Lumbar Spine Loads Research Articles

Estimation of lumbar spinal loading and trunk muscle forces during asymmetric lifting tasks: application of whole-body musculoskeletal modelling in OpenSim

Large spinal compressive force combined with axial torsional shear force during asymmetric lifting tasks is highly associated with lower back injury (LBI). The aim of this study was to estimate lumbar spinal loading and muscle forces during symmetric lifting (SL) and asymmetric lifting (AL) tasks using a whole-body musculoskeletal modelling approach. Thirteen healthy males lifted loads of 7 and 12 kg under two lifting conditions (SL and AL). Kinematic data and ground reaction force data were collected and then processed by a whole-body musculoskeletal model. The results show AL produced a significantly higher peak lateral shear force as well as greater peak force of psoas major, quadratus lumborum, multifidus, iliocostalis lumborum pars lumborum, longissimus thoracis pars lumborum and external oblique than SL. The greater lateral shear forces combined with higher muscle force and asymmetrical muscle contractions may have the biomechanical mechanism responsible for the increased risk of LBI during AL.Practitioner Summary: Estimating lumbar spinal loading and muscle forces during free-dynamic asymmetric lifting tasks with a whole-body musculoskeletal modelling in OpenSim is the core value of this research. The results show that certain muscle groups are fundamentally responsible for asymmetric movement, thereby producing high lumbar spinal loading and muscle forces, which may increase risks of LBI during asymmetric lifting tasks.

Evaluation of Lumbar Spine Load by Computational Method in Order to Acknowledge Low-back Disorders as Occupational Diseases.

The aim of the study was to develop a computational module for the prediction of compressive force on the L4/L5 disc suitable for use in field settings. The value of compressive force is intended to be used as a proxy measure of the mechanical burden of low-back when performing work activities. The compressive force predicted by the module in a particular worker should be compared with the NIOSH limit value of 3,400 N for the assessment of lumbar spine load during manual lifting tasks. Exceeding the limit will be considered as the fulfilment of "hygienic criterion" that should be met to acknowledge low-back disorder as an occupational disease. To develop the computational module we used the ergonomic software TECNOMATIX Classic Jack taking into account the anthropometric parameters of a worker and ergonomic parameters of his/her work activity. We calculated compressive forces on the L4/L5 disc in about 1,300 simulated combinations of various factors influencing compressive force. Parameters which turned out to be crucial for the compression of L4/L5 disc were included in the computational algorithm. Our study was primarily aimed at the assessment of lumbar disorders as occupational diseases. Moreover, the study can contribute to the recommendation of preventive measures to decrease health risks in occupations associated with the overload of low-back region. The graphic maps generated by the computational module enable a fast and exact analysis of particular job.

Estimation of loads on human lumbar spine: A review of in vivo and computational model studies

Spinal loads are recognized to play a causative role in back disorders and pain. Knowledge of lumbar spinal loads is required in proper management of various spinal disorders, effective risk prevention and assessment in the workplace, sports and rehabilitation, realistic testing of spinal implants as well as adequate loading in in vitro studies. During the last few decades, researchers have used a number of techniques to estimate spinal loads by measuring in vivo changes in the intradiscal pressure, body height, or forces and moments transmitted via instrumented vertebral implants. In parallel, computational models have been employed to estimate muscle forces and spinal loads under various static and dynamic conditions. Noteworthy is the increasing growth in latter computational investigations.This paper aims to review, compare and critically evaluate the existing literature on in vivo measurements and computational model studies of lumbar spinal loads to lay the foundation for future biomechanical studies. Towards this goal, the paper reviews in separate sections models dealing with static postures (standing, sitting, lying) as well as slow and fast dynamic activities (lifting, sudden perturbations and vibrations). The findings are helpful in many areas such as work place safety design and ergonomics, injury prevention, performance enhancement, implant design and rehabilitation management.

