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### Research Papers

J. Med. Devices. 2010;4(2):021001-021001-7. doi:10.1115/1.4001387.

In this work three different cross section groups of stainless steel T-Spring, for tooth retraction, have been tested; each spring is activated for 1 mm, 2 mm, and 3 mm, and the resultant force system is evaluated by using a testing apparatus. The results showed that when the cross section and activation distances are increased, the horizontal force and moment increased, while for the moment-to-force ratio, the lowest mean value was at the first activation distance of the first group, and the highest mean values were at the third activation distance of the third group. All three groups at all activation distance are insufficient to produce bodily tooth movement. T-springs of the $(0.016×0.022 in.)$ cross section and with frequent activation provide the best in force system production. An artificial neural network model was trained for simulation of the correlation between input parameters: spring cross section and activation distance, and the outputs spring force system. The network model has prediction ability with low mean error of force prediction (5.707%), and for the moment is (4.048%), and it can successfully reflect the results that were obtained experimentally with less costs and efforts.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):021002-021002-7. doi:10.1115/1.4001862.

Boutonniere deformities are a common injury to the extensor mechanism of the finger. The deformity results in fixed contraction in the middle finger joint and is severely debilitating to functionality. Due to the complexity of the extensor mechanism, surgical repair is difficult, which usually requires multiple procedures, and in some cases is unsuccessful. Nonsurgical treatment of the deformity has not dramatically improved in many years and usually requires long-term use of braces and physical therapy. This work is focused on design and preliminary evaluation of an improved boutonniere brace to correct the deformity with emphasis on lower costs, integrating therapeutic techniques such as heat and motion to increase blood flow and patient comfort. A review of the current state of the art is presented along with the design approach used to develop an improved device. Experimental test results are also presented. This work demonstrates a new device and approach for treatment of boutonniere deformities that may translate to treatment of other conditions such as arthritis.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):021003-021003-7. doi:10.1115/1.4001861.

This work attempts to optimize stents that are implanted at the neck of coronary or cerebral aneurysms to effect a flow diversion. A two-dimensional version of the stent, which is a series of struts and gaps placed at the neck, is considered as the first step. Optimization is carried out based on the principles of exploration of design space using reductions in velocity and vorticity in the aneurysm dome as the objective functions. Latin hypercube sampling first develops 30–60 samples of a strut-gap arrangement. Flow past an aneurysm with each of these samples is computed using the commercial software FLUENT and the objective functions evaluated. This is followed by a Kriging procedure that identifies the nondominated solutions to the system, which are the optimized candidates. Three different cases of stents with rectangular or circular struts are considered. It is found that placing struts in the proximal region of the neck gives the best flow diversion.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):021004-021004-5. doi:10.1115/1.4001814.

Clubfoot is a common pediatric orthopaedic deformity. Despite the popularity of Ponseti’s method and night splints such as the Denis–Browne method, there is still an 11–47% rate of deformity relapse reported in the literature. The technique to make traditional orthotics is dependent on a nonweight-bearing casting or foot imprint. These splints outdate clinical treatment trends and only apply to patients who are of nonwalking age. This study shows that a new procedure utilizing computer aided design and the finite element method can be employed to develop a customized weight-bearing dynamic orthotic. In addition, the plantar pressure distribution and the trajectory of the center of this pressure distribution are used to design the orthotic. It is shown that the trajectory of the center of pressure, traditionally used in gait analysis, can be used not only to quantify the severity of the foot deformity but to design a custom orthotic as well. Also, the new procedure allows the custom orthotic to be designed and analyzed within a day. The new orthotic design is composed of soft foam interior layers and a polymer supportive exterior layer. It is proved that rapid prototyping technologies employing selective laser sintering can be used to construct these layers to produce a custom orthotic within a 24 h time frame.

Commentary by Dr. Valentin Fuster

### Technical Briefs

J. Med. Devices. 2010;4(2):024501-024501-6. doi:10.1115/1.4001519.

Soft contact lenses (SCLs) can be inserted inside out with consequences for optical, mechanical, and on-eye comfort performance. Wearing lenses inside out may also cause corneal deformation especially with silicone hydrogel lenses. Since inside out insertion of SCLs cannot always be avoided, it is important to study their effects, and it may even be feasible to use these inside out forces to reshape the cornea. To study these possible scenarios, a finite element (FE) based model capable of simulating the inversion of soft contact lenses was developed and validated by comparing modeled results with laboratory measurements of lenses in right side and inside out conformations. In this study, the front surface contour of five SCLs (four commercially available and one custom design) was determined using a profile projector. The lenses were turned inside out, and the front surface contour was remeasured. The thickness profile obtained by a profilometer was “added” to the front surface shape in both orientations to derive the back surface shape. A detailed nonlinear 2D axisymmetric FE model of each lens in its right side in state was created, and the lens was inverted by applying a rigid probe. The modeled and measured inverted lens shapes were compared with respect to parameter alterations (sagittal depth (sag) and diameter) and overall geometry changes using a Procrustes analysis. Measured and modeled results revealed very substantial geometry changes when turning the lens inside out; however, the maximum sagittal deviation between measured and modeled inside out lens shapes was less than 0.05 mm over the central 6 mm half chord. Overall, the modeled results matched the inverted geometries for both parameter changes as well as overall shape changes. The developed FE model is able to predict the geometry of soft contact lenses when they are inverted.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):024502-024502-4. doi:10.1115/1.4001865.

