Introduction Understanding how annular failure might occur following increased nuclear pressurisation requires an experimental approach that avoids artefactual injury to the annulus but reveals structural disruption resulting directly from the pressurisation event. The aim of this study was to investigate the fundamental mechanisms by which both intra and inter-lamellar relationships are disrupted by nuclear pressurisation, with the development of a model that might accurately reproduce mechanisms of intervertebral disc injury secondary to events causing raised
Aims. The presence of facet tropism has been correlated with an elevated susceptibility to lumbar disc pathology. Our objective was to evaluate the impact of facet tropism on chronic lumbosacral discogenic pain through the analysis of clinical data and finite element modelling (FEM). Methods. Retrospective analysis was conducted on clinical data, with a specific focus on the spinal units displaying facet tropism, utilizing FEM analysis for motion simulation. We studied 318 intervertebral levels in 156 patients who had undergone provocation discography. Significant predictors of clinical findings were identified by univariate and multivariate analyses. Loading conditions were applied in FEM simulations to mimic biomechanical effects on intervertebral discs, focusing on maximal displacement and
PEEK rods construct has been proposed to allow better load sharing among spinal components when compared to the more traditional Titanium rods constructs. However, such proposal has largely derived from single-load in-vitro testing and the biomechanical differences between the two constructs when subjected to fatigue loading remain unknown. Current study comparatively analyzed the in-vitro biomechanical performance of PEEK and Titanium rod constructs as spinal implants through a 5 hour fatigue loading test. The disc height and
As the intervertebral disc is largely avascular, needle injection is the most practical method for delivery of therapeutic agents used in treatments for degenerative disc disease.
Spinal deformations are posture dependent. Official data from the Netherlands show that youth are encountering increasing problems with the musculoskeletal system (>40% back pain, and sport injury proneness). Prolonged sloth and slumped sitting postures are causative factors. Dutch youth are “champion sitting” in Europe. The effects of sitting on the development of posture and function of locomotion (stiffness) during growth have only been reported clearly in classic textbooks (in German) of practical anatomy and orthopaedics. Research with relevant clinical examinations is being done to understand epidemiological data on the increasing posture-dependent problems. A cohort of adolescents (15–18 years) in secondary school was assessed for sagittal postural deviations while bending. 248 children completed a questionnaire, and tests were done on neuromuscular tightness. The femorotibial angle was used to measure hamstring tightness. Measurement of the dorsiflexion of the foot was used to assess the tightness of calf muscles and Achilles tendons. All adolescents were photographed laterally while performing the finger–floor test (used to test flexibility), assessed as a knockout test: “Can you reach the floor or not?” The spinal profiles while bending were classified as abnormal arcuate or angular kyphosis. Hamstring tightness was present in 62.1% of the cohort in both legs, and in 18.2% unilaterally. Achilles tendon tightness was present bilaterally in 59.3%, and unilaterally in 19.4%. Activities with presence of stiffness (finger–floor distance), in descending order, were football, running, no sports, field hockey, tennis, dance, and gymnastics. 93.5% of the soccer players had tight hamstrings in both legs compared with none of those performing gymnastics. The correlation of the finger–floor test with tight hamstrings was 73.2%. For sagittal bending deformities, the correlation between form and function deficits cannot be made yet. 80 of 248 spines were rated by the examiners as having deformed flexion. Since Andry (1741) and at the zenith of continental orthopaedics and anatomy around 1900, the prolonged flexed positions of a young spine were indicated as being the main cause of deformity by overload and shear loads on immature discs and cartilage, preventing normal development of the discs. Nachemson proved that the
Objective: To measure
Scoliosis is a disease characterised by vertebral rotation, lateral curvature and changes in sagittal profile. The role of mechanical forces in producing this deformity is not clear. It is thought that abnormal loading deforms the disc, which becomes permanently wedged. Modelling and in vitro studies suggest that such deformations should increase
