Load Share Mapping for Traditional PEEK vs Novel Hybrid PEEK With Expandable Porous Mesh Intervertebral Devices.

Background: A successful intervertebral fusion requires biomechanical stability created by the structural support of the interbody device and loading of the bone graft material to accelerate mechanotransduction and bone remodeling. The objective of this study was to generate a quantitative map of the contact area and stress profile for 2 implant designs; a rigid monolithic polyetheretherketone (PEEK) lateral cage (MPLC), and a unique hybrid interbody design, which includes PEEK terminal supports surrounding an expandable porous mesh (P+EPM) that serves to contain bone graft.

Methods: The construct for each test consisted of a device sandwiched between 2 flat or shaped Grade 15 foam blocks.

Kinematics Following 3-Screw Integrated Interbody Spacers in the Lumbar Spine.

Background: "Stand-alone" fusion implants attempt to alleviate the need for supplemental posterior instrumentation.

Objective: A biomechanical study was conducted to assess the stability of an integrated 3- screw interbody cage with, and without, supplemental posterior fixation.

Methods: Nondestructive biomechanical testing was performed on 19 healthy cadaver spine segments.

Range of motion, sacral screw and rod strain in long posterior spinal constructs: a biomechanical comparison between S2 alar iliac screws with traditional fixation strategies.

Background: S1 screw failure and L5/S1 non-union are issues with long fusions to S1. Improved construct stiffness and S1 screw offloading can help avoid this. S2AI screws have shown to provide similar stiffness to iliac screws when added to L3-S1 constructs.

Taking a Concept to Commercialization: Designing Relevant Tests to Address Safety.

Taking a product from concept to commercialization requires careful navigation of the regulatory pathway through a series of steps: (A) moving the idea through proof of concept and beyond; (B) evaluating new technologies that may provide added value to the idea; (C) designing appropriate test strategies and protocols; and (D) evaluating and mitigating risks. Moving an idea from the napkin stage of development to the final product requires a team effort. When finished, the product rarely resembles the original design, but careful steps throughout the product life cycle ensure that the product meets the vision.

Biomechanical effect of transforaminal lumbar interbody fusion and axial interbody threaded rod on range of motion and S1 screw loading in a destabilized L5-S1 spondylolisthesis model.

Study Design: A cadaveric lumbosacral spondylolytic spondylolisthesis model was used to evaluate the biomechanical function of 2 different interbody spacers.

Objective: To analyze and compare the reduction in pedicle screw strain and spine range of motion (ROM) between transforaminal lumbar interbody fusion (TLIF) and an axial interbody threaded rod (AxialITR) in a destabilized L5-S1 spondylolisthesis model.

Summary Of Background Data: Symptomatic spondylolytic spondylolisthesis is often treated with posterior instrumented fusion augmented by a variety of different interbody devices.

The biomechanics of cervical spondylosis.

Aging is the major risk factor that contributes to the onset of cervical spondylosis. Several acute and chronic symptoms can occur that start with neck pain and may progress into cervical radiculopathy. Eventually, the degenerative cascade causes desiccation of the intervertebral disc resulting in height loss along the ventral margin of the cervical spine.

Biomechanical analysis of sacral screw strain and range of motion in long posterior spinal fixation constructs: effects of lumbosacral fixation strategies in reducing sacral screw strains.

Study Design: A cadaveric biomechanical experiment was conducted to assess the range of motion (ROM) and screw strain at S1 in a long instrumented spinal fusion construct to compare the effects of various surgical strategies for L5-S1 stabilization.

Objective: To directly quantify and compare S1 screw strains and lumbosacral ROM for 4 different L2-S1 posterior segmental instrumented fusion constructs: an L2-S1 pedicle screw (PS) construct alone and PS with each of 3 different augmentations, anterior lumbar intebody fusion (ALIF), anterior axial interbody threaded rod (AxiaLITR), or iliac screws.

Summary Of Background Data: Iliac screws and anterior interbody devices are commonly used as augmentation to reduce the incidence of S1 screw loosening in long fusion constructs.

