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

In the past few decades, 3D-printed dental implants have been manufactured, and significant studies have demonstrated the pre-clinical validation of such systems. However, studies have yet to tackle the ever-present issue of preventing the jumping gap to enhance overall outcomes. The present study details the utilization of patient computed tomography (CT) data to design and subsequently fabricate a multi-component customized dental implant assembly and customized instruments using direct metal laser sintering (DMLS) technology. The workflow was validated for two patient data sets (cases 1 and 2), which were used to render and print custom implant assemblies; the simulation data for these were compared with a commercially available solution. The present study incorporated a prototype stage as well as subjecting the customized implant assemblies to both static (Case 1: 38.89-77.81 MPa vs 75.47-158.09 MPa; Case 2: 83.95-106.65 MPa vs 55.23-126.57 MPa) and dynamic finite element analysis (Case 1: 41.08-84.09 MPa vs 75.45-187.91 MPa; Case 2: 106.81-108.70 MPa vs 79.18-135.48 MPa) along with resonance frequency analysis (Case 1: 7763.2 Hz vs 7003.6 Hz; Case 2: 7910.1 Hz vs 7102.1 Hz) as well as residual stress analysis. The assembly's stress patterns and resonance frequencies were evaluated against a commercially available implant system. It was observed that the customized implant assemblies tended to outperform the commercially available solution in most simulated scenarios.

The formation of diabetic foot ulcers (DFU) is consequential of peripheral neuropathy, peripheral arterial disease and foot deformity, leading to altered foot biomechanics and plantar loads. Plantar load comprises of normal pressure and shear stress, however, there are currently no in-shoe devices capable of measuring both components. The STrain Analysis and Mapping of the Plantar Surface (STAMPS) system, developed at the University of Leeds, utilises Digital Image Correlation (DIC) to measure the strain captured by a plastically deformable insole, as a method to understand plantar load during gait. A 2D DIC software was used to capture cumulative plantar strain and displacement pointwise data, however this method was limited to the analysis of planar surfaces. To address this, 3D instrumentation and DIC methods have been developed and implemented into the STAMPS3D system, used as a tool to capture data that is representative of the non-planar nature of plantar surfaces of the foot. A case-study is used to demonstrate how STAMPS3D can measure multi-dimensional strain, bringing potential to improve clinical screening of DFU risk.

Muscle tissue is most frequently cut or separated in surgery. Waterjet as an emerging non-rigid cutting method is newly introduced into soft tissue dissection which shows a great potential in soft muscle cutting for low-trauma surgery. However, the cutting mechanisms of muscle material to waterjet impact remain unknown. This study reports the cutting responses of muscle tissue to waterjet impact. Waterjet morphology, depths of cut, cutting surface morphology and deformation of muscles were experimentally investigated using a computer-controlled waterjet machine. The mechanical properties of muscles were also measured to explore the property-processing relation. The conversion relationship between kinetic energy of waterjet and potential energy of muscle damage was established based on energy balance theory. Based on the experimental investigation and fracture mechanism analysis, the critical and the reasonable waterjet separation pressures for the muscles were respectively 0.8-1.1 MPa and 1.4-2.0 MPa for balancing separation efficiency and surrounding tissue protection. It was also found the muscle depth of cut under waterjet impact significantly increased with the impact pressure, but rapidly reduced with the increase in impact angle and transverse speed. In addition, a new phenomenon of swelling effect of the muscles was discovered in waterjet impact, which heavily affects the depths of cut. The proper stand-off distance was determined considering the muscle swelling effect and initial segment of waterjet. This research first provides practical insights into the process selection and quality control for waterjet cutting of soft muscles, advancing the clinical application of waterjet to muscle separation.

