Journal of Mechanics in Medicine and Biology

Regions of matrix metalloproteinase (MMP) activity potentially increase the susceptibility of the atherosclerotic lesion to complications associated with plaque rupture. Assessing the risk posed by this mechanism requires investigating the stress-strain environment associated with matrix metalloproteinase production in heterogeneous plaque. To this end, an experimental-computational technique was developed to perform mechanical analysis of physiologically loaded, diseased human aorta in vitro and to investigate relationships between vascular mechanics, histology, and histochemistry. Mechanical data and specimen histology were coupled through a heterogeneous finite element model, and tissue constituent material properties were determined by an optimization method. The cross-sectional distribution of MMP-1 was quantified using immunohistochemical techniques. Results show stresses and strains are strongly influenced by lesion structure and composition, and MMP-1 presence is correlated with histology and lesion mechanics. Interactions between lipid presence, mechanical stimuli, and extracellular matrix metabolism-catabolism likely affect arterial plaque remodeling, progression, and the risk of disruption and clinical symptoms.

Prosthesis is often used to restore the appearance and functional mobility to individuals following limb amputatio n. The purpose of this study is to investigate the correlation between the electromyogram (EMG) signals with the rectification of patellar tendon bearing (PTB) socket. Six PTB sockets are manufactured with different compression depths at the patellar tendon region. Experiments for the subject are carried out to obtain the EMG signals using EMG telemetry system. From this study, it is found that there exists some kinds of pattern as the depths of PTB rectification is changed. As the PTB rectification depth is increased, the EMG activity rises generally yet in an N pattern for the quadriceps group for both left and right legs of the amputee. The results of this case study will lead to an appropriate range of rectification depths for prosthetists in the manufacturing of PTB sockets, and perhaps the identification of the most suitable depth for optimum transtibial amputee ambulation.

In clinical research, knowledge of the mechanical behavior of bones is helpful for diagnostics and therapeutic processes and the failure of compact bones is a necessary study in clinical analysis, accidentology, and traumatology. The purpose of this paper is to analyse the failure properties of compact bones using a statistical model to interpret stress and strain measurements obtained by INSTRON and X-ray scanner devices. Samples were prepared from a lamellar structure of compact bovine bones and the density of each sample is controlled and taken to be constant (1.9 g/cm³). The experimental results data thus depend only on defects in the samples. This model may help physicians and surgeons predict bone failure when inserting a prosthesis, for example.

Tests have been performed on the high sensitive (HS) GAFChromic film to evaluate its densitometric response to external X-rays (photon beam). Several 2 cm by 2 cm pieces of HS and MD-55-2 GAFChromic films were prepared and irradiated for sensitivity comparison, and X-rays energy dependence study. The optical densities of three irradiated pieces of HS film were measured as a function of time to establish the time taken for the optical density to stabilize. The densitometric sensitivity curves comparison showed that the HS film is twice as sensitive as its predecessor, MD-55-2, more spatially uniform and dosimetric measurements can be made with high precision. Its sensitivity is independent of 6 MV and 15 MV X-ray beam energies and its optical density is stable after about 36 hours post-irradiation time.

This paper presents a finite-segment, human-body model for studying whole body vibration and for studying human response to jarring and jolting (impulses). The model is a multibody system based upon previously developed models for simulating vehicle occupant response in crashes. The model has 17 bodies representing the various limbs of the human body. Nonlinear springs and dampers are used at the joints to represent soft tissue restraint forces.

The model is tested and validated with experimental data. It is then illustrated with application with random whole-body vibration and impulsive loading simulating jarring and jolting.

This paper presents major medical applications of microwave radiation in therapy and diagnostics of disorders of thermoregulation, especially hyperthermia and thermography. Microwave thermography is a thermal imaging system produced by self-emission, using emissivity differences to extend our vision beyond the shortwave red. Human tissues are partially transparent to microwaves, thus it is possible to detect the microwave of subcutaneous tissues in thermography, and to allow microwave energy penetration through subcutaneous tissues for deep-tissue heating in hyperthermia. The physics of microwave thermography together with the microwave properties and emission of body tissues are introduced. It is followed by reviews of the literature pertinent to microwave hyperthermia in therapy and treatment. Recent development in this field is briefly discussed.

The assessment of the stability of implants in cancellous bone remains a clinical problem. It has been shown that orthopaedic screw fixation depends on the microstructure and orientation of the trabeculae. In the current study we have investigated the possibility of using natural frequency analysis as a means of ranking screw fixation in cancellous bone. A dynamic modal analysis has been completed using the finite element method as a means of measuring implant frequency in a simple description of cancellous bone. A range of impulse excitation values have been examined which lead to implant resonance in different cancellous bone architectures. These values are reported in order that the eventual provision of a clinical diagnostic tool may correctly assess frequency values from the applied impulse.

In this work, a testing protocol has been set up, in order to quantify the load-sharing imposed near the fracture site by an interlocking-type intramedullary nail. A simulated single-leg stance has been applied to a composite fiberglass femur in three different configurations simulating: an intact femur, a fractured nailed femur and a fully healed nailed femur. The repeatability of the measurements and the influence of ilio-tibial band muscle force have been investigated. The tested nail proved to share with the femoral shaft an amount of the total applied load ranging from 50% immediately after the nailing to 80% at full healing.

Many physiological and anatomical changes occurring during the pregnancy period have been widely documented and reported in the literature. This study involved the participation of pregnant subjects, divided into their respective trimester periods, with post-partum normal subjects. Kinetics analyses were performed on each subject using the Peak Motus 2000 system, and comparison between the pregnant subjects in different trimester, and also the post-partum normal subjects, were conducted. The step width generally increases as the subject is progressing through her pregnancy periods. From the average, the step width increases from 0.168 m in the first trimester to 0.350 m in the third trimester, which is an increase of nearly 50%. It can be generally appreciated that the step width increases as the pregnancy period progresses. It shows that these increases may be attributed to the increase of the body weight of the subject as she gains more weight towards the end of her pregnancy.