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

To effectively mitigate detrimental tissue stresses of the diabetic foot for preventing ulceration, contemporary strategies frequently utilize pressure-relief insoles. In this study, we have developed an innovative enhanced pressure-relief insole that integrate auxetic structures with a reverse graded-stiffness property. We introduce a novel modification to the insole internal structure, exhibiting untraditional regional stiffness from the center to the periphery. We utilize a validated finite element (FE) heel model of a diabetic patient to evaluate the effectiveness of the insole, computing internal stress of the heel (peak stresses, total stress concentration exposure, pressure on the fat pad, and tensile stress on the skin) and insole deformation. In addition, we conduct in-vitro uniaxial compression and in-vivo biomechanical experiments to assess its effects in static and gait. The FE results showed a significant reduction in internal stress within high-risk ulcer areas of the heel, with peak internal stresses reduced to 232.9 kPa (without insole: 374.6 kPa), and notable changes in the deformation across the insole's coronal plane. Additionally, uniaxial tensile tests demonstrated optimal energy dissipation at 28.76%. During gait, the auxetic insole resulted in a 19.72% reduction in peak pressure and 15.37% reduction in peak pressures-time integral compared to the conventional insole. A novel insole with auxetic structure and reverse graded-stiffness appear to better relieve the internal loads, gait-related pressure as well as enhanced energy dissipation for the plantar soft tissue under bony prominence of calcaneus of human foot. This research also holds substantial promise for optimizing other pressure-relief orthotic devices.

Lower limb fragility fractures included a break in bone from the pelvis to the foot. Weight-bearing and walking stability stand as key performance indicators to quantify fracture restoration. Normally, progress in fracture rehabilitation is observed through clinical assessments and patients' responses, and modern research also presents instrumented gait analysis. There exists a gap to statistically compute the regaining in patients' weight-bearing ability and walking stability following fractures. This study introduces methods to advance the analysis of instrumented signals and evaluate walking stability in fracture-healing patients. The centre of pressure (CoP) signals were captured for four conditions: tibia/fibula/talus fracture near the ankle (AF), lower-leg shaft fracture (LF), calcaneus fractures (CF), and normal ankle (NA). The time derivative for CoP signals showed impulsive responses during the loading and unloading transitions which were then modelled and transformed to the frequency domain. The developed models were further analysed by applying Nyquist and Bode methods and margins of stability were calculated for the fractured and healthy subjects. Results showed a substantial decline (Kruskal-Wallis's test, p < 0.001) in the intralimb stability of all three fractures. Also, there was a strong interlimb dependency (p < 0.001) observed between fractured and intact limbs applying Spearman's correlation during double limb support periods. Overall, the calcaneus fracture (CF) exhibited minimum intralimb stability and increased interlimb dependency. These methods stand clinically important in monitoring patients' rehabilitation and in decision-making about alternative treatment plans.

The objective of this study is to model the lateral collateral ligament (LCL) and medial collateral ligament (MCL) around the artificial knee joint in such a way that the virtual ligaments have the same behavior as the native ligaments around the artificial knee joint in reality. This study provides more accuracy in knee biomechanical simulation by introducing a nonlinear model for MCL and LCL ligaments and improved the modeling of ligaments by assigning nonlinear elastic behavior through achieving the force-displacement relationship in nonlinear form and assigned this relationship to the uniaxial connectors that represent the ligament bundles. The results showed that the virtual ligaments can only bear tensile loads and have the same behavior as the native ligaments that surround the artificial knee joint. In addition, the results obtained for tibiofemoral contact forces and ligament forces have been compared with the reference data and have shown significant agreement. This model serves as a biomechanical platform for simulating soft tissue balancing strategies in TKA. While the current study does not implement specific surgical techniques, the validated ligament representation enables future simulations involving clinical interventions such as ligament release, alignment adjustments, and gap balancing procedures and helps the surgeon to evaluate the result of treatment plan on the knee joint before the surgery.

