Femoral Antegrade Starting Tool (FAST) for intramedullary nailing.

Intramedullary (IM) nailing is the standard of care for adult lower extremity long bone fracture stabilisation. Key to this procedure is obtaining the correct entry point and trajectory for initial guide pin insertion. This work presents the Femoral Antegrade Starting Tool (FAST), a surgical tool that addresses the lack of connectivity in utilising sequential 2D fluoroscopic images to achieve 3D alignment of femoral guide pin placement. The user centred design and development of FAST is introduced and the performance of this device evaluated during guide pin insertion for femoral IM nailing in a series of sawbones and cadaveric models leading to a first in human clinical cohort study. The results demonstrated the potential of FAST to improve time and consistency of the guide pin insertion for femoral IM nailing for less experienced surgeons and trainees. Overall, FAST was found to be easy to use with a high degree of clinical interest (particularly for use in large patients) and acceptance motivating continued development of this new technology.

The relationship between serum levels of interleukin-2 and IL-8 with circulating microRNA-10b in patients with COVID-19.

BACKGROUND: The role of cytokine storm in the immunopathogenesis of coronavirus disease 2019 (COVID-19) has been implicated. OBJECTIVE: To determine the association of microRNA (miRNA)-10b and serum levels of IL-2 and IL-8 in patients with COVID-19. METHODS: Blood samples were obtained from 33 COVID-19 patients and 29 healthy subjects. After RNA extraction and cDNA synthesis, the transcript level of miR-10b was determined by Real-time PCR. In addition, the serum levels of IL-2 and IL-8 were measured in subjects using ELISA. RESULTS: The patient group comprised of 33 patients with COVID-19 (62.4 ± 3.7 years old), 13 (39%) males and 20 (61%) females. In the control group, 29 subjects (56.6 ± 1.6 years old), 9 (31%) males and 20 (69%) females, were included. The expression of miR-10b was significantly downregulated in the peripheral blood of COVID-19 patients in comparison to the healthy controls (fold change= 0.12, P< 0.0001). The levels of IL-2 (P< 0.001) and IL-8 (P< 0.001) were significantly increased in the serum samples of COVID-19 patients compared to the healthy subjects. The expression level of miR-10b was correlated significantly with the serum levels of IL-2 and IL-8 as well as with the age of patients, ESR and CRP levels. CONCLUSIONS: miR-10b is downregulated in the COVID-19 patients and might result in increased levels of IL-2 and IL-8, hence contributing to cytokine storm.

Non-ideal effects in bending response of soft substrates covered with biomimetic scales.

Biomimetic scales are known to substantially alter the mechanics response of the underlying substrate engendering complex nonlinearities that can manifest even in small deformations due to scales interaction. This interaction is typically modeled using a-priori homogenization with an enforced periodicity of engagement. Such a framework is fairly useful especially when dealing with the structural length scale which is at least one order of magnitude greater than the scales themselves since individual tracking of a large number of scales become insurmountable. On the other hand, this scheme makes several assumptions whose validity has not yet been investigated including infinite length of the substrate and rigidity of the scales. The validity of these assumptions and the accuracy and limitations of associated analytical models are investigated. Finite element based numerical studies were carried out to identify the critical role of edge effects and other non-ideal behavior such as violation of periodicity and nonlinear constitutive response on scale rotation. Our investigation shows that several important quantities show a strong saturation characteristic which justify many of the simplifying assumptions whereas others need much greater care.

Origami-based cellular metamaterial with auxetic, bistable, and self-locking properties.

We present a novel cellular metamaterial constructed from Origami building blocks based on Miura-ori fold. The proposed cellular metamaterial exhibits unusual properties some of which stemming from the inherent properties of its Origami building blocks, and others manifesting due to its unique geometrical construction and architecture. These properties include foldability with two fully-folded configurations, auxeticity (i.e., negative Poisson's ratio), bistability, and self-locking of Origami building blocks to construct load-bearing cellular metamaterials. The kinematics and force response of the cellular metamaterial during folding were studied to investigate the underlying mechanisms resulting in its unique properties using analytical modeling and experiments.

