Influence of bone microstructure on the mechanical properties of skull cortical bone - A combined experimental and computational approach.

The strength and compliance of the dense cortical layers of the human skull have been examined since the beginning of the 20th century with the wide range in the observed mechanical properties attributed to natural biological variance. Since this variance may be explained by the difference in structural arrangement of bone tissue, micro-computed tomography (µCT) was used in conjunction with mechanical testing to study the relationship between the microstructure of human skull cortical coupons and their mechanical response. Ninety-seven bone samples were machined from the cortical tables of the calvaria of ten fresh post mortem human surrogates and tested in dynamic tension until failure.

Lumbar spine endplate fractures: Biomechanical evaluation and clinical considerations through experimental induction of injury.

Lumbar endplate fractures were investigated in different experimental scenarios, however the biomechanical effect of segmental alignment was not outlined. The objectives of this study were to quantify effects of spinal orientation on lumbar spine injuries during single-cycle compressive loads and understand lumbar spine endplate injury tolerance. Twenty lumbar motion segments were compressed to failure.

Characterization of Lumbar Spine Annular Disruption in PMHS Using MRI, Cryomicrotomy and Histology Techniques.

Internal intervertebral disc disruption is involved in the onset of a wide range of spinal dysfunction, ultimately affecting not only the disc itself but the surrounding osseous and neural structures as well. The ability of disc to withstand and effectively distribute axial load is dependent upon whether peripherally located annular fibers provide the support necessary to contain and corral the pressure sensitive nucleus. Any alteration in the structures immediate to the nucleus jeopardize this ability.

Variation of bone layer thicknesses and trabecular volume fraction in the adult male human calvarium.

The human calvarium is a sandwich structure with two dense layers of cortical bone separated by porous cancellous bone. The variation of the three dimensional geometry, including the layer thicknesses and the volume fraction of the cancellous layer across the population, is unavailable in the current literature. This information is of particular importance to mathematical models of the human head used to simulate mechanical response.

Rate-dependent fracture characteristics of lumbar vertebral bodies.

Experimental testing incorporating lumbar columns and isolated components is essential to advance the understanding of injury tolerance and for the development of safety enhancements. This study incorporated a whole column axial acceleration model and an isolated vertebral body model to quantify compression rates during realistic loading and compressive tolerance of vertebrae. Eight lumbar columns and 53 vertebral bodies from 23 PMHS were used.

Effects of acceleration level on lumbar spine injuries in military populations.

Background Context: Clinical studies have indicated that thoracolumbar trauma occurs in the civilian population at its junction. In contrast, injury patterns in military populations indicate a shift to the inferior vertebral levels of the lumbar spine. Controlled studies offering an explanation for such migrations and the associated clinical biomechanics are sparse in literature.

Implementation and validation of probabilistic models of the anterior longitudinal ligament and posterior longitudinal ligament of the cervical spine.

The objective of this investigation was to develop probabilistic finite element (FE) models of the anterior longitudinal ligament (ALL) and posterior longitudinal ligament (PLL) of the cervical spine that incorporate the natural variability of biological specimens. In addition to the model development, a rigorous validation methodology was developed to quantify model performance. Experimental data for the geometry and dynamic properties of the ALL and PLL were used to create probabilistic FE models capable of predicting not only the mean dynamic relaxation response but also the observed experimental variation of that response.

A new PMHS model for lumbar spine injuries during vertical acceleration.

Ejection from military aircraft exerts substantial loads on the lumbar spine. Fractures remain common, although the overall survivability of the event has considerably increased over recent decades. The present study was performed to develop and validate a biomechanically accurate experimental model for the high vertical acceleration loading to the lumbar spine that occurs during the catapult phase of aircraft ejection.

Determination of normative neck muscle morphometry using upright MRI with comparison to supine data.

Background: Neck muscles are important in the static and dynamic stability of the head-neck complex. Deep neck muscles act to maintain upright posture and superficial muscles are responsible for gross movements. Previous studies have quantified neck muscle geometry using traditional supine magnetic resonance imaging (MRI).

Kinematic response of the spine during simulated aircraft ejections.

Introduction: Military aviators are susceptible to spinal injuries during high-speed ejection scenarios. These injuries commonly arise as a result of strains induced by extreme flexion or compression of the spinal column. This study characterizes the vertebral motion of two postmortem human surrogates (PMHS) during a simulated catapult phase of ejection on a horizontal decelerator sled.

Ejection injury to the spine in small aviators: sled tests of manikins vs. post mortem specimens.

Introduction: This study presents the results of seven aerospace manikin and three post mortem human surrogate (PMHS) horizontal deceleration sled tests. The objective of this study was to establish a body of baseline data that examines the ability of small (fifth percentile) manikins to predict whole-body kinematics associated with aircraft ejection, and whether currently available head and neck injury criteria are applicable in these situations.

Methods: Subjects were exposed to a short-duration local z-axis sled pulse while horizontally seated and restrained in an ejection seat.

Physical effects of ejection on the head-neck complex: demonstration of a cadaver model.

Vertebral fracture is the most common severe injury during high-speed pilot ejection. However, the loading paradigm experienced by pilots may also lead to soft-tissue spinal injuries that are more difficult to quantify and can lead to long-term deficits. This manuscript describes a new experimental protocol to simulate the effects of pilot ejection on the tissues of the head-neck complex.

Gender dependent cervical spine anatomical differences in size-matched volunteers - biomed 2009.

The objective was to examine significant differences in the bony structure of cervical spine vertebrae based on gender and spinal level that may influence injury risk in women following automotive rear impact. Male and female subjects were recruited for a separate study and data from two subsets were selected for inclusion in this study. Subjects were size-matched based on sitting height (17 males, 11 females) and head circumference (9 males, 18 females).