Biomechanical Stability Analysis of a Stand-alone Cage, Static and Rotational-dynamic Plate in a Two-level Cervical Fusion Construct.

Objective: To test the following hypotheses: (i) anterior cervical discetomy and fusion (ACDF) using stand-alone interbody spacers will significantly reduce the range of motion from intact spine; and (ii) the use of a static or a rotational-dynamic plate will significantly augment the stability of stand-alone interbody spacers, with similar beneficial effect when compared to each other.

Methods: Eleven human cadaveric subaxial cervical spines (age: 48.2 ± 5.

Effects of motion segment level, Pfirrmann intervertebral disc degeneration grade and gender on lumbar spine kinematics.

MRI allows non-invasive assessment of intervertebral disc degeneration with the added clinical benefit of using non-ionizing radiation. What has remained unclear is the relationship between assessed disc degeneration and lumbar spine kinematics. Kinematic outcomes of 54 multi-segment (L1-Sacrum) lumbar spine specimens were calculated to discover if such an underlying relationship exists with degeneration assessed using the Pfirrmann grading system.

Biomechanical characteristics of an integrated lumbar interbody fusion device.

Introduction: We hypothesized that an Integrated Lumbar Interbody Fusion Device (PILLAR SA, Orthofix, Lewisville, TX) will function biomechanically similar to a traditional anterior interbody spacer (PILLAR AL, Orthofix, Lewisville, TX) plus posterior instrumentation (FIREBIRD, Orthofix, Lewisville, TX). Purpose of this study was to determine if an Integrated Interbody Fusion Device (PILLAR SA) can stabilize single motion segments as well as an anterior interbody spacer (PILLAR AL) + pedicle screw construct (FIREBIRD).

Methods: Eight cadaveric lumbar spines (age: 43.

Relaxation response of lumbar segments undergoing disc-space distraction: implications to the stability of anterior lumbar interbody implants.

Study Design: A biomechanical study of human cadaveric lumbar spine segments undergoing disc-space distraction for insertion of anterior lumbar interbody implants.

Objective: To measure the distraction force and its relaxation during a period of up to 3 hours after disc-space distraction as a function of the distraction magnitude and disc level.

Summary Of Background Data: Interbody implants depend on compressive preload produced by disc-space distraction (annular pretension) for initial stabilization of the implant-bone interface.

Evaluation of pullout strength and failure mechanism of posterior instrumentation in normal and osteopenic thoracic vertebrae.

Object: There is limited data on the pullout strength of spinal fixation devices in the thoracic spine among individuals with different bone quality. An in vitro biomechanical study on the thoracic spine was performed to compare the pullout strength and the mechanism of failure of 4 posterior fixation thoracic constructs in relation to bone mineral density (BMD).

Methods: A total of 80 vertebrae from 11 fresh-frozen thoracic spines (T2-12) were used.

Anterior cervical discectomy and fusion with a locked plate and wedged graft effectively stabilizes flexion-distraction stage-3 injury in the lower cervical spine: a biomechanical study.

Study Design: An in vitro three-dimensional (3D) flexibility test of human C3-C7 cervical spine specimens.

Objective: To test the hypothesis that anterior cervical fusion with a wedged graft and a locked plate can effectively stabilize the cervical spine after complete anterior and posterior segmental ligamentous release.

Summary Of Background Data: Distraction-flexion Stage 3 injuries of the lower cervical spine (bilateral facet dislocations) are usually reduced under awake cranial traction.

Altered disc pressure profile after an osteoporotic vertebral fracture is a risk factor for adjacent vertebral body fracture.

This study investigated the effect of endplate deformity after an osteoporotic vertebral fracture in increasing the risk for adjacent vertebral fractures. Eight human lower thoracic or thoracolumbar specimens, each consisting of five vertebrae were used. To selectively fracture one of the endplates of the middle VB of each specimen a void was created under the target endplate and the specimen was flexed and compressed until failure.

An evidence-based medicine approach in determining factors that may affect outcome in lumbar total disc replacement.

Study Design: Literature research.

Objective: To analyze the available evidence about a variety of factors that might affect outcome of lumbar artificial disc replacement.

Summary Of Background Data: Evaluating the scientific merit of new technology is important for a clinician considering incorporating these techniques.

Response of Charité total disc replacement under physiologic loads: prosthesis component motion patterns.

Background Context: Total disc replacement (TDR) has been recommended to reduce pain of presumed discogenic origin while preserving spinal motion. The floating core of Charité TDR is professed to allow the replication of the kinematics of a healthy disc under physiologic loads. While segmental motion after Charité TDR has been measured, little is known about the effects of a physiologic compressive preload on vertebral motion and the motion of prosthesis components after TDR.

Restoring geometric and loading alignment of the thoracic spine with a vertebral compression fracture: effects of balloon (bone tamp) inflation and spinal extension.

Background Context: In patients with osteoporosis, changes in spinal alignment after a vertebral compression fracture (VCF) are believed to increase the risk of fracture of the adjacent vertebrae. The alterations in spinal biomechanics as a result of osteoporotic VCF and the effects of deformity correction on the loads in the adjacent vertebral bodies are not fully understood.

Purpose: To measure 1) the effect of thoracic VCFs on kyphosis (geometric alignment) and the shift of the physiologic compressive load path (loading alignment), 2) the effect of fracture reduction by balloon (bone tamp) inflation in restoring normal geometric and loading alignment and 3) the effect of spinal extension alone on fracture reduction and restoration of normal geometric and loading alignment.

Flexion-extension response of the thoracolumbar spine under compressive follower preload.

Study Design: The authors conducted an in vitro biomechanical flexibility study of T2-S1 specimens in flexion-extension under compressive follower preloads of physiological magnitudes.

Objectives: The objectives of this study were to test the hypotheses that 1) the thoracolumbar spine will support compressive preloads of in vivo magnitudes and 2) allow physiological mobility under flexion-extension moments if the preload is applied along an optimized follower load path that approximates the kypholordotic curve of the thoracolumbar spine.

Summary Of Background Data: In the absence of muscle forces, the ligamentous thoracolumbar spine specimens cannot support the compressive loads expected in vivo.