Journal of Mechanics in Medicine and Biology

Purpose: Based on rapid modeling 1 year after intramedullary nailing, personalized finite element modeling analysis was performed to predict whether the broken ends of fractured bones would break again after nail dislodgement. Methods: A total of 10 male volunteers with femur fractures who had undergone intramedullary nailing were selected 1 year after fixation and were divided into healing ($n=$5) and non-healing ($n=$5) groups based on X-ray analysis. We modeled each femoral fracture and performed finite element analyses after the intramedullary nail was dislodged. Static loads and constraints were applied to each model to simulate a person standing on one leg. Results: In the healing group, the von Mises stress concentrations and stress concentration point distribution were located outside the bone healing area, indicating that the stress was not concentrated at the fracture site. In the non-healing group, the maximum von Mises stress for various materials was located in the broken ends of the fractured bone, indicating that the stress was concentrated at the fracture site. Conclusion: Personalized modeling can be used to analyze bone healing before removal of a fixator to predict the stability of the fractured bone after fixator removal and to rapidly decide whether slow walking could refracture the broken ends.

The severe ambient temperature always disrupts the normal thermoregulatory system of the human body. The decrease in core temperature leads to hypothermia and the development of cold injuries takes place at the exposed shells of the human body. The intensity of the cold exposure and its duration leads to various degrees of frostbites and resulting cell damage and fluid passage from the necrotic regions. In this paper, variational finite element has been employed to estimate the thermal damage due to severe cold conditions. The formulation of the model is based on Pennes’ bioheat equation and mass diffusion equation. Moreover, the fluid passage from the cold injuries at the peripheral tissues of the human body with respect to extreme cold conditions has been analyzed in relation with other parameters.

The peristaltic flow of a carbon nanotubes (CNTs) water fluid investigate the effects of heat generation and magnetic field in permeable vertical diverging tube is studied. The mathematical formulation is presented, the resulting equations are solved exactly. The obtained expressions for pressure gradient, pressure rise, temperature, velocity profile are described through graphs for various pertinent parameters. The streamlines are drawn for some physical quantities to discuss the trapping phenomenon. It is observed that pressure gradient profile is decreasing by increase of Darcy number $D_a$ because Darcy number is due to porous permeable walls of the tube and when walls are porous fluid cannot easily flow in tube, so that will decrease the pressure gradient.

The physiological processes taking place in human body are disturbed by the abnormal changes in climate. The changes in environmental temperature are not effective only to compete with thermal stability of the system but also in the development of thermal injuries at the skin surfaces. Therefore, it is of great importance to estimate the temperature distribution and thermal damage in human peripherals at extreme temperatures. In this paper, the epidermis, dermis and subcutaneous tissue were modeled as uniform elements with distinct thermal properties. The bioheat equation with appropriate boundary conditions has been used to estimate the temperature profiles at the nodal points of the skin and subcutaneous tissue with variable ambient heat and metabolic activities. The model has been solved by variational finite element method and the results of the changes in temperature distribution of the body and the damage to the exposed living tissues has been interpreted graphically in relation with various atmospheric temperatures and rate of metabolic heat generation. By involving the metabolic heat generation term in bioheat equation and using the finite element approach the results obtained in this paper are more reasonable and appropriate than the results developed by Moritz and Henriques, Diller and Hayes, and Jiang et al.

Seasonal depression seriously diminishes the quality of life for many patients. To improve their condition, we propose LUXAMET, a bright light therapy system. This system has the potential to relieve patients from some of the symptoms caused by seasonal depression. The system was designed with a formal and model driven design methodology. This methodology enabled us to minimize systemic hazards, like blinding patients with an unhealthy dose of light. This was achieved by controlling race conditions and memory leaks, during design time. We prove that the system specification is deadlock as well as livelock free and there are no invariant violations. These proofs, together with the similarity between specification model and implementation code, make us confident that the implemented system is a reliable tool which can help patients during seasonal depression.

One of the main procedures in the most minimally invasive cardiothoracic surgery is clamping the ascending aorta to disconnect the heart from circulation. In this paper, a new aortic clamping instrument which is applicable in minimally invasive cardiac surgery has been presented. The instrument consists of a parallelogram mechanism for opening and closing the jaws, a detachable holder with a two degree of freedom joint that makes the precise position and orientation of the jaws and leaves the clamping component in the patient’s body to make the inserting port free, and a handle for easy manipulation. In vitro test has been performed to evaluate the performance of the clamper compared to the conventional clampers. For this purpose, the force required for aortic cross-clamping and the maximum aortic displacement have been studied in four groups including parallel clamper and conventional clamper with angles of 1${}^{\circ }$, 2${}^{\circ }$, and 3${}^{\circ }$ between jaws, with 10 bovine aorta specimens in each group. These experiments show that the amount of required force for cross-clamping by using the parallel clamper, is statistically significant ($P<0.001$) compared with the conventional clampers. Also, the increase of angle between jaws makes a significant increase in the percentage of aortic displacement.

