Volume 59, Issue 3

Induction of new bone formation through distraction osteogenesis (DO) has widespread clinical applications in the treatment of bone defects, limb deformities, and fracture nonunion. However, a lengthy period of external fixation is usually needed to allow the new bone to consolidate, and complications such as refracture at the distraction gap are often seen. To date, little has been reported on the use of biomaterials as carrier materials for sustained release of growth factors in bone regeneration. One area of focus is the delivery of osteogenic factors in an attempt to modulate the formation of bone. These applications allow the efficient delivery of osteogenic growth factors directly into the defect site, resulting in localized drug delivery and reducing possible toxic systemic effects. However, studies on these biomaterials have only just begun; there are still many unanswered questions and unexplored frontiers that can greatly influence the role of nanostructured materials as improved bone implants. This review article seeks to demonstrate the potential of biomaterials to improve biological applications pertinent to osteodistraction.

This work reviews the tremendous development in the field of vascular graft tissue engineering driven by a clear and increasing clinical need for functional vascular replacements able to grow and remodel. The different strategies to tissue engineer blood vessels are presented, from the classical approach of a living implant generated in vitro by conditioning a cell-seeded scaffold to remarkable paradigm shifts either i) toward a completely biology-driven strategy (scaffold-free approaches) or ii) the opposite tendency of cell-free scaffolds aiming at eliciting the host reaction for in situ tissue engineering. In the scaffold-based approaches emphasis is given to the material choice.

In only a few published finite element (FE) simulations have muscle forces been applied to the spine. Recently, muscle forces determined using an inverse static (IS) model of the spine were transferred to a spinal FE model, and the effect of methodical parameters was investigated. However, the sensitivity of anthropometric differences between FE and IS models, such as body height and spinal orientation, was not considered. The aim of this sensitivity study was to determine the influence of those differences on the intervertebral rotations (IVRs) following the transfer of muscle forces from an IS model to a FE model. Muscle forces were estimated for 20° flexion and 10° extension of the upper body using an inverse static musculoskeletal model. These forces were subsequently transferred to a nonlinear FE model of the spino-pelvic complex, which includes 243 muscle fascicles. Deviations of body height (±10 cm), spinal orientation in the sagittal plane (±10°), and body weight (±10 kg) between both models were intentionally generated, and their influences on IVRs were determined. The changes in each factor relative to their corresponding reference value of the IS model were calculated. Deviations in body height, spinal orientation, and body weight resulted in maximum changes in the IVR of 19.2%, 26% and 4.2%, respectively, relative to T12-S1 IVR. When transferring muscle forces from an IS to a FE model, it is crucial that both models have the same spinal orientation and height. Additionally, the body weight should be equal in both models.

Self-tapping dental implants offer the advantage of shortening the surgical insertion time of the implants and improve primary stability in poor bone quality. Using finite element analysis, a series of self-tapping implants with different diameters and lengths have been analysed with respect to their load transfer to the alveolar bone under axial and 45° loading conditions with a total force of 300 N. The implants were inserted in idealised bone beds with cortical thicknesses of 2 and 3 mm. The implants were considered to have osseointegrated condition. A linear decrease of the maximum stresses and strains in the bone around the implants was observed by increasing the diameter of the implants from 3.7 to 5.5 mm regardless of the length of these implants. Lateral loading of the implants caused a critical increase of the stresses and strains in the bone, in particular with the thin cortical layer of 2 mm. The determined biomechanical characteristics of the self-tapping implants showed their applicability in different bone qualities even with extreme reduced length of 7 mm.

Background: The aim of our study was to introduce a so-called “neutral shoe” as a tool to assess reference values for dynamic pedobarographic investigations. Materials and methods: Twelve healthy volunteers were asked to participate. During the first trial the participants were asked to walk with a neutral shoe (Breidbach, Germany). The second trial was performed with the running shoe “Faas 500” (Puma SE, Germany). Peak plantar pressure values were analyzed from nine foot regions using the Pedar ® X system (Novel Inc., Munich, Germany). Results: The mean peak pressure reduction for the total foot was 36% under the left (non-preferred) foot and 32% for the right (preferred) foot. A statistically significant reduction of peak pressure was observed for eight regions, from a mean 14% peak pressure reduction under the right metatarsal head 1 up to a 41% peak pressure reduction under the right big toe. Conclusions: The neutral shoe is a feasible tool to assess reference values for dynamic pedobarography. Such a reference tool may help to standardise several steps in the development and construction of shoes and orthotic devices.

