Scoliosis instrumentation alters primary and coupled motions of the spine: An in vitro study using entire thoracolumbar spine and rib cage specimens.

Background: Effects of rigid posterior instrumentation on the three-dimensional post-operative spinal flexibility are widely unknown. Purpose of this in vitro study was to quantify these effects for characteristic adolescent idiopathic scoliosis instrumentations.

Methods: Six fresh frozen human thoracic and lumbar spine specimens (C7-S) with entire rib cage from young adult donors (26-45 years) without clinically relevant deformity were loaded quasi-statically with pure moments of 5 Nm in flexion/extension, lateral bending, and axial rotation.

Spinal instrumentation length affects adjacent segment range of motion and intradiscal pressure.

Scoliosis instrumentation length depends on the type and degree of deformity and the individual preference of the surgeon. This in vitro study aimed to explore effects of increasing instrumentation length on adjacent segment mobility and intervertebral disc loading. Six fresh frozen human spine specimens (C7-sacrum) with entire rib cage from young adult donors (26-45 years) were loaded with pure moments of 5 Nm.

[Biology and mechanobiology of the intervertebral disc : Challenges for regenerative therapies].

The fibrocartilaginous intervertebral discs between the vertebrae give the spine mobility and flexibility. Age and degeneration contribute to tissue changes that affect the composition and structure of the intervertebral discs and can lead to loss of function and back pain. The intervertebral disc cells are responsible for the formation and maintenance of the tissue and are influenced by the physiological load.

[Biomechanics of the intervertebral disc : Consequences of degenerative changes].

The intervertebral disc represents the flexible connection between two adjacent vertebral bodies. Intervertebral discs, therefore, give the spine its enormous range of motion. At the same time, intervertebral discs distribute the load evenly over the bony vertebral bodies to ensure load transfer from the upper body to the pelvis, provide sufficient stability, and absorb shocks during everyday movements as well as under extreme loads.

Which spinal fixation technique achieves which degree of stability after thoracolumbar trauma? A systematic quantitative review.

Background Context: Unstable traumatic spinal injuries require surgical fixation to restore biomechanical stability.

Purpose: The purpose of this review was to summarize and quantify three-dimensional spinal stability after surgical fixation of traumatic thoracolumbar spinal injuries using different treatment strategies derived from experimental studies.

Study Design/setting: Systematic literature review.

How does thoracic scoliosis surgery affect thoracolumbar spinal flexibility and lumbar intradiscal pressure? An in vitro study confirming the importance of the rib cage.

Purpose: To evaluate effects of spinal and rib osteotomies on the resulting spinal flexibility for surgical correction of thoracic scoliosis and to explore effects of posterior fixation on thoracolumbar segmental range of motion and lumbar intervertebral disc loading.

Methods: Six fresh frozen human thoracolumbar spine and rib cage specimens (26-45 years, two female / four male) without clinically relevant deformity were loaded with pure moments of 5 Nm in flexion/extension, lateral bending, and axial rotation. Optical motion tracking of all segmental levels (C7-S) and intradiscal pressure measurements of the lumbar spine (L1-L5) were performed (1) in intact condition, (2) after Schwab grade 1, (3) Schwab grade 2, and (4) left rib osteotomies at T6-T10 levels, as well as (5) after posterior spinal fixation with pedicle screw-rod instrumentation at T4-L1 levels.

How cervical and cervicothoracic scoliosis influence the atlantoaxial joint.

Introduction: Children with cervical or cervicothoracic congenital scoliosis are limited in their ability to compensate for the main curve of the deformity because there are only a few mobile segments in their cervical spine. Over the years, we have frequently observed coronal atlantoaxial dislocation (CAAD) in a lateral direction (from left to right or vice versa) in these patients. It was anticipated that CAAD might compensate for the horizontal position of the head, and it is hypothesized that CAAD depends on the degree of scoliotic deformity.

Variability of intervertebral joint stiffness between specimens and spine levels.

Musculoskeletal multibody models of the spine can be used to investigate the biomechanical behaviour of the spine. In this context, a correct characterisation of the passive mechanical properties of the intervertebral joint is crucial. The intervertebral joint stiffness, in particular, is typically derived from the literature, and the differences between individuals and spine levels are often disregarded.

[Biomechanics of thoracic wall instability].