INTRODUCTION. The elimination of motion and disc stress produced by spinal fusion may have potential consequences beyond the index level overloading the spinal motion segments and leading to the appearance of degenerative changes. So the “topping-off” technique is a new concept instructing dynamic fixation such as interspinous process device (IPD) for the purpose of avoiding adjacent segment disease (ASD) proximal to the fusion construct. MATERIALS AND METHODS. The study simulated spinal fusion in L4-L5, fusion combined DIAM in L3-L4. The ROM and maximum von Miss stresses were analyzed in flexion, extension, lateral bending, and torsion in response to hybrid method, compared to intact modeland fusion model. RESULTS. The investigation revealed that decreased ROM, intradiscal stress in implanted level but a considerable increase in stresses at more upper level (L2-L3) during flexion and extension in hybrid model, comparing with the fusion model. CONCLUSIONS. The raise of
Low back pain (LBP) is the leading cause of disability worldwide, interfering with an individual's quality of life and work performance. Understanding the degeneration mechanism of the intervertebral disc (IVD), one of the key triggers of LBP, is hence of great interest. Disc degeneration can be mimicked in animal studies using the injection of enzymatic digestion, needle puncture, stab injury, or mechanical over-loading [1]. However, the detailed response of the artificial degenerated disc using needle puncture under physiological dynamic loading in diurnal activities has not yet been analyzed using FE-models. To fill the gap in literature, this study investigates the role of needle puncture injury on the biomechanical response of IVD using a combination of Finite Element (FE) simulations and in-vitro lumbar spine sheep experiments. 16 lumbar motion segments (LMS) were dissected from juvenile sheep lumbar spines. The harvested LMSs were assigned equally to two groups (control group with no incision and an injured group punctured with a 16-gauge needle). All specimens were mounted in a homemade chamber filled with saline solution and underwent a stress-relaxation test using a mechanical testing apparatus (Zwick/Roell, Ulm-Germany). A validated inverse poroelastic FE methodology [2] in conjunction with in-vitro experiments were used to find the elastic modulus and permeability. Subsequently, specimen-specific FE models for the 16 discs were simulated based on daily dynamic physiological activity (i.e., 8h rest followed by a 16h loading phase under compressive loads of 350 N and 1000 N, respectively). The results of the individual FE models were well fitted with the in-vitro stress-relaxation experiments, with an average error of 7.48 (±2.24)%. The results of the simulations demonstrated that the variation of axial displacement in the control discs was significantly higher than the injured ones (P=0.037). At the end of day, the
The purpose of this retrospective study, is to demonstrate the survivorship and clinical effectiveness of the Wallis implant, against low back pain and functional disability in patients with degenerative lumbar spine disease. The Wallis Interspinous implant, was developed as a minimally invasive and anatomically conserving procedure, without recourse to rigid fusion procedures. The initial finite element analysis and cadaver biomechanical studies showed that the Wallis ligament improves stability in the degenerate lumbar motion segment. Unloading the disc and facet joints reduces
Purpose of study. This RCT is to determine whether or not there is a clinical benefit from inserting a dynamic stabilising implant such as the Wallis ligament on the functional recovery of patients who have undergone lumbar decompression surgery. This Interspinous implant was developed as an anatomically conserving procedure without recourse to lumbar spinal fusion surgery. The biomechanical studies have shown that unloading the disc and facet joints reduces
Background and Objective. In industrialized societies, the prevalence of radicular low back pain has exploded in recent years. Lumbar disc prolaps, protrusion, or extrusion account for less than 5% of all low back problems, but are the most common causes of nerve root pain and surgical interventions. The primary rationale for any form of surgery for disc prolaps is to relieve nerve root irritation or compression due to herniated disc material. The primary modality of surgical treatment continues to be either open or microdiscectomy, but several alternative techniques including. Nucleoplasty. It provokes ablation of the nucleus of the disk by a controlled thermal effect produced by radiofrequency. Nucleoplasty is minimally invasive treatment aimed at removing nuclear material and lowering
