Journal of Mechanics in Medicine and Biology

Telemedicine is an emerging industry with the potential to revolutionize the delivery of healthcare for the benefit of consumers, providers and payors. In general, telemedicine refers to the use of information and telecommunication technologies to distribute both information and expertise necessary for healthcare service provision, collaboration or delivery among geographically separated participants — physicians and patients. In short, it is a generic term which is used to define various aspects of healthcare at a distance. Telemedicine has been heralded as one of several possible solutions to some of the medical dilemmas that are faced by many developing countries. In this paper, we will discuss the current state of telemedicine in developing countries in South-East Asia (SEA) in general, with Malaysia and Indonesia in particular.

This paper presents a new analysis of the physics of closed head injury caused by intense acceleration of the head. At rest a 1 cm gap filled with cerebrospinal fluid (CSF) separates the adult human brain from the skull. During impact, whole head acceleration induces artificial gravity within the skull. Because its density differs slightly from that of CSF, the brain accelerates, strikes the inner aspect of the rigid skull, and undergoes viscoelastic deformation. Analytical methods for a lumped parameter model of the brain predict internal brain motions that correlate well with published high-speed photographic studies. The same methods predict a truncated hyperbolic strength-duration curve for impacts that produce a given critical compressive strain. A family of such curves exists for different critical strains. Each truncated hyperbolic curve defines a head injury criterion (HIC) or threshold for injury, which is little changed by small offsetting corrections for curvature of the brain and for viscous damping. Such curves predict results of experimental studies of closed head injury, known limits for safe versus dangerous falls, and the relative resistance of smaller versus larger animals to acceleration of the head. The underlying theory provides improved understanding of closed head injury and better guidance to designers of protective equipment and to those extrapolating research results from animals to man.

Joint centers are obtained from data treatment of a set of markers placed on the skin of moving limb segments. Finite helical axis (FHA) parameters are calculated between time step increments. Artifacts associated with nonrigid body movements of markers entail ill-determination of FHA parameters. Mean centers of rotation may be calculated over the whole movement, when human articulations are likened to spherical joints. They are obtained using numerical technique, defining point with minimal amplitude, during joint movement. A new technique is presented. Hip, knee, and ankle mean centers of rotation are calculated. Their locations depend on the application of two constraints. The joint center must be located next to the estimated geometric joint center. The geometric joint center may migrate inside a cube of possible location. This cube of error is located with respect to the marker coordinate systems of the two limb segments adjacent to the joint. Its position depends on the joint and the patient height, and is obtained from a stereoradiographic study with specimen. The mean position of joint center and corresponding dispersion are obtained through a minimization procedure. The location of mean joint center is compared with the position of FHA calculated between different sequential steps: time sequential step, and rotation sequential step where a minimal rotation amplitude is imposed between two joint positions. Sticks are drawn connecting adjacent mean centers. The animation of stick diagrams allows clinical users to estimate the displacements of long bones (femur and tibia) from the whole data set.

In biomechanics, the knowledge of accurate location of a joint center is essential because equilibration of the external loads and muscular forces about the joint is performed about this specific point. This paper focuses on the location of centers of gleno-humeral joint and scapulo-thoracic joint in a subject moving their arm in the scapular plane with a magnitude of 120°. Biplanar radiography with successive exposures has been used locating anatomical axes of bones. Geometric models of bones were defined allowing access to bone morphology by superposing model projections onto X-ray imaged bone contours. Functional models were used so as to represent the behavior in motion of shoulder joints. These techniques allowed us to access to results describing the linear and angular relative displacements of the shoulder bones between two different postures. The gleno-humeral and scapulo-thoracic finite joint centers (F_H and F_S) are first defined through the location of the corresponding helical axis of motion (HAM) moving the joint from positions occupied in initial and final postures. The gleno-humeral and scapulo-thoracic mean joint centers (M_H and M_S) are then calculated using a new technique, which defines that each joint center has the point having the smallest migrations while moving continuously from initial to final postures. This allows for the analysis of the linear and angular clearances, which affect joint center migration. The whole continuous movement has been parsed into several steps to test the stability of the mean joint center throughout the motion.

