Development of a novel FE model for investigation of interactions of multi-motion segments of the lumbar spine.

The spinal anatomy is composed of a series of motion segments (MSs). Although finite element (FE) analysis has been extensively used to investigate the spinal biomechanics with various simplifications of the spinal structures, it is still a challenge to investigate the interactions of different MSs. Anatomical studies have shown that there are major spine ligaments connecting not only single-MS (i.

Biomechanical investigation of extragraft bone formation influences on the operated motion segment after anterior cervical spinal discectomy and fusion.

Although the clinical importance of extragraft bone formation (ExGBF) and bridging (ExGBB) has been reported, few studies have investigated the biomechanical influences of ExGBF on the motion segment. In this study, ExGBF was simulated at the C5-C6 motion segment after anterior cervical discectomy and fusion using a developed finite element model and a sequential bone-remodelling algorithm in flexion and extension. The computer simulation results showed that extragraft bone was primarily formed in the extension motion and grew to form ExGBB.

Interjoint coordination of the lower extremities in short-track speed skating.

In short-track speed skating, the three-dimensional kinematics of the lower extremities during the whole skating cycle have not been studied. Kinematic parameters of the lower extremities during skating are presented as joint angles versus time. However, the angle-time presentation is not sufficient to describe the relationship between multi-joint movement patterns.

Increased stress and strain on the spinal cord due to ossification of the posterior longitudinal ligament in the cervical spine under flexion after laminectomy.

Myelopathy in the cervical spine due to cervical ossification of the posterior longitudinal ligament could be induced by static compression and/or dynamic factors. It has been suggested that dynamic factors need to be considered when planning and performing the decompression surgery on patients with the ossification of the posterior longitudinal ligament. A finite element model of the C2-C7 cervical spine in the neutral position was developed and used to generate flexion and extension of the cervical spine.

Biomechanical investigation of post-operative C5 palsy due to ossification of the posterior longitudinal ligament in different types of cervical spinal alignment.

Post-operative C5palsies are among the most common complications seen after cervical surgery for ossification of the posterior longitudinal ligament (OPLL). Although C5 palsy is a well-known complication of cervical spine surgery, its pathogenesis is poorly understood and depends on many other factors. In this study, a finite element model of the cervical spine and spinal cord-nerve roots complex structures was developed.

Fatigue injury risk in anterior cruciate ligament of target side knee during golf swing.

A golf-related ACL injury can be linked with excessive golf play or practice because such over-use by repetitive golf swing motions can increase damage accumulation to the ACL bundles. In this study, joint angular rotations, forces, and moments, as well as the forces and strains on the ACL of the target-side knee joint, were investigated for ten professional golfers using the multi-body lower extremity model. The fatigue life of the ACL was also predicted by assuming the estimated ACL force as a cyclic load.

Biomechanical Behaviors in Three Types of Spinal Cord Injury Mechanisms.

Clinically, spinal cord injuries (SCIs) are radiographically evaluated and diagnosed from plain radiographs, computed tomography (CT), and magnetic resonance imaging. However, it is difficult to conclude that radiographic evaluation of SCI can directly explain the fundamental mechanism of spinal cord damage. The von-Mises stress and maximum principal strain are directly associated with neurological damage in the spinal cord from a biomechanical viewpoint.

Effect of posterior decompression extent on biomechanical parameters of the spinal cord in cervical ossification of the posterior longitudinal ligament.

Ossification of the posterior longitudinal ligament is a common cause of the cervical myelopathy due to compression of the spinal cord. Patients with ossification of the posterior longitudinal ligament usually require the decompression surgery, and there is a need to better understand the optimal surgical extent with which sufficient decompression without excessive posterior shifting can be achieved. However, few quantitative studies have clarified this optimal extent for decompression of cervical ossification of the posterior longitudinal ligament.

A Biomechanical Analysis of an Artificial Disc With a Shock-absorbing Core Property by Using Whole-cervical Spine Finite Element Analysis.