Traumatic injuries of the thorax can entail thoracic wall instability (flail chest), which can affect both the shape of the thorax and the mechanics of respiration; however, so far little is known about the biomechanics of the unstable thoracic wall and the optimal surgical fixation. This review article summarizes the current state of research regarding experimental models and previous findings. The thoracic wall is primarily burdened by complex muscle and compression forces during respiration and the mechanical coupling to spinal movement.

How Does the Rib Cage Affect the Biomechanical Properties of the Thoracic Spine? A Systematic Literature Review.

The vast majority of previous experimental studies on the thoracic spine were performed without the entire rib cage, while significant contributive aspects regarding stability and motion behavior were shown in several other studies. The aim of this literature review was to pool and increase evidence on the effect of the rib cage on human thoracic spinal biomechanical characteristics by collating and interrelating previous experimental findings in order to support interpretations of and studies disregarding the rib cage to create comparability and reproducibility for all studies including the rib cage and provide combined comparative data for future biomechanical studies on the thoracic spine. After a systematic literature search corresponding to PRISMA guidelines, eleven studies were included and quantitatively evaluated in this review.

Even mild intervertebral disc degeneration reduces the flexibility of the thoracic spine: an experimental study on 95 human specimens.

Background Context: Intervertebral disc degeneration represents one of multiple potential trigger factors for reduced passive spinal mobility and back pain. The effects of age-related degenerative intervertebral disc changes on spinal flexibility were however mainly investigated for the lumbar spine in the past, while intervertebral disc degeneration is also highly prevalent in the thoracic spine.

Purpose: To evaluate the effect of the degeneration grade on the range of motion and neutral zone of the thoracic spine.

Global and local characterization explains the different mechanisms of failure of the human ribs.

Knowledge of the mechanics and mechanistic reasons inducing rib fracture is fundamental for forensic investigations and for the design of implants and cardiopulmonary resuscitation devices. A mechanical rationale to explain the different rib mechanisms of failure is still a challenge. The aim of this work was to experimentally characterize human ribs to test the hypothesis that a correlation exists between the ribs properties and the mechanism of failure.

Validity and interobserver agreement of a new radiographic grading system for intervertebral disc degeneration: Part III. Thoracic spine.

Purpose: The aim of this study was to assess the validity and objectivity of a new quantitative radiographic grading system for thoracic intervertebral disc degeneration.

Methods: The new grading system involves the measurement variables "Height loss" and "Osteophyte formation", which are determined from lateral radiographs, resulting in the "Overall degree of degeneration" on a four-point scale from 0 (no degeneration) to 3 (severe degeneration). Validation was performed by comparing the radiographic degrees of degeneration of 54 human intervertebral discs to the respective macroscopic degrees, which were defined as the "real" degrees of degeneration.

Morphological patterns of the rib cage and lung in the healthy and adolescent idiopathic scoliosis.

The morphology of the rib cage affects both the biomechanics of the upper body's musculoskeletal structure and the respiratory mechanics. This becomes particularly important when evaluating skeletal deformities, as in adolescent idiopathic scoliosis (AIS). The aim of this study was to identify morphological characteristics of the rib cage in relation to the lung in patients with non-deformed and scoliotic spines.

Which traumatic spinal injury creates which degree of instability? A systematic quantitative review.

Background Context: Traumatic spinal injuries often require surgical fixation. Specific three-dimensional degrees of instability after spinal injury, which represent criteria for optimum treatment concepts, however, are still not well investigated.

Purpose: The aim of this review therefore was to summarize and quantify multiplanar instability increases due to spinal injury from experimental studies.

A biomechanical comparison of a cement-augmented odontoid screw with a posterior-instrumented fusion in geriatric patients with an odontoid fracture type IIb.

Purpose: Possible surgical therapies for odontoid fracture type IIb include odontoid screw osteosynthesis (OG) with preservation of mobility or dorsal C1/2 fusion with restriction of cervical rotation. In order to reduce material loosening in odontoid screw osteosynthesis in patients with low bone density, augmentation at the base of the axis using bone cement has been established as a suitable alternative. In this study, we compared cement-augmented OG and C1/2 fusion according to Harms (HG).

Experimental study exploring the factors that promote rib fragility in the elderly.

Rib fractures represent a common injury type due to blunt chest trauma, affecting hospital stay and mortality especially in elderly patients. Factors promoting rib fragility, however, are little investigated. The purpose of this in vitro study was to explore potential determinants of human rib fragility in the elderly.

