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

Dental implantation is the most reliable method for replacing missing teeth. Success rate of dental implants is influenced by osseointegration. Surface roughness of implants influences osseointegration by altering surface area and texture, providing stimulation to cells. Sandblasting and acid-etching are common methods for making implant surfaces rough. Main goal of this study was to investigate effects of sandblasting and acid-etching variables, that is, blasting-pressure and acid-temperature, on surface roughness of implants to find the controlled values of variables for a favorable surface roughness. An acceptable surface roughness was assumed to have an arithmetic average height (Sa) between 1 and 2 µm, and an area developed ratio (Sdr) over 50%. Seventy-two titanium-made analogs were sandblasted with three different pressures, that is, 4, 5, and 6 MPa, and three different durations, that is, 15, 30, and 45 s, and then were etched with two different etching temperature, that is, 60°C and 80°C, and two exposure-time, that is, 5 and 10 min (two repetition for each combination). Surface roughness parameters were then measured using a profilometer. Multi-factorial ANOVA was used as statistical analysis method. Results showed that 14 groups demonstrated favorable Sa (1-2 µm), among which just four groups had acceptable Sdr (Sdr > 50%). Among four parameters stated above, which affect sandblasting and acid-etching processes, it was found that blasting duration is the most effective variable on implants roughness. This work highlights the importance of sandblasting and acid-etching parameters for a controlled titanium dental implant surface, which can achieve surface roughness parameters that correspond to those previously reported in the literature as favorable ones for osseointegration.

Bone machining is a critical aspect of orthopedic surgeries, where excessive heat generation can cause thermal necrosis and hinder patient recovery. Ultrasonic-assisted micro-milling (UAM) offers advantages by reducing cutting forces and heat generation. This study examines the effects of feed rate, rotational speed, tool diameter, depth of cut, and vibration amplitude on cutting force and temperature in UAM of cortical bone. 64 experiments were performed on fresh bovine cortical bone specimens prepared to consistent dimensions and stored to prevent moisture loss. Repeated central points in the design quantified experimental error and repeatability. Precision, calibrated instruments ensured accurate force and temperature measurements. Data were analyzed using regression modeling and statistical methods. Results showed that increasing rotational speed and vibration amplitude generally reduced cutting force and temperature, while feed rate and tool diameter had complex interactive effects. Multi-objective optimization using NSGA-II identified optimal conditions: for the X-axis, 1047 rpm, 63 mm/min feed, 1.5 mm diameter, 0.6 mm depth, and 30 μm amplitude; for the Y-axis, 990 rpm, 22 mm/min, 0.8 mm diameter, 0.2 mm depth, and 20 μm amplitude. Predictive models achieved temperature errors of 1.6% (X) and 7.6% (Y), and force errors of 12.9% (X) and 14.5% (Y). These models can help surgeons anticipate cutting conditions preoperatively, reducing surgical risks and preserving bone integrity. The findings support optimization of orthopedic machining processes, improving surgical outcomes and advancing bone-milling techniques.

In recent years, hierarchical porous structures have garnered extensive attention across multiple disciplines, inspired by their natural counterparts. While structural hierarchy significantly affects overall performance, the mechanistic influence of multiple hierarchical parameters on scaffold mechanical properties remains insufficiently systematized. In this study, a series of hierarchical porous scaffolds (with macro-to-micro pore size ratios of at least 10) featuring different hierarchical parameters were designed and fabricated. The presence of hierarchical structures and the effects of varying hierarchical spacing and pore size parameters on macroscopic structural performance were analyzed through experimental and computational methods. Results indicate that the introduction of hierarchical structures has a significant impact on the mechanical properties of scaffolds. As hierarchical pore size increases or spacing decreases, the mechanical properties of the structure exhibit a decreasing trend, and the maximum reduction in the compressive modulus reaches 25.82% and 45.62%, respectively. Moreover, a coupling mechanism exists between pore size and spacing, and the trend of simulation and experimental results aligns. These findings demonstrate that synergistic tuning of hierarchical parameters enables effective control over scaffold mechanical behavior. This offers new insights and lays a solid theoretical and experimental foundation for developing ideal bone scaffolds with tunable mechanical properties.

