Journal of Mechanics in Medicine and Biology

In the recent years, poorly evaluated gynecological surgeries and urogynecological mesh implantations have been affecting millions of women in the US and across the globe. These failed surgeries could be mainly attributed to the nonavailability of vaginal tissues (due to ethical and biosafety issues), which does not allow any experimental testing of operation and mesh implantation techniques before an actual surgery. A surrogate which behaves biomechanically like the human vaginal tissue would be indispensable for simulating surgical suture of vaginal tissues in prolapse surgery, hysterectomy or surgery during traumatic child births (such as Cesarean). Also, vaginal tissue surrogates simulating the various prolapse conditions (such as vaginal tissue stiffening) would be very useful to evaluate tissue modifications due to prolapse, and also mesh and vaginal tissue interactions. In the current work, a low cost four-part silicone-based material was developed, which precisely simulates the linear and nonlinear mechanical behavior of the normal human vaginal tissue. Additionally, a range of four-part silicone-based novel materials were developed which precisely mimics the mechanical behavior of stiffened vaginal tissues at different degrees of prolapse. The linear and nonlinear mechanical behavior of all such novel materials were characterized using elastic and hyperelastic formulations. Such precisely characterized normal and prolapsed vaginal tissue surrogates have not been developed anywhere to date as per the best of our knowledge and would be clinically helpful for gynecological surgical planning in the future.

This study investigates the feasibility of using high-resolution ultrasound imaging echogenicity to quantitatively diagnose gingival inflammation. Gingival samples were extracted from the study participants during gingivectomy procedures. Ultrasound mechanical scanning of the samples was immediately conducted ex-vivo to render cross-sectional images of high resolution, at different locations. Samples’ histological preparation and analysis was followed after performing ultrasound imaging. Histological sections were then matched with ultrasound images at different sections for each gingival sample. The matched image pairs were used to estimate two quantitative measures; relative inflammation area and ultrasound image echogenicity. These parameters were employed to judge the diagnostic potential of gingival ultrasound imaging. The results show that ultrasound images exhibited low intensity levels at the inflamed gingival regions, while healthy layers showed higher intensity levels. The relative area parameter implied a strong relationship between ultrasound and histological images. Ultrasound echogenicity was found to be statistically significant in differentiating between some inflammation degrees in the studied gingival samples. In summary, ultrasound imaging has the potential to be a noninvasive adjunct diagnostic tool for gingival inflammation, and may help assess the stage of the disease and ultimately limit periodontal disease occurrence; taking into consideration the limits of this study.

This paper discusses several new mechanisms that may be used in prostate cancer seed implant robotics. Aiming at the limitation of human body structure space, and in order to improve robotic kinematic dexterity and execution efficiency. We have developed an articulated seed implantation robot with three-dimensional transrectal ultrasound navigation. It is noteworthy that the organization will produce displacement, deformation and needle tip deflection and other issues while needle inserting prostate. In order to improve positioning accuracy of robot to control the puncture needle, a piezoelectric vibration and rotation needle insertion device is designed and developed. Based on the evaluation experiment of vibration and rotation needle insertion, a high accuracy mixed needle insertion strategy is proposed and the corresponding control software is designed. Finally, the insertion force evaluation experiment is completed by mixed needle insertion strategy, and the experimental results validate the effectiveness of this method.

The use of custom implants has recently gained increasing importance in craniofacial surgery in order to optimize preoperative planning and reduce operative time. The design of patient-specific implants plays an important role to restore craniofacial bone. Nevertheless, the design method has become the bottleneck. In this study, a new design method of a maxillofacial prosthesis based on the topology optimization was proposed to realize lightweight custom implants. At first, parametric predesign of the optimized model was carried out to ensure that the optimized model conformed to the main physiological anatomical structure and recover basic function structure. Then, the design region is defined under given load and boundary conditions. The material interpolation technique of SIMP with the penalization factor is adopted to get the final optimized 3D model. Finally, the experimental results verify that the method of topology optimization for the maxillofacial prosthesis proposed is efficient.