Muscle activity and spinal loading in lifting symmetrical loads beside the body compared to in front of the body

Digital human modeling enables engineers in product development to address questions of ergonomics and human factors early on in the development. To build more accurate Digital human models (DHMs), the physiological standard reference data are necessary. We investigated the effects of lifting loads beside the body compared to in front of the body. Forty healthy subjects performed eight lifting tasks with combinations of two postures, and four loads. The magnitude of the erector spinae muscle activity: Median frequency (MF) and Normalized root-mean-square (N-RMS) was estimated using surface electromyography. The magnitude of the lumbar spinal loads about lumbar vertebrae was estimated using DHM software. The effect of the moment arms (5, 6, 7.5 and 8.5 cm) on the lumbar spinal loads was estimated biomechanically. Lifting loads beside the body significantly (p < 0.01) reduced the muscle fatigue, muscle activity, and spinal loads. The increased moment arms resulted in the reduction of compression (5-13%) and muscle force (16-41%). The result presented in this study could be used to build more accurate DHMs.

Sensitivity of lumbar spine loading to anatomical parameters

Musculoskeletal simulations of lumbar spine loading rely on a geometrical representation of the anatomy. However, this data has an inherent inaccuracy. This study evaluates the influence of defined geometrical parameters on lumbar spine loading utilising five parametrised musculoskeletal lumbar spine models for four different postures. The influence of the dimensions of vertebral body, disc, posterior parts of the vertebrae as well as the curvature of the lumbar spine was studied. Additionally, simulations with combinations of selected parameters were conducted. Changes in L4/L5 resultant joint force were used as outcome variable. Variations of the vertebral body height, disc height, transverse process width and the curvature of the lumbar spine were the most influential.These parameters can be easily acquired from X-rays and should be used to morph a musculoskeletal lumbar spine model for subject-specific approaches with respect to bone geometry. Furthermore, the model was very sensitive to uncommon configurations and therefore, it is advised that stiffness properties of discs and ligaments should be individualised.

Lumbar spinal loading during bowling in cricket: a kinetic analysis using a musculoskeletal modelling approach

ABSTRACTThe objective of the study was to evaluate two types of cricket bowling techniques by comparing the lumbar spinal loading using a musculoskeletal modelling approach. Three-dimensional kinematic data were recorded by a Vicon motion capture system under two cricket bowling conditions: (1) participants bowled at their absolute maximal speeds (max condition), and (2) participants bowled at their absolute maximal speeds while simultaneously forcing their navel down towards their thighs starting just prior to ball release (max-trunk condition). A three-dimensional musculoskeletal model comprised of the pelvis, sacrum, lumbar vertebrae and torso segments, which enabled the motion of the individual lumbar vertebrae in the sagittal, frontal and coronal planes to be actuated by 210 muscle-tendon units, was used to simulate spinal loading based on the recorded kinematic data. The maximal lumbar spine compressive force is 4.89 ± 0.88BW for the max condition and 4.58 ± 0.54BW for the max-trunk condition. Results showed that there was no significant difference between the two techniques in trunk moments and lumbar spine forces. This indicates that the max-trunk technique may not increase lower back injury risks. The method proposed in this study could be served as a tool to evaluate lower back injury risks for cricket bowling as well as other throwing activities.

Trunk kinematics and lower lumbar spinal loading during paediatric cerebral palsy gait

The purpose of this study was to determine the contributions of strength, dorsiflexion range of motion (DFROM), plantar cutaneous sensation (PCS), and static postural control to Star Excursion Balance Test (SEBT) performance in individuals with chronic ankle instability (CAI). Forty individuals with CAI completed isometric strength, weight-bearing DFROM, PCS, static and dynamic balance assessments. Three separate backward multiple linear regression models were calculated to determine how strength, DFROM, PCS, and static postural control contributed to each reach direction of the SEBT. Explanatory variables included dorsiflexion, inversion, and eversion strength, DFROM, PCS, and time-to-boundary mean minima (TTBMM) and standard deviation (TTBSD) in the medial–lateral (ML) and anterior–posterior (AP) directions. Criterion variables included SEBT-anterior, posteromedial, and posterolateral directions. The strength of each model was determined by the R2-value and Cohen's f2 effect size. Regression models with an effect size ≥0.15 were considered clinically relevant. All three SEBT directions produced clinically relevant regression models. DFROM and PCS accounted for 16% of the variance in SEBT-anterior reach (f2 = 0.19, p = 0.04). Eversion strength and TTBMM-ML accounted for 28% of the variance in SEBT-posteromedial reach (f2 = 0.39, p < 0.01). Eversion strength and TTBSD-ML accounted for 14% of the variance in SEBT-posterolateral reach (f2 = 0.16, p = 0.06). DFROM and PCS explained a clinically relevant proportion of the variance associated with SEBT-anterior reach. Eversion strength and TTB ML explained a clinically relevant proportion of the variance in SEBT-posteromedial and posterolateral reach distances. Therefore, rehabilitation strategies should emphasize DFROM, PCS, eversion strength, and static balance to enhance dynamic postural control in patients with CAI.