Load-sharing biomechanics of lumbar fixation and fusion with pedicle subtraction osteotomy.

Pedicle subtraction osteotomy (PSO) is an invasive surgical technique allowing the restoration of a well-balanced sagittal profile, however, the risks of pseudarthrosis and instrumentation breakage are still high. Literature studied primary stability and posterior instrumentation loads, neglecting the load shared by the anterior column, which is fundamental to promote fusion early after surgery. The study aimed at quantifying the load-sharing occurring after PSO procedure across the ventral spinal structures and the posterior instrumentation, as affected by simple bilateral fixation alone, with interbody cages adjacent to PSO level and supplementary accessory rods.

Analysis of the Intradiscal Pressure of the Thoracic Spine.

The hydrostatic pressure of the nucleus pulposus represents an important parameter in the characterization of spinal biomechanics, affecting the segmental stability as well as the stress distribution across the anulus fibrosus and the endplates. For the development of experimental setups and the validation of numerical models of the spine, intradiscal pressure (IDP) values under defined boundary conditions are therefore essential. Due to the lack of data regarding the thoracic spine, the purpose of this study was to quantify the IDP of human thoracic spinal motion segments under pure moment loading.

Thoracic Spinal Stability and Motion Behavior Are Affected by the Length of Posterior Instrumentation After Vertebral Body Replacement, but Not by the Surgical Approach Type: An Study With Entire Rib Cage Specimens.

Spinal tumors and unstable vertebral body fractures usually require surgical treatment including vertebral body replacement. Regarding primary stability, however, the best possible treatment depends on the spinal region. The purpose of this study was to evaluate the effects of instrumentation length and approach size on thoracic spinal stability including the entire rib cage.

In vitro comparison of personalized 3D printed versus standard expandable titanium vertebral body replacement implants in the mid-thoracic spine using entire rib cage specimens.

Background: Expandable titanium implants have proven their suitability as vertebral body replacement device in several clinical and biomechanical studies. Potential stabilizing features of personalized 3D printed titanium devices, however, have never been explored. This in vitro study aimed to prove their equivalence regarding primary stability and three-dimensional motion behavior in the mid-thoracic spine including the entire rib cage.

Rib Presence, Anterior Rib Cage Integrity, and Segmental Length Affect the Stability of the Human Thoracic Spine: An Study.

The effects of segmental length as well as anterior rib cage and costovertebral joint integrity on thoracic spinal stability have not been extensively investigated, but are essential for the calibration and validation of numerical models of the thoracic spine and rib cage. The aim of the study was to quantify these effects by experiments. Eight human thoracic spine specimens (C7-L1) including the rib cage were loaded with pure moments of 5 Nm in flexion/extension, lateral bending, and axial rotation while tracking the motions of all functional spinal units.

Digital Image Correlation (DIC) Assessment of the Non-Linear Response of the Anterior Longitudinal Ligament of the Spine during Flexion and Extension.

While the non-linear behavior of spine segments has been extensively investigated in the past, the behavior of the Anterior Longitudinal Ligament (ALL) and its contribution during flexion and extension has never been studied considering the spine as a whole. The aims of the present study were to exploit Digital Image Correlation (DIC) to: (I) characterize the strain distribution on the ALL during flexion-extension, (II) compare the strain on specific regions of interest (ROI) of the ALL in front of the vertebra and of the intervertebral disc, (III) analyze the non-linear relationship between the surface strain and the imposed rotation and the resultant moment. Three specimens consisting of 6 functional spinal units (FSUs) were tested in flexion-extension.

The strain distribution in the lumbar anterior longitudinal ligament is affected by the loading condition and bony features: An in vitro full-field analysis.

The role of the ligaments is fundamental in determining the spine biomechanics in physiological and pathological conditions. The anterior longitudinal ligament (ALL) is fundamental in constraining motions especially in the sagittal plane. The ALL also confines the intervertebral discs, preventing herniation.

Patterns of serial rib fractures after blunt chest trauma: An analysis of 380 cases.

Rib fractures represent the most common bone fracture, occurring in 10-20% of all blunt trauma patients and leading to concomitant injuries of the inner organs in severe cases. The purpose of this study was to identify specific serial rib fracture patterns after blunt chest trauma. 380 serial rib fracture cases were investigated.