Mathematical models to determine diverse parameters in biological systems have been a challenging and interesting topic for the scientific community. This work aimed to determine the angles of the lower and upper incisor teeth as a function of the angle of the lower facial height and the golden proportion. The cephalometric parameters reported by Ricketts like the lower facial height angle, the axis of the mandibular body (Xi-Pm), the line that forms the mandibular geometric center with the anterior nasal spine (Xi-ENA), the occlusal plane, the dental line, and the upper and lower incisors lines and some cephalometric constraints were used to determine the proposed models.The analysis of several values for the lower facial height in the Ricketts range showed that both the model for the upper incisor (A) and lower incisor (B) provide functional values for these angles, which are within the statistical range reported by Ricketts with a maximum mean deviation of 1.58° and a maximum percentage difference of up to 10.40%. Outside of the Ricketts range, a maximum mean deviation of 5.15° and a maximum difference of up to 49.72% was found regarding the mean values. As a first approximation, the proposed models let us determine and personalize the target angle for orthodontic treatment of the upper and lower incisors based on the lower facial height of each patient and the golden proportion. These models can be a starting point for further research in this area, considering other parameters to be added to the proposed models.

Metal porous structures are a common treatment for bone tissue loss when the loss exceeds the self-repair capacity of the human body. The structural characteristics, mechanical properties, and biological behavior of scaffold biomaterials exert a significant influence on the formation of new bone cells. The objective of this study was to ascertain the mechanical and cell biological behavior of scaffold structures with four distinct porosities (60%, 70%, 80%, and 90%). Scaffold structures with a diamond lattice unit cell were manufactured by the selective laser melting method using a CoCr alloy powder with a diameter of 4 mm and a height of 5 mm and were then subjected to a static compression test. Subsequently, human gingival fibroblast cells were seeded into each sample via the cell culture process, and cell formation was observed. According to the results obtained from the compression test, the sample with 60% porosity demonstrated optimal mechanical performance and effective modulus of elasticity. In the cell culture process, the sample with 60% porosity exhibited the highest adherence rate.

Circumduction of the hindfoot does not occur primarily in one of the traditional anatomic planes and can be difficult to describe precisely. The purpose of this study was to measure foot bone motion quickly and objectively to subsequently characterize differences among feet of varying shapes. As such, we have developed a quantitative characterization of foot bone motion during circumduction using electromagnetic tracking sensors. Five of these sensors were attached to the foot on specific bony landmarks, and one was attached to a footplate. The lower leg was held by padded clamps in a custom non-ferrous jig, and the foot was moved through a full range of circumduction. To describe the motion of the bones of the foot during circumduction, the sensor positions were fitted to 2D ellipses and 3D curves. A repeatability study on multiple feet (n = 7) demonstrated that multiple raters (n = 3) introduced more error than a single rater; therefore, a single rater was used for all subsequent data collection. Results from five neutrally aligned subjects demonstrated that bone motion was quantifiable by fitted ellipse parameters. Additional modeling with a paraboloid surface described the motion with improved accuracy. A further reduction in error was obtained using a 3D eighth-order Fourier series expansion fit. This method holds promise as a means for characterizing differences in foot bone motion among foot types during a clinical exam.

Custom-made insoles are designed to redistribute foot load and prevent potential pain. Common methods to investigate the effectiveness of insoles include finite element method and experimental approach. However, most finite element research has focused on the two-dimensional plantar fascia stresses during static standing with insoles, rather than those of three-dimensional plantar fascia. Furthermore, the effects of insole with design parameters (metatarsal pad, toe pad, and arch support) on dynamic plantar pressures still need further exploration. Therefore, this study aimed to quantify the impact of custom-made insoles on foot biomechanics by combining both methods. Finite element method was employed to evaluate stress on the plantar fascia and bony structures when static standing, both barefoot and with a custom-made insole. Furthermore, 10 participants were recruited to investigate dynamic plantar pressures during walking barefoot and with insole. The relative time of four subphases during stance phase, total contact time, peak plantar pressure (Peak P), and pressure time integral (PTI) were assessed. Finite element results revealed reduced plantar fascia stresses and more uniform stress distribution over metatarsals and phalanges when standing with insole. Additionally, Peak P and PTI values in the second and third metatarsals were significantly lower when walking with insole. With the presence of insole, Peak P and PTI values in medial regions were significantly reduced, except for the midfoot region. In conclusion, custom-made insole with the addition of a metatarsal pad, toe pad, and arch support can effectively distribute foot tissue stress evenly, alleviate plantar pressure, and thus prevent pain.