Study Design: A biomechanical comparison among the intact C2 to C7 segments, the C5 to C6 segments implanted with fusion cage, and three different artificial disc replacements (ADRs) by finite element (FE) model creation reflecting the entire cervical spine below C2.

Objective: The aim of this study was to analyze the biomechanical changes in subaxial cervical spine after ADR and to verify the efficacy of a new mobile core artificial disc Baguera C that is designed to absorb shock.

Summary Of Background Data: Scarce references could be found and compared regarding the cervical ADR devices' biomechanical differences that are consequently related to their different clinical results.

Effect of mechanical loading on heterotopic ossification in cervical total disc replacement: a three-dimensional finite element analysis.

The development of heterotopic ossification (HO) is considered one of the major complications following cervical total disc replacement (TDR). Even though previous studies have identified clinical and biomechanical conditions that may stimulate HO, the mechanism of HO formation has not been fully elucidated. The objective of this study is to investigate whether mechanical loading is a biomechanical condition that plays a substantial role to decide the HO formation.

Influence of sagittal and axial types of ossification of posterior longitudinal ligament on mechanical stress in cervical spinal cord: A finite element analysis.

Background: There are few studies focusing on the prediction of stress distribution according to the types of ossification of the posterior longitudinal ligament, which can be fundamental information associated with clinical aspects such as the relationship between stress level and neurological symptom severity. In this study, the influence of sagittal and axial types of ossification of the posterior longitudinal ligament on mechanical stress in the cervical spinal cord was investigated.

Methods: A three-dimensional finite element model of the cervical spine with spinal cord was developed and validated.

Biomechanical effects of fusion levels on the risk of proximal junctional failure and kyphosis in lumbar spinal fusion surgery.

Background: Spinal fusion surgery is a widely used surgical procedure for sagittal realignment. Clinical studies have reported that spinal fusion may cause proximal junctional kyphosis and failure with disc failure, vertebral fracture, and/or failure at the implant-bone interface. However, the biomechanical injury mechanisms of proximal junctional kyphosis and failure remain unclear.

The Change of Sagittal Alignment of the Lumbar Spine after Dynesys Stabilization and Proposal of a Refinement.

Objective: Dynesys® is one of the pedicle-based dynamic lumbar stabilization systems and good clinical outcome has been reported. However, the cylindrical spacer between the heads of the screws undergoes deformation during assembly of the system. The pre-strain probably change the angle of instrumented spine with time and oblique-shaped spacer may reduce the pre-strain.

Improvement of the knee center of rotation during walking after opening wedge high tibial osteotomy.

Accurate measurement of the center of rotation of the knee joint is indispensable for prediction of joint kinematics and kinetics in musculoskeletal models. However, no study has yet identified the knee center of rotations during several daily activities before and after high tibial osteotomy surgery, which is one surgical option for treating knee osteoarthritis. In this study, an estimation method for determining the knee joint center of rotation was developed by applying the optimal common shape technique and symmetrical axis of rotation approach techniques to motion-capture data and validated for typical activities (walking, squatting, climbing up stairs, walking down stairs) of 10 normal subjects.

Biomechanical analysis of two-step traction therapy in the lumbar spine.

Traction therapy is one of the most common conservative treatments for low back pain. However, the effects of traction therapy on lumbar spine biomechanics are not well known. We investigated biomechanical effects of two-step traction therapy, which consists of global axial traction and local decompression, on the lumbar spine using a validated three-dimensional finite element model of the lumbar spine.

Influence of bundle diameter and attachment point on kinematic behavior in double bundle anterior cruciate ligament reconstruction using computational model.

A protocol to choose the graft diameter attachment point of each bundle has not yet been determined since they are usually dependent on a surgeon's preference. Therefore, the influence of bundle diameters and attachment points on the kinematics of the knee joint needs to be quantitatively analyzed. A three-dimensional knee model was reconstructed with computed tomography images of a 26-year-old man.

Quantitative investigation of ligament strains during physical tests for sacroiliac joint pain using finite element analysis.