Intracytoplasmic sperm injection has attracted research interest from both biological and engineering groups. The technology is constantly evolving to perform this procedure with precision and speed. One such development is the contribution of this paper. We focus on a relatively recent procedure called Ros-Drill© (rotationally oscillating drill), of which the early versions have already been effectively utilized for the mice. Here, we present a procedure to automate a critical part of the operation: initiation of the rotational oscillation. Visual feedback is used to track the pipette tip. Predetermined species-specific penetration depth is successfully utilized to initiate the rotational oscillation command. Penetration-depth-based decisions concur with our earlier curvature-based approach.

Commentary by Dr. Valentin Fuster

J. Med. Devices. 2010;4(2):025001-025001-10. doi:10.1115/1.4001520.

Sleeve gastrectomy, which is based on reducing the size of the stomach, is one of the most successful bariatric surgeries and is yet to be standardized. One of the reasons is the lack of a method to obtain an accurate remnant stomach volume. The weight loss obtained postsurgery is highly correlated with the remnant stomach volume. Therefore, it is important to get consistently an accurate remnant stomach volume to be able to compare sleeve gastrectomy with other surgeries and in order to predict the weight loss. In addition, the measurement of the pyloric pressure is important for understanding the mechanism of weight loss and predicting complication postsurgery. A surgical assistive device for sleeve gastrectomy surgery is presented in this paper. The purpose of this instrument is to assist surgeons in obtaining an accurate remnant stomach volume and in measuring the pyloric pressure. The device consists of several inflatable compartments controllable by the surgeon. Prototype laboratory test results gave an accuracy of 96.7% and a repeatability of 97.6% for different desired volumes using air for compartment inflation, and an accuracy of 96.3% and a repeatability of 98.4% for different desired volumes using water for compartment inflation. The pressure measurement accuracies obtained are 96.8% using air and 99.7% using water. It is worth noting that these accuracies are expected to differ when the device is tested in vivo.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):025002-025002-4. doi:10.1115/1.4001585.

Microstereotactic frames are a subset of stereotactic frames. They are smaller than traditional frames, and they employ small discrete anchors that are screwed into a patient’s bony anatomy, typically the skull. These anchors provide points of attachment for the frame and also serve as markers that provide a bridge between image space and physical space. Both these markers and the anatomy of interest are imaged in a CT or MRI scanner, and their positions are established relative to one another. The microstereotactic frame is then custom made so that, when it is attached to the anchors, it will guide a surgical instrument to an anatomical target. These frames offer advantages over stereotactic frames, including increased targeting accuracy and patient comfort. Firm placement of these anchors is critical as any movement will cause errors in the imaging localization, frame design, or frame attachment. Anchor placement is complicated by the variation in bone density and by the obscuring tissue and bleeding that make visual confirmation of seating very difficult. A novel device called the PosiSeat™ is presented that provides assured seating for bone-implanted anchors.