Volume of Lytic Vertebral Body Metastatic Disease Quantified Using Computed Tomography-Based Image Segmentation Predicts Fracture Risk After Spine Stereotactic Body Radiation Therapy.

PURPOSE: To determine a threshold of vertebral body (VB) osteolytic or osteoblastic tumor involvement that would predict vertebral compression fracture (VCF) risk after stereotactic body radiation therapy (SBRT), using volumetric image-segmentation software. METHODS AND MATERIALS: A computational semiautomated skeletal metastasis segmentation process refined in our laboratory was applied to the pretreatment planning CT scan of 100 vertebral segments in 55 patients treated with spine SBRT. Each VB was segmented and the percentage of lytic and/or blastic disease by volume determined. RESULTS: The cumulative incidence of VCF at 3 and 12 months was 14.1% and 17.3%, respectively. The median follow-up was 7.3 months (range, 0.6-67.6 months). In all, 56% of segments were determined lytic, 23% blastic, and 21% mixed, according to clinical radiologic determination. Within these 3 clinical cohorts, the segmentation-determined mean percentages of lytic and blastic tumor were 8.9% and 6.0%, 0.2% and 26.9%, and 3.4% and 15.8% by volume, respectively. On the basis of the entire cohort (n=100), a significant association was observed for the osteolytic percentage measures and the occurrence of VCF (P<.001) but not for the osteoblastic measures. The most significant lytic disease threshold was observed at ≥11.6% (odds ratio 37.4, 95% confidence interval 9.4-148.9). On multivariable analysis, ≥11.6% lytic disease (P<.001), baseline VCF (P<.001), and SBRT with ≥20 Gy per fraction (P=.014) were predictive. CONCLUSIONS: Pretreatment lytic VB disease volumetric measures, independent of the blastic component, predict for SBRT-induced VCF. Larger-scale trials evaluating our software are planned to validate the results.

Surgical process analysis identifies lack of connectivity between sequential fluoroscopic 2D alignment as a critical impediment in femoral intramedullary nailing.

PURPOSE: Identifying key steps and barriers within complex and simple surgical procedures can be accomplished in a structured and rigorous manner using surgical process modeling. For lower extremity long bone fracture stabilization, the current standard of care is closed intramedullary (IM) nailing, which, despite its widespread use, is associated with challenges that greatly impact operative time and lead to the frustration of medical staff. The aim of this study was to identify challenging surgical steps in IM nailing and understand their underlying causation. METHODS: Eight semi-structured interviews with staff orthopedic surgeons and eight detailed surgical observations were conducted to understand the surgical steps, challenges and adapted techniques used in IM nailing. Hierarchical decomposition was then utilized to structure the IM nailing surgical procedure into phases, steps and activities. RESULTS: In the developed IM nailing surgical process model, the most challenging steps were identified as fracture reduction (75%) and entry point selection (25%), both of which were associated with high levels of frustration in the observed surgeries. Both of these steps utilize 2D fluoroscopic imaging to guide 3D alignment. Challenges arise when the alignment in one plane is lost while adjusting the alignment in the perpendicular plane. This leads to unpredictable repetition of activities which can be time-consuming and frustrating. CONCLUSION: Identifying the causation of surgical challenges in IM nailing through surgical process modeling forms a knowledge base that can be used to guide future improvements to techniques and surgical instrumentation.

Hierarchical honeycomb auxetic metamaterials.

