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Abstract:Spine is one of the most important skeletal structures in human body. It has the function of protecting the spinal cord, supporting body weight, slowing impact and allowing flexible movement of the trunk. The study of spinal biomechanics is very important for a comprehensive understanding of the structure and function of the spine and the pathogenesis of diseases. In 2023, scholars at home and abroad have done a lot of researches on spine related biomechanics, including the cognitive aspects on basic biomechanics of the spine, the changes in mechanical properties of the spine under pathological conditions, and the design of various treatment methods of spinal diseases based on biomechanical researches. This review focuses on the research progress of spinal biomechanics, and introduces several typical spinal diseases or pathological states as examples.

Abstract:Ankle sports medicine is an emerging discipline that has gradually emerged and flourished in recent years, and it mainly focuses on the diagnosis and treatment of ankle ligament, tendon, and cartilage injuries. In this article, the relevant literature on foot and ankle sports injuries published in internationally renowned journals in the year 2023 was searched, and the latest research progress in this field was reviewed, in order to provide new ideas for future research, diagnosis, and treatment.

Abstract:Osteocytes are the most abundant and long-lived cells in bone, serving as primary regulators of bone remodeling. Besides playing critical roles in endocrine regulation and calcium-phosphate metabolism, osteocytes are primary responders to mechanical stimuli, perceiving and responding to these stimuli directly and indirectly. The process of mechanotransduction in osteocytes is a complex and finely tuned regulation involving interactions between the cell and its surrounding environment, neighboring cells, and various mechanosensors within the cells with distinct functions. The known major mechanosensors in osteocytes include primary cilia, piezo ion channels, integrins, extracellular matrix, and connexin-based intercellular junctions. These mechanosensors play crucial roles in osteocytes, perceiving and transducing mechanical signals to regulate bone homeostasis. This review aims to provide a systematic introduction to these five mechanosensors, offering new perspectives and insights into understanding how osteocytes respond to mechanical stimuli and maintain bone tissue homeostasis.

Abstract:Objective To analyze coating properties of porous artificial joints, including coating morphology and coating mechanical properties, and summarize the range of coating properties of current mainstream products, to provide references for the design and development of new products, as well as provide the basis for the long-term implant removal analysis. Methods Samples for the surface morphology, shear strength, and tensile strength of the coatings used in the experiment were prepared in accordance with ASTM F1854, ASTM F1044, and ASTM F1147 standards, respectively. The coatings were processed using plasma spraying. The surface morphology (coating thickness, porosity, and pore intercept) of the coatings for all 17 products (Nos. 1－17) was tested; for products Nos. 1－7 and Nos. 15－16, the shear strength test between the coating and substrate was conducted first in accordance with the test method of ASTM F1044. Then, according to the test method of ASTM F1147, the tensile strength test between the coating and substrate was conducted. For product No.17, the shear and tensile strengths of the composite coating and simple titanium coating were tested, respectively, according to the test method of ASTM F1044 and ASTM F1147. Results A total of 15 products (88.2%) had coating thicknesses between 300 μm and 500 μm. There were 16 metal-coated products (Nos. 1－16), of which 11 (68.75% of the total) had coating porosities between 30% and 50%, and 14 (87.5% of the total) had coating pore intercepts between 50 μm and 150 μm. The mechanical properties of the coatings were independent of the substrate material used. The shear and tensile strengths of the composite coatings with hydroxyaptite (HA) were significantly lower than those of the pure metal coatings. Conclusions For the design and manufacture of artificial joints with porous coatings, the performance of the coating can be referred to the following indexes: the coating thickness is 300－500 μm, the coating porosity is 30%－50%, the coating pore intercept is 50－150 μm. The substrate materials can be selected based on the use of the product. The effects of a lower bonding force on product performance should be considered when designing prostheses with composite coatings containing HA. This range of performance metrics provides control for long-term clinical extraction analyses.

