Comparing adjacent segment biomechanics between anterior and posterior cervical fusion using patient-specific finite element modeling.

Study Design: This study employed a patient-specific finite element model.

Purpose: To quantify the effect of anterior and posterior surgical approaches on adjacent segment biomechanics of the patient-specific spine and spinal cord.

Overview Of Literature: Adjacent segment degeneration (ASD) is a well-documented complication following cervical fusion, typically resulting from accelerated osteoligamentous deterioration and subsequent symptomatic neural compression.

Behind Amor Blunt Trauma Lung and Liver Strains From Indenter Loading Via Finite Element Modeling.

To determine behind armor blunt trauma (BABT) injury criteria, experiments have been conducted by launching blunt projectiles at live swine at velocities up to 65 meters per second (m/s) using one type of indenter design. To ensure the generalizability of the developed injury criteria, additional tests with different indenter designs are needed. The objectives of this study were to evaluate the kinematics and injury parameters from two indenter designs using human body finite element modeling.

Mechanical Characterization of Non-degraded Porcine Annulus Fibrosus Material Properties.

Purpose: Porcine cervical spines are commonly used as a surrogate for human lumbar spines due to their similar anatomic and mechanical characteristics. Despite their use in spinal biomechanics research, porcine annulus fibrosus (AF) yield and ultimate properties have not been fully evaluated. This study sought to provide a novel dataset of elastic, yield, and ultimate properties of the porcine AF loaded in the circumferential direction.

Lumbar Spine Orientation Affects Compressive Fracture Outcome.

Purpose: Understanding how spinal orientation affects injury outcome is essential to understand lumbar injury biomechanics associated with high-rate vertical loading.

Methods: Whole-column human lumbar spines (T12-L5) were dynamically loaded using a drop tower to simulate peak axial forces associated with high-speed aircraft ejections and helicopter crashes. Spines were allowed to maintain natural lordotic curvature for loading, resulting in a range of orientations.

Expanded Combined Loading Injury Criterion for the Human Lumbar Spine Under Dynamic Compression.

Contemporary injury tolerance of the lumbar spine for under-body blast references axial compression and bending moments in a limited range. Since injuries often occur in a wider range of flexion and extension with increased moment contribution, this study expands a previously proposed combined loading injury criterion for the lumbar spine. Fifteen cadaveric lumbar spine failure tests with greater magnitudes of eccentric loading were incorporated into an existing injury criterion to augment its applicability and a combined loading injury risk model was proposed by means of survival analysis.

Comparative Biomechanical Analysis of Anterior Lumbar Interbody Fusion and Bilateral Expandable Transforaminal Lumbar Interbody Fusion Cages: A Finite Element Analysis Study.

Background: Expandable transforaminal lumbar interbody fusion (TLIF) cages could offer an alternative to anterior lumbar interbody fusion (ALIF). Bilateral cage insertion enhances endplate coverage, potentially improving stability and fusion rates and maximizing segmental lordosis. This study aims to compare the biomechanical properties of bilateral expandable TLIF cages to ALIF cages using finite element modeling.

Behind Armor Blunt Trauma: Liver Injuries Using a Live Animal Model.

Introduction: While the 44-mm clay penetration criterion was developed in the 1970s for soft body armor applications, and the researchers acknowledged the need to conduct additional tests, the same behind the armor blunt trauma displacement limit is used for both soft and hard body armor evaluations and design considerations. Because the human thoraco-abdominal contents are heterogeneous, have different skeletal coverage, and have different functional requirements, the same level of penetration limit does not imply the same level of protection. It is important to determine the regional responses of different thoraco-abdominal organs to better describe human tolerance and improve the current behind armor blunt trauma standard.

Hybrid III Manikin Lumbar Spine Loading Under Vertical Impact.

Introduction: Clinical investigations have attributed lumbar spine injuries in combat to the vertical vector. Injury prevention strategies include the determination of spine biomechanics under this vector and developing/evaluating physical devices for use in live fire and evaluation-type tests to enhance Warfighter safety. While biological models have replicated theater injuries in the laboratory, matched-pair tests with physical devices are needed for standardized tests.

Using Finite Element Models to Assess Spinal Cord Biomechanics after Cervical Laminoplasty for Degenerative Cervical Myelopathy.

Cervical laminoplasty is an established motion-preserving procedure for degenerative cervical myelopathy (DCM). However, patients with pre-existing cervical kyphosis often experience inferior outcomes compared to those with straight or lordotic spines. Limited dorsal spinal cord shift in kyphotic spines post-decompression and increased spinal cord tension may contribute to poor neurological recovery and spinal cord injury.

Effect of sagittal alignment on spinal cord biomechanics in the stenotic cervical spine during neck flexion and extension.

Spinal cord stress and strain contribute to degenerative cervical myelopathy (DCM), while cervical kyphosis is known to negatively impact surgical outcomes. In DCM, the relationship between spinal cord biomechanics, sagittal alignment, and cord compression is not well understood. Quantifying this relationship can guide surgical strategies.

Investigating the Impact of Blunt Force Trauma: A Probabilistic Study of Behind Armor Blunt Trauma Risk.

Evaluating Behind Armor Blunt Trauma (BABT) is a critical step in preventing non-penetrating injuries in military personnel, which can result from the transfer of kinetic energy from projectiles impacting body armor. While the current NIJ Standard-0101.06 standard focuses on preventing excessive armor backface deformation, this standard does not account for the variability in impact location, thorax organ and tissue material properties, and injury thresholds in order to assess potential injury.

Three-Dimensional-Digital Image Correlation Methodology for Kinematic Measurements of Non-Penetrating Blunt Impacts.

