Layer Of Bone Research Articles

Three‐dimensional bioprinting biphasic multicellular living scaffold facilitates osteochondral defect regeneration

AbstractDue to tissue lineage variances and the anisotropic physiological characteristics, regenerating complex osteochondral tissues (cartilage and subchondral bone) remains a great challenge, which is primarily due to the distinct requirements for cartilage and subchondral bone regeneration. For cartilage regeneration, a significant amount of newly generated chondrocytes is required while maintaining their phenotype. Conversely, bone regeneration necessitates inducing stem cells to differentiate into osteoblasts. Additionally, the construction of the osteochondral interface is crucial. In this study, we fabricated a biphasic multicellular bioprinted scaffold mimicking natural osteochondral tissue employing three‐dimensional (3D) bioprinting technology. Briefly, gelatin‐methacryloyl (GelMA) loaded with articular chondrocytes and bone marrow mesenchymal stem cells (ACs/BMSCs), serving as the cartilage layer, preserved the phenotype of ACs and promoted the differentiation of BMSCs into chondrocytes through the interaction between ACs and BMSCs, thereby facilitating cartilage regeneration. GelMA/strontium‐substituted xonotlite (Sr‐CSH) loaded with BMSCs, serving as the subchondral bone layer, regulated the differentiation of BMSCs into osteoblasts and enhanced the secretion of cartilage matrix by ACs in the cartilage layer through the slow release of bioactive ions from Sr‐CSH. Additionally, GelMA, serving as the matrix material, contributed to the reconstruction of the osteochondral interface. Ultimately, this biphasic multicellular bioprinted scaffold demonstrated satisfactory simultaneous regeneration of osteochondral defects. In this study, a promising strategy for the application of 3D bioprinting technology in complex tissue regeneration was proposed.

Exploring the biocompatibility and healing activity of actinobacterial-enhanced reduced nano-graphene oxide in in vitro and in vivo model and induce bone regeneration through modulation of OPG/RANKL/RUNX2/ALP pathways.

The development of cost-effective, simple, environment-friendly biographene is an area of interest. To accomplish environmentally safe, benign culturing that has advantages over other methods to reduce the graphene oxide (GO), extracellular metabolites from actinobacteria associated with mushrooms were used for the first time. Bactericidal effect of GO against methicillin-resistant Staphylococcus aureus, antioxidant activity, and hydroxyapatite-like bone layer formation, gene expression analysis and appropriate biodegradation of the microbe-mediated synthesis of graphene was studied. Isolated extracellular contents Streptomyces achromogenes sub sp rubradiris reduced nano-GO to graphene (rGO), which was further examined by spectrometry and suggested an efficient conversion and significant reduction in the intensity of all oxygen-containing moieties and shifted crystalline peaks. Electron microscopic results also suggested the reduction of GO layer. In addition, absence of significant toxicity in MG-63 cell line, intentional free radical scavenging prowess, liver and kidney histopathology, and Wistar rat bone regeneration through modulation of OPG/RANKL/RUNX2/ALP pathways show the feasibility of the prepared nano GO. The study demonstrates the successful synthesis of biographene from actinobacterial extracellular metabolites, its potential biomedical applications, and its promising role in addressing health and environmental concerns.

Customized 3D‐printed heterogeneous porous titanium scaffolds for bone tissue engineering

AbstractBone defect is a common clinical disease. Due to the uncertainty of trauma or infection areas, customized size features are often required for bone substitutes. By inspiration of the natural bone structure, this study designs porous scaffolds with a biomimetic design perspective by using different inner and outer pore units. The outer pore units adopt body‐centered cubic (BCC) structure to simulate the weight‐bearing function of human cortical bone, while inner pore units using I‐Wrapped Package structure, a kind of three periods minimum surface, to obtain a good permeability and simulates the inner layer of cancellous bone. To further regulate the overall modulus of the scaffold within the range of natural bone modulus in the human body, the scaffold was designed to axial gradient structure. Compression experiments were conducted, and the results indicated that when the volume fraction linearly increased from 20% to 50%, the Young's modulus was close to the cortical bone modulus in the human body. In vitro cell experiments further proved that osteoblasts have good cellular activity and spreading morphology on the surface of this scaffold. The customized 3D‐printed heterogeneous porous titanium scaffold has great application potential in bone tissue engineering.

