Biomechanical evaluation of different semi-rigid junctional fixation techniques using finite element analysis

BACKGROUND: Proximal junctional failure is a common complication attributed to the rigidity of long pedicle screw fixation constructs used for surgical correction of adult spinal deformity. Semi-rigid junctional fixation achieves a gradual transition in range of motion at the ends of spinal instrumentation, which could lead to reduced junctional stresses, and ultimately reduce the incidence of proximal junctional failure. This study investigates the biomechanical effect of different semi-rigid junctional fixation techniques in a T8-L3 finite element spine segment model.METHODS: First, degeneration of the intervertebral disc was successfully implemented by altering the height. Second, transverse process hooks, one- and two-level clamped tapes, and one- and two-level knotted tapes instrumented proximally to three-level pedicle screw fixation were validated against ex vivo range of motion data of a previous study. Finally, the posterior ligament complex forces and nucleus pulposus stresses were quantified.FINDINGS: Simulated range of motions demonstrated the fidelity of the general model and modelling of semi-rigid junctional fixation techniques. All semi-rigid junctional fixation techniques reduced the posterior ligament complex forces at the junctional zone compared to pedicle screw fixation. Transverse process hooks and knotted tapes reduced nucleus pulposus stresses, whereas clamped tapes increased nucleus pulposus stresses at the junctional zone.INTERPRETATION: The relationship between the range of motion transition and the reductions in posterior ligament complex and nucleus pulposus stresses was complex and dependent on the fixation techniques. Clinical trials are required to compare the effectiveness of semi-rigid junctional fixation techniques in terms of reducing proximal junctional failure incidence rates.</p

Matrix-assisted laser desorption/ionization mass spectrometry imaging for quorum sensing

Abstract Quorum sensing (QS) is a complex communication system in bacteria, directing their response to the environment. QS is also one of the main regulators of bacterial biofilms’ formation, maturation and dispersion. Matrix-assisted laser desorption ionization (MALDI) mass spectrometry imaging (MSI) is a molecular imaging technique that allows the mapping of QS molecules in bacterial biofilms. Here, we highlight the latest advances in MALDI-MSI in recent years and how this technology can improve QS understanding at the molecular level

Improving peri-prosthetic bone adaptation around cementless hip stems: a clinical and finite element study

This study assessed whether the Symax™ implant, a modification of the Omnifit® stem (in terms of shape, proximal coating and distal surface treatment), would yield improved bone remodelling in a clinical DEXA study, and if these results could be predicted in a finite element (FE) simulation study.In a randomized clinical trial, 2 year DEXA measurements between the uncemented Symax™ and Omnifit® stem (both n=25) showed bone mineral density (BMD) loss in Gruen zone 7 of 14% and 20%, respectively (p<0.05). In contrast, the FE models predicted a 28% (Symax™) and 26% (Omnifit®) bone loss. When the distal treatment to the Symax™ was not modelled in the simulation, bone loss of 35% was predicted, suggesting the benefit of this surface treatment for proximal bone maintenance.The theoretical concept for enhanced proximal bone loading by the Symax™, and the predicted remodelling pattern were confirmed by DEXA-results, but there was no quantitative match between clinical and FE findings. This was due to a simulation based on incomplete assumptions concerning the yet unknown biological and mechanical effects of the new coating and surface treatment

ELISA-based detection of gentamicin and vancomycin in protein-containing samples

Background: Orthopaedic implant infections are treated by surgical debridement, systematic antibiotic treatment or local antibiotic treatment with antibiotic-loaded beads. Currently antibiotic concentrations in wound exudate, serum, urine or tissue samples are determined with HPLC or fluorescent spectrometric assays. Both methods are heavily influenced due to proteins in the samples. Questions/purposes: Is ELISA capable to detect gentamicin and vancomycin in protein-containing samples like serum and wound exudate. Methods: Two specific competitive ELISA-assays were set-up to detect either gentamicin or vancomycin in protein-rich samples. An antibiotic-BSA hapten was generated as a coatable antigen and commercially available antibodies were applied for downstream immunodetection. Results: The developed ELISAs perform at a detection range of 2–500 ng/ml gentamycin and 20–5000 ng/ml vancomycin. Both ELISAs were capable of detecting these antibiotics in human serum and wound exudate without being compromised by the presence of proteins. We did not detect cross-reactivity for gentamicin in the vancomycin ELISA or vice versa. Conclusions: The antibiotic ELISAs detect gentamicin and vancomycin at low concentrations in protein-rich samples and they can be used as a high throughput and cost-effective alternative for chromatographic or fluorescent methods. Clinical relevance: These ELISAs can be used to detect very low gentamicin or vancomycin concentrations in clinical samples or assess novel orthopaedic antibiotic release systems in in vitro and in vivo studies

How to prepare a systematic review of economic evaluations for informing evidence-based healthcare decisions: a five-step approach (part 1/3)

Introduction: Systematic reviews of economic evaluations are useful for synthesizing economic evidence about health interventions and for informing evidence-based decisions. Areas covered: As there is no detailed description of the methods for performing a systematic review of economic evidence, this paper aims to provide an overview of state-of-the-art methodology. This is laid out in a 5-step approach, as follows: step 1) initiating a systematic review; step 2) identifying (full) economic evaluations; step 3) data extraction, risk of bias and transferability assessment; step 4) reporting results; step 5) discussion and interpretation of findings. Expert commentary: The paper aims to help inexperienced reviewers and clinical practice guideline developers, but also to be a resource for experts in the field who want to check on current methodological developments