Intervertebral Compressive Force Research Articles

The Biomechanical Effects of Different Bag-Carrying Styles on Lumbar Spine and Paraspinal Muscles: A Combined Musculoskeletal and Finite Element Study.

Bags such as handbags, shoulder bags, and backpacks are commonly used. However, it is difficult to assess the biomechanical effects of bag-carrying styles on the lumbar spine and paraspinal muscles using traditional methods. This study aimed to evaluate the biomechanical effects of bag-carrying styles on the lumbar spine. We developed a hybrid model that combined a finite element (FE) model of the lumbar spine and musculoskeletal models of three bag-carrying styles. The image data was collected from a 26-years-old, 176 cm and 70 kg volunteer. OpenSim and ABAQUS were used to do the musculoskeletal analysis and finite analysis. Paraspinal muscle force, intervertebral compressive force (ICF), and intervertebral shear force (ISF) on L1 were calculated and loaded into the FE model to assess the stress distribution on the lumbar spine. Different paraspinal muscle activation occurred in the three bag-carrying models. The increase in the ICF generated by all three bags was greater than the bags' weights. The handbag produced greater muscle force, ICF, ISF, and peak stress on the nucleus pulposus than the backpack and shoulder bag of the same weight. Peak stress on the intervertebral discs in the backpack model and the L1-L4 segments of the shoulder bag model increased linearly with bag weight, and increased exponentially with bag weight in the handbag model. Unbalanced bag-carrying styles (shoulder bags and handbags) led to greater muscle force, which generated greater ICF, ISF, and peak stress on the lumbar spine. The backpack produced the least burden on the lumbar spine and paraspinal muscles. Heavy handbags should be used carefully in daily life.

Investigation on the biomechanical behaviour of the lower cervical spine induced by facet tropism with respect to the sagittal plane

Clinic observations have shown that facet tropism with respect to the sagittal plane is associated with cervical degeneration, but their mechanisms haven't been clearly revealed. This study developed different levels of facet tropism musculoskeletal multi-body dynamics cervical models to investigate the biomechanical effect on the intervertebral compressive force (ICF), intervertebral shear force (ISF), facet joint force (FJF) and intervertebral disc displacement (IDD) during head flexion, extension, lateral bending and axial rotation movements. Results showed that the ICFs at the asymmetrical levels of the severe facet tropism models increased by 9.33% and 15.34% respectively during extension and right lateral bending, but did not change significantly during axial rotation. The ISFs at the asymmetrical levels of the severe facet tropism models increased by 56.64% and 164.40% respectively during right lateral bending and right axial rotation. The corresponding IDDs in medial-lateral direction at asymmetrical level also increased greatly during extension, right lateral bending and right axial rotation. The FJFs at asymmetrical level of the severe facet tropism models decreased by 3.41%, 10.55% and 9.19% during extension, right lateral bending and left axial rotation, but increased by 22.62% during right axial rotation. Facet tropism increased the ICFs, ISFs and IDDs of the asymmetrical level, but reduced the protection against cervical excessive motion during certain head movements. The results suggested that facet tropism may contribute to the initiation or enhancement of the process of intervertebral disc degeneration, especially intervertebral disc herniation.

Towards low back support with a passive biomimetic exo-spine.

Low-Back Pain (LBP) affects a large portion of the working population. Preventive exoskeletons have been proposed to reduce the moments on the lower back, specifically around the lumbosacral (L5/S1) joint. High correlation has been shown, between reducing the moments around the L5/S1 joint and intervertebral compression forces, which in turn have been identified as a risk factor for developing LBP. However, most passive back support exoskeletons use rigid plates or stiff beams to support the spine that limit the range of motion of the wearer. A large range of motion and versatility are especially desirable for industrial applications. To overcome these limitations, a passive biomimetic exo-spine has been designed, modelled and an initial prototype tested. Its potential to allow for a large range of motion, whilst at the same time limiting the most extreme and potentially harmful postures has been shown.

A biomechanical manikin for the evaluation of loads on the body

A simple tool to evaluate loads at body joints is described. Its function is to analyse static tasks performed in the sagittal plane. It consists of an articulated plastic manikin placed in the required posture on a magnetic board. The manikin has a set of scales which indicate moments of forces around the elbow, shoulder, lumbosacral or knee joints generated by any force exertion. The readings take into account several percentiles of stature and body weight and any value and direction of force applied in the task. A graph also provides an estimate of the intervertebral compression forces.

The Measurement of Spinal Loads Arising from Working Seats

The backrest on a working seat reduces back muscle tension and the need to lock the spine for the transmission of horizontal forces from the trunk to the chair. These effects reduce inter-vertebral compression forces, which cause the discs to collapse. A simple and precise method for measuring shrinkage in stature has been developed and used to examine variations in the design of seats. The findings are discussed in relation to the biomechanics of sitting, and conclusions for seat design presented.

The mechanical function of the lumbar apophyseal joints.

Experiments were carried out on cadaveric lumbar spines to determine the mechanical function of the apophyseal joints. It was found that they resist most of the intervertebral shear force and share in resisting the intervertebral compressive force, but only in lordotic postures. They prevent excessive movement from damaging the discs: the posterior annulus is protected in torsion by the facet surfaces and in flexion by the capsular ligaments.

The Effect of Posture on the Strength of the Lumbar Spine

Experiments were performed on cadaveric lumbar intervertebral joints in order to assess the effects of heavy lifting on the lumbar spine. It was found that in the simulated erect lordotic posture, the apophyseal joints can resist a significant proportion of the intervertebral compressive force. Slightly flexed lumbar joints have a compressive strength that comfortably exceeds the forces generated by heavy lifting. Hyperflexion just beyond the normal limit of motion can render lumbar intervertebral discs vulnerable to posterior prolapse when compressed by physiological loads. It is concluded that no injury should be sustained by the osteoligamentous lumbar spine as a result of a single heavy lift provided that the lumbar spine is kept slightly flexed.

Spondyloysis. The role of the posterior elements in resisting the intervertebral compressive force.

Compressive tests were carried out on cadaveric lumbar intervertebral joints, before and after the neural arch was fractured. The results show that although the neural arch can play some part in resisting the intervertebral compressive force, there is no bony contact between the downward projecting tips of the inferior articular processes and the laminae of the vertebra below.