Temporal bone marrow of the rat and its connections to the inner ear.

Calvarial bone marrow has been found to be central in the brain immune response, being connected to the dura through channels which allow leukocyte trafficking. Temporal bone marrow is thought to play important roles in relation to the inner ear, but is still largely uncharacterized, given this bone complex anatomy. We characterized the geometry and connectivity of rat temporal bone marrow using lightsheet imaging of cleared samples and microCT. Bone marrow was identified in cleared tissue by cellular content (and in particular by the presence of megakaryocytes); since air-filled cavities are absent in rodents, marrow clusters could be recognized in microCT scans by their geometry. In cleared petrosal bone, autofluorescence allowed delineation of the otic capsule layers. Within the endochondral layer, bone marrow was observed in association to the cochlear base and vestibule, and to the cochlear apex. Cochlear apex endochondral marrow (CAEM) was a separated cluster from the remaining endochondral marrow, which was therefore defined as "vestibular endochondral marrow" (VEM). A much larger marrow island (petrosal non-endochondral marrow, PNEM) extended outside the otic capsule surrounding semicircular canal arms. PNEM was mainly connected to the dura, through bone channels similar to those of calvarial bone, and only a few channels were directed toward the canal periosteum. On the contrary, endochondral bone marrow was well connected to the labyrinth through vascular loops (directed to the spiral ligament for CAEM and to the bony labyrinth periosteum for VEM), and to dural sinuses. In addition, CAEM was also connected to the tensor tympani fossa of the middle ear and VEM to the endolymphatic sac. Endochondral marrow was made up of small lobules connected to each other and to other structures by channels lined by elongated macrophages, whereas PNEM displayed larger lobules connected by channels with a sparse macrophage population. Our data suggest that the rat inner ear is surrounded by bone marrow at the junctions with middle ear and brain, most likely with "customs" role, restricting pathogen spread; a second marrow network with different structural features is found within the endochondral bone layer of the otic capsule and may play different functional roles.

Feasibility of Using Intraoperative Neurophysiological Monitoring for Detecting Bone Layer of Cervical Spine Surgery.

Intraoperative neurophysiological monitoring (IONM) as a guide to bone layer estimation was examined during posterior cervical spine lamina grinding. To explore the feasibility of IONM to estimate bone layer thickness. Cervical laminoplasty is a classic operation for cervical spondylosis. To increase safety and accuracy, surgery-assistant robots are currently being studied. It combines the advantages of various program awareness methods to form a feasible security strategy. In the field of spinal surgery, robots have been successfully used to help place pedicle screws. IONM is used to monitor intraoperative nerve conditions in spinal surgery. This study was designed to explore the feasibility of adding IONM to robot safety strategies. Chinese miniature pig model was used. Electrodes were placed on the lamina, and the minimum stimulation threshold of DNEP for each lamina was measured (Intact lamina, IL). The laminae were ground to measure the DNEP threshold after incomplete grinding (Inner cortical bone preserved, ICP) and complete grinding (Inner cortical bone grinded, ICG). Subsequently, the lateral cervical mass screw canal drilling was performed, and the t-EMG threshold of the intact and perforated screw canals was measured and compared. The threshold was significantly lower than that of the recommended threshold of DENP via percutaneous cervical laminae measurement. The DNEP threshold decreases with the process of laminae grinding. The DNEP threshold of the IL group was significantly higher than ICP and ICG group, while there was no significant difference between the ICP group and the ICG group. There was no significant relationship between the integrity of the cervical spine lateral mass screw path and t-EMG threshold. It is feasible to use DENP threshold to estimate lamina thickness. Cervical lateral mass screw canals by t-EMG showed no help to evaluate the integrity.

Enhancing spinal bone anchor pull-out resistance with an L-shaped anchor.

