Effect of Oscillation Speed and Thrust Force on Cortical Bone Temperature During Sagittal Sawing

Thermal necrosis of bone occurs at sustained temperatures above approximately 47°C. During joint replacement surgery, resection of bone by sawing can heat the bone above this necrotic threshold, thereby inducing cellular damage and negatively affecting surgical outcomes. The aim of this research was to investigate the effect of saw blade speed and applied thrust force on the heating of bone. A sagittal sawing fixture was used to make cuts in cortical bovine bone, while thermocouples were used to characterize the temperature profile from the cut surface. A full factorial Design of Experiments was performed to determine the relative effects of blade speed and applied thrust force on temperature. When comparing the effect of speed to force in the regression analysis, the effect of force on temperature (p < 0.001) was 2.5 times more significant than speed (p = 0.005). The interaction of speed and force was not statistically significant (p > 0.05). The results of this research can be used in the development of training simulators, where virtual surgeries with haptic feedback can be accompanied by the related temperatures in proximity to the cut. From a clinical perspective, the results indicate that aggressive cutting at higher blade speed and greater thrust force results in lower temperatures in the surrounding bone.

Design of a Counterweight Walker Active Therapeutic Movement Rehabilitation Rig

According to INEGI (National Institute for Statistics and Geography), in 2004 there were around 730,000 people in Mexico with the need of some kind of mechanical aid to regain ability to walk. Support equipment for regaining the ability to walk normally is manufactured outside of Mexico. This equipment is complex and very expensive. In this work, the design of a walking ability rehabilitation aid is presented. This work is carried out applying the modular design concept. This ensures that all client needs are fulfilled by the resultant product, and that these needs are measurable and controllable. Basic idea behind this design is supporting part of patient’s weight and that of an exoskeleton on a mechanical device. Basic kinematics and dynamic calculation are presented, as well as simulations results. This information shows the feasibility of building and operating this rehabilitation walking aid.

Studying the Intact, ACL-Deficient and Reconstructed Human Knee Joint Using a Finite Element Model

The human knee joint has a three dimensional geometry with multiple body articulations that produce complex mechanical responses under loads that occur in everyday life and sports activities. Knowledge of the complex mechanical interactions of these load bearing structures is of help when the treatment of relevant diseases is evaluated and assisting devices are designed. The anterior cruciate ligament in the knee connects the femur to the tibia and is often torn during a sudden twisting motion, resulting in knee instability. The objective of this work is to study the mechanical behavior of the human knee joint in typical everyday activities and evaluate the differences in its response for three different states, intact, injured and reconstructed knee. Three equivalent finite element models were developed. For the reconstructed model a novel repair device developed and patented by the authors was employed. For the verification of the developed models, static load cases presented in a previous modeling work were used. Mechanical stresses calculated for the load cases studied, were very close to results presented in previous experimentally verified work, in both load distribution and maximum calculated load values.

Measurement of Electrical Impedance and Eddy Currents in Tissue Phantoms

Measurement of the electromagnetic (EM) properties of tissue such as electrical conductivity, permittivity, and eddy current characteristics can be used in clinical medicine for characterizing and distinguishing soft tissue morphology. Such measurements can yield complementary information to what can be obtained using analysis with an optical microscope. An example is the assessment of margins during the surgical resection of occult tumors. In current practice, the surgeon relies on pre-operative imaging modalities, sight and palpation to locate and attempt to fully resect the tumor(s). Frozen section pathological assessment offers the only other resource available to the surgeon for margin analysis, but it is incomplete because only a small fraction of the resected tissue is examined and it is often not feasible to wait for the results of the frozen section analysis before completing the surgery. This paper describes a characterization and imaging method based on variations in electromagnetic tissue properties to assess the surgical margins of resected tissues. This is noteworthy because accurate margin assessment has been shown to significantly improve long term patient outcomes[1].

Design Considerations for Compression Gas Driven Shock Tube to Replicate Field Relevant Primary Blast Condition

Detonation of a high explosive (HE) produces shock-blast wave, noise, shrapnel, and gaseous product; while direct exposure to blast is a concern near the epicenter; shock-blast can affect subjects even at farther distances. The latter is characterized as the primary blast with blast overpressure, time duration, and impulse as shock-blast wave parameters (SWPs). These parameters in turn are a function of the strength of the HE and the distance from the epicenter. It is extremely important to carefully design and operate the shock tube to produce a field relevant SWPs. In this work, we examine the relationship between shock tube adjustable parameters (SAPs) and SWPs to deduce relationship that can be used to control the blast profile and emulate the field conditions. In order to determine these relationships, 30 experiments by varying the membrane thickness, breech length (66.68 to 1209.68 mm) and measurement location was performed. Finally, ConWep was utilized for the comparison of TNT shock-blast profiles with the profiles obtained from shock tube. From these experiments, we observed the following: (a) burst pressure increases with increase in the number of membrane used (membrane thickness) and does not vary significantly with increase in the breech length; (b) within the test section, overpressure and Mach number increases linearly with increase in the burst pressure; however, positive time duration increases with increase in the breech length; (c) near the exit of the shock tube, there is a significant reduction in the positive time duration (PTD) regardless of the breech length.