Arterial stenosis plays a key role in the development and formation of cardiovascular diseases. The effects of arterial stenosis on the global hemodynamic characteristics of human artery tree were studied based on a previously proposed transmission line model of 55 segment arterial tree. Different position, degree and length of the arterial stenosis were simulated to discuss the changes of blood pressure and flow waveform in human arterial tree. The stenosis degree of 50% to 90% were specified to represent a mild, moderate or severe stenosis. Three representative stenosis positions: aorta, carotid and iliac artery were selected. The stenosis length was specified to be 1cm to 4cm. The results of simulation were compared with the literature data. And ankle branchial index (ABI) was calculated to show its relationship with the stenosis position. The results showed that the influence of aorta stenosis on the blood pressure and flow waveforms of upstream artery is more obvious than those of downstream artery; branch artery stenosis has more influence on the blood pressure and flow waveforms of downstream artery than those of upstream artery. When the stenosis degree increased to 80%, the blood pressure and flow waveforms are affected significantly. The stenosis length causes a obvious change in the pressure and flow waveforms of stenosis inlet and outlet. The comparisons of literature and ABI demonstrated that the modeling method is a feasible tool to simulate and study the hemodynamics of the human artery stenosis.

Atherosclerosis is one of the main causes of death in the developed world. The disease, which is an inflammatory disease, has been the focus of many studies. A few studies attempted to model atherosclerosis lesion development mathematically while no attention has been paid to the multistage nature of the disease. The present study provides a mathematical model for atherosclerosis evolution by focusing on the inflammatory responses of the initial stage of the disease. In the model, the inflammatory response in type I lesion, which includes endothelium dysfunction, LDL oxidation, monocytes entry, foam cell formation and intima property changes, are coupled with the transport equations of blood and LDL in lumen and arterial wall. The innovation of the model is determination of the duration of the initial stage of lesion propagation for a specific patient while the presence of leaky junction in endothelial layer and LDL oxidation in the intima layer are considered. The greatest advantage of the study in comparison with previous studies is to provide a model for the initiating stage of the atherosclerosis development so that a more precise result of the disease evolution is obtained.

Many medical groups have used wireless battery charging technology for rechargeable batteries used in implantable devices. During charging, battery heat is lost from the battery and other heat sources within an implantable device, which may be harmful to patients’ tissues. Therefore, charging batteries with minimum discomfort to patients while replenishing battery capacity as much as possible is a challenge. In this paper, a constant voltage with a different limiting current strategy for a lithium-ion polymer battery is proposed, thereby modulating the limiting current rate that reduces battery temperature increase. Experiments show that better safety charging performance for 260, 600, and 1000mAh lithium-ion polymer batteries can be obtained by the proposed current-limiting method. Compared with conventional constant-current–constant-voltage charging strategies, the maximum battery temperature increase is improved.

Fixation strength of the cementless knee prostheses is dependent on the initial stability of the fixation and minimal relative motion across the prosthesis–bone interface. Broad mini-keels have been developed for tibial components to allow minimally invasive knee arthroplasty, but the effect of the change in fixation design is unknown. In this study, bone–prosthesis interface micromotions of the mini-keel tibial components (consisting of two designs; one is stemless and another with a stem extension of 45mm) induced by walking and stair climbing were investigated by finite element modeling and compared with standard stemmed design. The prosthesis surface area amenable for bone ingrowth for the mini-keel tibial components (both stemmed and unstemmed) was predicted to be at least 67% larger than the standard stemmed implant, thereby reducing the risk of long-term aseptic loosening. It was also found that while different load patterns may have led to diverse predictions of the magnitude of the interface micromotions and the extent of osseointegration onto the prosthesis, the outcome of design change evaluation in cementless tibial fixations remains unchanged. The mini-keel tibial components were predicted to anchor onto the periprosthetic bone better than the standard stemmed design under all loading conditions investigated.

Coupled mathematical models for the radiofrequency (RF) ablation performed in biomedical sciences have been developed based on the bioheat transfer theory. The heat exchange problem is important to be analytically studied in order to control the size of the necrosis zone caused by RF ablation. This lesion size in the tissue may be predicted by the knowledge of the internal tissue temperature. We propose an analytical solution for the Pennes heat transfer equation in bi- and tri-region domains, applicable to the RF ablation of cancerigeneous tissue — a clinical relevant problem. The model consists of two partial differential equations describing the spatio-temporal interactions between the electric and thermic effects. The aim is to find simple algebraic expressions of analytical solutions that may allow to generate quantitative results which in turn may be interpreted (including uncertainties). The dependence of the temperature as function of the electrothermal parameters in both diseased and surrounding healthy tissues is pointed out. Two cases, namely the tumor–tissue and tumor–tissue–skin systems, are graphically computed, and important findings include the fact that the presence of tissue with smaller value parameters protects somehow healthy cells. Moreover, the graphical representations are conducted to highlight the link of the profile of current density distribution in the physiological problem with the (neither oval nor circular) shape of the temperature isoclinic lines.

