those with gait asymmetry may not be due solely to level planar walking. During carrying tasks, gait asymmetry induced by the walking boot increased some metrics of lower back loading. Further, carrying a load in the hand contralateral to the walking boot produced larger forces than when carried on the same side. These results emphasize the importance of evaluating specific sources of gait asymmetry during daily activities other than walking when assessing LBP risk and would encourage more inclusive ergonomic carrying guidelines

A Comparison Of Fatigue Failure Responses Of Old Versus Middle-Aged Lumbar Motion Segments In Simulated Flexed Lifting

Study Design. Survival analysis techniques were used to compare the fatigue failure responses of elderly motion segments to a middle-aged sample. Objectives. To compare fatigue life of a middle-aged sample of lumbosacral motion segments to a previously tested elderly cohort. An additional objective was to evaluate the influence of bone mineral content on cycles to failure. Summary of Background Data. A previous investiga\uc2\uaction evaluated fatigue failure responses of 36 elderly lumbosacral motion segments (average age, 81 \uc2\ub1 8 years) subjected to spinal loads estimated when lifting a 9-kg load in 3 torso flexion angles (0\uc2\ub0, 22.5\uc2\ub0, and 45\uc2\ub0). Results demonstrated rapid fatigue failure with increased torso flexion; however, a key limitation of this study was the old age of the specimens. Methods. Each lumbosacral spine was dissected into 3 motion segments (L1-L2, L3-L4, and L5-S1). Motion segments within each spine were randomly assigned to a spinal loading condition corresponding to lifting 9 kg in 3 torso flexion angles (0\uc2\ub0, 22.5\uc2\ub0, or 45\uc2\ub0). Motion segments were statically loaded and allowed to creep for 15 minutes, then cyclically loaded at 0.33 Hz. Fatigue life was taken as the number of cycles to failure (10 mm displacement after creep loading). Results. Compared with the older sample of spines, the middle-aged sample exhibited increased fatigue life (cycles to failure) in all the torso flexion conditions. Increased fatigue life of the middle-aged specimens was associated with the increased bone mineral content (BMC) in younger motion segments (mean \uc2\ub1 SD, 30.7 11.1 g per motion segment vs. 27.8 \uc2\ub1 9.4 g). Increasing bone mineral content had a protective influence with each additional gram increasing survival times by approximately 12%. Conclusion. Younger motion segments survive considerably longer when exposed to similar spine loading conditions that simulate repetitive lifting in neutral and flexed torso postures, primarily associated with the increased bone mineral content possessed by younger motion segments. Cycles to failure of young specimens at 22.5\uc2\ub0 flexion were similar to that of older specimens at 0\uc2\ub0 flexion, and survivorship of young specimens at 45\uc2\ub0 flexion was similar to the older cohort at 22.5\uc2\ub0. Key words: biomechanics, low back disorders, fatigue failure, age, motion segments, vertebral endplate fractures, torso flexion, lifting, bone mass. Low back disorders (LBDs) are a major cause of both short- and long-term occupational disability in the United States, and it is clear that workers in certain occupations are more susceptible to LBD.2-5 Specifically, epidemiologic studies have shown that jobs involving heavy physical demands such as construction,2,3 mining,2,4 and farming,5 engender increased risk of back pain. These occupations are thought to experience high LBD rates as a result of their extreme postural and manual lifting demands. Studies have shown that jobs involving significant lifting 6-9 and jobs that involve frequent bending10-12 are associated with increased LBD risk. Workers in the mining industry, in particular, often have to lift heavy materials in restricted workspaces that compel torso flexion. An understanding of the impact of repeated loading of the spine in flexion on fatigue failure of spinal tissues is thus a critical issue for our research agency, which is concerned with reducing the pain and disability associated with LBD in the mining industry. It is well accepted that loads experienced by the spine during manual lifting tasks are sufficient to cause fractures in the endplates of lumbar vertebrae, particularly on repeated loading. 13-15 Endplate fractures may not be painful in and of themselves 16; however, evidence suggests that the process of internal disc disruption and disc degeneration may be initiated via endplate fractures. 16,17 It has been shown that endplate damage will alter the distribution of stress in the disc, resulting in buckling of the lamellas of the interna

Investigation into the prevalence, spinal kinematics and management of adolescent male rowers with low back pain