The effect of golf putter length upon lumbar spine loads during the putting stroke

The effect of golf putter length upon lumbar spine loads during the putting stroke

The effects of seat height and foot placement on lumbar spine load during sit-to-stand tasks

The purpose of this study was to determine the influence of seat height and foot position in the sagittal plane on L5-S1 joint load. Fourteen healthy male adults stood up from a chair with three different seat heights and positions of the feet in the sagittal plane. L5-S1 net joint torque, mechanical work, range of motion and electromyographic activity of the erector spinae muscle were measured. L5-S1 net joint work increased by about 50% from high to low seat position. The mean and peak L5-S1 net joint torques increased about 30% from foot-back to foot-neutral position. These results were reinforced by a greater integrated electromyography signal from the erector spinae from high to low seat position and from foot-back to foot-neutral position. A high chair and placement of the feet behind the knees may be advisable to lessen lumbar load during sit-to-stand movements.

Body segment inertial parameters and low back load in individuals with central adiposity

There is a paucity of information regarding the impact of central adiposity on the inertial characteristics of body segments. Deriving low back loads during lifting requires accurate estimate of inertial parameters. The purpose was to determine the body segment inertial parameters of people with central adiposity using a photogrammetric technique, and then to evaluate the impact on lumbar spine loading. Five participants with central adiposity (waist:hip ratio>0.9, waist circumference>102cm) were compared to a normal BMI group. A 3D wireframe model of the surface topography was constructed, partitioned into 8 body segments and then body segment inertial parameters were calculated using volumetric integration assuming uniform segment densities for the segments. Central adiposity dependent increases in body segment parameters ranged from 12 to 400%, varying across segments (greatest for trunk) and parameters. The increase in mass distribution to the trunk was accompanied by an anterior and inferior shift of the centre of mass. A proximal shift in centre of mass was detected for the extremities, along with a reduction in mass distribution to the lower extremity. L5/S1 torques (392 vs 263Nm) and compressive forces (5918 vs 3986N) were substantially elevated in comparison to the normal BMI group, as well as in comparison to torques and forces predicted using published BSIP equations. Central adiposity resulted in substantial but non-uniform increases in inertial parameters resulting in task specific increases in torque and compressive loads arising from different inertial and physical components.

Crash response optimisation of helicopter seat and subfloor

This paper describes the integrated analysis of energy absorbing stages of seat and subfloor in helicopters during a crash landing, and their influence on the occupant's response. Their optimisation, when performed considering both the stages and their mutual interaction, leads to significant reductions of the occupant's injury levels. The study is based on validated numerical models of an anthropomorphic test device, seat and subfloor developed in a multi-body technique. Beyond the optimisations, a series of response surfaces were generated that show the max lumbar spine load, seat stroke and subfloor deflection as functions of mechanical parameters of the seat and subfloor, pointing out the design regions. Different impact speeds were considered. The results suggest that the mechanical properties of the solutions currently adopted for helicopter energy absorption could be easily re-tuned to further improve occupant's protection during a crash landing.