Arthroscopic surgery has become the first option for the treatment of joint injuries. However, training outside the operating room is limited by the lack of portability and high cost of high-fidelity simulators. The aim of this study is to present the ArthSim hybrid simulator, a low-cost portable device for the training of psychomotor skills of orthopaedic surgeons in arthroscopic knee surgery. The ArthSim simulator consists of a physical model of the knee with an integrated motion tracking system with a virtual reality application that captures and replicates the movements of the knee joint and the two arthroscopic instruments inside the virtual model, in a mixed reality approach to arthroscopy training. The functionality of ArthSim's technology was evaluated in two experiments: static and dynamic. The interaction of the physical knee joint and the arthroscopic instruments within the virtual model was evaluated by eight orthopaedic surgeons, who recreated the common positions of the knee, arthroscope, and instruments during the exploration of the internal structures. The results indicated a surgical total workspace of 80 mm³ with a range of motion of 115° for flexion, 23° for abduction, and 33° for rotation in the knee joint. The measurements showed linearity and repeatability with errors below, for motion capture. Feedback provided by orthopaedic surgeons on ArthSim was used to identify the device's points of improvement. The ArthSim simulator provides an effective alternative for arthroscopic training in a hybrid simulation approach, offering natural haptics to enhance the surgical experience of orthopaedic surgeons.

Instrument separation during root canal treatment can hinder effective cleaning and shaping, making reliable retrieval techniques essential. Endoscopic visualization might aid in instrument removal procedures offering direct magnification of root canal anatomy. This ex vivo study evaluated the success rate and procedure time of three instrument retrieval techniques - Masserann, microsonic, and loop techniques - under the visualization of dental operation microscope (DOM) assisted by an endoscope. Sixty extracted human mandibular single-rooted teeth with simulated fractures were assigned to the Masserann, microsonic, or ultrasonic with loop techniques (n = 20/group), each performed under endoscopic visualization alongside DOM. The success rate of instrument removal and procedure time were recorded. Complications, such as root perforation, apical extrusion and secondary fracture, were recorded. Statistical analysis was conducted using Pearson χ² and Kruskal-Wallis tests with 5% significance threshold. Success rates for the microsonic, Masserann, and ultrasonic with loop techniques were 80%, 70%, and 80%, respectively (p > 0.05). The average procedure times were 13.02 min for the microsonic technique, 17.25 min for the Masserann technique, and 17 min for the ultrasonic with loop technique (p > 0.05). The Masserann technique demonstrated a higher complication rate, with two cases each of perforation and apical extrusion, whereas no secondary fractures occurred in any group. Conclusively, the microsonic technique showed the highest success rate with the shortest retrieval time, indicating its efficiency and suitability for instrument removal from root canals, particularly when combined with enhanced visualization through endoscopy.

Atrial fibrillation (AF) is a common cardiac arrhythmia, and ablation is the primary treatment for patients with drug intolerance. The success of AF ablation depends on the adhesion of the catheter to the tissue. Existing electrical coupling index (ECI) and electrode-interface resistance (IR) methods based on impedance measurement to evaluate the adhesion between catheters and tissues do not explore the internal changes of the tissue during the compression process. This study introduces a new method to understand these internal changes using multi-frequency impedance combined with Cole-Cole model fitting, which is critical for accurate characterization of the contact between catheter and tissue. We used four-electrodes impedance measurement, using customized circuits and compression platform, applying 5-400 g (3.6-228.2 Pa) pressure to the bullfrog thighs to collect impedance data at frequencies of 500-100 kHz. The Cole-Cole model was then used for data fitting and analysis. The customized circuit accurately detects impedance up to 2 kΩ with less than 5% amplitude error, less than 15% phase error, and less than 6% error in model component values. Correlation analysis showed a significant linear relationship between extracellular fluid resistance and applied pressure (Pearson R ≈ 0.9, p < 0.05), indicating that extracellular fluid resistance increases with compression. This suggests that there is a significant linear positive correlation between the extracellular fluid resistance and the applied pressure, meaning that as the pressure increases, the extracellular fluid resistance correspondingly rises. This may provide a new perspective for studying the degree of catheter-tissue contact during atrial fibrillation ablation procedures.