Topics: Bone , Design , Surgery
Commentary by Dr. Valentin Fuster

### 2010 Design of Medical Devices Conference Abstracts

J. Med. Devices. 2010;4(2):027501-027501-1. doi:10.1115/1.3476281.
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The following abstracts were submitted, peer reviewed and accepted for presentation at the 2010 University of Minnesotas Design of Medical Devices (DMD) Conference (www.dmd.umn.edu) held April 13–15, 2010 at the Radisson University Hotel in Minneapolis, MN.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027502-027502-1. doi:10.1115/1.3439644.
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Tracheostomy tubes (TTs) are used to provide a direct airway to a patient’s trachea when natural respiration is no longer possible. A TT generally includes an elongate outer cannula as well as a smaller inner cannula formed so as to have a gradual curve to facilitate insertion into a patient’s trachea. In order seal the airway around the tube, a conventional TT generally has an inflatable cuff attached to the perimeter of the outer cannula. When inflated, the cuff seals the airway around the cannula, thereby, requiring air to pass through only the cannula. In order to retain the distal end of the device in its operative position, the TT generally includes a neck plate or other fixation device, which is attached to the proximal end of the outer cannula. There are many potential drawbacks with current TTs, which can range in effect from minor irritation to death. Varying sizes of individuals and differences in anatomical dimensions leads to discomfort from TTs that fit poorly. The rigid ends of the outer cannula often put pressure on the walls of the trachea, which can cause irritation and ulceration. Cuffed inner cannulas are required to be replaced with uncuffed inner cannulas as soon as possible, after placement, to avoid pressure necrosis and allow for vocalization. The process of switching TTs may also be very hazardous, especially when treating obese patients. The stoma can easily be lost among layers of fat and skin, as well as the trachea, which all move independently of one another. Losing the stoma may cause suffocation and possibly death. Our novel device is a TT for use with a neck plate having an aperture. The TT comprises an elongate outer cannula having a lumen and configured to extend through the aperture. An elongate inner cannula having a lumen and an inflatable cuff and configured to extend through the lumen of the outer cannula such that the cuff extends beyond a distal end of the outer cannula and an interlocking mechanism configured to releasably secure a proximal end of the inner cannula to a proximal end of the outer cannula. This superior TT has the potential for wide application with a special emphasis on application within the obese population. Such patients experience the most difficulty with current devices. There is no single device in the market today that packages the numerous features of this particular design.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027502-027502-1. doi:10.1115/1.3442789.
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This paper presents a 3.0 mm diameter endoscopic forceps design for use in minimally invasive surgical procedures, which require significant grasping and spreading forces. Models of the proposed design predict considerable improvements in the opening range (140%) and force application (87%) for both grasping and spreading when compared with currently used endoscopic forceps. Several of the tool’s design characteristics promote fail-safe malfunctions, including locking before catastrophic failure and the decreased likelihood in detached parts. Initial benchtop testing showed good agreement between prototype performance and model prediction. Frictional losses experienced during testing were found to depend on load orientation. A surgical prototype is currently being manufactured for ex vivo testing.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027503-027503-1. doi:10.1115/1.3439645.
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Solving problems is simple. Understanding which problems should be solved is immensely challenging. Medical device design projects frequently begin with a search for solutions rather than a clear appraisal of needs. Understanding clinical needs, user needs, unmet needs and the differences between them is crucial. Through a process of filtering research into an array of needs the author prescribes a method to aid the designer in defining the overarching problem. This array can create a clear path to problem solutions while utilizing a methodology that fits in the context of a regulated design process. For medical device startups, design consulting firms, and corporate manufacturers, a clear understanding of the problem can mark the difference between a misguided solution and a solution that benefits physicians and patients.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027503-027503-1. doi:10.1115/1.3439646.
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Cricothyrotomy is one of the procedures used to ventilate upper airway blockage patients. The objectives of this paper are to examine the most regularly used cricothyrotomy devices, to suggest critical design specifications for improving the devices, and to introduce a new cricothyrotomy device as well as perform an engineering evaluation of the devices’ critical components. A review of the literature, manufacturer products and patents was performed to determine current cricothyrotomy devices in use. Four principal cricothyrotomy devices are currently in clinical use. From our review the Cookâ„¢ Melker device is the preferred method of clinicians but has acknowledged problems. Our group has developed a novel cricothyrotomy device, which addresses all design specifications and was shown to be very promising through engineering and in situ evaluations.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027504-027504-1. doi:10.1115/1.3439652.
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Jaw thrust is a common maneuver performed by medical care providers to open and maintain an airway in an unconscious patient. This essential procedure cannot only occupy significant amount of time for the health care provider, and also result in physical discomfort (low back pain) or fatigue, when it is needed for the extended period. A mechanical device can free up the care provider to perform other necessary tasks to manage critically patient and also prevent fatigue of the medical care provider. The aim of this study is to develop a novel mechanical device that can perform jaw thrust on children from 2 years old to 18 years old and maintain the airway open for extended periods of time. The designed jaw thrust device includes a base with an extension arm mounted on the base on each side of patient’s head. The mandible rest is mounted on each extension arm such that it can be positioned underneath the patient’s jaw. Chinstrap with rubber tubing is placed on the base on four points across the base such that, jaw thrusting pressure on the mandible rests causes rotational force on the chin straps opening patient’s mouth without substantially tilting patient’s head. The device maintains an airway open for extended time without any continuous attention; it also immobilizes the head in the midline thus maintaining the alignment of cervical vertebrae. Detailed finite element analyses of each of the components were done and a prototype was built for functional evaluation on a patient simulator. The device when tested and applied to a patient simulator in obstructed airway state was able to open the airway, evidenced by cough reflex elicited in response and “airway opened” timestamp noted in the computer attached to the simulator.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027504-027504-1. doi:10.1115/1.3439651.
