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

Lower extremity compression is effective in treating various vascular and wound conditions. Assessment of IP variations along limb length and under different compression applications are limited. This work quantified both local and gradient in vivo IP map with a piezoresistive (PR) sensor under three different compression applications when applied to the right leg of forty healthy subjects (n = 40). Compression applications included elastic stockinette, EdemaWear (EW), a pre-packaged compression set, CoFlex TLC (CF) and a combination application, CF applied over EW (Both = BO). Results showed statistical variations in local pressures and pressure gradients that varied by condition, body position, and post 10 min of exercise. Immediately post application significant differences between all compression conditions were observed at both distal and proximal measurement points, ranging from 10.8 ± 4.2 mmHg for supine EW to 38.2 ± 10.7 mmHg for standing BO. A non-uniform reduction in IP was observed post a brief period of wear under CF and BO, but not EW. The largest decrease was observed at the proximal measurement point under BO (37% reduction). Rate of change in IP proximal to distal ranging from -2.4 to 3.4 mmHg/in. Vertical patterning that mirrored the structural design of the EW was observed in some, but not all, of the pressure maps for the BO application only. The use of the PR sensor for capturing in vivo IP profiles may provide a more comprehensive understanding of the compression effect, highlighting the importance of considering variation in IP across the limb over a period of wear.

Subsidence is a common complication, especially in multisegment corpectomies. In addition to the characteristics of the cage, fixation method is also an effective means of preventing subsidence. We compared three different fixation methods used after the cage placement: Anterior fixation (AF), posterior fixation (PF), and circumferential fixation (CF). Low-density (LDB) and high-density (HDB) polyurethane blocks were used to mimic osteoporotic and normal bone, respectively. Five models within the groups loaded flexion-extension testing, and maximum compressive loads (MCL), bending moment and stiffness were determined in static tests. Subsequently, the specimens were subjected to dynamic fatigue tests then the amount of subsidence was calculated. The MCL and stiffness differences between AF, PF, and CF in the LDB were statistically significant, decreasing CF, PF, AF, respectively. In the HDB group, the difference in MCL between AF, PF, and CF was significant, decreasing from CF to PF to AF, respectively. The differences between the stiffness of these models were statistically significant, from high to low CF, PF, AF. The subsidence of AF, PF and CF in the LDB were 2.3 ± 1.59 mm, 7.5 ± 1.58 mm, and 0.65 ± 0.10 mm, respectively. In this group, CF is more successful in preventing subsidence than AF and PF. Subsidence of less than 1 mm was observed in all models in the HDB. This study suggests that AF is as effective as other methods in preventing subsidence following two-level corpectomy in patients with high bone quality. In those with low bone quality, CF could provide more stable fixation and may be more reliable in preventing subsidence and potential instrumentation failure.

Hand and foot digital radiography (DR) is an indispensable tool in medical imaging, with varying diagnostic requirements necessitating different hand and foot positionings. Accurate positioning is crucial for obtaining diagnostically valuable images. Furthermore, adjusting exposure parameters such as exposure area based on patient conditions helps minimize the likelihood of image retakes. We propose a personalized positioning and exposure assistant capable of automatically recognizing hand and foot positionings and recommending appropriate exposure parameters to achieve these objectives. The assistant comprises three modules: (1) Progressive Iterative Hand-Foot Tracker (PIHFT) to iteratively locate hands or feet in RGB images, providing the foundation for accurate pose estimation; (2) Multi-Task Shared Pose Estimation Transformer (MTSPET), a Transformer-based model that encompasses hand and foot estimation branches with similar network architectures, sharing a common backbone. MTSPET outperformed MediaPipe in the hand pose estimation task and successfully transferred this capability to the foot pose estimation task; (3) Domain Expertise-embedded Positioning and Exposure Assistant (DEPEA), which combines the key-point coordinates of hands and feet with specific positioning and exposure parameter requirements, capable of checking patient positioning and inferring exposure areas and Regions of Interest (ROIs) of Digital Automatic Exposure Control (DAEC). Additionally, two datasets were collected and used to train MTSPET. A preliminary clinical trial showed strong agreement between PPEA's outputs and manual annotations, indicating the system's effectiveness in typical clinical scenarios. The contributions of this study lay the foundation for personalized, patient-specific imaging strategies, ultimately enhancing diagnostic outcomes and minimizing the risk of errors in clinical settings.