Various strategies have been proposed to reduce operator-dependent variability in musculoskeletal ultrasound, including mechanical stabilization techniques. However, their effects on image reproducibility and transducer handling remain unclear in anatomically complex regions such as hand. This two-phase study aimed to (1) develop and validate a transducer guiding system for hand ultrasound and (2) evaluate its influence on image reproducibility and operational stability through image-based analyses. In Phase I, test-retest reliability of the guiding system was examined by repeatedly measuring soft-tissue thickness in 30 healthy participants. Intraclass Correlation Coefficients (ICC) ranged from 0.766 to 0.948, demonstrating good to excellent reliability. In Phase II, 16 ultrasound users acquired images under handheld and guiding-system-assisted conditions based on predefined reference images. Image reproducibility was evaluated using Normalized Cross-Correlation (NCC) and ICC, while operational stability was assessed via cosine similarity derived from M-mode segments during the pre-capture period, with group comparisons performed using the Wilcoxon signed-rank test. Novice users showed substantial ICC improvement when using the guiding system (0.487-0.681), approaching the consistency observed in experienced users. Both novice and experienced groups displayed higher NCC and cosine similarity values with the guiding system, indicating improved reproducibility and operational stability. Overall, the guiding system enhanced image outcomes by providing standardized positioning and mechanical stabilization. These findings highlight its potential to improve consistency in hand ultrasound assessments and serve as a supportive tool for novice ultrasound training. The results further demonstrate the feasibility of mechanical stabilization in reducing operator-related variability and enhancing image consistency in hand ultrasound examinations.

The aim of this study is to investigate the mechanical influence on the aortic tissue when exposed to the liquid jet blasting effect produced by the aortic cannula during cardiothoracic surgery. Aortic tissue from seven porcine hearts was exposed to a continuous liquid jet from an aortic cannula positioned in a simple flow loop. After 4 h of exposure, samples were obtained from the aortic root using a twin punch device. Additionally, tissue was harvested from seven untouched aortic roots serving as our control group. Uniaxial tensile testing was conducted to measure the ultimate strength and Young's modulus. Furthermore, we analysed the samples using dynamic mechanical analysis in the frequency range from 0.5 to 5 Hz. There were no significant differences in ultimate tensile strength or Young's modulus between the test group and control group. Dynamic mechanical analysis revealed significant increases in both mean storage modulus (44%) and mean loss modulus (73%) in the exposed samples. There was a tendency towards higher tanδ in the test group, suggesting altered viscoelastic behaviour. These findings indicates that the liquid jet exposure influences the viscoelastic properties of the aortic wall and makes it stiffer. Further studies should incorporate histological and microstructural analyses to confirm mechanical alterations at the tissue level. Clinically, such changes may contribute to local wall injury, altered flow dynamics, or plaque destabilisation during cardiopulmonary bypass. This highlighting the need for optimisation of cannula flow direction and velocity to minimise the mechanical impact on the aortic wall.

Constant force mechanisms have been widely applied in various industrial fields but encounter challenges in medical applications due to the risk of soft tissue injuries caused by clamping devices exerting excessive pressure. This study reviews existing design methods for constant force mechanisms through a comprehensive search of databases such as Google Scholar, ScienceDirect, and IEEE Xplore. The reviewed methods include constant force springs, mechanisms based on fixed pulleys, mechanisms utilizing spring energy storage, and compliant mechanisms. However, these designs have limitations, particularly in achieving miniaturization and adapting to the delicate environment of the human body. To address these issues, an emerging design approach combines the superelasticity of shape memory alloys (SMAs) with structural optimization. This method reduces structural complexity, weight, and size, making it highly suitable for medical applications that require simplicity and consistent force output. This approach holds significant potential for advancing the development of safe and effective medical clamping devices.

The viscoelastic characteristics of the intervertebral disc (IVD) govern spinal response to applied dynamic loading which is important in understanding how the spine responds to loads experienced in everyday activity. The common method of reporting experimental load response data in terms of linear stiffnesses represents a significant oversimplification of this behaviour. This study presents a method yielding substantially increased accuracy for principal direction load-displacement response of porcine lumbar spine segments. It compares quality of fit to experimental data of nonlinear viscoelastic models and the typical linear stiffness method. Experimental load response data were recorded from six porcine lumbar spine segments tested under 6 DOF cyclic displacement control at low strain rates (0.1 Hz). Model spring and damper coefficients were determined using an optimisation procedure to minimise the differences between model and experimental load response vectors in each axis. Experimental hysteresis area cannot be reproduced using the linear method but was replicated to within 17% by nonlinear viscoelastic models. Fit quality was substantially improved by nonlinear models compared to the linear stiffness model, with RMSE reduced by 60%. Results indicate that three-element nonlinear viscoelastic models are well-suited for characterisation of principal direction load response to cyclic loading, replicating key features.