Carrying and spine loading

The advantages and disadvantages of different methods of carrying objects on spine loading are still not fully understood. Previous studies have either examined the effects of carrying using physiological measures or examined isolated spine segments using biomechanical models. Additionally, most studies have been restricted to only a small number of carrying conditions. Very few studies have attempted to examine the various factors influencing spine loading together. To improve understanding of interacting factors on carrying, this study assessed the lumbar spine loads of 16 subjects as they assumed six styles of carrying at two weight levels and two activity levels (walking vs. standing). Concurrent with each trial, a subject-specific biomechanical model was used to assess spine forces over the full lumbar spine. Most carrying methods in the trials resulted in relatively low levels of spine loading. Anterior/posterior (A/P) shear loading was the only spine-loading dimension that reached biomechanically meaningful levels. Two carrying conditions, with bins carried in front of the body, significantly increased A/P shear compared with other carrying styles. This increase appeared to be due to the greater moment arms occurring in these conditions. Many of the other carrying styles produced A/P shears that were similar to those observed when carrying nothing at all. Of all the tasks, the backpack carry characteristically produced especially low spine loads. The findings of the study suggest that to achieve optimal carrying in terms of spine loading, loads should be positioned close to the body, even when carrying relatively light loads.

Porous biodegradable lumbar interbody fusion cage design and fabrication using integrated global-local topology optimization with laser sintering.

Biodegradable cages have received increasing attention for their use in spinal procedures involving interbody fusion to resolve complications associated with the use of nondegradable cages, such as stress shielding and long-term foreign body reaction. However, the relatively weak initial material strength compared to permanent materials and subsequent reduction due to degradation may be problematic. To design a porous biodegradable interbody fusion cage for a preclinical large animal study that can withstand physiological loads while possessing sufficient interconnected porosity for bony bridging and fusion, we developed a multiscale topology optimization technique. Topology optimization at the macroscopic scale provides optimal structural layout that ensures mechanical strength, while optimally designed microstructures, which replace the macroscopic material layout, ensure maximum permeability. Optimally designed cages were fabricated using solid, freeform fabrication of poly(ε-caprolactone) mixed with hydroxyapatite. Compression tests revealed that the yield strength of optimized fusion cages was two times that of typical human lumbar spine loads. Computational analysis further confirmed the mechanical integrity within the human lumbar spine, although the pore structure locally underwent higher stress than yield stress. This optimization technique may be utilized to balance the complex requirements of load-bearing, stress shielding, and interconnected porosity when using biodegradable materials for fusion cages.

Lumbar spinal loads vary with body height and weight

Knowledge about spinal loading is required for designing and preclinical testing of spinal implants. It is assumed that loading of the spine depends upon body weight and height, as well as on the spine level, but a direct measurement of the loading conditions throughout the spine is not yet possible. Here, computer models can allow an estimation of the forces and moments acting in the spine. The objective of the present study was to calculate spinal loads for different postures and activities at several levels of the thoracolumbar spine for various combinations of body height and weight.A validated musculoskeletal model, together with commercially available software (AnyBody Technology), were used to calculate the segmental loads acting on the centre of the upper endplate of the vertebrae T12 to L5. The body height was varied between 150 and 200cm and the weight between 50 and 120kg. The loads were determined for five standard static postures and three lifting tasks.The resultant forces and moments increased approximately linearly with increasing body weight. The body height had a nearly linear effect on the spinal loads, but in almost all loading cases, the effect on spinal loads was stronger for variation of body weight than of body height. Spinal loads generally increased from cranial to caudal.The presented data now allow the estimation of the spinal load during activities of daily living on a subject specific basis, if body height and weight are known.

Lumbar spinal loads and muscle activity during a golf swing

This study estimated the lumbar spinal loads at the L4–L5 level and evaluated electromyographic (EMG) activity of right and left rectus abdominis, external and internal obliques, erector spinae, and latissimus dorsi muscles during a golf swing. Four super VHS camcorders and two force plates were used to obtain three-dimensional (3D) kinematics and kinetics of golf swings performed by five male collegiate golfers. Average EMG levels for different phases of golf swing were determined. An EMG-assisted optimization model was applied to compute the contact forces acting on the L4–L5. The results revealed a mean peak compressive load of over six times the body weight (BW) during the downswing and mean peak anterior and medial shear loads approaching 1.6 and 0.6 BW during the follow-through phases. The peak compressive load estimated in this study was high, but less than the corresponding value (over 8 BW) reported by a previous study. Average EMG levels of different muscles were the highest in the acceleration and follow-through phases, suggesting a likely link between co-contractions of paraspinal muscles and lumbar spinal loads.