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An international collaborative effort to develop a computational fluid dynamics (CFD) model of the human cardiovascular system (HCVS) has been initiated in 2008. The HCVS model is designed to describe (a) the blood flow hydrodynamics and associated heat transport phenomena, (b) the blood flow interactions with the essential organs, and (c) the vessel blockage formation associated with atherosclerosis and thrombosis. The CFD-HCVS model is being developed as a new specialized software module using as a foundation the CFD code, STAR-CD , that is developed and distributed by CD-adapco, Ltd., a member of the project team. The CFD-HCVS module includes the following components and capabilities. (1) A simplified 3D coarse mesh CFD model of the HCVS, which allows the simulation of hemodynamic transient phenomena. The circulatory system model is closed with porous-media flow components having a hydraulic resistance equivalent to the lumped flow resistance of the smaller vessels, including microcirculation. Both hydrodynamic and thermodynamic phenomena are described, allowing the study of blood flow transients in the presence of temperature changes. (2) Simplified zero-dimensional models of the essential organs (e.g., heart, kidneys, brain, liver, etc.) describing the time-dependent consumption or production of various blood components of interest. The organ models exchange information with the CFD system model through interfaces designed to allow their replacement, in the future, with more complex 3D organ models. (3) Selected sections of the circulatory system can be replaced by realistic 3 fine mesh vessel models allowing the detailed study of the 3D blood flow field and the vascular geometry changes due to blockage formation. (4) Models of local blockage formation due to atherosclerosis and thrombosis. Three HCVS models of increasing complexity have been designed. These models contain 27 vessels, 113 vessels, and 395 vessels. The initial CFD-HCVS model development is based on the medium HCVS model with 113 vessels. A closed circuit CFD model describing the major vessels and containing 0D models of the heart and kidneys has been developed. The CFD-HCVS model includes porous-media models describing the blood flow in the smaller vessels and capillaries. Initial simulations show that the calculated blood flow rates in the vessels modeled are in reasonably good agreement with the corresponding physiological values. A simplified model of thrombosis has also been developed. Current development efforts are focused on the addition of new vessels and 0D organ models and the development of atherosclerosis models. The HCVS model provides a flexible and expandable modeling framework that will allow the researchers from universities, research hospitals and the medical industry to study the impact of a wide range of phenomena associated with diseases of the circulatory system and will help them develop new diagnostics and treatments.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027505-027505-1. doi:10.1115/1.3439653.
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A monopolar electrosurgical device is the most commonly used energy-based surgical instrument. Monopolar devices are primarily applied to incise, ablate, dissect, and coagulate tissue by transferring electrical energy to the tissue in the form of heat generation through resistive heating. The substantial amount of heat created by the monopolar device has been shown to spread throughout the tissue, creating unintended tissue damage, which can lead to nerve thermal damage and loss of normal bodily functions. Due to this fact, energy-based devices have had a limited use in surgical procedures performed near neurovascular bundles. The extent to which the generated heat raises the temperature of the surrounding tissue is referred to as the device’s thermal spread. In this study, ex vivo and in vivo experiments have shown that a novel thermal management system (TMS) can reduce the amount of thermal spread created by a typical monopolar device, thus eliminating the thermal collateral tissue damage typically caused during a monopolar procedure. The incorporation of a TMS consisting of adjacent cooling channels reduces the thermal spread of the device, as illustrated in a reduction as high as 50% in the maximum temperature recorded during an in vivo experimental procedure. The design of the TMS was aided by finite element modeling (FEM). The phenomenon of monopolar resistive heating was modeled to analyze the temperature distributions in biological tissue subjected to heat generation by a commonly used monopolar electrosurgical device. The mathematical model was verified by comparing the model’s predicted temperature distribution with experimental results. Ex vivo experiments were performed with liver tissue heated by a monopolar pencil electrode. The experimental data for 1 mm distance from the electrode are seen to fit within 1% of the predicted temperature values by the FEM simulation.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027505-027505-1. doi:10.1115/1.3439665.
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Public health officials are currently supporting adult male circumcision as a public health policy to minimize the transmission of HIV during intercourse. Estimates indicate that more than 3 million lives could be saved in sub-Saharan Africa alone if the procedure becomes widely used. Complications including infection and accidental cutting/amputation of the glans during traditional circumcision ceremonies can lead to permanent injury or death. A low cost, adjustable (one-size-fits-most), culturally appropriate adult male circumcision tool was designed for use in traditional circumcision ceremonies. A surgical procedure for using the device has also been defined, which can be performed in either a clinical or nonclinical setting.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027506-027506-1. doi:10.1115/1.3439667.
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The engineering design of surgical instrumentation to apply mechanical forces and linear moments on the human bones during the operations constitutes a rather difficult task. This is due both to the natural and pathological irregularities of the human bone morphology and surfaces and also to the individual variations from one patient to another. Usually, the forces are applied by the surgeon only on a determined part of the bone surfaces. This paper describes an innovative computational design method to digitalize, simulate, and fit mathematically the anterior vertebral body facet. We used real experimental data from 17 human cadaveric specimens to get and store a large amount of numerical surface digital values. The complete anterior vertebral body side was visualized and analyzed with grid data Subroutine, which was also used first to select the so-called natural regions of interest (ROIs). These ROIs correspond to those parts of the surface in contact with the surgical instrumentation, where the mechanical forces are applied. Subsequently, a numerical mathematical fitting-model was implemented for these ROIs. This was carried out with the development of a 3D geometrical least-squares optimization algorithm and appropriate software designed according to the proper numerical method selected. In doing so, the 3D superficies equations of the anterior vertebral body (L3, L4, L5, and S1) were determined after these fittings were mathematically checked as appropriate. Statistical parameters and determination coefficients that define the error boundaries and the goodness of this optimal fitting-model were calculated and NURBS error data in similar studies were commented. It was proven that the principal source of error was the micro- and macro-irregularities of human bone facets. The final surface equations, and their geodesics, were used to obtain accurate data for the spinal surgery instrumentation manufacturing. The industrial bioengineering result was the application of these equations for the design of a new spinal vertebral surgical distractor. This innovative distractor separates two adjacent vertebrae while keeping them parallel. That is, at their natural inclination, avoiding hammering the vertebrae to make the intervertebral space wider. The device mechanics also minimizes the necessary force to be carried out by the surgeon during the operation.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027506-027506-1. doi:10.1115/1.3442439.
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Apnea in premature infants is a common medical problem faced daily by neonatal intensive-care unit staff worldwide. The condition is defined as a pause in breathing that lasts for 20 s or longer and is traditionally treated by manual simulation administered by a nurse. This work proposes a design of an automatic apnea interruption system for infants, which utilizes a noninvasive vibrotactile (vibration feedback) unit to replace the traditional manual stimulation. The overall system consists of a vibrotactile unit and a device/user control interface that are used with a commercial patient monitoring device. The system monitors physiological signals associated with apnea, such as heart rate and blood oxygen level, and activates the vibrotactile unit in a closed-loop fashion. The system provides multimode haptic feedback for individualized patient treatment by allowing the care provider to adjust the magnitude and duration of the tactile stimulation from the user interface. As a preliminary evaluation, the system is tested for safety and performance using simulated data.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027507-027507-1. doi:10.1115/1.3442441.