Abstract:Objective To analyze and compare the strength of titanium alloy crystalline porous scaffolds and porous scaffolds with a triply periodic minimal surface (TPMS) structure and explore the effect of porosity on the equivalent elastic modulus and permeability. Methods Crystalline porous scaffolds (cell 1-4) and TPMS porous scaffolds (P-, G-, D-, and FKS-type) with The same porosity were constructed, and the equivalent elastic modulus, equivalent yield strength, and permeability of the scaffolds were calculated using finite element simulation. Results The elastic modulus of eight scaffolds was in the range of 5.1－10.4 GPa, the yield strength was in the range of 69－110 MPa, and the permeability of 4 crystalline scaffolds was in the range of 0.015－0.030 mm2. Conclusions With an increase in porosity, the elastic modulus and yield strength of the scaffold gradually decreased, and the permeability gradually increased. The cell 2-type scaffold is suitable for repairing defects at load-bearing bone sites because of its high elastic modulus and yield strength. The cell 3-type scaffold with a uniform stress distribution and a longer linear elasticity phase may be suitable for designing porous tibial platforms for knee joint prostheses.

Abstract:Objective To study the biomechanical differences between hollow compression screws and shape-memory alloy staples in triple arthrodesis internal fixation and to provide references for the clinical application of shape-memory alloy staples. Methods Two-dimensional (2D) computed tomography (CT) foot data from a patient with severe horseshoe foot stiffness were selected, and a triple arthrodesis model was established using Mimics and Geomagic software. A geometric triple arthrodesis internal fixation model was established using SolidWorks 2021 software. Four fixation schemes (A, B, C, and D) were established according to the type and combination of fixed screws (hollow compression screws and shape-memory alloy riding nails). The biomechanical characteristics of models with different internal fixation schemes under neutral physiological loading were simulated and analyzed using ABAQUS software. Results The maximum end-face displacements of the fused surfaces of the talocalcaneal talonavicular and calcaneocuboid joints in the internal fixation model of scheme D were greater than those in schemes A, B, and C. The differences between the medial and lateral displacements of the fused surfaces of the talonavicular and calcaneocuboid joints in the internal fixation model of scheme D were 13.10% and 13.60%, respectively. The fused surface displacements were closer to the parallel displacements than those in the other three fixation schemes. The von Mises stresses were greater than those of schemes A, B, and C. Conclusions The application of scheme D (internal fixation at fusion surfaces of the talonavicular and calcaneocuboid joints with staples and at fusion surfaces of the talocalcaneal joints with compression hollow screws) provides stability at fusion surfaces of the internal fixation after triple arthrodesis surgery with near-parallel micromovement, which produces appropriate fusion stresses to make contact at the fusion end closer, promote the growth of bone scabs, and achieve better fusion results.

Abstract:Objective To study the effects of different posterior slope installations of unicompartmental knee arthroplasty (UKA) prostheses on the loading and motion of the knee joint and insert wear. Methods A combined approach involving The UKA musculoskeletal multibody dynamic, finite element, and wear prediction models was used to investigate the effects of five different posterior slope installation positions of the UKA prosthesis on the postoperative knee joint force and motion, insert contact stress, linear wear depth, and wear volume. Results At a 0° posterior slope, the maximum von Mises stress of the insert was 24.84 MPa, maximum contact stress was 47.61 MPa, and volumetric wear after 5 million cycles (MC) was 47.29 mm3. As the posterior slope angle of the UKA prosthesis increased, the internal rotation and posterior translation during the gait cycle increased, the medial joint force during the swing phase increased, the von Mises and contact stresses of the insert after 5 MC decreased significantly, and the wear area, maximum linear wear depth, and volumetric wear volume of the insert were consequently reduced. Compared to the 0° posterior slope, the linear wear depths of the insert at the 3°, 5°, and 7°posterior slopes decreased by 17.8%, 19.2%, and 20.6%, respectively. The volumetric wear volumes of the inserts decreased by 24.5%, 30.9%, and 34.3%, respectively. Conclusion Installing a UKA prosthesis with a posterior slope exceeding 3° significantly increases internal rotation and posterior translation during the gait cycle, further reducing the articular volumetric wear of the polyethylene insert.