Predictive equations for lumbar spine loads in load-dependent asymmetric one- and two-handed lifting activities

BackgroundAsymmetric lifting activities are associated with low back pain. MethodsA finite element biomechanical model is used to estimate spinal loads during one- and two-handed asymmetric static lifting activities. Model input variables are thorax flexion angle, load magnitude as well as load sagittal and lateral positions while response variables are L4–L5 and L5–S1 disc compression and shear forces. A number of levels are considered for each input variable and all their possible combinations are introduced into the model. Robust yet user-friendly predictive equations that relate model responses to its inputs are established. FindingsPredictive equations with adequate goodness-of-fit (R2 ranged from ~94% to 99%, P≤0.001) that relate spinal loads to task (input) variables are established. Contour plots are used to identify combinations of task variable levels that yield spine loads beyond the recommended limits. The effect of uncertainties in the measurements of asymmetry-related inputs on spinal loads is studied. InterpretationA number of issues regarding the NIOSH asymmetry multiplier are discussed and it is concluded that this multiplier should depend on the trunk posture and be defined in terms of the load vertical and horizontal positions. Due to an imprecise adjustment of the handled load magnitude this multiplier inadequately controls the biomechanical loading of the spine. Ergonomists and bioengineers, faced with the dilemma of using either complex but more accurate models on one hand or less accurate but simple models on the other hand, have hereby easy-to-use predictive equations that quantify spinal loads under various occupational tasks.

Role of optimization criterion in static asymmetric analysis of lumbar spine load

A common method for load estimation in biomechanics is the inverse dynamics optimization, where the muscle activation pattern is found by minimizing or maximizing the optimization criterion. It has been shown that various optimization criteria predict remarkably similar muscle activation pattern and intra-articular contact forces during leg motion. The aim of this paper is to study the effect of the choice of optimization criterion on L4/L5 loading during static asymmetric loading. Upright standing with weight in one stretched arm was taken as a representative position. Musculoskeletal model of lumbar spine model was created from CT images of Visible Human Project. Several criteria were tested based on the minimization of muscle forces, muscle stresses, and spinal load. All criteria provide the same level of lumbar spine loading (difference is below 25%), except the criterion of minimum lumbar shear force which predicts unrealistically high spinal load and should not be considered further. Estimated spinal load and predicted muscle force activation pattern are in accordance with the intradiscal pressure measurements and EMG measurements. The L4/L5 spine loads 1312 N, 1674 N, and 1993 N were predicted for mass of weight in hand 2, 5, and 8 kg, respectively using criterion of mininum muscle stress cubed. As the optimization criteria do not considerably affect the spinal load, their choice is not critical in further clinical or ergonomic studies and computationally simpler criterion can be used.

An EMG-based model to estimate lumbar muscle forces and spinal loads during complex, high-effort tasks: Development and application to residential construction using prefabricated walls

Residential building construction is moving toward more industrialized construction methods (e.g., use of prefabricated wall or “panels”), yet remains one of highest risk sectors for work-related musculoskeletal disorders. The centralized design process inherent in the use of wall panels offers the potential for proactive control of musculoskeletal risks, consistent with the prevention-through-design (or PtD) philosophy. As part of an ongoing effort to incorporate ergonomics into panel design, estimates of low back loading and injury risk were needed over a range of tasks performed during panelized construction. Here, a free-dynamic, three-dimensional, electromyography-based model was developed to provide such estimates, which was a modification of an earlier, relatively coarser model. Specific modifications included a more detailed representation of lumbar muscle anatomy and contraction dynamics, high-pass filtering of electromyograms to better represent muscle activation levels, and an enhanced calibration procedure through which five model parameters are specified on an individual basis and used to estimate lumbar muscle forces. With these enhancements, the predictive ability of the model was assessed over a wide range of simulated panel erection tasks. Predicted model parameters corresponded well with values reported earlier. Reasonable levels of correspondence were found between measured and predicted lumbosacral moments, though predictive ability varied between tasks and rotation planes. Relevance to industry Wall panels are representative of the current trend toward increasing use of industrialized methods in residential construction. Model-based estimates can be used as part of a larger project to facilitate proactive design of residential construction using panelized walls in order to reduce musculoskeletal exposures and spine injury risks.