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Pressure sensors are requisite for many medical implantable devices to monitor physiological pressures or fluid pressure and flow from a subsystem. Size, power consumption, accuracy, sensitivity, stability, and biocompatibility are all key considerations in the design and fabrication of such sensors. Conventional designs, based on piezoresistive technologies, are power consuming with significant drift and temperature error, whereas capacitive solutions are often cumbersome when packaged for biocompatibility. Tronics Microsystems has developed absolute pressure sensors, which achieve the benefits of both technologies. Miniaturization is achieved using a MEMS sensing element and a multifunction ASIC with small form factors. Low power consumption, low drift, high resolution, and waveform capture capability are obtained by using a capacitive MEMS coupled with a sigma-delta, direct capacitance to digital converter. Biocompatibility is achieved with grade II titanium packaging in two form factors (“tubular” or “pancake”) for incorporation into various applications. These sensors have been fabricated, calibrated, and tested extensively over physiologic temperature ranges. The design has achieved power consumption lower than $500 ÂμW$ at 100 Hz and a drift lower than 0.5% full scale per year. An accuracy of $+/−1%$ full scale, over the temperature range is obtained by on-ASIC nonlinearity and temperature compensation. The two packaging configurations allow analysis of the trade-offs on the temperature range, sensitivity, volume, sterilization, etc. Different feed-through materials permit optimization of the form factors for the tube and the flat sensor and wired or wireless communication.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027507-027507-1. doi:10.1115/1.3442440.
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Ergonomic problems of surgical lighting systems have been indicated by surgeons. However, the underlying causes are not clear. The aim of this study is to assess the problems in detail. Luminaire use during 46 h of surgery was observed and quantified. Furthermore, a questionnaire on perceived illumination of and usability problems with surgical luminaires was issued among OR-staff in 13 hospitals. The results showed that every 7.5 min a luminaire action (LA) takes place, intended to reposition the luminaire. Of these LAs, 74% was performed by surgeons and residents. For 64% of these LAs the surgical tasks of OR-staff were interrupted. The amount of LAs to obtain a well-lit wound, illumination level, shadows, and illumination of deep wounds were most frequently indicated lighting aspects needing improvement. Different kinematic aspects of the pendant system of the lights that influence usability were also mentioned: high forces for repositioning, ease of focusing and aiming, ease of moving, collisions of the luminaire, entangling of pendant arms, and maneuverability. Based on these results, conclusions regarding to improvement of surgical lighting systems are formulated. Focus for improvements should be on minimizing the need for repositioning the luminaire, and on minimizing the effort for repositioning.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027508-027508-1. doi:10.1115/1.3442444.
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The commercialization of university-developed technology is described in this paper, which is predicated on the application of pulsating, low magnitude forces (cyclic forces) to the teeth and surrounding bone as a means of accelerating orthodontic tooth movement. The resulting product is a compact device with an external activator that houses the electrical, mechanical, and energy components that apply cyclical mechanical forces to a mouthpiece that is put in a patient’s mouth.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027508-027508-1. doi:10.1115/1.3442442.
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In a composite of various activities, the normal knee moves through a range of flexion of up to 155 deg, while at all angles there are normal ranges of “laxity,” both in an anterioposterior direction and in internal-external rotation. The ideal goal is that after a total knee replacement (TKR), the knee moves in a similar way, hence, providing the same amount of stability and freedom of motion. Our goal was to device a standardized testing method for evaluating proposed new TKR designs or existing designs. We developed a desktop knee machine, which subjects knees to combinations of forces and moments at a range of flexion angles. The proposed test method would compare the laxity motions of a given design model with the data from normal knee specimens. The TKRs were designed in the computer and then SLA models were made for testing. Computer analysis used RAPIDFORM software to calculate the laxities. In order to specify the testing method, in particular, the compressive, shear, and torque loads, we tested three different knee models with a range of loads. The magnitudes of the loads were proportionately less than in vivo due to the limitations of SLA models. When testing normal knee specimens, there were no frictional effects due to the exceedingly low coefficient of friction at the joint surfaces. However, in metal-plastic TKRs, the friction can affect the laxity and, hence, the kinematics, considerably. Hence this behavior had to be reproduced in our test method. The conclusion from our experiments was that testing should be carried out at a minimum of two compressive loading conditions, one representing low shear/torque ratios and the other, high shear/torque ratios, in order to obtain a realistic representation of the behavior of new TKR designs.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027509-027509-1. doi:10.1115/1.3442644.
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This paper describes a 3D scanning system based on an active vision method using structured light in order to obtain the CAD model of a dental arch. Presently, dental prosthesization requires long times in between detecting the shape of the dental arch, plaster model generation, scanning of it, prosthesis preparation, and implant. The situation is even worse when use of dental implants is required, while early loading of the implants is considered a positive solution. For this reason many devices are actually presented for the intra oral determination of the shape of dental prostheses and inserts. These devices however are able to detect limited portions of the dental arch, since they must be hand held by the doctor. This work presents a new device able to detect with high precision the entire dental arch.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027509-027509-1. doi:10.1115/1.3442645.
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Bacterial colonization of needleless injection sites (NISs) frequently results in catheter related bloodstream infections (CRBSIs). Hospitals have instituted protocols aimed at disinfecting NIS prior to access. Furthermore, several manufactures have developed devices that facilitate disinfection of NIS. Despite these steps, the incidence of CRBSI is still alarmingly high. Currently, there is no protocol or device intended to disinfect male luer connectors such as those found on IV tubing that are commonly coupled and decoupled from the NISs. Since these IV tubing connectors directly contact the NIS (which have been repeatedly shown to have varying levels of bacterial colonization), it is highly likely that they, too, will have varying levels of contamination. In order for disinfection of the NIS to be effective, the IV tubing connector must also be disinfected. Our design goal was to develop a device that could be used to disinfect a male luer style connector without allowing antiseptic into the inner lumen of the male luer. We designed a three component system that utilizes a silicone sealing cone to seal the male luer, a reservoir foam that holds 70% isopropyl alcohol (IPA), and a reaction force foam that increases the seal pressure of the sealing cone while the reservoir foam is compressed delivering the IPA to the outside surface of the male luer post. Sealing cone geometry was optimized using a custom built seal pressure test apparatus. Reservoir and reaction force foam functional parameters were assessed using an Instron test apparatus. A two phase compression stroke was designed into the device to allow for sealing and dispensing of IPA. An IPA transfer test was used to assess the transfer of disinfectant from the reservoir foam to a liquid filled male luer connector (modeling an IV tubing connector). No disinfectant was found to be transferred from the device to the inner lumen of the IV tubing connector model $(n=30)$. To test the efficacy of the device on reducing bacterial count on the male luer, a disinfection study was performed using the optimized device. Male luers were immersed in bacterial suspensions of S. aureus, S. epidermis, P. aerginosa, and E. coli. A 4 log reduction compared with a positive control was found in each sample treated with our disinfection cap $(n=120)$. In conclusion, we developed a device that effectively delivers an antiseptic to a male luer style connector without leaking any antiseptic to the inner lumen of the luer post