The success rate of spinal fusion surgery is mainly determined by the fixation strength of the spinal bone anchors. This study explores the use of an L-shaped spinal bone anchor that is intended to establish a macro-shape lock with the posterior cortical layer of the vertebral body, thereby increasing the pull-out resistance of the anchor. The performance of this L-shaped anchor was evaluated in lumbar vertebra phantoms (L1-L5) across four distinct perpendicular orientations (lateral, medial, superior, and inferior). During the pull-out experiments, the pull-out force, and the displacement of the anchor with respect to the vertebra was measured which allowed the determination of the maximal pull-out force (mean: 123 N ± 25 N) and the initial pull-out force, the initial force required to start motion of the anchor (mean: 23 N ± 16 N). Notably, the maximum pull-out force was observed when the anchor engaged the cortical bone layer. The results demonstrate the potential benefits of utilising a spinal bone anchor featuring a macro-shape lock with the cortical bone layer to increase the pull-out force. Combining the macro shape-lock fixation method with the conventional pedicle screw shows the potential to significantly enhance the fixation strength of spinal bone anchors.

Functionally graded hydrogels with opposing biochemical cues for osteochondral tissue engineering.

Osteochondral tissue (OC) repair remains a significant challenge in the field of musculoskeletal tissue engineering. OC tissue displays a gradient structure characterized by variations in both cell types and extracellular matrix components, from cartilage to the subchondral bone. These functional gradients observed in the native tissue have been replicated to engineer OC tissuein vitro. While diverse fabrication methods have been employed to create these microenvironments, emulating the natural gradients and effective regeneration of the tissue continues to present a significant challenge. In this study, we present the design and development of CMC-silk interpenetrating (IPN) hydrogel with opposing dual biochemical gradients similar to native tissue with the aim to regenerate the complete OC unit. The gradients of biochemical cues were generated using an in-house-built extrusion system. Firstly, we fabricated a hydrogel that exhibits a smooth transition of sulfated carboxymethyl cellulose (sCMC) and TGF-β1 (SCT gradient hydrogel) from the upper to the lower region of the IPN hydrogel to regenerate the cartilage layer. Secondly, a hydrogel with a hydroxyapatite (HAp) gradient (HAp gradient hydrogel) from the lower to the upper region was fabricated to facilitate the regeneration of the subchondral bone layer. Subsequently, we developed a dual biochemical gradient hydrogel with a smooth transition of sCMC + TGF-β1 and HAp gradients in opposing directions, along with a blend of both biochemical cues in the middle. The results showed that the dual biochemical gradient hydrogels with biochemical cues corresponding to the three zones (i.e. cartilage, interface and bone) of the OC tissue led to differentiation of bone-marrow-derived mesenchymal stem cells to zone-specific lineages, thereby demonstrating their efficacy in directing the fate of progenitor cells. In summary, our study provided a simple and innovative method for incorporating gradients of biochemical cues into hydrogels. The gradients of biochemical cues spatially guided the differentiation of stem cells and facilitated tissue growth, which would eventually lead to the regeneration of the entire OC tissue with a smooth transition from cartilage (soft) to bone (hard) tissues. This promising approach is translatable and has the potential to generate numerous biochemical and biophysical gradients for regeneration of other interface tissues, such as tendon-to-muscle and ligament-to-bone.

Acoustic Signal-Based Robotic Cutting Depth Control Under Uncertain Bone Layer Distribution

Acoustic Signal-Based Robotic Cutting Depth Control Under Uncertain Bone Layer Distribution

Controlled Mechanical Property Gradients Within a Digital Light Processing Printed Hydrogel-Composite Osteochondral Scaffold.

Tissue engineered scaffolds are needed to support physiological loads and emulate the micrometer-scale strain gradients within tissues that guide cell mechanobiological responses. We designed and fabricated micro-truss structures to possess spatially varying geometry and controlled stiffness gradients. Using a custom projection microstereolithography (μSLA) system, using digital light projection (DLP), and photopolymerizable poly(ethylene glycol) diacrylate (PEGDA) hydrogel monomers, three designs with feature sizes < 200μm were formed: (1) uniform structure with 1MPa structural modulus ( ) designed to match equilibrium modulus of healthy articular cartilage, (2) = 1MPa gradient structure designed to vary strain with depth, and (3) osteochondral bilayer with distinct cartilage ( = 1MPa) and bone ( = 7MPa) layers. Finite element models (FEM) guided design and predicted the local mechanical environment. Empty trusses and poly(ethylene glycol) norbornene hydrogel-infilled composite trusses were compressed during X-ray microscopy (XRM) imaging to evaluate regional stiffnesses. Our designs achieved target moduli for cartilage and bone while maintaining 68-81% porosity. Combined XRM imaging and compression of empty and hydrogel-infilled micro-truss structures revealed regional stiffnesses that were accurately predicted by FEM. In the infilling hydrogel, FEM demonstrated the stress-shielding effect of reinforcing structures while predicting strain distributions. Composite scaffolds made from stiff μSLA-printed polymers support physiological load levels and enable controlled mechanical property gradients which may improve in vivo outcomes for osteochondral defect tissue regeneration. Advanced 3D imaging and FE analysis provide insights into the local mechanical environment surrounding cells in composite scaffolds.