Abstract:Objective To obtain the range of anatomical parameters of healthy knee joints in Chinese males and validate a statistical shape model (SSM) based on the geometric shape of a healthy knee to provide references for the design of knee SSM-based prostheses. Methods Computed tomography (CT) images of knee joints from 112 healthy males were acquired to build three-dimensional (3D) knee joint models. Each model was the target model separately, and the remaining models were used as the training set for principal component analysis (PCA). The obtained knee SSM was fitted to the target model to predict the SSM. The exact anatomical measurement points were marked on the sample and SSM prediction models, and 17 linear and 3 angular parameters were derived. The values of the anatomical parameters were statistically tested using an independent samples t-test and Mann-Whitney U-test, and the validity of the SSM in terms of geometric shape was demonstrated if the resulting P-values were all greater than 0.05. Results Qualitative and quantitative comparative analyses of anatomical parameters showed that The mean deviation of linear parameters was less than 6 mm, and that of angular parameters was less than 2.5°. The results of statistical tests showed P>0.05 for all anatomical parameters, proving that the knee SSM prediction model was not statistically different from the true healthy model in terms of geometric shape. Conclusions This study derived a reference range of anatomical parameters for a healthy knee and demonstrated that the knee SSM model was consistent with the real healthy model in terms of shape. The results provide a reference for the design of knee SSM-based prostheses.

Abstract:Objective To establish a finite element model of the T2-L5 thoracolumbar spine and verify its validity to provide numerical model support for exploring the dynamic response characteristics and injury mechanism under spinal impact loads. Methods A three-dimensional (3D) finite element model of T2-L5 thoracolumbar spine was established based on CT scanning data. The load-rotation angle curve of the T12-L1 segment under different moments (flexion, extension, rotation, and lateral bending conditions) was calculated and compared with the data reported in the literature. Free-fall loads at different heights were applied to the finite element models of the T2-6, T7-11, and T12-L5 spine. The peak axial force and bending moment were obtained by finite element simulation analysis and compared with data reported in the literature. Results The maximum rotation angle of the T12-L1 finite element model was -2.24°－1.55° under moments in different directions, which was in good agreement with the literature data. The peak axial force of T2-6, T7-11, and T12-L5 spine finite element models subjected to different free-fall loads was 1.7－5.3 kN, 1.3－5.5 kN, and 1.3－7.5 kN respectively, which were within the error range reported in the literature. Stress nephograms of the spine and intervertebral discs showed that the vertebral body was first stressed from the outer edge. The intervertebral disc was subjected to the main load by the nucleus pulposus, consistent with the actual spinal injury mechanism. Conclusions The T2-L5 spine model established in this study can correctly simulate the biomechanical behavioral characteristics of the spine under different working conditions, and the analysis results are effective.

Abstract:Objective To study the effect of pain on the lumbar and hip joint moments in patients with lumbar disc herniation (LDH) while sitting and standing. Methods Dynamic data from 20 healthy controls and 20 patients with LDH were collected using an AMTI dynamometer. The differences in moments between the lumbar spine and hip joints in the sagittal and coronal planes for the two groups of subjects performing sitting-standing tasks were analyzed using statistical parameter mapping (SPM). Results Compared to the healthy control group, the LDH group showed a significant increase in the maximum lumbar flexion moment and the maximum hip adduction moment from standing to sitting (P<0.05). SPM analysis showed that during the initial phase of standing (37%－42%), the hip abduction moment of the LDH group was significantly greater than that of the healthy control group (P=0.007). Conclusions Subjects with LDH have an unstable lumbar spine and pelvis during sitting and standing, especially at the stationary stage, which makes it difficult to achieve balance in their body. Therefore, increasing the hip abduction moment is necessary to maintain pelvic stability. During clinical evaluation and treatment, emphasis should be placed on the stable function of the spine and pelvis.

