Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine最新文献

Knee braces are commonly used to support the knee joint and improve function. However, brace sliding caused by the misalignment between brace and knee during motion is a common problem, which reduces the therapeutic effect and leads to brace abandonment. To investigate the effect of mechanism combinations on sliding, an experimental brace was designed to isolate the mechanism as the sole variable. Ten healthy participants were recruited, each of whom worn four combinations of lateral/medial mechanisms: lateral and medial single-axis (SA), lateral super gear (SG) and medial non-circular gear (NCG), lateral four-bar linkage (FL) and medial SG, and lateral FL and medial NCG. The knee flexion angle was collected using inertial measurement units, and brace sliding was measured by 3D motion capture system. All combinations had significant changes in peak sliding of thigh and shank compared to the SA combination (p < 0.05), but lateral FL and medial NCG combination had the lowest peak and final sliding during walking and leg-raising, with significant reductions of 40.7 and 85.3% in peak sliding of thigh, and significant reductions of 56.3 and 72.0% in peak sliding of shank, respectively (p < 0.05). Moreover, the mechanism combination did not significantly impact the knee range of motion (p > 0.05). The mechanism combination that fit the instantaneous center of rotation of lateral/medial condyle of knee joint demonstrates a significant reduction in brace sliding. Additionally, the peak sliding during motion is significantly higher than the final sliding.

The current study aims to comprehend how different bone densities affect stress distribution at the bone-implant interface. This will help understand the behaviour and help predict success rates of the implant planted in different bone densities. The process of implantation involves the removal of bone from a small portion of the jawbone to replace either a lost tooth or an infected one and an implant is inserted in the cavity made as a result. Now the extent of fixation due to osseointegration is largely dependent on the condition of the bone in terms of the density. Generally, the density of the bone is classified into four categories namely D1, D2, D3, and D4; with D1 being purely cortical and D4 having higher percentage of cancellous bordered by cortical bone. A bone model with a form closely resembling the actual bone was made using 3D CAD software and was meshed using Hyper Mesh. The model was subjected to an oblique load of 120 N at 70° to the vertical to replicate occlusal loading. A finite element static analysis was done using Abaqus software. The stress distribution contours at the bone-implant contact zone were studied closely to understand the changes as a result of the varying density. It was revealed that as the quantity of the cancellous bone increased from D1 to D4 the cortical peak stress levels dropped. The bone density and the corresponding change in the material characteristics was also responsible for the variation in the peak stress and displacement values.

Constructing surface topography with a certain roughness is a widely used, non-toxic, cost-effective and effective method for improving the microenvironment of cells, promoting the proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs), and promoting the osseointegration of grafts and further improving their biocompatibility under clinical environmental conditions. SIRT1 plays an important regulatory role in the osteogenic differentiation of bone marrow-derived MSCs (BM-MSCs). However, it remains unknown whether SIRT1 plays an important regulatory role in the osteogenic differentiation of BM-MSCs with regard to surface morphology. Polydimethylsiloxane (PDMS) with different surface morphologies were prepared using different grits of sandpaper. The value for BMSCs added on different surfaces was detected by cell proliferation assays. RT-qPCR and Western blotting were performed to detect SIRT1 activation and osteogenic differentiation of MSCs. Osteogenesis of MSCs was detected by alkaline phosphatase (ALP) and alizarin red S staining. SIRT1 inhibition experiments were performed to investigate the role of SIRT1 in the osteogenic differentiation of MSCs induced by surface morphology. We found that BM-MSCs have better value and osteogenic differentiation ability on a surface with roughness of PDMS-1000M. SIRT1 showed higher gene and protein expression on a PDMS-1000M surface with a roughness of 13.741 ± 1.388 µm. The promotion of the osteogenic differentiation of MSCs on the PDMS-1000M surface was significantly decreased after inhibiting SIRT1 expression. Our study demonstrated that a surface morphology with certain roughness can activate the SIRT1 pathway of MSCs and promote the osteogenic differentiation of BMSCs via the SIRT1 pathway.