Up until now, the noise and intensity inhomogeneity are considered one of the major drawbacks in the field of brain magnetic resonance (MR) image segmentation. This paper introduces the energy image feature approach for intensity inhomogeneity correction. Our approach of segmentation takes the advantage of image features and preserves the advantages of the level set methods in region-based active contours framework. The energy image feature represents a new image obtained from the original image when the pixels’ values are replaced by local energy values computed in the 3×3 mask size. The performance and utility of the energy image features were tested and compared through two different variants of level set methods: one as the encompassed local and global intensity fitting method and the other as the selective binary and Gaussian filtering regularized level set method. The reported results demonstrate the flexibility of the energy image feature to adapt to level set segmentation framework and to perform the challenging task of brain lesion segmentation in a rather robust way.

Electroencephalography (EEG) is often employed to measure electrical activity in the living human brain. Simulation studies can help unravel how the brain electrical activity pattern generates the EEG signal, still a widely unresolved question. This article describes a method to simulate brain electrical activity by using neuronal populations of a neural mass model. Implementing these populations in a finite element model of the head offers the opportunity to investigate the influence of each group of neurons to the scalp potential. This model is based on structural magnetic resonance imaging data to specify tissue composition, and diffusion tensor imaging data to model local anisotropy. We simulated the EEG signals of five neuronal populations generating α waves in the visual cortex. Our results indicate that radially oriented sources dominate over tangential sources in the generation of the scalp signal. Investigating the influence of anisotropic conductivity, we found small differences in topography and phase and larger ones for the potential amplitude compared with an isotropic conductivity distribution. The outcome of this article is a fast method based on superposition of sources for simulating time-dependent EEG signals, which can be used for further studies of neurodegenerative diseases.

Emotional intelligence is one of the key research areas in human-computer interaction. This paper reports the development of an emotion recognition system using facial electromyogram (EMG) signals focusing the ambiguity on the frequency ranges used by different research works. The six emotional states (happiness, sadness, fear, surprise, disgust, and neutral) were elicited in 60 subjects using audio visual stimuli. Statistical features were extracted from the signals at high, medium, low, and very low frequency levels. They were then classified using four classifiers – naïve Bayes, regression tree, K-nearest neighbor, and fuzzy K-nearest neighbor, and the performance of the system at the different frequency levels were studied using three metrics, namely, % accuracy, sensitivity, and specificity. The post hoc tests in analysis of variance (ANOVA) indicate that the features contain significant emotional information at the very low-frequency range (<0.08 Hz). Similarly, the performance metrics of the classifiers also ensure better recognition rate at very low-frequency range. Though this range of frequency has not been used by researchers, the results of this work indicate that it should not be ignored. Further investigation of the very low frequency range to identify emotional information is still in progress.

In this study, a “time domain” system based on a partial coherence interferometry method is presented. The classic technique of varying the reference arm using a linear motor is replaced by the use of a rotating glass cube. The theoretical definition of the variation of the optical path length and first measurements in a human model eye and a real human eye are presented.

Use of transcutaneous inductive links is a widely known method for the wireless powering of bio-implanted devices such as implanted microsystems. The design of the coil for inductive links is generally not optimal. In this study, inductive links were used on the basis of the small loop antenna theory to reduce the effects of lateral coil misalignments on the biological human tissue model at 13.56 MHz. The tissue, which measures 60 mm×70 mm×5 mm, separates the reader and the implanted coils. The aligned coils and the lateral misalignment coils were investigated in different parametric x -distance misalignments. The optimal coil layout was developed on the basis of the layout rules presented in previous studies. Results show that the gain around the coils, which were separated by wet and dry skin, was constant and confirmed the omnidirectional radiation pattern even though the lateral misalignment between coils was smaller or greater than the implanted coil radius. This misalignment can be <4 mm or >6 mm up to 8 mm. Moreover, coil misalignments and skin condition do not affect the efficient performance of the coil.