Abstract:Objective To investigate the biomechanical properties of a novel sacroiliac lag screw with a spiral blade. Methods: Percutaneous sacroiliac lag screws were used as The controls. Polyurethane material was used to simulate the trabecular bone, and the pullout resistance performance was tested on an Instron mechanical testing machine. Subsequently, pelvic specimens were utilized to analyze the static stiffness and dynamic stability of the novel sacroiliac lag screw in repairing sacroiliac joint injuries under normal standing conditions, with normal pelvis, single-sided sacroiliac joint injury pelvis, percutaneous sacroiliac lag screw-single screw repair, and percutaneous sacroiliac lag screw-double screw repair as controls. Results The damage to the polyurethane material after screw extraction was smaller in the novel sacroiliac lag screw group. The average effective holding displacement of the novel sacroiliac lag screw was significantly greater than that of the percutaneous sacroiliac lag screw (P<0.05). However, the maximum resistance to the pullout force for the percutaneous sacroiliac lag screw was significantly higher than that for the novel sacroiliac lag screw (P<0.05). The stiffness after repair of sacroiliac joint injuries was significantly higher when using a single sacroiliac lag screw than when using two percutaneous sacroiliac lag screws (P<0.05). The displacement amplitude was the highest in the sacroiliac joint injury group, followed by that in the normal group. The displacement amplitudes in the other groups were similar; however, the differences were statistically significant (P<0.05). The dynamic stability of the sacroiliac lag screw repair group was the best, slightly better than that of the percutaneous sacroiliac lag screw-double screw repair group, and the dynamic stability of the sacroiliac joint injury group was the worst. The novel sacroiliac lag screw effectively repaired the sacroiliac joint injuries. Conclusions The novel sacroiliac lag screw can effectively hold the trabecular bone and has practical clinical utility.

Abstract:Objective To establish a finite element model of the hallux valgus foot and study the stress and displacement changes in the first and second rays of the hallux valgus under different tensile forces. Methods Foot CT images of a patient with hallux valgus were imported into Mimics to reconstruct a three-dimensional (3D) skeletal model of The foot. The 3-matic software was used to mesh the reconstructed model and generate the volume mesh. The optimized model was imported into ANSYS for finite element analysis. The relationship between the tensile forces and the stress/displacement of the first and second rays of the hallux valgus was verified by changing the size and direction of the tensile forces. Results Tensile forces of different magnitudes and directions were applied to The first proximal phalanx. When the force was less than 12 N, with an increase in tension, the displacement of the first phalange changed more significantly. For every 2 N increase in tension, the displacement increased by approximately 1 mm. When the force was greater than 12 N, with an increase in tension, the stress on the first phalange increased, whereas the displacement only changed slightly. In addition, when the magnitude of the force remained unchanged at 12 N and the direction of the force changed at intervals of 15°, the stress and stress distributions of the first and second rays changed with direction, and the displacement also changed accordingly. When the direction of the force was perpendicular to that of the second phalanx, the displacement of the first phalanx increased. Conclusions Finite element analysis technology can vividly and accurately analyze The stress and displacement changes of the first and second rays of hallux valgus under different tensile forces, and it lays a foundation for the design of hallux valgus orthoses.

Abstract:Objective To investigate the relationship between plantar pressure and plantar sensation in people with different foot types and provide theoretical references for injury evaluation and sports recovery in patients with flat feet. Methods Recruited participants were initially screened using a three-dimensional (3D) foot scanner. They were divided according to the arch index as follows: 16 in the normal foot group and 16 in the flat foot group. Plantar pressure and sensation tests were performed in different groups using the Footscan high-frequency plantar pressure test system and the Semmes–Weinstein monofilament test, respectively. The test results were analyzed for statistical descriptions and correlations. Results The plantar pressure impulses of the left and right arches and the medial area in the flat foot group increased significantly compared with those in the normal foot group (P<0.05). The plantar sensory thresholds of the first metatarsal bone and arch position in the flatfoot group were lower than those in the normal foot group (P<0.05). There was a significant positive correlation between left foot sole sensation, right foot arch position, and plantar pressure in the flat foot group. Conclusions The structural features of reduced arches and excessive valgus in people with flat feet result in increased plantar pressure impulses and lower thresholds of plantar sensory sensitivity in the arch and medial heel positions. Meanwhile, there is a correlation between plantar sensation and plantar pressure; the greater the load of plantar pressure, the lower the threshold of plantar sensation.