It may be assumed that the stability is affected when some ligaments are injured or loosened, and this joint instability causes sacroiliac joint pain. Several physical examinations have been used to diagnose sacroiliac pain and to isolate the source of the pain. However, more quantitative and objective information may be necessary to identify unstable or injured ligaments during these tests due to the lack of understanding of the quantitative relationship between the physical tests and the biomechanical parameters that may be related to pains in the sacroiliac joint and the surrounding ligaments.

In vivo loads in the lumbar L3-4 disc during a weight lifting extension.

Background: Knowledge of in vivo human lumbar loading is critical for understanding the lumbar function and for improving surgical treatments of lumbar pathology. Although numerous experimental measurements and computational simulations have been reported, non-invasive determination of in vivo spinal disc loads is still a challenge in biomedical engineering. The object of the study is to investigate the in vivo human lumbar disc loads using a subject-specific and kinematic driven finite element approach.

Effects of degenerated intervertebral discs on intersegmental rotations, intradiscal pressures, and facet joint forces of the whole lumbar spine.

The effects of intervertebral disc (IVD) degeneration on biomechanics of the lumbar spine were analyzed. Finite element models of the lumbar spine with various degrees of IVD degeneration at the L4-L5 functional spinal unit (FSU) were developed and validated. With progression of degeneration, intersegmental rotation at the degenerated FSU decreased in flexion-extension and left-right lateral bending, intradiscal pressure at the adjacent FSUs increased in flexion and lateral bending, and facet joint forces at the degenerated FSU increased in lateral bending and axial rotation.

Effect of centers of rotation on spinal loads and muscle forces in total disk replacement of lumbar spine.

The placement of artificial disks can alter the center of rotation and kinematic pattern; therefore, forces in the spine during the motion will be affected as a result. The relationship between the location of joint center of artificial disks and forces in the spinal components is not investigated. A musculoskeletal model of the spine was developed, and three location cases of center of rotation were investigated varying 5 mm anteriorly and posteriorly from the default center.

Segmental spinal canal volume in patients with degenerative spondylolisthesis.

Background Context: Lumbar degenerative spondylolisthesis (DS), typically characterized by the forward slippage of the superior vertebra of a lumbar motion segment, is a common spinal pathological condition in elderly individuals. Significant deformation and volume changes of the spinal canal can occur because of the vertebral slippage, but few data have been reported on these anatomic variations in DS patients. Whether to restore normal anatomy, such as reduction of the slippage and restoration of disc height, is still not clear in surgery.

Quantification of soft tissue balance in total knee arthroplasty using finite element analysis.

Unbalanced contact force on the tibial component has been considered a factor leading to loosening of the implant and increased wear of the bearing surface in total knee arthroplasty. Because it has been reported that good alignment cannot guarantee successful clinical outcomes, the soft tissue balance should be checked together with the alignment. Finite element models of patients' lower extremities were developed to analyse the medial and lateral contact force distribution on the tibial insert.

Motion characteristics of the vertebral segments with lumbar degenerative spondylolisthesis in elderly patients.

Objective: Although some studies have reported on the kinematics of the lumbar segments with degenerative spondylolisthesis (DS), few data have been reported on the in vivo 6 degree-of-freedom kinematics of different anatomical structures of the diseased levels under physiological loading conditions. This research is to study the in vivo motion characteristics of the lumbar vertebral segments with L4 DS during weight-bearing activities.

Methods: Nine asymptomatic volunteers (mean age 54.

A combined numerical and experimental technique for estimation of the forces and moments in the lumbar intervertebral disc.

Evaluation of the loads on lumbar intervertebral discs (IVD) is critically important since it is closely related to spine biomechanics, pathology and prosthesis design. Non-invasive estimation of the loads in the discs remains a challenge. In this study, we proposed a new technique to estimate in vivo loads in the IVD using a subject-specific finite element (FE) model of the disc and the kinematics of the disc endplates as input boundary conditions.