To investigate whether restoration of mechanical function and spinal load-sharing following vertebroplasty depends upon cement distribution. Fifteen pairs of cadaver motion segments (51-91 yr) were loaded to induce fracture. One from each pair underwent vertebroplasty with PMMA, the other with a resin (Cortoss). Various mechanical parameters were measured before and after vertebroplasty. Micro-CT was used to determine volumetric cement fill, and plane radiographs (sagittal, frontal, and axial) to determine areal fill, for the whole vertebral body and for several specific regions. Correlations between volumetric fill and areal fill for the whole vertebral body, and between regional volumetric fill and changes in mechanical parameters following vertebroplasty, were assessed using linear regression. For Cortoss, areal and volumetric fills were significantly correlated (R=0.58-0.84) but cement distribution had no significant effect on any mechanical parameters following vertebroplasty. For PMMA, areal fills showed no correlation with volumetric fill, suggesting a non-uniform distribution of cement that influenced mechanical outcome. Increased filling of the vertebral body adjacent to the disc was associated with increased
Introduction. Disc degeneration is often scored using macroscopic and microscopic scoring systems. Although reproducible, these scores may not accurately reflect declining function in a degenerated disc. Accordingly, we compared macroscopic and microscopic degeneration scores with measurements of disc function. Methods. Thirteen cadaveric motion segments (62–93 yrs) were compressed to 1kN while a pressure-transducer was pulled across the mid-sagittal diameter of the disc. Resulting stress profiles indicated
We attempted to correlate the findings of MRI and discography in patients with low back pain, examining 108 lumbar intervertebral discs in 33 consecutive patients. MRI results were assessed from the intensity and shape of the signal obtained from the central part of the disc. Discography was classified according to the pattern of contrast material, the pressure accepted and the pain reproduced. All discs which were abnormal on MRI had altered patterns on discography, but 18 of the 60 discs with normal MRI had abnormal discograms. Of 39 asymptomatic discs, 33 had normal MRI signals and 24 had normal discograms. None of the 15 discs showing severe degeneration on MRI sustained high levels of
Introduction. Osteoporotic fracture reduces vertebral stiffness, and alters spinal load-sharing. Vertebroplasty partially reverses these changes at the fractured level, but is suspected to increase deformations and stress at adjacent levels. We examined this possibility. Methods. Twelve pairs of three-vertebra cadaver spine specimens (67-92 yr) were loaded to induce fracture. One of each pair underwent vertebroplasty with PMMA, the other with a resin (Cortoss). Specimens were then creep-loaded at 1.0kN for 1hr. In 15 specimens, either the uppermost or lowest vertebra was fractured, so that compressive stress distributions could be determined in the disc between adjacent non-fractured vertebrae. Stress was measured in flexion and extension, at each stage of the experiment, by pulling a pressure-transducer through the disc whilst under 1.0kN load. Stress profiles quantified
Introduction. Vertebroplasty helps to restore mechanical function to a fractured vertebra. We investigated how the distribution of injected cement benefits both fractured and neighbouring vertebrae. Methods. Nine pairs of three-vertebra cadaver spine specimens (aged 67–90 yr) were compressed to induce fracture. One of each pair underwent vertebroplasty with PMMA, the other with a resin (Cortoss). Specimens were then creep-loaded at 1.0kN for 1hr. Before and after vertebroplasty, compressive stiffness was determined, and stress profilometry was performed by pulling a pressure-transducer through each disc whilst under 1.0kN load. Profiles indicated
Background: Intervertebral discs and vertebrae deform under load, narrowing the intervertebral foramen and increasing the risk of nerve entrapment. Little is known about these deformations in elderly spines. Purpose: To test the hypothesis that, in ageing spines, vertebrae deform more than discs, and contribute to time-dependent creep. Methods: 117 thoracolumbar motion segments, mean age 69 yr, were compressed at 1 kN for 0.5, 1 or 2 hr. Immediate “elastic” deformations were followed by “creep”. A three-parameter model was fitted to experimental data to characterise their viscous modulus E1, elastic modulus E2 (initial stiffness), and viscosity η (resistance to fluid flow).
Purpose: To determine how cement volume during vertebroplasty influences:. stress distributions on fractured and adjacent vertebral bodies,. load-sharing between the vertebral bodies and neural arch, and. cement leakage. Methods: Nineteen thoracolumbar motion segments from 13 cadavers (42–91 yrs) were loaded to induce fracture. Fractured vertebrae received two sequential injections (VP1 and VP2) of 3.5cm3 of polymethylmethacrylate cement. Before and after each injection, motion segment stiffness was measured in compression and in bending, and the distribution of compressive “stress” in the intervertebral disc was measured in flexed and extended postures. Stress profiles yielded the