Abstract:Objective To study the effects of vision on human postural control and the connection mechanisms of the brain’s functional network. Methods 15 healthy male adults were required to perform 30 s of balanced standing on both legs with eyes open and eyes closed. The center of pressure (COP) and electroencephalograph (EEG) were recorded during balance. The sample entropy (sample En) of the COP was calculated. The phase lag index (PLI) in θ-, α-, β-band of EEG was calculated to construct the brain functional networks, and the clustering coefficient (C), characteristic path length (L), and the criteria (σ) of the small-world network were calculated based on graph theory. Results During balanced standing on both legs, the SampleEn of the COPY with eyes closed was significantly higher than that with eyes open (P<0.05). The mean value of PLI in the α-band under the eyes closed state was significantly higher than that under the eyes open state (P<0.05). The C and σ values in the α-band under the eyes closed state were significantly higher than those under the eyes open state, and the L value was significantly lower than that under the eyes open state (P<0.05). The frontal-central-parietal connectivity and the central-parietal connectivity strength in the α-band under the eyes closed state were significantly higher than those under the eyes open state (P<0.05). The average PLI and C values in the α-band were moderately negatively correlated with the SampleEn of COPY (P<0.05). The average PLI of the left prefrontal area, left parietal area, and left occipital area in the α-band under the eyes closed state had a moderate negative correlation with the SampleEn of COPY. The average PLI of the left central region and the right occipital area in the eyes-closed state was moderately negatively correlated with the SampleEn of COPY. Conclusions During the standing balance, when there is no visual input, the stability of body balance decreases, accompanied by enhanced brain network connectivity in α-band and the requirement for efficiency enhancement in information processing in the brain. The brain adopts different neural strategies when performing postural control under various visual conditions.

Abstract:Objective To investigate the effects of high-definition transcranial direct current stimulation (HD-tDCS) on the modulation of the H-reflex and M-wave during ankle dorsiflexion-plantar flexion fatigue tasks to provide direction for the application of HD-tDCS in mitigating neuromuscular fatigue. Methods Twenty healthy young male participants were recruited and randomly assigned to either the real stimulation or sham stimulation group, with 10 participants in each group. The intervention consisted of a 5-day single-blind HD-tDCS application (duration: 20 min; intensity: 2 mA; target: Cz). Baseline measurements of the H-reflex and M-wave under resting conditions, M-wave during maximal voluntary isometric contraction (MVIC) of the dorsiflexor muscle, and MVIC torque of the dorsiflexor and plantar flexor muscles were obtained. An ankle dorsiflexion fatigue task was performed to determine the time to achieve fatigue for the task. The same fatigue task was repeated and evaluated one day after the intervention. A repeated-measures two-factor (stimulation condition × pre/post fatigue) analysis of variance (ANOVA) was used to analyze the effects of independent variables on the mechanical properties of the muscles and α-motoneuron conduction characteristics. Results After fatigue, voluntary activation (VA), maximal H-reflex (Hmax), maximal M-wave (Mmax), and dorsiflexor and plantar flexor MVIC torques in both groups were significantly reduced compared with pre-fatigue levels (P<0.05). However, compared to the real stimulation group, the sham stimulation group showed a more significant decline in VA and plantar flexor MVIC torque (P<0.05). Conclusions A continuous 5-day HD-tDCS intervention can effectively increase α-motoneuron activity at the spinal segment. It can also exert an inhibitory effect on reducing information transmission capacity at the peripheral neuromuscular junction under the ankle dorsi-plantarflexion fatigue task.

Abstract:Objective To conduct a multidisciplinary holistic intervention considering physical, behavioral, and psychological aspects to explain the internal mechanism of non-specific low back pain (NSLBP). Methods Surface electromyography (sEMG) signals, three-dimensional (3D) gait analysis system signals, and psychological scale conclusions related to the ‘crouching tiger’ treatment of NSLBP by Yijinjing were collected. The collected data were analyzed and modeled using the structural equation method. A multifidus muscle-motor function-quality of life (QOL) model was developed to elucidate the mechanism of action of NSLBP treatment using Yijinjing ‘crouching tiger’ training. Results The sEMG signals from the L5-S1 multifidus muscles of patients with NSLBP were significantly increased after treatment (P<0.05). After treatment, the patients’ step length, step frequency, step speed, maximum hip flexion angle, and maximum knee flexion angle significantly increased (P<0.05). The support, swing, and maximum ankle dorsiflexion angles significantly decreased (P<0.05). The SF-36 physiological, psychological, spiritual, and emotional scores of the patients before and after the ‘crouching tiger’ training were statistically significant (P<0.05). Structural equation model (SEM) showed that average electromyography (AEMG) and step size significantly impacted the Roland Morris and SF-36 scores at a level of 0.001. AEMG and step size had a positive impact on Roland-Morris and SF-36 scores. The standardized load coefficients were greater than 0.6, and the model fit was good. Conclusions The SEM model has good fitting effects and reliable results and can effectively describe the mechanism of NSLBP treatment by Yijinjing ‘crouching tiger’ training at multiple levels.