Development of Bio-MEMS Device for Cell Cluster Patterning by Using Dielectrophoresis Method

Recently, the investigation of cell-activation and tissue regeneration process has shown the great progress in the biomedical and biomechanical research fields. In this study fabricated Biomedical-Micro Electric Mechanical System (Bio-MEMS) to examine accurately the cell activation by introducing the cell patterning assignment technique, which consists of the photolithograph method to generate the MEMS device and the cell patterning technique by using the dielectrophoresis (DEP) method. In the development of Bio-MEMS devices for cell culture and micro-bioreactor system, unresolved subjects, 1) the fundamental mechanism of cell activation, 2) the flow control of culture medium 3) the accurate cell pattern technique and 4) the implementation of positive DEP methods, are remained. In this study, we fabricate 2-D patterns of point by using the DEP method introducing the positive effects and the trap method by employing the gravity effect and the adhesion technique, to reveal the fundamental mechanism of cell activations, such as the nerve cell axon extension. We succeed to establish the cell patterning technique by using a novel electrode design technique, such as 2-D patterns of point. The results is shown that our novel approach using comprehensive designed electrodes is superior to cell patterning. Therefore, our device able to produce neural network consists of a large number of cells.

Effects of Process Parameters on Formation of Hybrid Tissue Constructs

Tissue engineering is a promising aspect of regenerative medicine that is aimed at constructing functional tissues and organs. While progresses in tissue engineering have led successful clinic applications, challenges remain for more complex tissues/organs that require concerted efforts from multiple types of cells. One of the key issues in building replacements for complex tissues/organs is to mimic the organ’s complex natural organization using a mixture of engineered materials and living cells [1]. Electrospinning has shown promise as a technique to create the microenvironment necessary for cell growth and proliferation for tissue engineering applications[2–4], while multiple fabrication methods have been developed to manipulate live cells(e.g. cell printing) [5–7]. To this end, a system integrating polymer electrospinning technique and pressure-driven cell deposition method is currently under development for forming hybrid tissue constructs with living cells and polymers. This study focuses on examining morphology of electrospun fibers as function of processing parameters including working distance and solution flow rate.

Framework for Management of Internet Objects in Their Relation With Human Sensations and Emotions

Emotions are what make us human and emotions are what make us different. A person can make a list of such expressions about the role of human emotions, as they play a central role in our lives, in our interactions with others and the surrounding environment. Emotions are in a broad sense the regulators of our interaction with the world as they play a central role in our perception of the world and in our knowledge construction. In another angle, sensations are our immediate detector of the surrounding environment as, since ever, we see, touch and smell what is around us, we ear friendly voices or run from predator’s sounds and taste food that keep us alive. Both emotions and sensations can be used to describe our living and our main interactions with the world. However, despite that important role of senses and emotions, there is a poor representation of sensorial information and lack of understanding of emotions from the side of computational systems. Subsequently it is noticeable the absence of support to acquire and fully represent human sensorial experience and lack of ability to represent, and appropriately react, from those systems to emotional activity. The proposed work consists in developing a framework that acquires knowledge about human emotions from self-reporting or the interaction with Internet objects and media. In particular, it intends to facilitate their emotions description at the Internet from proposed samples of sensorial information allowing a later management of that knowledge for the most diverse objectives, as an example, for searching objects or media through similarities of emotional and sensorial patterns.

Effect of Sagittal Sawing Parameters on Histopathology of Bone

A sagittal saw is used for resection of bone during joint replacement surgery. During sawing, tissue at the cut surface can be damaged by high temperatures, which may lead to aseptic loosening of implants. To date, there have been no studies relating sagittal sawing parameters to the level of tissue necrosis. The aim of this study was to determine the feasibility of using histopathological analysis in assessing the severity of thermal necrosis due to sawing. All sawing experiments were performed on cortical bone taken from fresh bovine femur. A two factor, two level design of experiments was performed looking at applied thrust force from 15 N to 30 N and blade oscillation speed from 12,000 cpm to 18,000 cpm. Each cut was subjected to standard histological preparation and the depth of empty lacunae was measured. Both experimental factors, force and speed, showed a statistically significant effect on the depth of thermal necrosis (p< 0.05). However, the interaction of speed and force did not prove to be statistically significant (p = 0.22). From a clinical perspective, the results indicate that choosing higher blade speeds and applying greater force can reduce the amount of thermal damage during sagittal sawing.

Effect of Operating Parameters on the Removal of Bone Cement by a Sawing Process

Currently, there are approximately 33,000 total knee arthroplasty revision surgeries each year. This number is expected to increase with the aging population. During revision surgeries, metal implants are often secured to the tibial plateau by creating a mantel of polymethylmethacrylate (bone cement) that must be removed during revision, often times by sagittal sawing. Presently, there are no published studies on the mechanics of bone cement removal by a sawing process. The aim of this research was to quantify the effect of blade speed and applied thrust force on the volumetric cutting rate of bone cement. A custom reciprocating saw with variable stroke length was used to conduct a three factor Design of Experiments. Two levels, without center-points, were sufficient to model the effect of stroke length, thrust force, and reciprocating speed on cutting rate. The results demonstrate a linear relationship between both force and cutting rate, and blade speed and cutting rate. A cutting rate model was developed by regression analysis of the experimental data. The model has applications in haptic feedback for surgical simulators. This study provides a basis for understanding the operational parameters of the bone saw, which is the first step in designing saw blades for cutting bone cement as these designs may differ significantly from those optimized to cut cortical bone.