Compressive strength of interbody cages in the lumbar spine: the effect of cage shape, posterior instrumentation and bone density

One goal of interbody fusion is to increase the height of the degenerated disc space. Interbody cages in particular have been promoted with the claim that they can maintain the disc space better than other methods. There are many factors that can affect the disc height maintenance, including graft or cage design, the quality of the surrounding bone and the presence of supplementary posterior fixation. The present study is an in vitro biomechanical investigation of the compressive behaviour of three different interbody cage designs in a human cadaveric model. The effect of bone density and posterior instrumentation were assessed. Thirty-six lumbar functional spinal units were instrumented with one of three interbody cages: (1) a porous titanium implant with endplate fit (Stratec), (2) a porous, rectangular carbon-fibre implant (Brantigan) and (3) a porous, cylindrical threaded implant (Ray). Posterior instrumentation (USS) was applied to half of the specimens. All specimens were subjected to axial compression displacement until failure. Correlations between both the failure load and the load at 3 mm displacement with the bone density measurements were observed. Neither the cage design nor the presence of posterior instrumentation had a significant effect on the failure load. The loads at 3 mm were slightly less for the Stratec cage, implying lower axial stiffness, but were not different with posterior instrumentation. The large range of observed failure loads overlaps the potential in vivo compressive loads, implying that failure of the bone-implant interface may occur clinically. Preoperative measurements of bone density may be an effective tool to predict settling around interbody cages

Narrowing of band gap at source/drain contact scheme of nanoscale InAs–nMOS

A multi-scale simulation study of Ni/InAs nano-scale contact aimed for the sub-14 nm technology is carried out to understand material and transport properties at a metal-semiconductor interface. The deposited Ni metal contact on an 11 nm thick InAs channel forms an 8.5 nm thick InAs leaving a 2.5 nm thick InAs channel on a p-type doped (1×1016 cm-3) AlAs0.47Sb0.53 buffer. The density functional theory (DFT) calculations reveal a band gap narrowing in the InAs at the metal-semiconductor interface. The one-dimensional (1D) self-consistent Poisson-Schrödinger transport simulations using real-space material parameters extracted from the DFT calculations at the metal-semiconductor interface, exhibiting band gap narrowing, give a specific sheet resistance of Rsh = 90.9 Ω/sq which is in a good agreement with an experimental value of 97 Ω/sq

Differential Histopathological and Behavioral Outcomes Eight Weeks after Rat Spinal Cord Injury by Contusion, Dislocation, and Distraction Mechanisms

The objective of this study was to compare the long-term histological and behavioral outcomes after spinal cord injury (SCI) induced by one of three distinct biomechanical mechanisms: dislocation, contusion, and distraction. Thirty male Sprague-Dawley rats were randomized to incur a traumatic cervical SCI by one of these three clinically relevant mechanisms. The injured cervical spines were surgically stabilized, and motor function was assessed for the following 8 weeks. The spinal cords were then harvested for histologic analysis. Quantification of white matter sparing using Luxol fast blue staining revealed that dislocation injury caused the greatest overall loss of white matter, both laterally and along the rostrocaudal axis of the injured cord. Distraction caused enlarged extracellular spaces and structural alteration in the white matter but spared the most myelinated axons overall. Contusion caused the most severe loss of myelinated axons in the dorsal white matter. Immunohistochemistry for the neuronal marker NeuN combined with Fluoro Nissl revealed that the dislocation mechanism resulted in the greatest neuronal cell losses in both the ventral and dorsal horns. After the distraction injury mechanism, animals displayed no recovery of grip strength over time, in contrast to the animals subjected to contusion or dislocation injuries. After the dislocation injury mechanism, animals displayed no improvement in the grooming test, in contrast to the animals subjected to contusion or distraction injuries. These data indicate that different SCI mechanisms result in distinct patterns of histopathology and behavioral recovery. Understanding this heterogeneity may be important for the future development of therapeutic interventions that target specific neuropathology after SCI

Augmenting virtual spaces: affective feedback in computer games

Computer games can be considered a form of art insomuch as they are critiqued, revered and collected for their aesthetics in addition to their ludic qualities. Perhaps most significantly, computer games incite a plethora of emotional responses in their players as a deliberate and defining mechanism. However, unlike other forms of traditional media and art, another key feature of games is their intrinsic interactivity, reliance upon technology and non-linearity. These traits make them particularly noteworthy if one wishes to consider how art forms might respond and adapt to their audience’s emotions. The field of affective computing has been developing for several decades and many of its applications have been in the analysis and modelling of emotional responses to forms of media, such as music and film. In gaming, recent developments have led to an increasing number of consumer-grade biofeedback devices which are available on the market, some of which are explicitly sold as ‘gaming controllers’, giving rise to greater opportunity for affective feedback to be incorporated. In this chapter, a review is provided of the affective gaming field. Specifically, it is proposed that these developments give rise to interesting opportunities whereby virtual environments can be augmented with player affective and contextual information. An overview is provided of affective computing fundamentals and their manifestation in developments relating specifically to games. The chapter considers the impact this biometric information has upon games players, in terms of their experience of the game and the social connections between competitors. A number of associated practical and technological challenges are highlighted along with areas for future research and development activities. It is hoped that by exploring these developments in gaming that the longer established forms of art and media might be inspired to further embrace the possibilities offered by utilising affective feedback