Abstract:Objective The reliability and validity of the SGGC-Net-based motion capture system (SGGC-Net system) and SIMI system for parsing walking gait were compared using a three-dimensional (3D) motion capture system (Vicon) with marker points as a reference standard. Methods Thirty healthy college students were recruited, and their gait characteristics while walking on a treadmill were analyzed. Kinematic data were collected using the Vicon system, and video data were collected synchronously using four cameras to obtain the right shoulder, elbow, hip, knee, and ankle joint angles. Reliability was assessed using intraclass correlation coefficients (ICCs) with 95% confidence intervals and standard error of measurement (SEM). Validity was assessed using multiple correlation coefficients (MCCs) and root mean square errors (RMSEs). Results The ICCs of the maximum and minimum 3D coordinate angles of the upper and lower limb joints of the SGGC-Net system ranged from 0.798－0.990 with an SEM of 0.04°－0.95°, and the ICCs of the SIMI system ranged from 0.650－0.967, with an SEM of 0.31°－1.24°. The ICCs of the SGGC-Net system were higher than those of the SIMI system for all joint angles except for the minimum hip and maximum knee angles. Compared to the joint angle curves derived from the SIMI system, the MCCs of the curves derived from the SGGC-Net system ranged from 0.945－0.996, with RMSEs of 1.44°－4.65°, and the multiple correlation coefficients of the SIMI system ranged from 0.815－0.986, with RMSEs of 2.56° － 9.99°. The MCCs of the SGGC-Net system were greater than those of the SIMI system at all angles except for the ankle joint. The RMSEs of the SGGC-Net system were smaller than those of the SIMI system at all angles except for the ankle joints. Conclusions The SGGC-Net system has better reliability and validity than the SIMI system in most of the variables, and it has better repeatability and accuracy in analyzing walking gait. It can be applied to motion capture environments without marker points, such as technical analysis of athletes’ movements and clinical gait analysis of special populations.

Abstract:Objective To propose a method for optimizing the design of diabetic foot insoles by combining the elastic modulus and thickness of footwear to reduce plantar pressure and internal stress in soft tissues. Methods A finite element model of The foot was established using reverse engineering techniques. Orthotic pressure regions were identified based on the characteristics of plantar pressure distributions. Contact mechanics were studied using the finite element method to lay the foundation for adjusting the elastic modulus of the materials and the thickness of the forefoot and rearfoot insoles in different regions during the optimization process. The optimal parameter combination was obtained using an optimal Latin hypercube design. Results The plantar contact area of the designed insole increased by approximately 37.55%, and the peak pressures in the metatarsal and heel regions were reduced by 15.07% and 36.96%, respectively. The internal stress in the soft tissues of the heel decreased by 20.83%. Tension in the plantar fascia decreased by 60%. Conclusions The proposed method can be used for designing customized insoles, and such designed personalized insoles have a greater contact area, with great potential in reducing diabetic foot ulcers.

Abstract:Objective To clarify the characteristics of shock wave sources generated at different medium interfaces. Methods The experiment used an in vitro adjustable impact pressure shock wave generation and signal acquisition system combined with a flexible PVDF sensor. The waveform of the shock wave generated by the applicator at the interface of different media (soft tissue-mimicking phantom, water and air) was explored. The characteristics of the shock wave source in the time and frequency domains were analyzed. Results When the same impact pressure was applied, shock waveforms generated at the interfaces of the phantom and water exhibited similar characteristics from a time-domain perspective. At the same time, both differed significantly from those generated at the air interface, where the absolute values of the positive and negative pressures were noticeably reduced. The characteristics of the shockwave spectra in various media revealed three distinct peak frequencies, with the modulation frequencies varying in the phantom (12.2 kHz), water (8.5 kHz), and air (7.2 kHz). In contrast, the carrier frequency remained relatively constant (between 82 and 83 kHz). When different impact pressures were applied, there was little influence on the waveform at the same medium interface, indicating that the impact pressure affected only the shockwave amplitude and not the peak frequency. As the impact pressure increases, the absolute values of the positive and negative pressures at the medium interface increase linearly. Conclusions Shockwave sources can be effectively measured using a flexible PVDF sensor. Shock waves generated at different medium interfaces exhibit temporal and spectral differences, indicating that the characteristics of shock wave propagation in air or water cannot be substituted for those in biological soft tissues. These findings provide crucial information for evaluating shockwave devices and formulating treatment protocols in the clinic.