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027510-027510-1. doi:10.1115/1.3442751.
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This paper summarizes the design and testing of a biopsy needle to be used through a flexible endoscope. There is a need for a biopsy needle that can be used through the endoscopic channel to perform zero invasive biopsies on the gastrointestinal system and other organs. In this project, a novel biopsy needle is designed, tested, and compared with an Olympus EZShot single use aspiration needle. The new needle was found to have a higher ratio of mass removed versus removal force.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027510-027510-1. doi:10.1115/1.3442752.
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There is a very large need for prosthetic components in developing countries, where such devices are imported and prohibitively expensive. The present work explores the possibility of developing and manufacturing prosthetic components locally in Venezuela, preserving high quality and function. We aimed to develop a kit of plastic modular adaptors for external transtibial prostheses. The project was divided in four stages that covered design, stress analyses, manufacture, and function assessment of the components. The design process is presented in detail, resulting in a prototype that comprises four adaptors of simple design. Their response was studied with stress analysis using the Finite Element Method applying static loads for different instants of gait during the stance phase. Then, five kits of adaptors were manufactured with thermoplastic material using conventional metal-working machines. The resulting components were lighter and cheaper than equivalent imported metallic ones. The kits were adapted to four patients and assessed via gait analysis. A very good function was observed with no significant differences in spatiotemporal gait parameters.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027511-027511-1. doi:10.1115/1.3442754.
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An upper-arm wearable exoskeleton has been designed for assistance and functional training of humans. One of the goals of this design is to provide passive assistance to a user by gravity balancing, while keeping the transmitted forces to the shoulder joints at a minimum. Consistent with this goal, this paper addresses the following questions: (i) an analytical study of gravity balancing design conditions for the structure of the human arm, (ii) minimization of transmitted shoulder joint forces while satisfying the gravity balancing conditions, and (iii) possible implementation of these conditions into practical designs using zero-free length springs.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027511-027511-1. doi:10.1115/1.3442755.
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External counterpulsation is a noninvasive method of applying external pressures to vascular beds of the lower extremities synchronous with the cardiac cycle. Numerous animal experiments and a number of clinical trials have been conducted over the years in patients with various forms of cardiac disease to evaluate the effectiveness of external counterpulsation. The external counterpulsation machines (known as ECP and EECP machines) are currently widely available for use in the treatment of angina by applying positive pressure to the lower extremities during cardiac diastole to increase coronary flow. External counterpulsation has also been shown to be capable of perfusing the ischemic myocardium following an AMI and of assisting the failing left ventricle in patients with CHF. In these applications, positive pressure is applied externally to the lower extremities during cardiac diastole and negative pressure during cardiac systole so as to increase coronary flow and reduce the work of the heart. This paper provides a review of the developments in the area of external counterpulsation and the related devices. The paper also reviews the experimental evidence that provides the scientific basis for the design of a device now under development and called external left ventricular assist device (XLVAD) that should provide effective support of the left ventricle of a patient in congestive heart failure or following an AMI. The evolutionary development of the external counterpulsation devices into the XLVAD is presented in detail. The clinical and mechanical advantages as well as the shortcomings of each device are described.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027512-027512-1. doi:10.1115/1.3442757.
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Most current sit-to-stand devices are electrically powered. These devices, typically chairs, are for home use and are not portable. Yet there is a great need for a device that can be used anywhere. This paper proposes a novel portable device, named the QuickStand. Its working principle is based on a spring which provides partial support. When sitting down, this spring stores energy, which becomes available in getting up. A lock avoids undesired release of spring energy. The device is adjustable to subjects and chairs, making it very versatile. A prototype was manufactured. Technical evaluation showed the ability to provide around 150 N of support force over the whole range of motion. The device was successfully tested on a subject with a full body muscle disorder.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027512-027512-1. doi:10.1115/1.3442759.
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Systematic methods for descriptive analysis of physician hand movements during surgical or catheter based interventions have not been previously reported. Although such data would provide critical guidance in the design of surgical instruments, there is currently little to no information about the chronological and spatial integration of operator movements and user conditions during catheter based interventions. The essential function of the hand is to provide physical coupling between the cognitive process and the environment, translating intention to action. The ideal surgical instrument is a contiguous extension of the haptic unit (the hand) that enables an expanded range of effector actions and environmental effects. In reality, however, there is an interface between the hand and the surgical instrument creating a barrier that can introduce variable levels of interference and impedance between the cognitive process and the intended task. The objective of this project is to analyze surgical effector outputs as a function of operator psychomotor inputs using synchronized multimodal image data recorded during clinical cases of transcatheter neurological intervention. Research methodology consisted of observations and digital recording (video and/or still photography) of 24 diagnostic cerebral angiograms. These were analyzed to synchronously document physician hand movement, surgical effector output (as represented by the fluoroscopic image monitor), spatial orientation feedback (as represented by rotational movements of the fluoroscopic imaging plane with respect to patient anatomical axes), and to identify user specific conditions. The results are presented in a defined procedure map and user behaviors based upon physician experience (e.g., fellow/trainee versus attending physician). As stated in the Association for the Advancement of Medical Instrumentation HE 75 human factors standards for medical device design, there is a clear need to develop human factors standards for endovascular devices. This research will serve as a guide to this effort. The models and multimodal image database generated by this project will also be used in the development of interactive educational tools to train physicians to perform these advanced applications.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027513-027513-1. doi:10.1115/1.3442761.