This study aimed to evaluate the effects of different irrigation activation techniques on root canal sealer penetration during non-surgical root canal retreatment and to determine which sealer type demonstrated greater penetrability into dentinal tubules. Instrumented root canals were allocated to a control group (needle technique) and three experimental groups: sonic activation (EDDY), passive ultrasonic irrigation (PUI), and Laser. The canals were obturated using AH+ and Totalfill BC Hiflow (BC) sealers. Retreatment was performed, and after 2 weeks, three sections from the apex at 3-, 8-, and 12-mm levels were examined using a confocal laser scanning microscope (CLSM) to investigate secondary sealer penetration. A three-way ANOVA followed by a post hoc test was used to analyze penetration depth and percentage. The BC sealer showed a marked difference in penetration depth and percentage compared with the AH+ sealer. The maximum penetration depth was observed in the middle region, where Laser and EDDY activation showed higher penetration depth and percentage values. PUI activation showed the lowest percentage of AH+ sealer penetration. Variations in results were observed in the coronal and apical regions; however, the differences were statistically nonsignificant. The use of Laser and EDDY for irrigation activation is promising in terms of tubule penetration of sealers, and Totalfill BC sealer showed better results than AH plus.

Talar replacement procedures offer good clinical outcomes for patients experiencing talar osteonecrosis with collapse. However, there is a potential for cartilage wear as the artificial talus prosthesis articulates against the native articular cartilage (AC) in the ankle joint. Therefore, this study investigated the wear of AC against candidate implant biomaterials with the aim of selecting an appropriate material for use in talar replacement procedures. Cobalt chrome alloy (Co-28Cr-6Mo), titanium alloy (Ti-6Al-4V), ultra-high molecular weight polyethylene (UHMWPE), industrial grade natural polyether ether ketone (PEEK), and polycarbonate-urethane (PCU) were tested against porcine AC submerged in bovine serum using an in vitro customized dual-motion wear testing setup. A total of 43,200 cycles at a frequency of 3 Hz were completed for each test. Both macroscopic and microscopic analyses were used to quantify cartilage wear using the Outerbridge and Osteoarthritis Research Society International (OARSI) clinical grading systems, respectively. In the macroscopic analysis, Ti-6Al-4V demonstrated the most AC wear, followed by Co-28Cr-6Mo, PEEK, UHMWPE, and PCU. In the microscopic analysis, PEEK demonstrated the most AC wear, followed by Ti-6Al-4V, Co-28Cr-6Mo, UHMWPE, and PCU. PCU demonstrated the least amount of AC wear compared to all other biomaterials and showed statistically insignificant differences with the control group (porcine cartilage-on-cartilage) in both macroscopic and microscopic inspections. These results suggest that PCU may be a suitable candidate material for coating talus implants as it demonstrated superior AC wear performance compared to the other biomaterials investigated in this study.

Open-wedge High-Tibial Osteotomy is the most commonly employed technique addressing varus knee osteoarthritis. During this procedure, the osteotome passes through cortical and trabecular bone. A common complication is lateral hinge fractures, which depends upon when the surgeon stops impacting the osteotome. The aim of the present study is to determine whether an instrumented hammer can be employed to detect (i) the bone type (cortical or trabecular) surrounding the osteotome tip and (ii) when bone is fractured by the osteotome. Seventeen lower-limb specimens were obtained from nine fresh human anatomical subjects. The osteotome was impacted using the instrumented hammer until rupture. Each impact signal was recorded and analyzed. An algorithm was developed to detect the transitions between cortical and trabecular bone and vice versa. Detection was based on the relative variation of τ derived from the force signal as a function of time as the time difference between the second and first impact peaks. The values of τ were significantly lower in cortical bone compared to trabecular bone. Considering the arrival of the osteotome tip in trabecular bone during a medial, a difference of less than 2 impacts between the surgeon and the algorithm was obtained for 71% of the cases. For the lateral osteotomy it was obtained in 81% of the cases. This cadaveric study demonstrated that the instrumented hammer could prevent impacts leading to hinge rupture, which suggests that future clinical trials are warranted.