Spinal metastases can increase the risks of vertebral fracture due to bony destruction and instability in the spine. There are concerns that cross-links may impair adjuvant treatments, such as radiotherapy and proton beam therapy. The aim of this study was to assess the biomechanical effects of cross-link stabilisation for a growing tumour in order to provide recommendations on the use and placement of the cross-link. A finite element (FE) model of a fixation device was developed. The device was inserted virtually into a FE model of the lumbar spine (L1-S1) between L2 and L4. Tumour deposit of either 1.3%, 10.1%, 38.3%, 71.5% and 92.1% of the vertebral body was simulated. A 1000 N compressive, a 10° lateral bending and a 7.5 Nm torsional load were simulated on the top of L1. Results indicate that the stabilisation is capable of reducing the stress of the L3 lumbar spine under torsion with a growing tumour. However, compressive loading is concentrated in the L3 anterior vertebra when the tumour volume was greater than 10.1% of the vertebra volume. The cross-link stabilisation reduced the stress of the posterior body within the stabilised segments (L2-L4), especially under torsion. The position of the cross-link does affect the ability of stabilisation to reduce concentrated stress of both vertebrae and screws, which indicates that the position of the cross-link should be considered in clinical surgery to refine the stress concentration, spinal stability and structural stiffness, without compromising adjuvant treatments.

Pelvic organ prolapse (POP) is a prevalent pelvic floor dysfunction (PFD) that significantly impacts women's quality of life, driving the need for innovative and less invasive treatment options. Surgical intervention remains the primary treatment for POP; however, it is often associated with high invasiveness, substantial risks, and a notable rate of failure. In this study, we investigate the potential of biodegradable cog threads, commonly used in cosmetic facial lifting, as an alternative surgical solution for reinforcing vaginal wall defects. Specifically, we evaluate the performance of commercially available 360° 4D barb threads made of polycaprolactone (PCL) under simulated physiological conditions. The degradation and mechanical properties of the threads were analyzed after immersion in Phosphate Buffer Solution (PBS) and Potassium Hydrogen Phthalate (KHP) for periods of 90 and 180 days, with comparisons to a control group. Fourier-transform infrared (FTIR) spectroscopy revealed mild to moderate degradation of the threads over 180 days in both mediums. Tensile strength tests indicated a reduction in maximum load-bearing capacity, with declines of 13% to 19%, more pronounced in the PBS medium. Despite this, cyclic tests demonstrated that the threads retained sufficient mechanical integrity to endure 100 loading cycles across all conditions, suggesting their durability under repetitive stress. These preliminary in vitro findings highlight the potential of biodegradable cog threads as a promising material for developing a novel, minimally invasive technique for POP correction. The threads' ability to maintain mechanical strength despite degradation supports their viability for long-term pelvic floor reinforcement.

This study evaluates the reliability of an underactuated wearable lower-limb exoskeleton designed to assist with gait rehabilitation. Recognizing the complexity of system reliability, a deep learning framework augmented with Long short-term Memory (LSTM) was utilized for the time-dependent reliability analysis of dynamic systems. The research commenced with the development of a lower-limb gait robot, modeled on a Stephenson III six-bar linkage mechanism. Following the mechanical design, computer-aided design (CAD) tools were employed to conceptualize a lower-limb robotic exoskeleton for rehabilitation purposes. The design incorporated two metallic materials (aluminum and steel), and a composite material (carbon fiber) tested using SolidWorks^®. The prototype achieved a lightweight design (~1.63 kg) for carbon fiber material. An LSTM-enhanced deep neural network algorithm was implemented to predict the time-dependent reliability of joint displacements and end-effector trajectories. Finally, conditional probability methods were applied to complete the time-dependent system reliability assessment. The designed mechanical system for gait rehabilitation demonstrated high reliability (R ≈ 0.87). Over 200 simulation runs, reliability trends showed consistent and robust predictions.

One of the most common diseases of the spine is the degenerative intervertebral disc, which in extreme cases requires surgery. Replacing a damaged disc with an artificial disc (AD) is a common treatment method. Nowadays, due to the extensive use of smartphones and other similar devices, our cervical spine is often in a vulnerable position, such as a bent position, which results in more stress on the components of the spine, especially intervertebral discs. In this research, the effects of geometrical parameters of an AD on the biomechanics of the cervical spine are investigated in a bent neck position, using the finite element method. In this regard, computed tomography scans of the neck of a 29-year-old male in two states of straight and bent neck are used. Nine different AD geometries are generated by varying three geometric design variables, including the height, position of the centre of rotation and rotation radius of the AD. The results of stress distribution in the spine for the straight and bent neck positions are compared, and the maximum von Mises stress on the AD and healthy discs are assessed to choose an optimum geometry. The results show that proper selection of the geometrical parameters of the AD can lead to up to an 85% reduction in the AD's maximum von Mises stress for a bent neck position. The sensitivity analysis shows that the location of the rotation centre has the highest impact on the distribution of von Mises stress in the artificial disc.

