Biomechanics of Circumferential Cervical Fixation Using Posterior Facet Cages: A Cadaveric Study.

OBJECTIVE: Anterior cervical discectomy and fusion (ACDF) is a common procedure for the treatment of cervical disease. Circumferential procedures are options for multilevel pathology. Potential complications of multilevel anterior procedures are dysphagia and pseudarthrosis, whereas potential complications of posterior surgery include development of cervical kyphosis and postoperative chronic neck pain. The addition of posterior cervical cages (PCCs) to multilevel ACDF is a minimally invasive option to perform circumferential fusion. This study evaluated the biomechanical performance of 3-level circumferential fusion with PCCs as supplemental fixation to anteriorly placed allografts, with and without anterior plate fixation. METHODS: Nondestructive flexibility tests (1.5 Nm) performed on 6 cervical C2-7 cadaveric specimens intact and after discectomy (C3-6) in 3 instrumented conditions: allograft with anterior plate (G+P), PCC with allograft and plate (PCC+G+P), and PCC with allograft alone (PCC+G). Range of motion (ROM) data were analyzed using 1-way repeated-measures analysis of variance. RESULTS: All instrumented conditions resulted in significantly reduced ROM at the 3 instrumented levels (C3-6) compared to intact spinal segments in flexion, extension, lateral bending, and axial rotation (p \u3c 0.001). No significant difference in ROM was found between G+P and PCC+G+P conditions or between G+P and PCC+G conditions, indicating similar stability between these conditions in all directions of motion. CONCLUSION: All instrumented conditions resulted in considerable reduction in ROM. The added reduction in ROM through the addition of PCCs did not reach statistical significance. Circumferential fusion with anterior allograft, without plate and with PCCs, has comparable stability to ACDF with allograft and plate

Oligosaccharyltransferase Inhibition Induces Senescence in RTK-Driven Tumor Cells

Asparagine (N)-linked glycosylation is a protein modification critical for glycoprotein folding, stability, and cellular localization. To identify small molecules that inhibit new targets in this biosynthetic pathway, we initiated a cell-based high throughput screen and lead compound optimization campaign that delivered a cell permeable inhibitor (NGI-1). NGI-1 targets the oligosaccharyltransferase (OST), a hetero-oligomeric enzyme that exists in multiple isoforms and transfers oligosaccharides to recipient proteins. In non-small cell lung cancer cells NGI-1 blocks cell surface localization and signaling of the EGFR glycoprotein, but selectively arrests proliferation in only those cell lines that are dependent on EGFR (or FGFR) for survival. In these cell lines OST inhibition causes cell cycle arrest accompanied by induction of p21, autofluorescence, and changes in cell morphology; all hallmarks of senescence. These results identify OST inhibition as a potential therapeutic approach for treating receptor tyrosine kinase-dependent tumors and provides a chemical probe for reversibly regulating N-linked glycosylation in mammalian cells

Mapping the medical outcomes study HIV health survey (MOS-HIV) to the EuroQoL 5 Dimension (EQ-5D-3L) utility index

10.1186/s12955-019-1135-8Health and Quality of Life Outcomes1718

Variations among human lumbar spine segments and their relationships to in vitro biomechanics: A retrospective analysis of 281 motion segments from 85 cadaveric spines

© International Society for the Advancement of Spine Surgery Background: Biomechanical properties of intact spinal motion segments are used to establish baseline values during in vitro studies evaluating spinal surgical techniques and implants. These properties are also used to validate computational models (ie, patient-specific finite element models) of human lumbar spine segments. Our laboratory has performed a large number of in vitro mechanical studies of lumbar spinal segments, using a consistent methodology. This provides extensive biomechanical data for a large number of intact motion segments, along with donor demographic variables, bone mineral density (BMD) measurements, and geometric properties. The objective of this study was to analyze how donor demographics, BMD, and geometric properties of cadaveric lumbar spine segments affect motion segment flexibility, including the range of motion (ROM), lax zone (LZ), and stiff zone (SZ), to help improve our understanding of spinal biomechanics. Methods: A retrospective study examined the relationships between the biomechanical properties of 281 lumbar motion segments from 85 human cadaveric spines, donor demographic variables (age, sex, weight, height, and body mass index), and specimen measurements (vertebral body height, intervertebral disc height, and BMD). Results: Statistical correlation and regression analyses showed that the flexibility of a lumbar motion segment is affected by lumbar level, donor age, sex, and weight as well as the intervertebral disc height, vertebral body height, and bone quality. Increased disc height was associated with decreased ROM (axial rotation), decreased LZ (flexion-extension and axial rotation), and increased SZ (flexion-extension and lateral bending) in the male group, but increased ROM (lateral bending) in the female group. Increased vertebral body height correlated with increased LZ (lateral bending) in the female group. Increased BMD correlated with decreased ROM overall. Conclusions: Biomechanical measurements from flexibility testing of cadaveric lumbar spine segments are significantly correlated with donor demographics and specimen measurements. Many of these correlations are sex-dependent