Abstract:Objective To compare the effects of clear-aligner orthodontics with two orthodontic sequences on molar distalization. Methods A finite-element model of seven right mandibular teeth with periodontal alveolar bone and braces was established. Two molar distalization sequences were selected to simulate the distal movement of the second molar (0.5 mm), and the long-term tooth movement was simulated using the alveolar bone reconstruction technique. Results The maximum distal displacement of the second molar with V-pattern and ZC sequences was 0.27 mm and 0.34 mm, respectively, and the ZC distal displacement efficiency was increased by 13.34%. The tooth inclination was corrected by 0.18 mm and 0.44 mm, the lingual inclination was corrected by 1.15° and 2.69°, respectively, and the correction rate of ZC lingual inclination was increased by 15.01%. The distal tilt of the ZC increased by 1.83° and 0.84°, and the distal tilt of the ZC decreased by 54.10%. Conclusions The ZC sequence method can realize distal molar movement more effectively, reduce the distal inclination of the molar, and correct the lingual inclination of the molar, providing favorable conditions for orthodontic treatment of anterior teeth.

Abstract:Objective To evaluate the accuracy of three-dimensional (3D) reconstruction of the gallbladder volume based on computed tomography (CT) images and study the biomechanical changes in gallbladder motility to explore the relationship between gallbladder dynamics and gallstone formation. Methods A method for calculating gallbladder volume based on CT 3D reconstruction of The gallbladder model was proposed and compared with the ellipsoid method. A finite element model of the gallbladder was constructed for fluid dynamics analysis to simulate changes in gallbladder motor function under different angles of convergence between the cystic and common bile ducts and in the presence of gallstones. Results The mean errors of the specific gallbladder model volume and ellipsoid volume of the 50 patients were 7.26% and 25.35%, respectively. During the refilling period, the maximum pressure, deformation, and flow velocity of the pear-shaped gallbladder were significantly higher than those of the gourd-shaped gallbladder. The angle between the gallbladder and common bile duct had little effect on the bile flow pattern, and the maximum bile flow rate was reached at an angle of 120°. The bile flow velocity of the gallbladder with calculus was lower than that of the gallbladder without calculus, and there was a vortex near the calculus. Conclusions Calculating gallbladder volume based on CT 3D reconstruction is more accurate than the ellipsoid method. Compared with a pear-shaped gallbladder, a gourd-shaped gallbladder has lower gallbladder wall contraction, bile flow rate, and poor motor function. The bile flow rate in the gallbladder is slow, which is more likely to lead to the enlargement of gallstones or the formation of new gallstones.

Abstract:Objective To simulate the microflow field environment between the anastomotic nail surface and intestinal wall tissue after implantation and to study the effect of hydrophobic surfaces on the flow rate of extracellular fluid and the fluid shear force on the wall to regulate bacterial adhesion through changes in the flow field. Methods The microstructure of shark skin was observed, and a simplified two-dimensional (2D) movement model of bacteria in a microflow field was established. Using computational fluid dynamics (CFD) numerical simulation, the movement of bacteria on a smooth surface and micro-textured surface in a static and dynamic flow field were simulated. The flow field characteristics around bacteria and the magnitude of fluid shear force under the two surface environments were compared, and the internal mechanism of the fluid shear force affecting bacterial adhesion was analyzed. Results The addition of the biomimetic microtexture enhanced the flow rate of the extracellular fluid in the microflow field, and the fluid had little viscous effect on the bacteria in the static flow field. The fluid in the dynamic flow field had a stronger pushing effect on the bacteria. The fluid shear force on the microtextured wall increased when the pit width was within a specific range. Conclusions The bionic micro-textured surface of the anastomotic nail can accelerate the flow rate of extracellular fluid, increase the fluid shear force of micro-textured walls and bacteria, and influence bacterial adhesion. These results provide a theoretical basis for studying bacteriostatic surfaces of anastomotic nails.