Due to its ability to induce heterogenous, patient-specific damage in pulmonary alveoli and capillaries, COVID-19 poses challenges in defining a uniform profile to elucidate infection across all patients. Computational models that integrate changes in ventilation and perfusion with heterogeneous damage profiles offer valuable insights into the impact of COVID-19 on pulmonary health. This study aims to develop an in silico hypothesis-testing platform specifically focused on studying microvascular pulmonary perfusion in COVID-19-infected lungs. Through this platform, we explore the effects of various acinar-level pulmonary perfusion abnormalities on global lung function. Our modelling approach simulates changes in pulmonary perfusion and the resulting mismatch of ventilation and perfusion in COVID-19-afflicted lungs. Using this coupled modelling platform, we conducted multiple simulations to assess different scenarios of perfusion abnormalities in COVID-19-infected lungs. The simulation results showed an overall decrease in ventilation-perfusion (V/Q) ratio with inclusion of various types of perfusion abnormalities such as hypoperfusion with and without microangiopathy. This model serves as a foundation for comprehending and comparing the spectrum of findings associated with COVID-19 in the lung, paving the way for patient-specific modelling of microscale lung damage in emerging pulmonary pathologies like COVID-19.

In the past studies, the resistance of magnetically controlled capsules running through the small intestine has been modeled assuming that the small intestine was a circular tube with a constant diameter. Peristalsis is an important character of the human gastrointestinal system, and it would result in some changes in the diameter of the intestine, meaning that the existing resistance models would no longer be applicable. In this paper, based on the assumption that intestinal peristalsis is actually a sinusoidal wave, a resistance model of the capsule running in the peristaltic intestine is established, and then it is validated experimentally. The model provides a realistic foundation for the optimization and control of the magnetically controlled endoscopy.

Emergency ambulances play a vital role in medical rescue and patient transportation, but their transit can impact patient health due to vehicle dynamic forces and vibrations. This study evaluates patient transport conditions on a stretcher subjected to vertical vibration excitation from road unevenness. Using an eight-degree-of-freedom numerical model, we analyze the construction parameters of a medical stretcher's support and vehicle suspension. Actual experimental data from an emergency vehicle were utilized to assess the vibration conditions experienced by both the stretcher and the ambulance floor. The model is adjusted based on measurements, specifically targeting the main vibration modes. The investigation involves determining temporal responses for vertical accelerations and characterizing vibration modal parameters under various transportation conditions. Notably, several system natural frequencies fall within the range of human body frequencies, making them susceptible to mechanical excitation, particularly in the human neck, abdomen, and spine. A sensitivity analysis underscores the influence of medical stretcher support structure parameters on patient comfort. Increasing support stiffness, which alters the stretcher's natural frequency, and damping coefficient reduce vibration propagation between the vehicle and the patient. Additionally, the research predicts the model's dynamic behavior on roads with low-quality pavement, indicating vibrational amplitudes that could potentially be discomforting and unhealthy for individuals. The study illustrates a vibration exposure period on a class E road, revealing that transportation longer than 25 min may cause damage to patient health.

Component-on-component impingement in total hip arthroplasty may lead to post-operative complications including dislocation. Despite numerous clinical studies focusing on reducing this risk, assessment methods remain limited to qualitative radiography, finite element analysis, and cadaver studies. There is a need for more precise measurements of impingement in the research setting. We aimed to validate a novel RSA-based impingement metric to measure component-on-component impingement in vivo. A phantom experiment of a standard metal-on-polyethylene total hip system was performed. RSA examinations were performed as typical for a traditional weight-bearing RSA exam for large joints. The phantom was placed in 10 possible impinged positions and one neutral position. Double exposure radiographs were taken to measure repeatability. The closest distance between the skirt of the head and the inner circumference of the acetabular cup liner was measured to assess impingement risk. Distances between the closest point of the hood to the edge of the cup in 10 impinged positions ranged from 0.05 to 1.03 mm, with the average being 0.67 mm. In the neutral position, the distance measured is 11.02 mm. Excellent repeatability was observed, with a standard deviation of 0.03 mm with an r value of 0.09. A validated RSA-based risk metric was established to evaluate in vivo hip impingement. A 1 mm threshold may be proposed to define impingement where distances approaching 1.00 mm are at a greater risk of impingement. This simplified metric holds promise for upcoming clinical studies on component-on-component impingement.