Reverse shoulder arthroplasty (RSA), in which anatomic concavities of glenohumeral (GH) joint are inverted, is a popular treatment of arthritic shoulders with deficient rotator cuff. The correct positioning of the glenohumeral center of rotation and initial setting of the deltoid length (Deltoid Tension) plays an important role in the outcome of the RSA. A study of the key literature has shown that despite common use of RSA, its biomechanical characteristics during motion are not fully understood. This study investigates the influence of some of the key parameters on the intensity of the moment in a shoulder after RSA during abduction in scapular plane. The kinematics after RSA are then compared with the anatomic shoulder kinematics and differences are discussed. Mathematical models of both the anatomical and reverse shoulder (RS) were developed in MATLAB and in MSC ADAMS. The anatomical and RSA geometries were defined using measurements obtained from X-ray and magnetic resonance imaging (MRI) images of the shoulder girdle. The results show that in RSA, the intensity of the moment generated in the GH joint improves. However, this improvement does not show a constant trend and its intensity can dramatically decrease in higher GH joint abduction.

This work considers a theoretical study for the conversion of the pulsating arterial pressure into electrical energy using piezoelectric layer on a micro-plate with axial load. The mathematical modeling of the device is carried out. Analytical and numerical methods are used to analyze the dynamical behavior of the plate and the variation of the electric power output. Pulsatile voltage is obtained with electric power of the order of 3.07nW for a plate of $84\cdot 10^{-6}$cm³. The power increases with the pressure frequency and attains its maximal value for a load resistance of about 5k$\mathrm{\Omega }$.

In this paper, the biomechanical effectiveness of prophylactic augmentation in preventing fracture was investigated. In vitro biomechanical tests were performed to assess which factors make prophylactic augmentation effective/ineffective in reducing fracture risk. Nondestructive and destructive in vitro tests were performed on isolated osteoporotic vertebrae. Five sets of three-adjacent-vertebrae were tested. The central vertebra of each triplet was tested in the natural condition (control) non-destructively (axial-compression, torsion) and destructively (axial-compression). The two adjacent vertebrae were first tested nondestructively (axial-compression, torsion) pre-augmentation; prophylactic augmentation (uni- or bi-pedicular access) was then performed delivering 5.04mL to 8.44mL of acrylic cement by means of a customized device; quality of augmentation was CT-assessed; the augmented vertebrae were re-tested nondestructively (axial-compression, torsion), and eventually loaded to failure (axial-compression). Vertebral stiffness was correlated with the first-failure, but not with ultimate failure. The force and work to ultimate failure in prophylactic-augmented vertebrae was consistently larger than in the controls. However, in some cases the first-failure force and work in the augmented vertebrae were lower than for the controls. To investigate the reasons for such unpredictable results, the correlation with augmentation quality was analyzed. Some augmentation parameters seemed more correlated with mechanical outcome (statistically not-significant due to the limited sample size): uni-pedicular access resulted in a single cement mass, which tended to increase the force and work to first- and ultimate failure. The specimens with the highest strength and toughness also had: at least 25% cement filling, cement mass shifted anteriorly, and cement-endplate contact. These findings seem to confirm that prophylactic augmentation may aid reducing the risk of fracture. However, inadequate augmentation may have detrimental consequences. This study suggests that, to improve the strength of the augmented vertebrae, more attention should be dedicated to the quality of augmentation in terms of amount and position of the injected cement.

The aim of the present study was to analyze the surface electromyography (sEMG) activities generated by the three heads of the triceps brachii (TB) muscle among the different phases during fast and spin bowling. sEMG signals from the lateral, long and medial heads of the TB from 20 bowlers were measured individually during bowling. To analyze the sEMG activities, the root mean square (RMS) value in each bowling phase for every trial per bowler was calculated from the sEMG signals from the three heads of the TB. Higher sEMG activities at the three heads of the TB were found during the fifth phase followed by the sixth, seventh, third, fourth, second and first phases in both types of bowling. sEMG activities were significantly different among the three heads of the TB and among the seven bowling phases for both bowling types at an alpha level of $p<0.05$. These findings will be of particular importance for assessing different physical therapies for the three headed TB muscle which can improve the performance in ball delivery of cricket bowlers.