Mechanical characterization of a novel biomimetic artificial disc for the cervical spine

A novel biomimetic artificial intervertebral disc (bioAID) replacement implant has been developed containing a swelling hydrogel representing the nucleus pulposus, a tensile strong fiber jacket as annulus fibrosus and titanium endplates with pins to primarily secure the device between the vertebral bodies. In this study, the design safety of this novel implant was evaluated based on several biomechanical parameters, namely compressive strength, shear-compressive strength, risk of subsidence and device expulsion as well as identifying the diurnal creep-recovery characteristics of the device. The bioAID remained intact up to 1 kN under static axial compression and only 0.4 mm of translation was observed under a compressive shear load of 20 N. No subsidence was observed after 0.5 million cycles of sinusoidal compressive loading between 50 and 225 N. After applying 400 N in antero-posterior direction under 100 N axial compressive preload, approximately 2 mm displacement was found, being within the range of displacements reported for other commercially available cervical disc replacement devices. The diurnal creep recovery behavior of the bioAID closely resembled what has been reported for natural intervertebral discs in literature. Overall, these results indicate that the current design can withstand (shear-compression loads and is able to remain fixed in a mechanical design resembling the vertebral bodies. Moreover, it is one of the first implants that can closely mimic the poroelastic and viscoelastic behavior of natural disc under a diurnal loading pattern

Biomechanical evaluation of a novel biomimetic artificial intervertebral disc in canine cervical cadaveric spines

Background Context Cervical disc replacement (CDR) aims to restore motion of the treated level to reduce the risk of adjacent segment disease (ASD) compared with spinal fusion. However, first-generation articulating devices are unable to mimic the complex deformation kinematics of a natural disc. Thus, a biomimetic artificial intervertebral CDR (bioAID), containing a hydroxyethylmethacrylate (HEMA)—sodium methacrylate (NaMA) hydrogel core representing the nucleus pulposus, an ultra-high-molecular-weight-polyethylene fiber jacket as annulus fibrosus, and titanium endplates with pins for primary mechanical fixation, was developed. Purpose To assess the initial biomechanical effect of the bioAID on the kinematic behavior of the canine spine, an ex vivo biomechanical study in 6-degrees-of-freedom was performed. Study Design A canine cadaveric biomechanical study. Methods Six cadaveric canine specimens (C3-C6) were tested in flexion-extension (FE), lateral bending (LB) axial rotation (AR) using a spine tester in three conditions: intact, after C4-C5 disc replacement with bioAID, and after C4-C5 interbody fusion. A hybrid protocol was used where first the intact spines were subjected to a pure moment of ±1 Nm, whereafter the treated spines were subjected to the full range of motion (ROM) of the intact condition. 3D segmental motions at all levels were measured while recording the reaction torsion. Biomechanical parameters studied included ROM, neutral zone (NZ), and intradiscal pressure (IDP) at the adjacent cranial level (C3-C4). Results The bioAID retained the sigmoid shape of the moment-rotation curves with a NZ similar to the intact condition in LB and FE. Additionally, the normalized ROMs at the bioAID-treated level were statistically equivalent to intact during FE and AR while slightly decreased in LB. At the two adjacent levels, ROMs showed similar values for the intact compared to the bioAID for FE and AR and an increase in LB. In contrast, levels adjacent to the fused segment showed an increased motion in FE and LB as compensation for the loss of motion at the treated level. The IDP at the adjacent C3-C4 level after implantation of bioAID was close to intact values. After fusion, increased IDP was found compared with intact but did not reach statistical significance. Conclusion This study indicates that the bioAID can mimic the kinematic behavior of the replaced intervertebral disc and preserves that for the adjacent levels better than fusion. As a result, CDR using the novel bioAID is a promising alternative treatment for replacing severely degenerated intervertebral discs

Wavefront shaping with disorder-engineered metasurfaces

Recently, wavefront shaping with disordered media has demonstrated optical manipulation capabilities beyond those of conventional optics, including extended volume, aberration-free focusing and subwavelength focusing. However, translating these capabilities to useful applications has remained challenging as the input–output characteristics of the disordered media (P variables) need to be exhaustively determined via O(P) measurements. Here, we propose a paradigm shift where the disorder is specifically designed so its exact input–output characteristics are known a priori and can be used with only a few alignment steps. We implement this concept with a disorder-engineered metasurface, which exhibits additional unique features for wavefront shaping such as a large optical memory effect range in combination with a wide angular scattering range, excellent stability, and a tailorable angular scattering profile. Using this designed metasurface with wavefront shaping, we demonstrate high numerical aperture (NA > 0.5) focusing and fluorescence imaging with an estimated ~2.2 × 10^8 addressable points in an ~8 mm field of view

Isolation of Aspergillus species from Nasal Cavity and Bedroom of Healthy Volunteers and Patients with Allergic Rhinitis in Mashhad, Iran Article information Abstract

Background: The purpose of this study was to investigate the presence, frequency and comparison of Aspergillus spp. in nasal cavity and bedroom of healthy volunteers and patients with allergic rhinitis. Materials and Methods: In this cross-sectional study, a group of patients with allergic rhinitis (N=50) were selected based on positive skin prick test. Healthy volunteers were chosen to be in the comparison group by matching in age, gender, and no history of respiratory system disease. Samples from nasal cavity and different parts of bedroom were collected and cultured. Cultured Aspergillus spp. was identified by standard mycological techniques. Results: The most common species isolated from all samples of healthy volunteers was A. flavus (88%), followed by A. niger (76%) and A. fumigatus (74%). A. flavus (56%) was the predominant species isolated from all samples of patients, followed by A. niger (34%) and A. fumigatus (6%). Conclusion: A. flavus was the most prevalent species of Aspergillus both healthy volunteers and patients. The presence of Aspergillus in homes does not necessarily imply a cause and effect relationship with illness, but we speculate that A. flavus may be a major source of aeroallergens along with A. niger and A. fumigatus; and should alert physicians and healthcare professionals to do more vigorous environmental testing