Microsurgical reconstruction of the skull base and midface after orbitomaxillary resections for malignant tumors

Background. Orbitomaxillary resection includes exenteration of the orbital contents with resection of the inferior orbital and medial walls. The main goals are: reconstruction of soft tissue and bone structure defects, tamponade of the orbital cavity and/or its preparation for further ocular prosthetics, and reconstruction of the skull base defect. The purpose of the study to present the immediate results of orbitomaxillary resections in patients with malignant neoplasms of the skull base and midface. Material and methods. Between 2014 and 2020, 6 patients who previously underwent surgery for primary cancer (n=3) and recurrent cancer (n=3) were treated at the Head and Neck cancer department of N.N. Blokhin National medical Research center of oncology. To reconstruct defects after resection of bone structures (maxilla, frontal and nasal bones) and skin, a musculocutaneous alt-flap was used in 3 (50 %) cases and a fascial skin radial flap in 3 (50 %) cases. Results. The aesthetic result was assessed in 6 patients. In all cases, a satisfactory result was obtained. None of the patients who underwent resection of the dura mater followed by reconstruction had no symptoms of liquorrhea in the postoperative period. Conclusion. Flap selection depends on the defect size. In cases with a small defect size (up to 70 cm3), reconstruction with the radial fascial skin flap can be performed. If the defect size is more than 71 cm3, reconstruction with musculocutaneous alt flap can be the method of choice.

Fully Automatic Knee Bone Detection and Segmentation on Three-Dimensional MRI

In the medical sector, three-dimensional (3D) images are commonly used like computed tomography (CT) and magnetic resonance imaging (MRI). The 3D MRI is a non-invasive method of studying the soft-tissue structures in a knee joint for osteoarthritis studies. It can greatly improve the accuracy of segmenting structures such as cartilage, bone marrow lesion, and meniscus by identifying the bone structure first. U-net is a convolutional neural network that was originally designed to segment the biological images with limited training data. The input of the original U-net is a single 2D image and the output is a binary 2D image. In this study, we modified the U-net model to identify the knee bone structures using 3D MRI, which is a sequence of 2D slices. A fully automatic model has been proposed to detect and segment knee bones. The proposed model was trained, tested, and validated using 99 knee MRI cases where each case consists of 160 2D slices for a single knee scan. To evaluate the model’s performance, the similarity, dice coefficient (DICE), and area error metrics were calculated. Separate models were trained using different knee bone components including tibia, femur, patella, as well as a combined model for segmenting all the knee bones. Using the whole MRI sequence (160 slices), the method was able to detect the beginning and ending bone slices first, and then segment the bone structures for all the slices in between. On the testing set, the detection model accomplished 98.79% accuracy and the segmentation model achieved DICE 96.94% and similarity 93.98%. The proposed method outperforms several state-of-the-art methods, i.e., it outperforms U-net by 3.68%, SegNet by 14.45%, and FCN-8 by 2.34%, in terms of DICE score using the same dataset.

Application of decellularized bone matrix as a bioscaffold in bone tissue engineering

Autologous bone grafts are commonly used as the gold standard to repair and regenerate diseased bones. However, they are strongly associated with postoperative complications, especially at the donor site, and increased surgical costs. In an effort to overcome these limitations, tissue engineering (TE) has been proposed as an alternative to promote bone repair. The successful outcome of tissue engineering depends on the microstructure and composition of the materials used as scaffold. Decellularized bone matrix-based biomaterials have been applied as bioscaffolds in bone tissue engineering. These biomaterials play an important role in providing the mechanical and physical microenvironment needed by cells to proliferate and survive. Decellularized extracellular matrix (dECM) can be used as a powder, hydrogel and electrospun scaffolds. These bioscaffolds mimic the native microenvironment due to their structure similar to the original tissue. The aim of this review is to highlight the bone decellularization techniques. Herein we discuss: (1) bone structure; (2) properties of an ideal scaffold; (3) the potential of decellularized bone as bioscaffolds; (4) terminal sterilization of decellularized bone; (5) cell removing confirmation in decellularized tissues; and (6) post decellularization procedures. Finally, the improvement of bone formation by dECM and the immunogenicity aspect of using the decellularized bone matrix are presented, to illustrate how novel dECM-based materials can be used as bioscaffold in tissue engineering. A comprehensive understanding of tissue engineering may allow for better incorporation of therapeutic approaches in bone defects allowing for bone repair and regeneration.