Electrophysiological mechanisms of co-transmission by serotonin (5-HT) and acetylcholine (ACh), co-expression of their receptor types, i.e., 5-HT type 3 and 4, nicotinic cholinerginc (nACh) and muscarinic cholinergic (μACh), and effects of selective and non-selective 5-HT₃ and 5-HT₄ receptor agonists/antagonists, on electromechanical activity of the gut were studied numerically. Two series of numerical experiments were performed. First, the dynamics of the generation and propagation of electrical signals interconnected with the primary sensory (AH) neurons, motor (S) neurons and smooth muscle cells were studied in a one-dimensional model. Simulations showed that stimulation of the 5-HT₃ receptors reduced the threshold of activation of the mechanoreceptors by 17.6%. Conjoint excitation of the 5-HT₃ and 5-HT₄ receptors by endogenous serotonin converted the regular firing pattern of electrical discharges of the AH and S neurons to a beating mode. Activation confined to 5-HT₃ receptors, located on the somas of the adjacent AH and S type neurons, could not sustain normal signal transduction between them. It required ACh as a co-transmitter and co-activation of the nACh receptors. Application of selective 5-HT₃ receptor antagonists inhibited dose-dependently the production of action potentials at the level of mechanoreceptors and the soma of the primary sensory neuron and increased the threshold activation of the mechanoreceptors. Normal mechanical contractile activity depended on co-stimulation of the 5-HT₄ and μACh receptors on the membrane of smooth muscle cells. In the second series of simulations, which involved a spatio-temporal model of the functional unit, effects of co-transmission by ACh and 5-HT on the electromechanical response in a segment of the gut were analyzed. Results indicated that propagation of the wave of excitation between the AH and S neurons within the myenteric nervous plexus in the presence of 5-HT₃ receptor antagonists was supported by co-release of ACh. Co-stimulation of 5-HT₃, nACh and μACh receptors impaired propulsive activity of the gut. The bolus showed uncoordinated movements. In an ACh-free environment Lotronex (GlaxoSmithKline), a 5-HT₃ receptor antagonist, significantly increased the transit time of the pellet along the gut. In the presence of ACh, Lotronex produced intensive tonic-type contractions in the longitudinal and circular smooth muscle layers and eliminated propulsive activity. The 5HT₄ receptor agonist, Zelnorm (Novartis), preserved the reciprocal electromechanical relationships between the longitudinal and circular smooth muscle layers. The drug changed the normal propulsive pattern of activity to an expulsive (non-mixing) type. Treatment of the gut with selective 5HT₄ receptor antagonists increased the transit time by disrupting the migrating myoelectrical complex. Cisapride (Janssen), a mixed 5HT₃ and 5HT₄ receptor agonist, increased excitability of the AH and S neurons and the frequency of slow waves. Longitudinal and circular smooth muscle syncytia responded with the generation of long-lasting tonic contractions, resulting in a "squeezing" type of pellet movement. Comparison of the theoretical results obtained on one-dimensional and spatio-temporal models to in vivo and in vitro experimental data indicated satisfactory qualitative, and where available, quantitative agreement.

A new method of physical activity monitoring that is able to detect posture transitions using two acceleration signals attached on the shoulder part of a garment is presented. Posture transition activities in continuous accelerometer records were classified into two steps. In the first step, wavelet-reconstructed antero-posterior acceleration signal was applied to extract the transition segments from the continuous accelerometer record. When compared with the reference system in segment extraction, averaged absolute error 0.21 s for sit–stand posture transitions and 0.26 s for stand–sit posture transitions were achieved. The overall sensitivity and specificity of sit–stand posture transitions were 90.852% and 98.98% and those of stand–sit posture transitions were 91.367% and 98.55%. In the second step, wavelet coefficients of extracted segments of vertical acceleration signals were used as features in classification. The classification rate (segments that are extracted and classified correctly/total number of segments) of sit–stand and stand–sit activities are 93.65% and 95.24%, respectively. Our results proved a reliable technique of detecting posture transition activities in physical activity monitoring.

Corticosteroid injection using hypodermic needles is one of the commonly accepted treatments for patients with hand conditions. However, in some cases the needle perforations may cause tendon ruptures. This paper aims to investigate the relationships between a tendon's ultimate tensile strength (UTS) and the number of hypodermic needle perforations as well as needle sizes. The UTS was determined for all specimens at the loading rate of 0.4 mm/s. Tendon specimens with perforations punctured by large-sized (19 G) hypodermic needles were found to have significantly lower UTS than those with perforations punctured by medium-sized (23 G) and small-sized (27 G) needles. For specimens punctured by medium- and small-sized needles, no significant difference in UTS was observed between tendons with three perforations and those with one perforation.

The virtual electrode (VE) has been recognized as an important factor for success or failure of cardiac defibrillation. Many researches have been performed to study characteristics of the VE. However, there are some questions which remain unanswered. In this study, we developed a simulator to solve a three-dimensional bidomain model and performed several simulations to elucidate the basic characteristics of VE in a simplified cardiac tissue with passive membrane when a constant unipolar cathodal stimulus was applied. The results showed that for smaller electrodes, VE has a typical dog-bone shaped virtual cathode (VC) and two egg-shaped virtual anodes (VAs). The distributions both in intra- and extracellular potentials have concentric ellipsoidal isosurfaces, but their ellipticities are subtly different, producing VE. For larger electrodes, VC becomes larger and has a flat-dish shape rather than dog-bone, and VA becomes smaller and also flattens and collapses. The peak values of VE are larger for smaller electrodes, but their time courses show similar tendency among the different sized electrodes. The change of stimulus strength and polarity only affects the magnitude of VE in a linear manner and the distribution pattern is unchanged. These results provide us fundamental knowledge about VE.