Overshooting during trocar insertion may injury patient viscera and arteries or even lead to death. It has been extensively cited as a kind of common medical negligence. Hence, this paper investigated the force characteristics during a trocar inserted into the abdominal wall and developed strategies for effective stopping upon the trocar penetrated out of the abdominal wall. First, an experimental platform with two degrees of freedom was assembled. Second, two insertion methods were compared and the insertion forces using three types of trocars were measured respectively. Subsequently, we interpreted the force characteristics in terms of insertion principle and the abdominal structure. And based on the force characteristics, we generated two algorithms for the two insertion methods, which can be utilized to stop inserting effectively upon the trocar penetrated out of the abdominal wall. Finally, we evaluated the merits and demerits of the two algorithms. This paper proposed the interpretation of force characteristics during trocar insertion and achieved effective stopping to avoid overshooting. It provides foundations for the development of automatic trocar insertion device in the future.

Thermal osteonecrosis of bone in drilling procedure is caused by improper parameters which can lead to poor bone-implant integration and loss of fixation. In this study, Taguchi technique for parameter optimization and multiple regression models for temperature prediction were employed. The main aim of the study was to determine the optimal parameters of bone drilling to control the temperature rise below the thermal osteonecrosis threshold (47${}^{\circ }$C) in respect of the bone density variations at different drilling directions. A 3² full factorial design with nine sets of parameters was used in the study. Drilling operations were performed along the longitudinal, radial and circumferential directions at the proximal-diaphysis, mid-diaphysis and distal-diaphysis regions of the 10 adult cadaveric femurs with different feed rates (40, 60 and 80mm/min) and spindle speeds (500, 1000 and 1500rpm) using 3.2mm diameter surgical drill bit. The in-situ drilling temperatures were measured with T-type thermocouple. The optimum drilling parameters for each drilling direction were determined from signal to noise ratios and the effect of each parameter was determined using analysis of variance. By using computed tomography scan data of patients, the proposed method is able to predict the temperature rise at the bone-drilling sites, optimal parameters and possibility for the occurrence of thermal osteonecrosis. This important tool could assist in reducing localized temperature induced from surgical drilling by up to 32% and 18${}^{\circ }$C and as such significantly reduce associated osteonecrosis and improve patient outcome and quality of life.

In this study, our attention is mainly on elaborating a computational strategy to effectively predict the influence of prism profiles on the overall anisotropic property of human enamels (HEs). At first, two distinct schemes are developed separately with the aid of the polynomial fitting technique and the general power functions to mathematically describe the practical irregular and simplified regular profiles of enamel prisms. Hereafter, two parametric piecewise formulas, which facilitate the definition of anisotropic material properties of finite elements at different locations and make the numerical simulation of HE microstructures consisting of irregularly shaped prisms feasible, are presented to describe the orientation of hydroxyapatite (HAP) crystallites embedded in microprisms. The effective anisotropic moduli over a representative unit cell (RUC) under the periodic displacement constraint is concisely introduced according to the micromechanics, and a computational strategy is established to calculate these moduli numerically. Finally, the evaluations in the open literature are employed to demonstrate the validity of the elaborated computational strategy, and more investigations are conducted and yield the conclusions such that the material property of the inter-prism regions as well as the prism shapes plays a crucial role in determining the overall anisotropy of HEs.

Under the widespread umbrella of dementia, Alzheimer’s disease is the most common form of dementia. Most of the aged people are suffering from Alzheimer’s disease around the world. The reasons for the same are not known in detail and thus various experimental and computational attempts need to be carried out. Calcium, being a second messenger has an immense role in transformation of information. This transformation takes place in the form of signaling in which several parameters play an active role. In present work, an attempt has been made to describe the effect of calcium signaling in nerve cells for Alzheimer’s disease. Here, parameters like advection diffusion and buffering are taken into consideration to visualize the effects of the same on cytosolic calcium concentration. This physiological process is modeled two dimensionally and solved analytically. Laplace and similarity transforms are employed to obtain the desired results. The results are simulated and graphically plotted using MATLAB. The known fact that the higher concentration of calcium has adverse effects on the cell which may result into progression of AD is considered as a lantern in enlightening the physiology of Alzheimer’s disease.