Value Of Routine X-rays Of The Lumbar Spine In Orthopedic Preparticipation Screening

BACKGROUND: Considering orthopedic preparticipation screening in athletes of disciplines with high lumbar spine loads, it is unclear whether routinely performed x-rays of the lumbar spine are of additional value in detecting pathologies. Furthermore, it has to be discussed if findings lead to a limitation of eligibility for competitive sports or if medical follow-up examinations and specific training are required. PURPOSE: To analyze radiographic findings of either routinely performed or indicated x-rays of the lumbar spine during preparticipation examinations in young athletes with sport specific loads of the lumbar spine. METHODS: Radiographic findings of the lumbar spine in 325 children (12.2 ± 0.6 years; 173 boys, 152 girls) of an elite sport school were analyzed. Findings were categorized into: 0 = inconspicuous; 1 = findings without clinical relevance (e.g. side deviation, spina bifida occulta); 2 = findings requiring follow-up examinations, physical therapy or specific training (e.g. scoliosis, unilateral spondylolysis); and 3 = findings limiting sports eligibility (spondylolisthesis, spinal instability). Data were analyzed using the Chi Square test and the Fisher Exact test. RESULTS: X-rays were performed in 325 cases. In 21 athletes lumbar pain in history or clinical findings in examination led to additional radiographs. Radiographs were inconspicuous in 285 (88 %), without clinical relevance in 13 (4 %), needed to be controlled in 11 (3 %) and led to a limited sports eligibility in 16 (5 %) children. Findings in 9 of 21 (43 %) indicated and in 18 of 304 (6 %) routinely performed radiographs were classified into grades 2 and 3 (p<0.01). Spondylolisthesis or spinal instability were found in 2 indicated (11 %) and 14 routine x-rays (5 %; p>0.05). CONCLUSION: X-rays of the lumbar spine without any clinical indication have to be questioned in preparticipation screening of young athletes.

Effect of aspirin administration for the treatment of osteoporosis in ovariectomized rat model

To explore the therapeutic effects of aspirin on postmenopausal osteoporosis and understand its action mechanism. Forty three-month-old female SD rats were randomly divided into 5 groups (n = 8 each): sham group, OVX group and aspirin groups (A1, A2 & A3). The OVX and aspirin groups were ovariectomized (OVX). All rats underwent BMD (bone mineral density) scan at the time of OVX and 3 months after OVX. After the animal model of osteoporosis was established, aspirin groups were intragastrically administered at a dose of 8.93 mg×kg(-1)×d(-1) (A1), 26.79 mg×kg(-1)×d(-1) (A2) and 80.36 mg×kg(-1)×d(-1) (A3) daily in OVX rats. Three months later, the BMD and micro-architecture of vertebrae were measured by dual-energy X-ray absorptiometry and microtomography. Alkaline phosphatase and osteocalcin were measured in peripheral blood. The trabecular architecture changes were observed by histomorphology. Axial compression tests were used to evaluate the mechanical properties of vertebral specimens and three-point bending tests used for femur shaft. Three months after ovariectomy, BMD was significantly lower than preoperative. BMD in aspirin treated groups was significantly higher than that in OVX group. Alkaline phosphatase in peripheral blood decreased significantly in aspirin groups than those in OVX, but osteocalcin had no significant difference between aspirin and OVX groups. The microtomography reconstruction analysis also showed that the trabecular thickness, trabecular number and BMD increased significantly in aspirin groups than those in OVX. And there was no significant difference between A3 and sham groups. The results of biomechanical test showed that the maximum compression load of lumbar spine and three-point bending load of femur shaft were significantly higher in aspirin groups than those in OVX group. Aspirin can promote trabecular bone remodeling, improve three-dimensional structure of trabecular bone and increase bone density of cancellous in osteoporotic rats by stimulating bone formation. It may become a new drug for the treatment of osteoporosis.