Customized cranial implants play a crucial role in neurosurgery, serving to restore cranial integrity and protect the underlying brain tissue after trauma or surgical intervention. Ti-6Al-4V cranial implants exhibit high mechanical strength; however, their solid forms can be excessively heavy and possess a high elastic modulus, leading to stress shielding effects. This study focuses on designing a cranial implant utilizing computer tomography data, incorporating different lattice and porous structures to optimize weight and mechanical performance. The analysis, conducted with nTop software, compared displacement and von Mises stress values across different structures. The isotruss lattice structure emerged as the most effective, achieving a weight reduction of approximately 50% while maintaining a von Mises stress of 40 MPa. Following the computational analysis, Laser Beam Powder Bed Fusion (PBF-LB) was employed to fabricate the isotruss implant and the compression test was performed to mimic the cranial implant under realistic conditions. The isotruss lattice cranial implant exhibited a remarkable load-bearing capacity of up to 18,000 N while achieving a 50% weight reduction compared to the solid implant, indicating that this lightweight structure not only offers high-performance load-bearing capabilities but also shows great potential for use in surgical applications.

Polymethylmethacrylate (PMMA) is the most used bone cement in orthopaedic surgery for the fixation of prosthetic components or filling bone defects. PMMA bone cements containing magnetic particles have been explored for the treatment of bone cancers using magnetic induction hyperthermia. In this study, different formulations of magnetic bone cements were developed by mixing up to 40 wt% of magnetic glass-ceramics with Palacos^® MV, a commercial PMMA bone cement with medium viscosity. Mechanical properties of these magnetic bone cements were investigated and compared to the non-magnetic commercial Palacos^® MV cement, which was used as control. Setting time, setting temperature, compressive strength, bending strength and bending modulus of these magnetic bone cements were evaluated using the ISO 5833:2002 standard guidelines. Vickers hardness tests were carried out using ASTM E384-22 standard. Setting time increased with the amount of magnetic glass-ceramic in the bone cement. Setting temperatures of magnetic cements and non-magnetic control are similar. All magnetic bone cements have the average compressive strength above 70 MPa and the average bending modulus above 1.8 GPa, and meet the requirements of the ISO 5833:2002 standard. Only magnetic cements containing up to 30 wt% of magnetic glass-ceramic have the average bending strength above 50 MPa and comply with the ISO 5833:2002 standard requirement. All magnetic bone cements have Vickers hardness higher than the control cements. Thus, magnetic cements containing up to 30 wt% of magnetic glass-ceramic have the potential to be used for the treatment of bone cancers.

Degradation of implants by fretting-corrosion is the main source of released metal ions and debris, leading to adverse tissue reactions. Cemented stems have two interfaces that could be degraded: stem-cement and stem-head. This study aimed to identify which interface suffers the most severe degradation and, for this reason, is potentially more harmful to the human body. For this purpose, six pairs of stems and femoral heads made of stainless steel were divided into two groups according to the interface to be evaluated: I (stem-cement) and II (stem-head). The implants of both groups were subjected to a fretting-corrosion test, applying cyclic loading in corrosive environment for five million cycles. Fretting-corrosion mechanism was evaluated using electrochemical tests, optical microscopy, SEM/EDS analysis, and ions and particles analysis. The fretting current of the stem-cement interfaces was greater than that of the stem-head interfaces. SEM analysis showed the occurrence of corrosion and wear mechanisms, which are found in many published cases of retrieval analyses, indicating that there is a correlation between the mechanisms identified in benchtop test and those in retrieved stems. The amount of particles released in both interfaces was similar to that identified in retrieval analyses. For the stem-cement interface, the amount of particles released was higher than that associated with the stem-head interface. The stem-cement interface resulted in a greater release of ions than the stem-head interface. This reinforces the hypothesis that stem degradation at the stem-cement interface could be more harmful to the human body than that at the stem-head interface.

Scaffolds developed from Triply Periodic Minimal Surface (TPMS) structures effectively mimic the geometric, mechanical, and fluid transport characteristics of human bones. These porous architectures facilitate fluid flow and augment bone cell adhesion and proliferation through their substantial surface area. In this study, the potential of network solid and sheet solid TPMS scaffolds with the same Schwarz Primitive architecture was compared for bone regeneration. Both types were modeled at 50%, 60%, 70%, and 80% porosity. A computational fluid dynamics (CFD) analysis was conducted to assess parameters such as surface area, pore size, permeability, wall shear stress, and flow rate. These parameters are known to exert a significant influence on the behavior of bone cells. The results demonstrated that network solids exhibited enhanced permeability and augmented pore sizes, thereby facilitating cell migration and nutrient delivery. Conversely, sheet solids exhibited elevated surface areas, thereby fostering cell adhesion and proliferation. Despite exhibiting equivalent porosity, the two structures manifested discernible disparities in geometry and flow performance. Network solid structures generally provided more favorable conditions for fluid flow and mechanical stimulation. Nevertheless, the selection of network or sheet architectures should be informed by specific clinical needs and tissue requirements. The findings demonstrate that architectural differences significantly affect scaffold performance, and understanding these effects can help optimize scaffold design for bone tissue engineering applications.

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.