This thesis investigated back pain in adolescent rowers. A high prevalence of low back pain was found in adolescent male rowers. Differences in lumbar spine movement patterns during ergometer rowing were observed between genders and in adolescent males with back pain compared to those without. A cognitive functional intervention was tested in a randomized controlled trial and was demonstrated to reduce pain and disability, improve muscle endurance and alter sitting spinal postures in adolescent male rowers

Field and laboratory analyses of manual tasks in the South African automotive industry

The present study adopted a “field-laboratory-field” approach in the assessment of the efficacy of ergonomics interventions specific to two selected tasks evaluated in a South African automotive industry. Initial field testing was conducted in an Eastern Cape (South Africa) automotive plant where high risk areas were identified during walkthrough ergonomics surveys in conjunction with interaction with operators. Temporal factors and working postures of 12 industrial workers were recorded and observed, while physiological and perceptual responses were assessed. Two priority areas were focused upon for analysis, namely the Paintshop and Bodyshop with the former identified as being the more taxing of the two tasks. Responses of 30 students participating in rigourously controlled laboratory simulations were subsequently collected while completing the two tasks, namely the Paintshop Trolley Transfer (PTT) and Car Door Carriage (CDC) for participants. Working postures, kinematic, physiological and perceptual responses were assessed pre- and post-intervention. Following the laboratory experimentation a basic re-evaluation was conducted at the plant to assess whether the proposed changes had a positive effect on working postures, physiological and perceptual responses. The results of the preliminary field investigation revealed a prevalence of awkward working postures and excessive manual work in both areas. Laboratory experimentation revealed a notable reduction in task demands pre- versus post-intervention. The PTT mean lean angle for two-handed pre-intervention pulling observations of 23.7° (±3.51) was reduced to 13.9° (±2.21) post-intervention. Low back disorder (LBD) risk was reduced during the two-handed pull intervention (from 36.8% ±8.03 to 21.7% ±5.31). A significant decrement in heart rate responses from 103 bt.min-1 (±11.62) to 93 bt.min[superscript -1] (±11.77) was recorded during the two-handed symmetrical pushing intervention. The electromyography (EMG) responses for one-handed pushing and pulling pre-intervention showed the highest levels of muscular activity in the right medial deltoid due to an awkward and asymmetrical posture. CDC responses demonstrated that minor changes in the storage height of the door resulted in a significant reduction in sagittal flexion from 28.0° (±4.78) to 20.7° (±5.65). Predictions of average probability of LBD risk were significantly reduced from 50.3% (±5.91) to 39.8% (±5.10) for post-intervention car door lifting. In addition, the greatest reduction in EMG activity as a %MVC was achieved during sub-task ii (reduced from 35.1 to 13.7% and 30.5 to 13.9% for left and right erector spinae respectively) which was associated with the introduction of the transfer trolley for the door transfer phase of the CDC. Re-evaluation in the automotive plant revealed that the most notable change has been the implementation of automated ride on trolleys in the Paintshop. The Bodyshop area has also been modified to allow more effective job rotation and the step into the storage bin has been reduced via a “low-cost” stepping platform. Mean heart rate recordings were reduced from 94 (±9.77) bt.min[superscript -1] to 81 (±3.72) bt.min[superscript -1] in the Paintshop. Overall the results demonstrate the effect of “low-cost” interventions in reducing the physical stresses placed on workers in the automotive industry where much of the work is still done manually

Comparing the Kinematic and Kinetic Outputs from Digital Human Modeling Tools to a Lab-Based Rigid-Link Model for the Investigation of Musculoskeletal Disorder Hazards During Patient Handling