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Microelectromechanical systems (MEMS) devices have gained considerable attention in medical and automotive applications due to their vast advantages in fault detection. However, the cost for MEMS devices has been a challenge for the device manufacturing industry due to the final packaging of the devices. It is considered expensive compared with device fabrication in certain applications. Majority of MEMS devices are still housing traditional packaging methods due to difficulty in handling and yield loss. The advanced interconnect solutions based on thin silicon carrier and through silicon via are being developed to interconnect integrated circuits and other devices at high densities. Can such technologies be used for MEMS device interconnections? It is really a challenge for MEMS designers and engineers due to the MEMS elements present in the devices. In this paper, we present a device fabrication process to realize interconnects that are fabricated prior to the MEMS elements are defined and processed in the device wafer. The interconnects are filled by doped polysilicon and device wafers with such prefabricated vertical interconnects can be used as the starting wafers for any device processing including optoelectronic and MEMS. The process details and their characterization are elaborated along with the physical and electrical analysis of such interconnections.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027513-027513-1. doi:10.1115/1.3442760.
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An alternative to conventional revision surgery of loosened hip prostheses is a new minimally invasive refixation procedure. This procedure requires the removal of periprosthetic fibrous tissue. The aim of this preliminary study is to evaluate which technique is most suitable for minimally invasive periprosthetic tissue removal: a Ho:YAG laser or a VAPR-2 coblation system. The clinical situation of a loosened prosthesis was simulated by several cadaveric femora, each implanted with a hip prosthesis. Artificially created periprosthetic lesions were filled with a fibrous tissue substitute. Using this fibrous tissue substitute, we measured temperatures in vitro at different distances from the site of removal. Temperatures during removal were recorded both inside the fibrous tissue and in the surrounding bone. This study demonstrated that temperatures generated in the bone do not result in thermal damage. Temperatures inside the fibrous tissue are sufficiently high to remove the fibrous tissue. Using the laser instead of the coblation system for the removal of fibrous tissue resulted in higher temperatures, thus, a faster removal of fibrous tissue. Additionally, the laser takes less effort to be integrated with the new surgical instrument and, therefore, we consider it a promising tool. However, when translating the results to clinical practice, the limitations of this study should be kept in mind. The equipment was set to typical presets; different settings (pulse frequency, pulse energy, and activated time) might affect the procedure’s success and risks. Care must be taken with respect to generated temperatures at larger distances from the place of removal. The use of the Ho:YAG laser, as well as VAPR coblation, might form a small risk for thermal damage to healthy surrounding tissues. Further research on apparatus settings and removal strategy is necessary before this technique can be applied for the removal of fibrous tissue in the clinical setting.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027514-027514-1. doi:10.1115/1.3442765.
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Every year more than 15.000 total hysterectomy procedures are performed in the Netherlands. From all these procedures, only a minor part is done via a laparoscopic approach. One reason for this is the high complexity of the procedure. The uterus is difficult to reach with the laparoscopic tools and nearby structures are easily damaged. Especially, the separation of the uterus at the fornix needs to be done with great care and is time consuming (i.e., typically takes more than 15–20 min). This results in long procedure times. To resolve part of these difficulties, a new instrument has been designed that enables separation of the uterus via a vaginal approach. The device uses a cutting mechanism to safely separate the uterus from the vagina wall. The design allows the application of an existing manipulator to mobilize the uterus for better access of laparoscopic tools. A prototype of the separation tool, MobiSep, has been manufactured. The new separation principle has been evaluated in a test setup. Over the device a tubular piece of tissue was mounted, resembling the vagina wall. The results show that the time needed for full separation is on average 102 (s). The maximum driving force needed to cut the tissue is found to be 50 (N), which can be applied manually. It is expected that this prototype is intuitive to use, can contribute to the reduction of the complexity of laparoscopic hysterectomy procedures and can reduce the total procedure time.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027514-027514-1. doi:10.1115/1.3442790.
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This paper describes the design and prototyping of a low-cost portable mechanical ventilator for use in mass casualty cases and resource-poor environments. The ventilator delivers breaths by compressing a conventional bag-valve mask (BVM) with a pivoting cam arm, eliminating the need for a human operator for the BVM. An initial prototype was built out of acrylic, measuring $11.25×6.7×8 in.3$ and weighing 9 lbs. It is driven by an electric motor powered by a 14.8 VDC battery and features an adjustable tidal volume up to a maximum of 750 ml. Tidal volume and number of breaths per minute are set via user-friendly input knobs. The prototype also features an assist-control mode and an alarm to indicate overpressurization of the system. Future iterations of the device will include a controllable inspiration to expiration time ratio, a pressure relief valve, PEEP capabilities, and an LCD screen. With a prototyping cost of only \$420, the bulk-manufacturing price for the ventilator is estimated to be less than \$200. Through this prototype, the strategy of cam-actuated BVM compression is proven to be a viable option to achieve low-cost, low-power portable ventilator technology that provides essential ventilator features at a fraction of the cost of existing technology.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027515-027515-1. doi:10.1115/1.3442791.
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In order to test small scale medical devices, it is often necessary to prototype them on a larger scale such that proof-of-concept tests can be made more affordably and design details can be tested more easily. This article discusses a method of scaling large needle prototypes for testing in a gelatin phantom such that puncture forces match those expected for the actual-size needle when puncturing tissue. Using Hertz contact force equations to account for the differences in prototype materials and size, as well as for the tissue phantom properties, 10× scale prototype needles were inserted into a gelatin phantom and puncture forces were compared with those of a real scale prototype in bovine liver tissue. Results showed that for a 19 gauge (1.06 mm) stainless steel needle tip, where a maximum doctor-applied load of 5 N was desired to pierce liver tissue, loads of 0.44 N using Hertz point contact, and 0.31 N using Hertz line contact methods were predicted to puncture liver tissue, and an average load of 0.31 N was observed in force-displacement measurements. With a 10× scale stereolithographed needle prototype, Hertz point contact predicted a load of 0.31 N to puncture a gelatin phantom, Hertz line contact theory predicted 0.37 N, and an average load of 0.73 N observed in force displacement measurements. Similar contact mechanics based scaling methods might be applied to cutting devices.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027515-027515-1. doi:10.1115/1.3442792.