Biomechanics of a posture-controlling cervical artificial disc: mechanical, in vitro, and finite-element analysis.

Different methods have been described by numerous investigators for experimentally assessing the kinematics of cervical artificial discs. However, in addition to understanding how artificial discs affect range of motion, it is also clinically relevant to understand how artificial discs affect segmental posture. The purpose of this paper is to describe novel considerations and methods for experimentally assessing cervical spine postural control in the laboratory.

In Vivo Assessment of Bone Graft/Endplate Contact Pressure in a Caprine Interbody Pseudarthrosis Model: A Preliminary Biomechanical Characterization of the Fusion Process for the Development of a Microelectromechanical Systems (MEMS) Biosensor.

Background: In this preliminary study we used a goat model to quantify pressure at an interbody bone graft interface. Although the study was designed to assess fusion status, the concept behind the technology could lead to early detection of implant failure and potential hazardous complications related to motion-preservation devices. The purpose of this study was to investigate the feasibility of in vivo pressure monitoring as a strategy to determine fusion status.

A preliminary biomechanical evaluation in a simulated spinal fusion model. Laboratory investigation.

Object: A preliminary in vitro biomechanical study was conducted to determine if the pressure at a bone graft-mortise interface and the load transmitted along a ventral cervical plate could be used as parameters to assess fusion status.

Methods: An interbody bone graft and a ventral plate were placed at the C3-4 motion segment in six fresh cadaveric goat spines. Polymethylmethacrylate (PMMA) was used to simulate early bone fusion at the bone graft site.

Load sharing within a human thoracic vertebral body: an in vitro biomechanical study.

Objective: The vertebral body is the major load bearing part of the vertebra and consists of a central trabecular core surrounded by a thin cortical shell. The aim of this in vitro biomechanical study is to determine the debated issue of load sharing in a vertebral body.

Methods: A series of non-destructive compressive testing on excised human thoracic vertebral bodies were performed.

Effects of angle and laminectomy on triangulated pedicle screws.

We aimed to demonstrate the effect of angle and laminectomy on paired pedicle screws to determine whether a 90 degrees screw angle is optimal as has been previously suggested. According to the angle between right and left screws, 28 calf vertebrae were divided into three groups and instrumented as follows: Group I: 60 degrees screw angle; Group II: 90 degrees angle; Group III: 60 degrees angle with laminectomy. The screws were connected using rods and cross-fixators and tested to peak pullout force.

Biomechanical evaluation of the ventral and lateral surface shear strain distributions in central compared with dorsolateral placement of cages for lumbar interbody fusion.

Object: The purpose of this study was to measure and compare the ventral and lateral surface strain distributions and stiffness for two types of interbody cage placement: 1) central placement for anterior lumbar interbody fusion (ALIF); and 2) dorsolateral placement for extraforaminal lumbar interbody fusion (ELIF).

Methods: Two functional spine units were obtained for testing in each of 13 cadaveric spines, yielding 26 segments (three of which were not used because of bone abnormalities). Bilateral strain gauges were mounted adjacent to the endplate on the lateral and ventral walls of each vertebral body in the 23 motion segments.

Distribution of anterior cortical shear strain after a thoracic wedge compression fracture.

Background Context: Vertebral compression fractures (VCFs) are a common clinical problem and may follow trauma or be pathological. Osteoporosis increases susceptibility to fracture by reducing bone mass and weakening bone architecture. Approximately 2.

A biomechanical comparison of facet screw fixation and pedicle screw fixation: effects of short-term and long-term repetitive cycling.

Study Design: A biomechanical study was conducted to assess the stabilization performance of transfacet pedicle screw fixation.

Objective: To compare the biomechanical effects of short-term and long-term cyclic loading on lumbar motion segments instrumented with either a pedicle screw or a transfacet pedicle screw construct.

Summary Of Background Data: Facet screw fixation is an alternative to pedicle screw fixation that permits the use of a minimally invasive strategy.