Most conventional materials expand in transverse directions when they are compressed uniaxially resulting in the familiar positive Poisson's ratio. Here we develop a new class of two dimensional (2D) metamaterials with negative Poisson's ratio that contract in transverse directions under uniaxial compressive loads leading to auxeticity. This is achieved through mechanical instabilities (i.e., buckling) introduced by structural hierarchy and retained over a wide range of applied compression. This unusual behavior is demonstrated experimentally and analyzed computationally. The work provides new insights into the role of structural organization and hierarchy in designing 2D auxetic metamaterials, and new opportunities for developing energy absorbing materials, tunable membrane filters, and acoustic dampeners.

Anisotropic blistering instability of highly ellipsoidal shells.

The formation of localized periodic structures in the deformation of elastic shells is well documented and is a familiar first stage in the crushing of a spherical shell such as a ping-pong ball. While spherical shells manifest such periodic structures as polygons, we present a new instability that is observed in the indentation of a highly ellipsoidal shell by a horizontal plate. Above a critical indentation depth, the plate loses contact with the shell in a series of well-defined "blisters" along the long axis of the ellipsoid. We characterize the onset of this instability and explain it using scaling arguments, numerical simulations, and experiments. We also characterize the properties of the blistering pattern by showing how the number of blisters and their size depend on both the geometrical properties of the shell and the indentation but not on the shell's elastic modulus. This blistering instability may be used to determine the thickness of highly ellipsoidal shells simply by squashing them between two plates.

Biomechanical properties of an intact, injured, repaired, and healed femur: an experimental and computational study.

There is no "gold standard" treatment for femoral mid-shaft fractures near the tip of a hip implant. Moreover, no study has quantified the changes in a femur's mechanical properties from injury through to healing. The present aim was to predict overall stiffness and peak bone stress in the same femur after injury, repair, and healing with respect to its intact condition. Stage 1 was an intact femur. Stage 2 mimicked a femur with a hip stem. Stage 3 had a 5-mm fracture gap repaired with a plate and screws. Stage 4 represented complete fracture union. Experiments were done on a synthetic femur with strain gages and subjected to 1500 N of axial force. Finite element (FE) models were validated against experiments and then re-analyzed using a clinical-level force of 3000 N. At 1500 N, FE vs. experimental strains had excellent linear agreement (R=0.94; slope=0.97). At 3000 N, FE stiffnesses were 2167 N/mm (Stage 1), 2359 N/mm (Stage 2), 973 N/mm (Stage 3), and 3348 N/mm (Stage 4), showing that Stage 3 was the least stable compared to Stage 1. At 3000 N, FE bone stresses yielded peaks of 75.7 MPa at the load application point (Stage 1), 29.0 MPa near the hip implant tip (Stage 2), 126.3 MPa at the distal portion of the plate (Stage 3), and 69.3 MPa at the proximal portion of the plate (Stage 4), showing that Stage 3 was most vulnerable to re-injury compared to Stage 1. Stress shielding and high stresses were present not only after hip implantation and plating, but also after healing.

Voltammetric determination of homocysteine using multiwall carbon nanotube paste electrode in the presence of chlorpromazine as a mediator.

We propose chlorpromazine (CHP) as a new mediator for the rapid, sensitive, and highly selective voltammetric determination of homocysteine (Hcy) using multiwall carbon nanotube paste electrode (MWCNTPE). The experimental results showed that the carbon nanotube paste electrode has a highly electrocatalytic activity for the oxidation of Hcy in the presence of CHP as a mediator. Cyclic voltammetry, double potential step chronoamperometry, and square wave voltammetry (SWV) are used to investigate the suitability of CHP at the surface of MWCNTPE as a mediator for the electrocatalytic oxidation of Hcy in aqueous solutions. The kinetic parameters of the system, including electron transfer coefficient, and catalytic rate constant were also determined using the electrochemical approaches. In addition, SWV was used for quantitative analysis. SWV showed wide linear dynamic range (0.1-210.0 µM Hcy) with a detection limit of 0.08 µM Hcy. Finally, this method was also examined as a selective, simple, and precise electrochemical sensor for the determination of Hcy in real samples.