Patient repositioning tasks expose healthcare providers (HCPs) to high bone-on-bone forces, resulting in the development of musculoskeletal disorders (MSDs) (Fragala,2011). Researchers have been able to estimate biomechanical exposures during patient turning using kinematic and kinetic data collected from HCPs (e.g., Marras et al., 1999); however, many of these laboratory-based studies require considerable time and resources to execute and it also remains challenging to gather reliable data (Jäger et al., 2013). Digital human modeling (DHM) may offer unique advantages over direct measurement to estimate biomechanically relevant exposures. Investigators have used DHM to evaluate MSD hazards (Cao et al., 2013; Potvin, 2017); however, there is limited evidence on the fidelity of their outputs. The objective of this study was to compare the kinematic and kinetic outputs produced by two commercial DHM software packages against those generated using a lab-based motion-capture driven approach when analyzing HCPs performance of patient turns. Twenty-five (25) HCPs (eight males) performed a patient turn in the laboratory using a hospital bed with a live 82kg male patient. Whole body kinematics and sagittal plane video were collected. External peak hand force was measured using a force gauge. An accelerometer was placed on the sternum of the patient to identify point of initial patient motion which was assumed to represent the time-point of peak hand force application. Whole body kinematics were used to drive a rigid linked segment model for each participant using Visual3D (C-Motion Inc., Germantown, USA). Measured peak hand force was divided by two and applied to the model at the grip center of each hand at the frame of peak force application. A top down modeling approach was used to calculate trunk and shoulder joint angles and L4-L5 and shoulder joint moments about the flexion/extension axis. These outputs were extracted and compared against DHM software outputs. Siemens Jack (V 8.4) and Santos Pro DHM software packages were used to simulate the patient turn. The static patient turn posture used by the HCP was modeled using the manual joint manipulation, posture prediction and motion capture data importing approaches available in both software. Anthropometrics and peak hand force gathered from the laboratory experiment were inputted into the digital models. trunk and shoulder joint angles and L4-L5 and shoulder joint moments were computed and extracted about the flexion/extension axis from each digitally modeled posture. RMANOVAs, Pearson Product Moment correlation coefficients and Bland Altman analyses were used to compare DHM outputs to the lab-based model outputs. Results from this investigation indicate that the use of Siemens Jack’s (V 8.4) manual joint manipulation approach estimated low back and shoulder kinematics and kinetics that were in agreement with lab-based model outputs. The kinematics and kinetics computed using the posture prediction and motion capture driven approaches to modeling the patient repositioning task, using both Siemens Jack (V 8.4) and Santos Pro were not in agreement with the lab-based outputs. This may have been a result of differences in kinematic modeling assumptions related to the structure of skeletal linkage models, joint decompositions, degrees of freedom in each model and anthropometrics used in DHM software. The use of DHM tools for biomechanical analyses of patient repositioning tasks has the possibility to aide in the investigation of MSD exposures; however, it is important for investigators to understand the purpose of each DHM modeling approach as well as the underlying assumptions of digital human models that may affect kinematic and kinetic outputs used to quantify the exposure to MSDs

The effect of Core Stability Exercises (CSE) on trunk sagittal acceleration

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Aims: The aim of this study was to investigate Core Stability Exercise (CSE) induced changes in trunk sagittal acceleration as a measure of performance in participants following an acute onset of non-specific low back pain (LBP). Methodology: A Lumbar Motion Monitor (LMM) was used to measure trunk sagittal acceleration. The LMM was demonstrated to be reliable [Intra-Class Correlation (ICC) for average sagittal acceleration (0.96, 95% CI 0.90-0.98) and peak sagittal acceleration (0.89, 95% CI 0.75-0.96) with a 95% limit of agreement for the repeated measure of between -100.64 and +59.84 Deg/s2 ]. Pain was measured using the Visual Analogue Scale (VAS) and disability was measured with the Roland Morris Disability Questionnaire (RMDQ). Results: Differences in mean trunk sagittal acceleration between control and experimental groups at time points were assessed using a regression analysis (ratio of geometric means [95%CI]) and demonstrated to be not statistically significant (3 weeks (20%) 1.2 [0.9 to 1.6], p=0.2; 6 weeks (10%) 1.1 [0.8 to 1.5], p=0.7; 3 months (20%) 1.2 [0.8 to 1.9], p=0.9). Similarly, differences in mean pain score (3 weeks (30%) 1.3 [0.8-2.2], p= 0.3); 6 weeks (20%) 1.2 [0.7-2.0], p=0.6; 3 months (0%) 1.0 [0.5-1.9], p=1.0) and difference in mean disability score (6 weeks (0%) 1.0 [0.7-1.5], p= 1.0, 3 months (30%) 1.3 [0.8-1.9], p= 0.3) between groups were also not statistically significant. Conclusions: This work does not infer that CSE are definitively effective in reducing pain, improving subjective disability and improving trunk performance after an onset acute of non-specific LBP. However, there is a suggestion of clinical importance and a possible mechanism by which they may work. Further investigation into this mechanism may provide future effective management strategies for intervention of acute non-specific low back pain with optimistic cost implications for healthcare delivery in general and Physiotherapy in particular