Perfused Platforms to Mimic Bone Microenvironment at the Macro/Milli/Microscale: Pros and Cons

As life expectancy increases, the population experiences progressive ageing. Ageing, in turn, is connected to an increase in bone-related diseases (i.e., osteoporosis and increased risk of fractures). Hence, the search for new approaches to study the occurrence of bone-related diseases and to develop new drugs for their prevention and treatment becomes more pressing. However, to date, a reliable in vitro model that can fully recapitulate the characteristics of bone tissue, either in physiological or altered conditions, is not available. Indeed, current methods for modelling normal and pathological bone are poor predictors of treatment outcomes in humans, as they fail to mimic the in vivo cellular microenvironment and tissue complexity. Bone, in fact, is a dynamic network including differently specialized cells and the extracellular matrix, constantly subjected to external and internal stimuli. To this regard, perfused vascularized models are a novel field of investigation that can offer a new technological approach to overcome the limitations of traditional cell culture methods. It allows the combination of perfusion, mechanical and biochemical stimuli, biological cues, biomaterials (mimicking the extracellular matrix of bone), and multiple cell types. This review will discuss macro, milli, and microscale perfused devices designed to model bone structure and microenvironment, focusing on the role of perfusion and encompassing different degrees of complexity. These devices are a very first, though promising, step for the development of 3D in vitro platforms for preclinical screening of novel anabolic or anti-catabolic therapeutic approaches to improve bone health.

Effect of Nesfatin-1 on Rat Humerus Mechanical Properties under Quasi-Static and Impact Loading Conditions

The investigations on the response of bone tissue under different loading conditions are important from clinical and engineering points of view. In this paper, the influence of nesfatin-1 administration on rat humerus mechanical properties was analyzed. The classical three-point bending and impact tests were carried out for three rat bone groups: control (SHO), the humerus of animals under the conditions of established osteopenia (OVX), and bones of rats receiving nesfatin-1 after ovariectomy (NES). The experiments proved that the bone strength parameters measured under various mechanical loading conditions increased after the nesfatin-1 administration. The OVX bones were most susceptible to deformation and had the smallest fracture toughness. The SEM images of humerus fracture surface in this group showed that ovariectomized rats had a much looser bone structure compared to the SHO and NES females. Loosening of the bone structure was also confirmed by the densitometric and qualitative EDS analysis, showing a decrease in the OVX bones’ mineral content. The samples of the NES group were characterized by the largest values of maximum force obtained under both quasi-static and impact conditions. The energies absorbed during the impact and the critical energy for fracture (from the three-point bending test) were similar for the SHO and NES groups. Statistically significant differences were observed between the mean Fi max values of all analyzed sample groups. The obtained results suggest that the impact test was more sensitive than the classical quasi-static three-point bending one. Hence, Fi max could be used as a parameter to predict bone fracture toughness.

Dynamics of the mandible bone tissue condition after the dental implantation and shockwave therapy

Background. The problem of restoration the integrity of the dentition after tooth loss remains one of the most problematic dental issues. Мodern dental technologies open a promising direction in its solution, in particular - the method of dental implantation. Objective. The aim of our work was to study the changes that occur in the bone tissue of the mandible after implantation of titanium foam and to determine the effect of shock wave therapy (SWT) on its structure restoration. Methods. The study was performed on 15 adult rabbits aged 6-7 months, weighing 2.5-3 kg. The animals from the experimental groups were implanted with titanium pin, 3 mm long. The pin was implanted under combined anesthesia bilaterally into the body of the mandible. One day after the operation, the animals received SWT 500 pulses with a frequency of 5 Hz and a maximum pressure at the wavefront of 1.2 Bar per implantation site using the device Storz Medical Master Plus MP 100. The animals were removed from the experiment on 15-th day, after which the mandible was disarticulated and radiographically performed. The obtained results were statistically significant. The differences at p<0.05 were considered significant. Results. The results showed that the bone tissue of the jaws during implantation undergoes traumatic injury, the results of which, two weeks after surgery on radiographs we can clearly see a violation of the bone tissue structure and a significant increase in its density. Using the SWT method, we obtained a positive dynamics of bone density after titanium pin implantation and slight Rh-changes in bone structure compared with normal. Conclusion. Аfter implantation with titanium pin the bone density of the rabbit lower jaw body is significantly reduced, X-ray shows the heterogeneity of bone structure, areas of sclerosis are expressed. Shock wave therapy helps to restore the quality of bone tissue, this is confirmed by the fact that the density indicators are close to the norm and X-ray shows some separate small areas of restructuring of bone tissue heterogeneity, mainly due to merging the pattern of the bone trabeculae of the bone cancellous part.

The Regulation of Collagen Processing by miRNAs in Disease and Possible Implications for Bone Turnover

This article describes several recent examples of miRNA governing the regulation of the gene expression involved in bone matrix construction. We present the impact of miRNA on the subsequent steps in the formation of collagen type I. Collagen type I is a main factor of mechanical bone stiffness because it constitutes 90–95% of the organic components of the bone. Therefore, the precise epigenetic regulation of collagen formation may have a significant influence on bone structure. We also describe miRNA involvement in the expression of genes, the protein products of which participate in collagen maturation in various tissues and cancer cells. We show how non-collagenous proteins in the extracellular matrix are epigenetically regulated by miRNA in bone and other tissues. We also delineate collagen mineralisation in bones by factors that depend on miRNA molecules. This review reveals the tissue variability of miRNA regulation at different levels of collagen maturation and mineralisation. The functionality of collagen mRNA regulation by miRNA, as proven in other tissues, has not yet been shown in osteoblasts. Several collagen-regulating miRNAs are co-expressed with collagen in bone. We suggest that collagen mRNA regulation by miRNA could also be potentially important in bone metabolism.