Journal of Mechanics in Medicine and Biology

A novel healthy state monitor method of upper limb for space flight task is proposed. Without taking other complex diagnosis equipment in orbit, this method only uses the ordinary exercise instruments to collect and analyze the multiple muscle forces of astronauts, and deduces where the serious muscle atrophy occurs in their muscle groups of upper limb. First, the typical multiple muscle forces data of upper limb are accumulated. A 45-day 6-degree head-down tilt bed rest experiment together with a multiple muscle forces test experiment are carried out to collect the corresponding data. These data include both the muscle force data of healthy state and the related data of unhealthy state. Second, the Wavelet Packet Transform (WPT) and the Empirical Mode Decomposition (EMD) methods are used to compute the signal features of these data above. Third, a Support Vector Machine (SVM) classifier is trained by the related signal features. Finally, the trained SVM can be utilized to evaluate the healthy state of upper limb in orbit for astronaut. If the output of SVM is negative, the C-means method and the Euclidean distance can be used to locate the abnormal muscle forces and muscle groups. The concept of typical muscle group health state evaluation for upper limb is emphasized in this paper. The comparisons among the traditional diagnosis-based method, the electromyogram (EMG)-based muscle forces analysis method, and the proposed method are made. Many experiment results on ground have verified the effectiveness of proposed method.

Uncertainty quantification in rigid musculoskeletal modeling is essential to analyze the risks related to the simulation outcomes. Data fusion from multiple sources is a potential solution to reduce data uncertainties. This present study aimed at proposing a new data fusion rule leading to a more consistent and coherent data for uncertainty quantification. Moreover, a new uncertainty representation was developed using imprecise probability approach. A biggest maximal coherent subsets (BMCS) operator was defined to fuse interval-valued data ranges from multiple sources. Fusion-based probability-box structure was developed to represent the data uncertainty. Case studies were performed for uncertainty propagation through inverse dynamics and static optimization algorithms. Hip joint moment and muscle force estimation were computed under effect of the uncertainties of thigh mass and muscle properties. Respective p-boxes of these properties were generated. Regarding the uncertainty propagation analysis, correlation coefficients showed a very good value ($R=1$) for the proposed fusion operator according to classical operators. Muscle force variation of the rectus femoris was computed. Peak-to-peak (i.e., difference between maximal values) rectus femoris forces showed deviations of 55N and 40N for the first and second peaks, respectively. The development of the new fusion operator and fusion-based probability-box leads to a more consistent uncertainty quantification. This allows the estimation of risks associated with the simulation outcomes under input data uncertainties for rigid musculoskeletal modeling and simulation.

The morphometry of the abdominal aortic aneurysms (AAA) has been recognized as one of the main factors that may predispose its rupture. The variation of the AAA morphometry, over time, induces modifications in hemodynamic behavior which, in turn, alters the spatial and temporal distribution of hemodynamic stress on the aneurismatic wall, establishing a bidirectional process that can influence the rupture phenomenon. In order to evaluate potential correlations between the main geometric parameters characterizing the AAA and hemodynamic stresses, 13 unrupture AAA patient-specific models were created. To AAA geometric characterization, 12 indices based on lumen center line were defined and determined. The computing of temporal and spatial distributions of hemodynamic stresses was conducted through Computational Fluid Dynamics. Statistical techniques were used to assess the relationships between the hemodynamic parameters and the different geometrical indices of the AAA. Regression analyses were conducted to obtain linear predictor models for hemodynamic stresses using the different indices defined in this paper as predictor variables. The statistical analysis confirmed that the length L, the asymmetry and the saccular index significantly influenced the hemodynamic stresses. The results obtained show the potential of the use of statistical techniques in predicting the rupture risk of patient-specific AAA.

False tendons (FT) are additional chord-like structures in left ventricle (LV) cavity considered as a phenotypic feature of the connective tissue dysplasia (CTD) syndrome. The search for a range of heart adaptability to exercise loads of young athletes with FT in LV is the aim of the proposed study. Sixty six members of student basketball and indoor soccer teams (mean age: 19.8$\pm$3.9 years) underwent treadmill stress-test and heart ultrasound transthoracic examination. Further, image processing to perform the tendons mapping within LV 3D-reconstructed model was applied. The number of FT located in different parts of LV varied from 1 to 6 units per LV. Based on the comparative and correlation analyses of data obtained, we found that the more the number of FT per LV, the less is a range of the heart adaptation to increased exercise loads. In accordance with the results of two-way multivariate analysis of variance, we concluded that the FT, located in basal and median LV zones, connecting interventricular septum and posterior-lateral parts of LV wall mainly affect the ability of the heart to adapt to exercise loads. Therefore, athletes with certain number and types of FT in the LV critically need individual prescription for exercise loads.