Indium phosphide heterojunction bipolar transistors as magnetic field sensors

This paper describes the design, fabrication, and characterization of a sensor for moderately strong magnetic fields (~0.1 T and above) based on a heterojunction bipolar transistor (HBT). Our ferromagnetic-semiconductor hybrid device consisted of a mesa-isolated multistep single heterojunction InGaAs/InP HBT with an integrated 3-D thin-film magnetic structure formed on the base-collector mesa. The latter structure was optimized by simulation to focus the magnetic field into the base region of the HBT, where the interaction of the charge carriers and the magnetic field takes place. We report a minimum signal-to-noise ratio for the sensors of 36.4 dB, magnetic field sensitivity of at least 33.9% T-1, an angle sensitivity of 10% rad-1, and an equivalent noise of at most 2 mT. The sensors are novel in that they are fabricated using a highly scaled layer design of the type used in radio-frequency monolithic microwave integrated circuits and are suitable for incorporation in such circuits to increase functionality for low overhead in, for example, distributed sensor networks

An ultra-low power OOK RF transceiver for wireless sensor networks

An ultra-low power On-Off Keying (OOK) RF transceiver using a quasi-Monolithic Microwave Integrated Circuits (quasi-MMICs) method has been designed and fabricated on GaAs substrate for wireless sensor networks. To minimize power consumption, the transceiver was implemented using commercial 0.25 mu mx200 mu m Pseudomorphic High Electron Mobility Transistors (PHEMTs), with a switched oscillator for transmitter and direct detection architecture for receiver. The transceiver successfully operates at the center frequency of 10GHz for compact antenna and with ultra-low power consumption and shows an output power of -15dBm for the transmitter, an output voltage of 35mV(P-P) at an input power of -40dBm for the receiver and a total power consumption of less than 0.9mW

Low complexity, low power, 10 GHz super-regenerative transceiver

In this paper a 10 GHz quasi-Hybrid/MMIC super-regenerative transceiver/antenna chip is presented. The circuit is the highest frequency super-regenerative transceiver presented in the literature and is amongst the lowest power - certainly the lowest power at X-band frequency. The chip is fabricated on GaAs substrate and uses a MMIC process for the passive components and an RFMD PHEMT chip device bonded into the circuit for the active components. The transceiver chip measures 10 x 10 mm and consumes 0.75 mW Tx and 0.9mW Rx. When mounted into a pcb carrier substrate containing antenna, bias circuitry and low pass filtering the board measures 26 x 42 mm and operates over a range of 1m

The relative importance of vertebral bone density and disc degeneration in spinal flexibility and interbody implant performance. An in vitro study

An in vitro biomechanical investigation in the human lumbar spine focuses on the functional significance of vertebral bone density and intervertebral disc degenerations

Regional trabecular morphology assessed by micro-CT is correlated with failure of aged thoracic vertebrae under a posteroanterior load and may determine the site of fracture

Introduction: Spinal mobilization is commonly used in the treatment of patients with back pain, including individuals with osteoporosis. Previous data indicated that traditional predictors of skeletal failure–lateral or anteroposterior bone mineral density (BMD) by dual energy X-ray absorptiometry (DXA) or geometry of the spinous process or vertebral body–do not predict failure load during posteroanterior spinal mobilization. Morphological differences and inhomogeneities in BMD may have important effects on vertebral strength but integral BMD values by DXA cannot reflect these potentially important differences. We investigated the determinants of spinal fracture using μCT. Materials and methods: We measured failure load and failure site in 11 T5–8 cadaveric specimens (mean age 78 years) when a posteroanterior load was applied at the spinous process of T6 using a servohydraulic material testing machine. Radiography and CT scan were used to verify failure site. We observed no damage to the adjacent T7 vertebrae following the T6 posteroanterior failure test. The T7 vertebrae were sectioned to produce regional samples of the spinous process, the lamina and a vertebral body core. Each sample was scanned with μCT to measure bone microarchitectural parameters. We segmented and analysed four trabecular regions (spinous process base and middle, central lamina and central vertebral body). We used one-way repeated measures ANOVA to compare regions and computed Pearson correlations to assess the relation between PA failure load of T6 and the morphological parameters of T7. Results: The BV/TV at the base or middle of the T7 spinous process (fracture sites), Tb.N and Tb.Th at the base were significantly correlated with posteroanterior failure load of T6 (BV/TV base: r=0.74, p=0.01; BV/TV middle: r=0.73, p=0.01; Tb.N base: r=0.64, p=0.03; Tb.Th base: r=0.65, p=0.03). The Tb.Th of the lamina was significantly greater than Tb.Th of the spinous process base (p=0.002). Conclusions: Whereas previous data indicated that BMD by DXA was not a good predictor of posteroanterior failure load, regional BV/TVof the spinous process base and middle regions, the sites of fracture, are correlated with posteroanterior failure load. Trabecular thickness differed significantly between the base of the spinous process and the lamina, and may have influenced the site of fracture