Thoracic endovascular aortic repair (TEVAR) is an effective treatment method for Stanford type B aortic dissection (TB-AD). In the investigation of treatment methods of TEVAR, numerical simulation technologies play a pivotal role. However, current finite element simulations of AD often use overly simplified vascular models and fail to adequately consider the complex interactions between stents, vessels, and blood. In this study, a Boolean operation was adopted to establish 3D models of TB-AD based on patient-specific CT images. The 3D software was used to construct 5, 6, and 8-peak stent grafts. A finite element method was applied to simulate the compression and release processing of stent graft deployment. Finally, a fluid-solid interaction module was constructed for the multiphase fluid-solid interaction simulation. The results showed that after stent graft deployment, the cross-sectional area of the vessels in the aortic coarctation region increased by 60.0%-65.5%. The maximum blood flow velocity in the true lumen decreased from 1.585 m/s to 1.125-1.238 m/s. The maximum blood pressure increased from 1574 Pa (true lumen) and 1853 Pa (false lumen) to 2021-2165 Pa (true lumen). The distribution of wall equivalent stress was more uniform, and the maximum value decreased from 0.5475 MPa to 0.1667-0.1758 MPa. The maximum equivalent stress of the stent was 3.815-4.315 MPa. Comprehensive comparisons showed that the eight-peak stent graft exhibited lower equivalent stress and superior improvement in vascular morphology, blood flow, and vessel stress, providing an optimal stent graft option for the clinical treatment of TB-AD.

This study aimed to investigate the biocompatibility and toxicity of biodegradable composites reinforced with hemp fibers in a polylactic acid (PLA) matrix. To enhance the compatibility of hemp fibers with PLA, various polymer structures, including maleic anhydride (MA), polybutylene succinate (PBS), and thermoplastic polyurethane (TPU), were incorporated. Additionally, surface modification of hemp fibers was carried out using sodium hydroxide (NaOH) and 3-(2-aminoethylamino) propyl trimethoxy silane (APTES) to improve interfacial adhesion. The in vitro biocompatibility and genotoxicity of the produced composites were evaluated using L-929 fibroblast and CHO-K1 cell lines. In the cytotoxicity tests, cells were exposed to composite extracts for 24 h, after which viability rates were determined to assess possible toxic effects. Genotoxicity tests were performed to examine potential DNA damage induced by the composites. The results demonstrated that the hemp fiber-reinforced PLA composites exhibited high biocompatibility, with cell viability reaching up to 120%, while no DNA damage was observed in genotoxicity analyses. These findings indicate that the developed composites are non-toxic and have promising potential for biomedical applications. However, further in vivo studies are required to gain a more comprehensive understanding of their long-term biocompatibility and safety profile.

Mechanical heart valves (MHVs) are indispensable in managing valvular disease, yet they often lack the hemodynamic efficiency of native valves and require lifelong anticoagulation therapy to mitigate thrombus formation. This study introduces a novel bileaflet mechanical heart valve (BMHV), the iValve, designed to address these challenges by more closely emulating native valve performance. Central to this research is the development of a custom-built steady-state flow simulator, which provides a cost-effective and innovative approach to visualizing flow dynamics through MHVs. Unlike traditional methods, this simulator allows for detailed observation of flow patterns, focusing on critical regions such as the central flow and hinge areas.Using the novel flow simulator, the flow through the iValve was compared to that of conventional BMHVs, including the SJM/Abbott Regent and On-X valves. The iValve exhibited significantly reduced flow disturbances and vortex formation in the central flow region and effective hinge washing during the forward flow phase. These preliminary findings suggest that the iValve design minimizes energy loss and shear stress on blood elements, potentially reducing or eliminating the need for anticoagulation therapy. The steady-state flow simulator proved invaluable in these assessments, offering precise, qualitative insights into flow behavior that would be challenging to achieve with other methods. Future work, including pulsatile flow simulations and in vivo testing, will further explore the iValve's clinical potential and validate these promising results.