Does semi-rigid instrumentation using both flexion and extension dampening spacers truly provide an intermediate level of stabilization?

Conventional posterior dynamic stabilization devices demonstrated a tendency towards highly rigid stabilization approximating that of titanium rods in flexion. In extension, they excessively offload the index segment, making the device as the sole load-bearing structure, with concerns of device failure. The goal of this study was to compare the kinematics and intradiscal pressure of monosegmental stabilization utilizing a new device that incorporates both a flexion and extension dampening spacer to that of rigid internal fixation and a conventional posterior dynamic stabilization device.

Kinematics of a selectively constrained radiolucent anterior lumbar disc: comparisons to hybrid and circumferential fusion.

Background: Despite encouraging clinical outcomes of one-level total disc replacements reported in literature, there is no compelling evidence regarding the stability following two-level disc replacement and hybrid constructs. The current study is aimed at evaluating the multidirectional kinematics of a two-level disc arthroplasty and hybrid construct with disc replacement adjacent to rigid circumferential fusion, compared to two-level fusion using a novel selectively constrained radiolucent anterior lumbar disc.

Methods: Nine osteoligamentous lumbosacral spines (L1-S1) were tested in the following sequence: 1) Intact; 2) One-level disc replacement; 3) Hybrid; 4) Two-level disc replacement; and 5) Two-level fusion.

Biomechanical stability of a posterior-alone fixation technique after craniovertebral junction realignment.

Objective: The aim of the current study was to investigate the biomechanical stability and fixation strength provided by a posterior approach reconstruction technique to realign the craniovertebral junction.

Methods: We tested seven human cadaver occipito-cervical spines (occiput-C4) by applying pure moments of ± 1.5 Nm on a spine tester.

Biomechanical analysis of a novel posterior construct in a transforaminal lumbar interbody fusion model an in vitro study.

Background Context: Spinal fusion is a commonly performed surgical procedure. It is used to treat a variety of spinal pathologies, including degenerative disease, trauma, spondylolisthesis, and deformities. A mechanically stable spine provides an ideal environment for the formation of a fusion mass.

Could junctional problems at the end of a long construct be addressed by providing a graduated reduction in stiffness? A biomechanical investigation.

Study Design: The effect of long, rigid fixation on adjacent level hypermobility was investigated in a human cadaver model with and without a transitional posterior dynamic stabilization (PDS) device placed at the last caudal level.

Objective: To evaluate if PDS devices are useful in the setting of spinal deformities to restore increased adjacent level motions, which occur in long constructs. The hypothesis is that load-sharing benefits of these devices will be most suitable in long constructs and may reduce thoracolumbar junctional effects.

A novel crossed rod configuration incorporating translaminar screws for occipitocervical internal fixation: an in vitro biomechanical study.

Background Context: Occipitocervical (OC) spinal instrumentation involving the axis (C2) entails the use of transarticular screws through C1-C2 or lateral mass screws at C1 and pedicle screws at C2 to achieve fusion. Because of the anatomical complexity, interpatient anomalous variation, and danger to the vertebral artery injury, there has been an increased interest in alternate sites for fixation. Recent studies have involved the placement of screws bilaterally into the C2 lamina.

Effect of lumbar total disc arthroplasty on the segmental motion and intradiscal pressure at the adjacent level: an in vitro biomechanical study: presented at the 2008 Joint Spine Section Meeting Laboratory investigation.

Object: The artificial disc has been proposed as an alternative to spinal fusion for degenerative disc disease. The primary aim of this biomechanical study was to compare motion and intradiscal pressure (IDP) in a ball-and-socket artificial disc-implanted cadaveric lumbar spine, at the operative and adjacent levels, using a displacement-controlled setup. A secondary comparison involved a "salvage" construct, consisting of pedicle screws (PSs) added in supplementation to the artificial disc construct.

Biomechanical rigidity of an all-polyetheretherketone anterior thoracolumbar spinal reconstruction construct: an in vitro corpectomy model.

Background Context: Polyetheretherketone (PEEK) is gaining favor as a spinal implant material for interbody and corpectomy cages as well as stabilizing rods. However, there has been little correlation to a relevant and reproducible clinical model. Biomechanical data on PEEK rod constructs have not been reported.

Biomechanical comparison of single- and dual-lead pedicle screws in cadaveric spine.

Object: The pedicle screw (PS) is the cornerstone of spinal instrumentation, and its failure often entails additional surgery. Screw pullout is one of the most common reasons for screw failure, particularly in the elderly population. In this study the authors undertook a biomechanical comparison of the maximum pullout force (MPF) required for single- and dual-lead PSs in cadaver vertebrae.

In vitro biomechanical comparison of transpedicular versus translaminar C-2 screw fixation in C2-3 instrumentation.

Object: In instrumentation of the upper cervical spine, placement of pedicle screws into C-2 is generally safe, although there is the potential for injury to the vertebral arteries. Owing to this risk, translaminar screws into C-2 have been used. The aim of this study was to compare the stability of the in vitro cadaveric spine using C-2 laminar compared with C-2 pedicle screws in C2-3 instrumentation.

Biomechanical studies of an artificial disc implant in the human cadaveric spine.

Object: The authors compared the biomechanical performance of the human cadaveric spine implanted with a metallic ball-and-cup artificial disc at L4-5 with the spine's intact state and after anterior discectomy.

Methods: Seven human L2-S1 cadaveric spines were mounted on a biomechanical testing frame. Pure moments of 0, 1.