Blunt force trauma remains a serious threat to many populations and is commonly seen in motor vehicle crashes, sports, and military environments. Effective design of helmets and protective armor should consider biomechanical tolerances of organs in which they intend to protect and require accurate measurements of deformation as a primary injury metric during impact. To overcome challenges found in velocity and displacement measurements during blunt impact using an integrated accelerometer and two-dimensional (2D) high-speed video, three-dimensional (3D) digital image correlation (DIC) measurements were taken and compared to the accepted techniques.

Analysis of Injury Metrics From Experimental Cardiac Injuries From Behind Armor Blunt Trauma Using Live Swine Tests: A Pilot Study.

Introduction: Warfighters are issued hard body armor designed to defeat ballistic projectiles. The resulting backface deformation can injure different thoracoabdominal organs. Developed over decades ago, the behind armor blunt impact criterion of maximum 44 mm depth in clay continues to be used independent of armor type or impact location on the thoracoabdominal region covered by the armor.

Matched-pair hybrid test paradigm for behind armor blunt trauma using an experimental animal model.

Background: The current behind armor blunt trauma (BABT) injury criterion uses a single penetration limit of 44 mm in Roma Plastilina clay and is not specific to thoracoabdominal regions. However, different regions in the human body have different injury tolerances. This manuscript presents a matched-pair hybrid test paradigm with different experimental models and candidate metrics to develop regional human injury criteria.

Do expandable cage size and number of cages matter in transforaminal lumbar interbody fusion at L5-S1? A comparative biomechanical analysis using finite element modeling.

Objective: Expandable transforaminal lumbar interbody fusion (TLIF) cages were designed to address the limitations of static cages. Bilateral cage insertion can potentially enhance stability, fusion rates, and segmental lordosis. However, the benefits of unilateral versus bilateral expandable cages with varying sizes in TLIF remain unclear.

Complex Neck Loading and Injury Tolerance in Lateral Bending With Head Rotation From Human Cadaver Tests.

Advancements in automated vehicles may position the occupant in postures different from the current standard posture. It may affect human tolerance responses. The objective of this study was to determine the lateral bending tolerance of the head-cervical spine with initial head rotation posture using loads at the occipital condyles and lower neck and describe injuries.

Subaxial Cervical Spine Motion With Different Sizes of Head-supported Mass Under Accelerative Forces.

Introduction: The evolution of military helmet devices has increased the amount of head-supported mass (HSM) worn by warfighters. HSM has important implications for spine biomechanics, and yet, there is a paucity of studies that investigated the effects of differing HSM and accelerative profiles on spine biomechanics. The aim of this study is to investigate the segmental motions in the subaxial cervical spine with different sizes of HSM under Gx accelerative loading.

Regional Strain Response of an Anatomically Accurate Human Finite Element Head Model Under Frontal Versus Lateral Loading.

Introduction: Because brain regions are responsible for specific functions, regional damage may cause specific, predictable symptoms. However, the existing brain injury criteria focus on whole brain response. This study developed and validated a detailed human brain computational model with sufficient fidelity to include regional components and demonstrate its feasibility to obtain region-specific brain strains under selected loading.

Strain Response of an Anatomically Accurate Nonhuman Primate Finite Element Brain Model Under Sagittal Loading.

Introduction: Prevention and treatment of traumatic brain injuries is critical to preserving soldier brain health. Laboratory studies are commonly used to reproduce injuries, understand injury mechanisms, and develop tolerance limits; however, this approach has limitations for studying brain injury, which requires a physiological response. The nonhuman primate (NHP) has been used as an effective model for investigating brain injury for many years.

Preliminary Data of Neck Muscle Morphology With Head-Supported Mass in Male and Female Volunteers.

Introduction: This study quantified parameters related to muscle morphology using a group of upright seated female and male volunteers with a head-supported mass.

Materials And Methods: Upright magnetic resonance images (MRIs) were obtained from 23 healthy volunteers after approval from the U.S.

Pelvis-Sacrum-Lumbar Spine Injury Characteristics From Underbody Blast Loading.

Introduction: Combat-related injuries from improvised explosive devices occur commonly to the lower extremity and spine. As the underbody blast impact loading traverses from the seat to pelvis to spine, energy transfer occurs through deformations of the combined pelvis-sacrum-lumbar spine complex, and the time factor plays a role in injury to any of these components. Previous studies have largely ignored the role of the time variable in injuries, injury mechanisms, and warfighter tolerance.

A Novel Paradigm to Develop Regional Thoracoabdominal Criteria for Behind Armor Blunt Trauma Based on Original Data.

Introduction: For behind armor blunt trauma (BABT), recent prominent BABT standards for chest plate define a maximum deformation distance of 44 mm in clay. It was developed for soft body armor applications with limited animal, gelatin, and clay tests. The legacy criterion does not account for differing regional thoracoabdominal tolerances to behind armor-induced injury.

Cervical Column and Cord and Column Responses in Whiplash With Stenosis: A Finite Element Modeling Study.

Spine degeneration is a normal aging process. It may lead to stenotic spines that may have implications for pain and quality of life. The diagnosis is based on clinical symptomatology and imaging.

Comparison of Load-Sharing Responses Between Graded Posterior Cervical Foraminotomy and Conventional Fusion Using Finite Element Modeling.

Following the diagnosis of unilateral cervical radiculopathy and need for surgical intervention, anterior cervical diskectomy and fusion (conventional fusion) and posterior cervical foraminotomy are common options. Although patient outcomes may be similar between the two procedures, their biomechanical effects have not been fully compared using a head-to-head approach, particularly, in relation to the amount of facet resection and internal load-sharing between spinal segments and components. The objective of this investigation was to compare load-sharing between conventional fusion and graded foraminotomy facet resections under physiological loading.