The geographic distribution of different viruses has developed widely, giving rise to an escalating number of cases during the past two decades. The deterministic Susceptible, Exposed, Infectious (SEI) models can demonstrate the spatio-temporal dynamics of the diseases and have been used extensively in modern mathematical and mechano-biological simulations. This article presents a functional technique to model the stochastic effects and seasonal forcing in a reliable manner by satisfying the Lipschitz criteria. We have emphasized that the graphical portrayal can prove to be a powerful tool to demonstrate the stability analysis of the deterministic as well as the stochastic modeling. Emphasis is made on the dynamical effects of the force of infection. Such analysis based on the parametric sweep can prove to be helpful in predicting the disease spread in urban as well as rural areas and should be of interest to mathematical biosciences researchers.

High early failure rates occur in the treatment of isolated symptomatic patellofemoral arthritis with commercially available patellofemoral arthroplasty (PFA) prostheses. We postulate that PFA changes the trochlear groove angle, thereby causing patellar maltracking, catching and pain. We examined the extent of this change in trochlear groove angle by virtually implanting five commercially available patellofemoral prostheses into two 3D reconstructed knees, one with a normal and the other with a dysplastic trochlea. The axial and coronal trochlear groove angles were measured pre- and post PFA for the five different prostheses in both the normal and the dysplastic knee. Post PFA, the trochlear groove angle changed from the original in both the axial and coronal planes for all the prostheses in both the normal and the dysplastic knee. The trochlear groove change is dependent on the design of the specific prosthesis. To avoid excessive changes post PFA, both the wide variation of changes between different generic PFA prostheses, as well as the wide variation in patient femoral anatomy should be considered.

Surface electromyography (sEMG) is a useful tool for revealing the underlying musculoskeletal dynamic properties in the human body movement. In this paper, a musculoskeletal biomechanical model which relates the sEMG and knee joint torque is proposed. First, the dynamic model relating sEMG to skeletal muscle activation considering frequency and amplitude is built. Second, a muscle contraction model based on sliding-filament theory is developed to reflect the physiological structure and micro mechanical properties of the muscle. The muscle force and displacement vectors are determined and the transformation from muscle force to knee joint moment is realized, and finally a genetic algorithm-based calibration method for the Newton–Euler dynamics and overall musculoskeletal biomechanical model is put forward. Following the model calibration, the flexion/extension (FE) knee joint torque of eight subjects under different walking speeds was predicted. Results show that the forward biomechanical model can capture the general shape and timing of the joint torque, with normalized mean residual error (NMRE) of $\sim$10.01%, normalized root mean square error (NRMSE) of $\sim$12.39% and cross-correlation coefficient of $\sim$0.926. The musculoskeletal biomechanical model proposed and validated in this work could facilitate the study of neural control and how muscle forces generate and contribute to the knee joint torque during human movement.

Monitoring the fetal growth and diagnosing any possible abnormality plays a vital role in ensuring the healthy growth of a fetus. Certain health issues like Hyperthermia, Premature Rupture of Membranes (PROM) and Intrauterine Growth Restriction (IUGR) has to be diagnosed early. A pilot study comprising of 27 pregnant and 2 non-pregnant subjects was conducted to check the effectiveness of Thermal imaging in predicting the fetal growth. The heat dissipated by the fetus to the maternal abdominal wall is acquired as a surface thermal distribution. These images were processed qualitatively and quantitatively for better understanding. There was a consistent higher thermal pattern for pregnant women. A more pronounced temperature pattern is notable in the umbilical region that correlates with gestation age. However, as thermal pattern varies with age, gestation period and BMI, it is advisable to track the same person and compare the images for better assessment. This pilot study justifies the need for more elaborate study in building a database for classification and interpretation of thermogram to detect fetal abnormality with reduced human interpretation.

This paper presents an analytical solution for the hyperbolic bioheat equation in spherical coordinates under nonuniform distributed heat source term, which is theoretically modeling the Radiofrequency Heating (RFH) technique. In RFH technique a spherical electrode is inserted into the diseased tissue which leads to the heat generation there due to the imposed electromagnetic field. Because of the non-Fourier behavior of biological tissues, the hyperbolic Penne’s equation is adopted as perfused thermal model. The equation has been solved using Eigenvalue method and the closed form solutions are introduced. The temperature profiles are determined for a sample RFH procedure in cornea and liver and the effect of perfusion term in Penne’s bioheat equation is shown. The effective parameters in the RFH process such as electrode radius, power and different material are studied analytically too. The derived solution can play a role of verification basis of other numerical ones in this area.