Abstract:Objective To explore the prognostic value of the coronary angiography-derived index of microcirculatory resistance (caIMR) for major adverse cardiovascular events (MACE) in patients with acute ST-segment elevation myocardial infarction (STEMI) after primary percutaneous coronary intervention (PCI). Methods Between September 2019 and March 2022, 541 patients diagnosed with STEMI at the Affiliated Hospital of Xuzhou Medical University were enrolled. The caIMR was calculated using the FlashAngio system (Suzhou Rainmed Medical Technology Co., Ltd.). The patients were divided into MACE and non-MACE groups according to the occurrence of MACE during hospitalization or follow-up, with MACE defined as all-cause mortality, heart failure readmission, and unplanned revascularization. COX regression analysis, receiver operating characteristic (ROC) curves, and Kaplan-Meier survival curves were used to evaluate the prognostic value of caIMR for STEMI patients after primary PCI. Results During the 1-year follow-up, 61 patients (11.28%) experienced MACE. The patients in the MACE group had higher caIMR values than those in the non-MACE group. Multivariate COX analysis showed that caIMR was an independent risk factor for MACE. ROC curve analysis showed that caIMR predicted MACE with an area under the curve of 0.688, and the optimal cutoff value was 25.3 U. caIMR significantly increased the discriminant and reclassification indexes when added to a model with clinical risk factors. The patients were further divided into a low caIMR group (caIMR<25 U, n=377) and a high caIMR group (caIMR≥25 U, n=164). Kaplan-Meier curve showed that patients with caIMR≥25 U had a worse prognosis. Conclusions caIMR is an independent risk factor for poor prognosis after PCI in patients with STEMI, and patients with caIMR≥25 U had a worse prognosis.

Abstract:In recent years, the incidence of cardiovascular diseases has been gradually increasing, leading to a growing demand for regenerative blood vessels in clinic. Currently, large-caliber artificial blood vessels (diameter>6 mm) have been successfully applied in clinical practice. However, small-caliber artificial blood vessels (diameter< 6 mm) still face challenges in long-term patency rates after transplantation due to thrombosis, intimal hyperplasia, inflammatory reactions, and poor compliance which leads to hemodynamic changes. Achieving rapid endothelialization, inhibiting thrombus formation, and matching the compliance of autologous vessels remain key factors to be addressed. This article provides a brief overview of commonly used materials and techniques for preparing small-caliber artificial blood vessels, with a focus on discussing strategies to improve biocompatibility and compliance. Furthermore, future research work is also prospected.

Abstract:The role of photoplethysmography (PPG) in the functional assessment of the cardiovascular system at home and abroad was summarized to provide theoretical references and lessons for the medical application of PPG and innovative research. Currently, functional assessment indices such as heart rate, heart rhythm, blood pressure, and volume can be analyzed from PPG signals, which can also assist in identifying and diagnosing abnormal blood pressure, diabetes mellitus, cardiac arrhythmia, sleep apnea syndrome, early ischemic shock, and other diseases. However, the accuracy and precision of PPG, data interpretation and standardization, waveform analysis, and clinical applications remain controversial. PPG has been widely used in medical and scientific research to effectively assess the functional status of the cardiovascular system and assist in diagnosing various diseases. In the future, PPG is expected to show a multipath development trend in high-precision, multi-parameter, noncontact, remote monitoring, and medical treatment.

Abstract:The endothelial glycocalyx (EG) is a polyglycoprotein complex present on the internal vascular surface, and its impairment is associated with the progression of multiple diseases, including atherosclerosis, stroke, sepsis, diabetes, kidney disease, hypertension, and lung edema. Therefore, glycocalyx health can be used as a biomarker to evaluate vascular health. Aging leads to dysfunctional changes in the glycocalyx; for example, its thickness decreases, and the genes of enzymes involved in its synthesis and digestion are dysregulated. As a natural barrier to the vascular system, age-related glycocalyx disruption is associated with vascular dysfunction, including impairment of vascular contraction and dilation, enhancement of permeability, dysregulation of inflammatory and immune reactions, and imbalance of anticoagulation and thrombin. From the perspective of ‘structure determines function’ studies on the changing regularity of the thickness, components, microstructure, and mechanical properties of EG with aging and its relationship with vascular dysfunction are of great significance for the prevention, diagnosis, and treatment of atherosclerosis and other age-related cardiovascular diseases.