Trilayered biomimetic hydrogel scaffolds with dual-differential microenvironment for articular osteochondral defect repair

Commonly, articular osteochondral tissue exists significant differences in physiological architecture, mechanical function, and biological microenvironment. However, the development of biomimetic scaffolds incorporating upper cartilage, middle tidemark-like, and lower subchondral bone layers for precise articular osteochondral repair remains elusive. This study proposed here a novel strategy to construct the trilayered biomimetic hydrogel scaffolds with dual-differential microenvironment of both mechanical and biological factors. The cartilage-specific microenvironment was achieved through the grafting of kartogenin (KGN) into gelatin via p-hydroxyphenylpropionic acid (HPA)-based enzyme crosslinking reaction as the upper cartilage layer. The bone-specific microenvironment was achieved through the grafting of atorvastatin (AT) into gelatin via dual-crosslinked network of both HP-based enzyme crosslinking and glycidyl methacrylate (GMA)-based photo-crosslinking reactions as the lower subchondral bone layer. The introduction of tidemark-like middle layer is conducive to the formation of well-defined cartilage-bone integrated architecture. The in vitro experiments demonstrated the significant mechanical difference of three layers, successful grafting of drugs, good cytocompatibility and tissue-specific induced function. The results of in vivo experiments also confirmed the mechanical difference of the trilayered bionic scaffold and the ability of inducing osteogenesis and chondrogenesis. Furthermore, the articular osteochondral defects were successfully repaired using the trilayered biomimetic hydrogel scaffolds by the activation of endogenous recovery, which offers a promising alternative for future clinical treatment.

Evaluation of oVEMP and cVEMP in Superior Semicircular Canal Dehiscence Cases

Superior semisircular canal dehiscence (SSCD) is a disease of the audiovestibular system, which occurs as a result of the lack of bone layer covering the superior semisircular canal. The disease forms a third window in the inner ear due to the lack of bone layer. The third window that occurs forms a pseudo conductive type of hearing loss, which has decreased bone thresholds in the audiometry test. Vestibular evoked myogenic potentials are an electrophysiological measurement method in which the responses of the neck or eye muscles to an acoustic stimulus are recorded by means of electrodes. The purpose of use is to evaluate the functions of the urticle and saccule, which are the vestibular end organs. Therefore its primary purpose is to diagnose semicircular canal dehiscence. This review is based on research from the last decade; diagnostic results of ocular vestibular evoked myogenic potentials (oVEMP) and cervical vestibular evoked myogenic potentials (cVEMP) tests were evaluated in cases of superior semicircular canal dehiscence (SSCD). Studies indicate abnormal decreases in cVEMP test thresholds on the affected side in SSCD cases. Additionally, a significant increase in oVEMP amplitude on the affected side has been reported. Results; It shows that evaluating these two tests together will contribute to the diagnosis of semicircular canal dehiscence cases.

Using a Bone Density Measuring Micromotor to Distinguish Different Cortical/Cancellous Combinations in Vitro: A Study Using Polyurethane Foam Blocks.

To assess whether a recently introduced implant placement micromotor that provides site-specific, operator independent cancellous bone density measurements can detect the presence of a cortical bone layer and measure its thickness and density. An in vitro experiment was performed on six double-layer polyurethane foam blocks mimicking the jawbone with different cortical thickness/cancellous density combinations. The densities were measured using the micromotor after either removing the cortical layer or leaving it intact, both with and without irrigation. The results were compared by means of nonparametric statistical tests. Independent of irrigation, the micromotor detected the cortical layer when it was left intact and accurately estimated its thickness. The micromotor did not discriminate between blocks when they were considered separately, but it did when they were grouped into four or three classes. The present study suggests that the micromotor may represent a valid device to quantitatively assess bone quality and density. If the micromotor can quantitatively distinguish different cortical/cancellous bone combinations in humans, it may be a helpful tool for performing finely tuned, patient-tailored preparations of the implant seat, making tooth rehabilitation in challenging clinical conditions more predictable.