Bones of the murine cranial vault are formed by differentiation of mesenchymal cells into osteoblasts, a process that is primarily understood to be controlled by a cascade of reactions between extracellular molecules and cells. We assume that the process can be modeled using Turing's reaction–diffusion equations, a mathematical model describing the pattern formation controlled by two interacting molecules (activator and inhibitor). In addition to the processes modeled by reaction–diffusion equations, we hypothesize that mechanical stimuli of the cells due to growth of the underlying brain contribute significantly to the process of cell differentiation in cranial vault development. Structural analysis of the surface of the brain was conducted to explore the effects of the mechanical strain on bone formation. We propose a mechanobiological model for the formation of cranial vault bones by coupling the reaction-–diffusion model with structural mechanics. The mathematical formulation was solved using the finite volume method. The computational domain and model parameters are determined using a large collection of experimental data that provide precise three-dimensional (3D) measures of murine cranial geometry and cranial vault bone formation for specific embryonic time points. The results of this study suggest that mechanical strain contributes information to specific aspects of bone formation. Our mechanobiological model predicts some key features of cranial vault bone formation that were verified by experimental observations including the relative location of ossification centers of individual vault bones, the pattern of cranial vault bone growth over time, and the position of cranial vault sutures.

This study compares the biomechanical behavior of a mandibular full-arch fixed implant prosthesis with four implants under lingualized and conventional balanced occlusion schemes. The acrylic resin denture was supported by four titanium cylindrical implants and connected via a titanium prosthetic rectangular bar. Orthotropic material was used for the cortical and cancellous bones. The applied loadings were vertical and bilateral: 100N on first molar and 50N on first and second premolars each. For the lingualized balanced occlusion, the loadings were applied in central fossae of the posterior teeth, whereas for the conventional balanced occlusion the loadings were applied in central fossae and buccal cusps. The maximum von-Mises stresses for the lingualized and conventional balanced schemes were 301MPa and 25MPa, respectively, and were located at the neck of the posterior implants. In the denture teeth, the highest stress was located at the beginning of the cantilever extension. In the cortical bone, according to Tsai–Wu criterion, the failure index for the lingualized balanced occlusion was 1.10 and for the conventional balanced occlusion was 0.83. Thus, the conventional balanced occlusion demonstrated more favorable stress distribution in the implants and the cortical bone than the lingualized balanced occlusion.

Braided stents are commonly used to treat cerebral aneurysm, but there is little information about the bending characteristic of braided stent used for cerebral aneurysm. This paper investigates how geometrical parameters of braided stent influence its flexibility. Eight groups of braided stent models with different geometries (i.e., nominal diameter, length, braiding angle, number of wires, diameter of wire, frictional coefficient among wires and porosity) were constructed. Parametric analyses of these models were carried out by using Abaqus/Explicit. When the nominal diameter varied from 2mm to 5.5mm, the forces required for flexural deformation decrease from $2.64\mathrm{\text{E}}-04$N to $1.06\mathrm{\text{E}}-04$N; when the axial length varied from 10mm to 40mm, the forces required for flexural deformation decrease from $2.16\mathrm{\text{E}}-04$N to $4.38\mathrm{\text{E}}-05$N; when the braiding angle increases from 30${}^{\circ }$ to 75${}^{\circ }$ (the number of wires is 48 and the diameter of the wire is 0.026mm), the forces required for bending deformation decrease from $2.3\mathrm{\text{E}}-03$N to $2.4\mathrm{\text{E}}-04$N; when the diameter of wires increases from 0.026mm to 0.052mm (the number of wires is 24 and the braiding angle is 60${}^{\circ }$), the forces required for flexural deformation increase from $1.0\mathrm{\text{E}}-04$N to $9.3\mathrm{\text{E}}-04$N; and when the number of wires increases from 14 to 48 (the braiding angle is 75${}^{\circ }$ and the diameter of the wire is 0.026mm), the forces required for flexural deformation increase from $2.1\mathrm{\text{E}}-05$N to $2.4\mathrm{\text{E}}-04$N. From the data above it can be seen that the diameter of wires, the number of wires and braiding angle have a larger impact on bending characteristics of braided stent; and the axial length and nominal diameter have a smaller impact on bending characteristics of braided stent. Results of the present study may provide theoretical guidance for the design of self-expanding braided stent and its clinical practice.