A Novel C2 Screw Trajectory: Preliminary Anatomic Feasibility And Biomechanical Comparison

Background: Pedicle screw and translaminar screw fixation in C2 may not be applicable in many patients with anatomic abnormalities or narrow laminar thickness and spinous process height. The aim of this study was to assess morphometric and mechanical feasibilities of a novel alternative screw trajectory that pierces the bifid base of C2. Methods: Anatomic measurements that determined the feasibility of spinous process bifid base (SPB) screw fixation were assessed in 14 cadaveric C2 vertebrae. Pullout tests to assess ultimate fixation strength for 3 screw trajectories (transpedicular, translaminar, and SPB) were performed in cadaveric vertebrae for comparison. Results: Anatomic measurements included mean spinous process height (10.4 ± 4.2 mm) and mean bilateral bifid base length (10.1 ± 2.2 mm) and thickness (left, 4.4 ± 1.0 mm; right, 4.3 ± 0.9 mm). In 64% (9/14) of specimens, bifid base length was ≥9 mm. Mean pullout strength for transpedicle, translaminar, and SPB screws in 9 viable specimens was 648 ± 305 N, 628 ± 417 N, and 755 ± 279 N. Conclusions: SPB screw fixation may be viable anatomically and mechanically for C2 fixation. Feasibility of SPB screw fixation is determined by length, thickness, and mutual angle of the bilateral bifid bases. Patients with thin (\u3c4 mm) and short (\u3c9 mm) bifid bases are not likely to be suitable candidates. SPB screw fixation shows potential as an alternative approach or a salvage technique for patients with high-riding vertebral arteries or severely thin C2 lamina and warrants further investigation

The Histone Deacetylase Inhibitor Entinostat Enhances Polymer-Mediated Transgene Expression in Cancer Cell Lines

Eukaryotic cells maintain an immense amount of genetic information by tightly wrapping their DNA around positively charged histones. While this strategy allows human cells to maintain more than 25,000 genes, histone binding can also block gene expression. Consequently, cells express histone acetyl transferases (HATs) to acetylate histone lysines and release DNA for transcription. Conversely, histone deacetylases (HDACs) are employed for restoring the positive charge on the histones, thereby silencing gene expression by increasing histone-DNA binding. It has previously been shown that histones bind and silence viral DNA, while hyperacetylation of histones via HDAC inhibition restores viral gene expression. In this study, we demonstrate that treatment with Entinostat, an HDAC inhibitor, enhances transgene (luciferase) expression by up to 25-fold in human prostate and murine bladder cancer cell lines when used with cationic polymers for plasmid DNA delivery. Entinostat treatment altered cell cycle progression, resulting in a significant increase in the fraction of cells present in the G0/G1 phase at low micromolar concentrations. While this moderate G0/G1 arrest disappeared at higher concentrations, a modest increase in the fraction of apoptotic cells and a decrease in cell proliferation were observed, consistent with the known anticancer effects of the drug. DNase accessibility studies revealed no significant change in plasmid transcriptional availability with Entinostat treatment. However, quantitative PCR studies indicated that Entinostat treatment, at the optimal dose for enhancing transgene expression, led to an increase in the amount of plasmid present in the nucleus in two cancer cell lines. Taken together, our results show that Entinostat enhances polymer- mediated transgene expression and can be useful in applications related to transient protein expression in mammalian cells

Biomechanics of Circumferential Cervical Fixation Using Posterior Facet Cages: A Cadaveric Study

OBJECTIVE: Anterior cervical discectomy and fusion (ACDF) is a common procedure for the treatment of cervical disease. Circumferential procedures are options for multilevel pathology. Potential complications of multilevel anterior procedures are dysphagia and pseudarthrosis, whereas potential complications of posterior surgery include development of cervical kyphosis and postoperative chronic neck pain. The addition of posterior cervical cages (PCCs) to multilevel ACDF is a minimally invasive option to perform circumferential fusion. This study evaluated the biomechanical performance of 3-level circumferential fusion with PCCs as supplemental fixation to anteriorly placed allografts, with and without anterior plate fixation. METHODS: Nondestructive flexibility tests (1.5 Nm) performed on 6 cervical C2-7 cadaveric specimens intact and after discectomy (C3-6) in 3 instrumented conditions: allograft with anterior plate (G+P), PCC with allograft and plate (PCC+G+P), and PCC with allograft alone (PCC+G). Range of motion (ROM) data were analyzed using 1-way repeated-measures analysis of variance. RESULTS: All instrumented conditions resulted in significantly reduced ROM at the 3 instrumented levels (C3-6) compared to intact spinal segments in flexion, extension, lateral bending, and axial rotation (p \u3c 0.001). No significant difference in ROM was found between G+P and PCC+G+P conditions or between G+P and PCC+G conditions, indicating similar stability between these conditions in all directions of motion. CONCLUSION: All instrumented conditions resulted in considerable reduction in ROM. The added reduction in ROM through the addition of PCCs did not reach statistical significance. Circumferential fusion with anterior allograft, without plate and with PCCs, has comparable stability to ACDF with allograft and plate