Fabrication of biomimetic scaffold through hybrid forming technique

AbstractBone tissue engineering procedures require the use of a scaffold with a sufficiently porous structure, which serves as a three‐dimensional template for cell attachment, followed by tissue regeneration and vascularization both in vitro and in vivo. This study aimed to create scaffold material with a unique hybrid forming that met these parameters. Slip casting and freeze‐drying processes were used with a hybrid forming approach to create a bone scaffold based on hydroxyapatite (HA) mimicking the structure of cortical and cancellous bones, respectively. HA was synthesized by the wet chemical precipitation method. Fourier‐transform infrared spectroscopy, dynamic light scattering, X‐ray diffraction, thermogravimetric analysis‐differential thermal analysis, Brunauer‐Emmett‐Teller, He Pycnometer, and scanning electron microscope analyses were performed to characterize the scaffold. According to analysis results, HA particle size was found at 137.8 nm. The optimum sintering temperature was determined to be 1300°C. The specific surface area of the HA powder was measured as 55.11 m2/g. The total open porosity of the hybrid scaffold was calculated as 70%. Scaffold successfully substituted both cancellous and cortical layers of bone regarding structural characteristics, porosity, and mechanical strength. Considering morphological characteristics, a hybrid scaffold might facilitate vascularization, osteoinduction, and osteoconduction. Research findings suggest that the hybrid design strongly resembled natural bone and is suitable for both load‐bearing and non‐bearing bones.

RADIOLOGICAL FEATURES OF THE LOCATION OF CYSTIC FORMATIONS IN THE MAXILLARY SINUS AND THEIR RELATIONSHIP WITH ALVEOLAR BONE PATHOLOGY OF THE UPPER JAW

The aim of the study. To study the features of the location of cystic formations in the maxillary sinus based on CT scans and to determine their relationship with the pathology of the upper jaw teeth.&#x0D; Materials and methods. The study involved the analysis of 552 head computed tomography scans of patients referred for examination by an otolaryngologist or dentist. The total number of individuals examined was 552, comprising 44.7% females and 55.3% males, aged 18-74 years. The investigation was conducted using the NewTom GO device with a measurement range of 155-172 mGy/cm±10%, with an error of ±4.24%. Statistical processing of data was carried out using the STATISTICA v.12.6 software.&#x0D; Results. Out of 552 computed tomography images analyzed, 92 images of individual maxillary sinuses (MS) of 79 patients with single cysts were selected. They were divided into two groups. Group 1 involved patients with cysts on the lower wall of MS (n=76). Group 2 included patients with cysts on other walls (n=16). The assessment of the ratio of 4, 5, 6, 7 tooth roots of the upper jaw to the lower wall of the upper jaw showed that the protrusion frequency in Group 1 was significantly higher (42.1%) compared to Group 2 (18.7%). Meanwhile, the average thickness of the bone over these teeth in Group 2 was significantly greater (3.4 ± 1.09 mm) than in Group 1 (1.9 ± 0.92 mm) (p=0.0003). In both patient groups, the greatest thickness was observed over tooth 4, and the smallest over tooth 7. Additionally, in 33.7% of cases, the cyst was associated with involvement of deep structures of the projecting teeth and the spread of inflammation to the lower wall of MS.&#x0D; Conclusions. Among patients referred by an otolaryngologist or dentist for CT examination to radiologically verify pathological processes in the nasal cavity, paranasal sinuses, and the upper jaw teeth, MS cysts were detected in 19.6% of cases, with 83% of them being localized in its lower parts. In patients with cysts located in the lower parts of MS, the roots protruding into the sinus cavity and a thinner layer of bone over them are more frequently observed compared to those where cysts are located in other areas of MS. In patients with cystic formations in the alveolar recess of MS, radiological signs of pathology of the upper jaw teeth are detected in 34% of cases.