This study compares certain kinematic and kinetic parameters in giant circles performed before twisting, double stretched and double tucked dismounts using the dynamic model in the SimMechanics environment. The joint moments calculated using the designed model were investigated for the three different dismounts. The study included a 13-year-old voluntary national gymnast with seven years of training history. Markers were placed on the wrist, elbow, shoulder, hip, knee and ankle joints of the gymnast. The gymnast was asked to perform twisting, double stretched and double tucked dismounts. MATLAB and SimMechanics were used to calculate joint moments. The moves were simulated and the joint moments during the moves were calculated using the SimMechanics toolbox. The study observed that the highest joint moment was in the wrist joint in all three dismounts, in line with the findings of previous studies. However, unlike other studies, higher joint moments were calculated in the accelerated giant circle performed together with thrusts, compared with the regular giant circle. While there were similar maximum moment values in twisting dismounts and double tucked dismounts, an almost three times higher moment was observed in double stretched dismounts. In terms of joint moments, stretched dismount is obviously the most difficult move, which is consistent with the difficulty levels. A recorded performance of the mechanical model created in the SimMechanics environment was investigated in terms of the twist angle and moments generated on the bar, and found to be sufficient and useful. However, there are certain restrictions regarding the methods employed in this study. We concluded that the mechanical model will allow for the performance of kinematic and kinetic analyses of different gymnasts and types of moves thanks to its flexible structure.

Acoustic emission (AE) is a nondestructive testing (NDT) technique used for detecting damages, cracks, and leaks in different structures such as metals, composites, wood, fiberglass, ceramics, plastics, etc. In recent years, AE has gained popularity within the field of biomedical applications. The structure of bone is similar to composite materials, therefore, it is advantageous to use NDT technique. Thus, it can be used for monitoring the fracture behavior, crack initiation/propagation, and fatigue detection in bones. The goal of this study was to determine the usefulness of AE techniques in fracture detection phase of bones and to develop an NDT methodology for the monitoring of crack initiation and propagation in bones. This study describes AE activity during fracture of bone tissue under tensile loads. The experiments were carried out in vitro techniques using intact and fracture-simulated bovine tibias. The specimens were loaded to failure in tension using a mechanical testing machine. During the mechanical tests, AE signals were measured and recorded by using AE system processor equipped with two wideband piezoelectric sensors fixed to the surfaces of both ends of the test specimens. By superposing the load–time curve and the cumulative AE event–time curve, AE activities of crack initiation and propagation were identified. In all experiments, the cumulative AE number for each period of time rose up exponentially with the incremental tensile load. Load for AE initiation demonstrated a convincing linear interaction with AE event generation.

Starting from experimental data, this work exploit the similarity of pressure and axial wave’s propagation of both pressure and axial waves in large vessel (e.g., aorta) with the solution of a mathematical model developed to describe the motion of acoustic waves in solid. In particular, we show how the motion parameters derived by fitting the experimental data measured in living dog arteries are related to mechanical properties of the vessel tissue using the same theoretical model. Furthermore, we briefly discuss the consequence on the predicted forced wave motion of inferring from experimental data a phase velocity depending from frequency.

According to the vibration characteristics of the round window membrane, a mechanical model that contains round window membrane and the soft tissue is established. The Euler equation of the whole of round window membrane and the soft tissue and the complementary boundary conditions are derived by the variational principle. Combined with the Bessel function, the analytical solution of the total displacement of round window membrane and the soft tissue is obtained by using Mathematica. The results are in good agreement with experimental data, which confirms the validity of the analytical solution of the model. At the same time, the effect of different thicknesses and different elastic modulus of soft tissue on the total displacement of round window membrane and soft tissue is studied by analytical method. The results show that with the thickening of the soft tissue, the total displacement of round window membrane and the soft tissue decreased gradually. However, with the decrease of elastic modulus of the soft tissue, the total displacement of round window membrane and the soft tissue increased gradually. Furthermore, the relationship between thickness and elastic modulus of the soft tissue and the corresponding range selection is achieved, which can evaluate the transmission performance of round window membrane efficiently and provide theoretical basis for the reverse excitation of artificial prosthesis.

Of concern in the paper is the development of a mathematical model of blood flow in the microcirculatory system. The study pertains to a situation, where the system is subject to the action of an external AC electric field and the flow is oscillatory. The general case when the frequency of the electric field is different from that of the flow has been studied. Blood is treated as a couple stress fluid. The flow is supposed to take place between two oscillatory plates and is considered to be of electro-osmotic type. Our study is aimed at examining the effect of couple stress at different frequencies of the capillary wall and the applied AC electric field on electroosmotic flow of blood. The computational results indicate very clearly that the electrokinetic velocity of blood reduces as the couple stress effect increases and that the velocity reduces, when the Reynolds number rises. The results of the present study will serve as a reasonably good estimate for electro-osmotic transport of blood in small blood vessels.