In Vitro Biomechanical Evaluation Of A Novel Minimally Invasive Sacroiliac Joint Fixation Device

Background: Sacroiliac (SI) joint pathology may result in low-back pain, which causes substantial disability. Treatment failure with operative management of SI pain may be related to incomplete fusion of the joint and to fixation failure. The objective of this study was to evaluate the initial biomechanical stability of SI joint fixation with a novel implantable device in an in vitro human cadaveric model. Methods: The right and left sides of 3 cadaveric L4-pelvis specimens were tested (1) intact, (2) destabilized, and (3) instrumented with an implantable SI joint fixation device using a simulated single-stance load condition. Right-leg and left-leg stance data were grouped together for a sample size of 6, and angular range of motion (ROM) was determined during application of flexion-extension, lateral bending, and axial rotation bending moments to a limit of 7.5 Nm. Results: Following intact testing, destabilization by severing the posterior SI joint capsule and ligaments and the pubic symphysis reliably produced a significantly destabilized joint with the mean angular ROM more than doubling in flexion-extension and lateral bending and more than tripling in axial rotation (P .003) compared to the intact condition. Instrumentation with the SI screw fixation device significantly reduced mean joint ROM compared to the destabilized condition in all 3 anatomic planes tested (P, .001). When compared to the intact condition, the SI-instrumented condition significantly reduced lateral bending (P ¼ .01) and had a similar ROM in flexion-extension (P ¼ .14) and axial rotation (P ¼ .85). Conclusions: Instrumentation with the SI screw fixation device significantly reduced mean joint ROM compared to the destabilized condition, with similar ROM in flexion-extension and axial rotation, and it significantly reduced ROM in lateral bending compared to that for the intact joint. The ROM values observed with the instrumented condition were comparable to levels of mobility considered favorable for spinal fusion

Modulation of Cellular Behavior by Inhibition of Intracellular Enzymes to Enhance in Vitro Transient Non-Viral Polymer-Mediated Transgene Expression

Transgene delivery is a ubiquitously applied approach in which nucleic acids (DNA or RNA) are delivered from an external source to a target cell. This approach can be used a biological study tool or as a therapy to correct a mutated, over-expressed, under-expressed, or non-expressing gene. Many cationic vehicles (eg. polymers, liposomes, metal-phosphates, and magnetic nanoparticles) have been applied for delivering negatively charged nucleic acids to the nucleus of target cells, where the cell\u27s machinery can transcribe the delivered gene, ultimately leading to protein expression. However, most applications of gene delivery, including those in clinical trials for therapeutic applications, utilize viral vehicles due to their relatively high efficacy in delivering transgene to the target nucleus. While viral vehicles have evolved to become incredibly efficient gene delivery vehicles, they pose issues including induction of host immune response, toxicity, and they can be expensive to synthesize. Additionally, their cargo load is generally limited when compared to chemically synthesized non-viral delivery vehicles. Given these drawbacks with viral carriers, it is imperative that a focus on the improvement of non-viral gene delivery efficacy ensues. Fortunately, much work on this research topic is underway. One approach to improving non-viral gene delivery is to introduce functional groups to the delivery vehicles that assist the transgene/delivery complex in overcoming intracellular barriers. These include introducing proton sponge groups that help the transgene escape the endosomes, and conjugation of nuclear localization sequences, assisting the transgene in entering the host cell nucleus. A second approach to improve non-viral gene delivery is to modulate target cellular behavior by inhibiting enzymes within the cell, and this approach has been employed thoroughly in our laboratory. We have identified a multitude of enzymatic targets in cancer cells, whose inhibition leads to significant enhancement in expression of an exogenously delivered transgene. These targets include enzymes involved in cell cycle, transcription, as well as epigenetic modifiers. This project focuses mainly on enhancing transgene expression using the second method, modulating intracellular behavior in a way that makes cells more vulnerable to transgene expression. One key advantage to this method is the potential for synergistic therapeutic treatments. Enzyme inhibition can have therapeutic effects (eg. inhibition of cell cycle proteins is used in cancer treatments). If inhibition of this enzyme simultaneously enhances transgene delivery, then a gene with a therapeutic effect can be delivered with improved efficacy when treated with this inhibitor already possessing therapeutic value. This method of non-viral gene delivery is promising direction for future gene therapy applications