Enhanced osteochondral regeneration with a 3D-Printed biomimetic scaffold featuring a calcified interfacial layer

The integrative regeneration of both articular cartilage and subchondral bone remains an unmet clinical need due to the difficulties of mimicking spatial complexity in native osteochondral tissues for artificial implants. Layer-by-layer fabrication strategies, such as 3D printing, have emerged as a promising technology replicating the stratified zonal architecture and varying microstructures and mechanical properties. However, the dynamic and circulating physiological environments, such as mass transportation or cell migration, usually distort the pre-confined biological properties in the layered implants, leading to undistinguished spatial variations and subsequently inefficient regenerations. This study introduced a biomimetic calcified interfacial layer into the scaffold as a compact barrier between a cartilage layer and a subchondral bone layer to facilitate osteogenic–chondrogenic repair. The calcified interfacial layer consisting of compact polycaprolactone (PCL), nano-hydroxyapatite, and tasquinimod (TA) can physically and biologically separate the cartilage layer (TA-mixed, chondrocytes-load gelatin methacrylate) from the subchondral bond layer (porous PCL). This introduction preserved the as-designed independent biological environment in each layer for both cartilage and bone regeneration, successfully inhibiting vascular invasion into the cartilage layer and preventing hyaluronic cartilage calcification owing to devascularization of TA. The improved integrative regeneration of cartilage and subchondral bone was validated through gross examination, micro-computed tomography (micro-CT), and histological and immunohistochemical analyses based on an in vivo rat model. Moreover, gene and protein expression studies identified a key role of Caveolin (CAV-1) in promoting angiogenesis through the Wnt/β-catenin pathway and indicated that TA in the calcified layer blocked angiogenesis by inhibiting CAV-1.

Evaluation of rabbit adipose derived stem cells fate in perfused multilayered silk fibroin composite scaffold for Osteochondral repair.

Development of osteochondral tissue engineering approaches using scaffolds seeded with stem cells in association with mechanical stimulations has been recently considered as a promising technique for the repair of this tissue. In this study, an integrated and biomimetic trilayered silk fibroin (SF) scaffold containing SF nanofibers in each layer was fabricated. The osteogenesis and chondrogenesis of stem cells seeded on the fabricated scaffolds were investigated under a perfusion flow. 3-Dimethylthiazol-2,5-diphenyltetrazolium bromide assay showed that the perfusion flow significantly enhanced cell viability and proliferation. Analysis of gene expression by stem cells revealed that perfusion flow had significantly upregulated the expression of osteogenic and chondrogenic genes in the bone and cartilage layers and downregulated the hypertrophic gene expression in the intermediate layer of the scaffold. In conclusion, applying flow perfusion on the prepared integrated trilayered SF-based scaffold can support osteogenic and chondrogenic differentiation for repairing osteochondral defects.

Differences in scalp-to-cortex tissues across age groups, sexes and brain regions: Implications for neuroimaging and brain stimulation techniques

Aging affects the scalp-to-cortex distance (SCD) and the comprising tissues. This is crucial for noninvasive neuroimaging and brain stimulation modalities as they rely on traversing from the scalp to the cortex or vice versa. The specific relationship between aging and these tissues has not been comprehensively investigated. We conducted a study on 250 younger and older adults to examine age-related differences in SCD and its constituent tissues. We identified region-specific differences in tissue thicknesses related to age and sex. Older adults exhibit larger SCD in the frontocentral regions compared to younger adults. Men exhibit greater SCD in the inferior scalp regions, while women show similar-to-greater SCD values in regions closer to the vertex compared to men. Younger adults and men have thicker soft tissue layers, whereas women and older adults exhibit thicker compact bone layers. CSF is considerably thicker in older adults, particularly in men. These findings emphasize the need to consider age, sex, and regional differences when interpreting SCD and its implications for noninvasive neuroimaging and brain stimulation.

Microporous titanium and hydroxyapatite improve fixation of the tibial wall in unicompartmental knee replacement.

Cementless Oxford unicompartmental knee replacement (OUKR) is associated with less pain than cemented OUKR 5 years postoperatively. This may be due to improved fixation at the tibial wall, which transmits tension and reduces stress in the bone below the tibial component. This study compares tibial wall fixation with three different types of fixation: cemented, cementless with hydroxyapatite (HA)and cementless with a microporous titanium coat and HA (HA + MPC). Three consecutive cohorts were identified (n = 221 cemented in 2005-2007, n = 118 HA in 2014-2015, n = 125 HA + MPC in 2016-2017). Analysis was performed on anterior-posterior radiographs aligned on the tibial component taken 1-2 years postoperatively. Aligned radiographs are needed to see narrow radiolucencies adjacent to the wall. Alignment was assessed with rotation ratio (RR = wall width/internal wall height). Perfect RR is 0.3, and a maximum threshold of 0.5 was used. Quality of fixation to the wall was assessed with fixation ratio (FR = bone wall contact height/total wall height). Notable radiographic features at the tibial wall were also recorded. A total of 33knees with cement, 37 knees with cementless with HAand 57 knees cementless with HA + MPC had adequately aligned radiographs. Fixation was significantly better with HA compared with cement (55% vs. 25%, p = 0.0016). The microporous coat further improved fixation (81% vs. 55%, p < 0.0001). FR > 80% was achieved in 3% of the cemented implants, 32% of HAand 68% of HA + MPC. In cementless cohorts, features suggestive of a layer of bone that had delaminated from the wall were seen in 8 (22%) HA and 3 (5%) HA + MPC knees. Radiographic tibial wall fixation in OUKR is poor with cement. It improves with an HA coating and improves further with an intermediary MPC. Improved tibial wall fixation may explain the lower levels of pain observed with cementless rather than cemented fixation described in the literature, but further clinical correlation is needed. Level III, retrospective cohort study.

The Shunt Valve Recession Technique as a Neuroplastic Surgery Adjunct in Complex and High-Risk Shunt Revisions: Technical Note and Case Series.

Ventricular shunting is one of the most common procedures in neurosurgery. However, complications and revisions are frequent. Patients requiring multiple revisions often suffer secondary issues with scalp healing over hardware. Many common ventricular shunt valves have an obligate thickness that creates a visible protrusion and can potentially cause local tissue ischemia and breakdown in the setting of repeated surgery. The authors present a simple technique for recessing the shunt valve into the underlying bone to alleviate protrusion in high-risk cases. Three example cases utilizing this technique are presented. The skull directly underlying the planned valve site is uniformly recessed with a cutting burr several millimeters as desired while maintaining the inner cortical bone layer. The valve is fixed with standard cranial plating hardware. Three patients are reported who underwent shunt valve recession as an adjunct to their shunt revision with neuroplastic surgery assistance. All patients had undergone multiple prior surgeries that had resulted in thin and high-risk fragile scalp. In 1 patient, the prior valve was eroding through the scalp before the described revision. All patients had satisfactory cosmetic outcomes, and there were no revisions in the 2-month follow-up period. Complex and high-risk ventricular shunt patients should be considered for shunt valve recession into the bone to reduce wound-related complications and enhance healing. This is a technically simple, safe, and effective technique to include as a neuroplastic adjunct.

Low-velocity impact response of a novel bionic turtle shell back armor sandwich structure

Turtle shell dorsal armor comprises a typical lightweight laminated composite structural material, which is constructed by cuticle and bone layer, with high specific strength and high fracture toughness. The red-eared slider turtle, a widely studied species of turtle, has a rich hierarchical structure. In this paper, according to the structure of red-eared slider turtle shell dorsal armor and the characteristics of each layer as well as by taking into full consideration of the fine structure of cuticle and ventral cortex of the shell dorsal armor, two bionic foam silicone rubber sandwich structures of different levels were prepared. Low-velocity impact test and finite element simulation analysis were carried out to study the mechanical response, specific absorbed energy, and damage mode of the two bionic sandwich structures under different impact energies, hammerhead shapes, and hammerhead radii. By comparing the mechanical response and specific energy absorption with the existing ordinary sandwich structure, we find that the two sandwich structures modeled in this paper exhibit better impact resistance than the ordinary sandwich structure. The shape and radius of the hammer head have a significant effect on the energy absorption characteristics of the sandwich structure, and the damage mode under the hemispherical hammer head is mainly dominated by tensile tearing damage, while the damage mode of extrusion fracture is more obvious under the impact of the conical hammer head. With the increase of the radius of the hammer head, the absorbed energy and specific energy absorption of the sandwich structure increases.