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In recent years, laparoscopic surgical procedures have revolutionized many gynecological and abdominal procedures, leading to dramatic reductions in recovery time and scarring for the patient. While techniques and instruments for performing laparoscopic surgery have improved over the years, loss of vision through the endoscopic lens caused by fog, liquid, and solid debris common to laparoscopic procedures remains a significant problem. In this paper, a shielding mechanism that maintains visibility through the laparoscope by removing debris from the distal end of the lens is presented. This device provides an inexpensive and convenient alternative to the current practice of removing, cleaning, and re-inserting the laparoscope during surgical procedures. This device is shown in multiple trials to repeatably remove debris from the distal tip of the lens, thereby restoring vision for the surgeon without requiring removal or reinsertion of the endoscope.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027516-027516-1. doi:10.1115/1.3442793.
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A multiphase empirical field study is being conducted at Stanford University to examine the process of physician interaction during medical device development. The initial component of this study involved creating an analytic framework for case-based research that provided a conceptual guide for the pilot case study documented in this paper. The pilot case study examined the process of engaging physicians in medical device development within the context of an entrepreneurial device company. The methods used in this study included a combination of interviews with cross-functional team members, a quantitative survey, and the collection of archival data. Data analysis first involved documenting physician-developer interaction practices that had been used within the company, from needs finding to post-market surveillance, across multiple product generations. Leading development factors involving physicians that had influenced the company’s clinical and financial outcomes were next identified. The case study illustrated the importance of working with and understanding the user experiences of a wide range of physicians when developing new products. The case also captured how physician interaction influences risk perceptions toward medical device performance for both surgeons and developers. The case likewise highlighted the benefits of a systems-based design approach, as opposed to designing products for a single technical end point. From a methodological perspective, the case study revealed the importance of examining user interaction within a contextual framework, as opposed to an isolated examination of input and output variables. The study presented in this paper has provided a foundation for future case-based analyses regarding the process of physician interaction in medical device development.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027516-027516-1. doi:10.1115/1.3442795.
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Commercially available dental computer aided design/computer aided manufacture (CAD/CAM) systems usually use abrasive machining processes such as diamond grinding and milling. One of the major disadvantages of abrasive machining processes is subsurface cracks. In the present paper, rotary ultrasonic machining (RUM) technology is introduced into machining of alumina dental ceramics. The subsurface cracks are observed under scanning electron microscope. Effects of ultrasonic vibration on the subsurface cracks are also investigated. Results show that RUM is a very promising process to significantly reduce subsurface cracks in CAD/CAM of dental ceramics.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027517-027517-1. doi:10.1115/1.3442796.
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The geometric configuration of material specimens can present challenges in fixturing such that the boundary conditions influence test results and skew accurate assessment of material properties. This can further be complicated by specimens of low stiffness such that existing equipment is not optimized for the necessary range of forces and displacements. In this paper, we describe a new device for determining viscoelastic material properties of small biologic specimens and show early results from its use. The mechanical design, control system, and theoretical underpinnings are presented.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027517-027517-1. doi:10.1115/1.3443168.
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Careful diagnosis of ankle joints with suspected ligamentous trauma is necessary. Accurate 3D stress test techniques can assist in this but the devices used to stress the foot relative to the lower leg are inapt for clinical application. The goal was to evaluate whether a newly designed 3D foot plate fulfills the requirements of the intended users who are the radiology technicians and the patients. Criteria on functionality included position and fixation of the foot in extreme dorsiflexion $(45 Å)$, plantarflexion $(85 Å)$, inversion $(55 Å)$, eversion $(55 Å)$, internal $(50 Å)$ and external rotation $(50 Å)$, compatibility with imaging systems, and sufficient accuracy and reliability. Criteria on usability included the presence of sense of control by manual loading, successful application in 95% of an adult human population, operation within around 100 s. and low mental effort by self-explaining capability of the device. The design was based on a Stewart platform. The dimensions were determined graphically and a fixation mechanism was developed based on friction. A prototype was built from wood and plastics. This was evaluated in a CT-scanner for accuracy and reliability with four subjects. A usability test was performed with 20 radiology technicians who were asked to perform four tasks with the prototype and fill out a questionnaire. The prototype can reach all extreme foot positions for adults with varying anthropometric dimensions. Except two outliers, the accuracy of reaching an extreme foot position is $0.3–6 Å$ and its reliability is $0.3–3.5 Å$. All radiology technicians agreed that the device could be operated by one person with minor physical and mental effort (NASA XLT median 3.5–11%). The tasks were executed with a median time of 91 s. (20–513 s.) and a median error of 0 (0–6). Its appearance was found professional and reliable. Improvement of the rubber hinges, the fixation mechanism and loading protocol could increase accuracy. Concluding, the 3D foot plate fulfills the majority of criteria and is well-received by the intended users. This demonstrates its high potential for clinical use.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027518-027518-1. doi:10.1115/1.3443169.
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Laparoscopic surgery is carried out using long and slender endoscopes and instruments that are inserted through small incisions in the abdominal wall. Current endoscopes and instruments are rigid and have the drawback that their motion is restricted to 4-degrees of freedom (DOF). This paper describes a 6-DOF steerable laparoscopic grasping forceps incorporating a novel and very simple “cable-ring” mechanism consisting out of a ring of cables surrounded by two coil springs. Methods are described to increase stiffness and to improve manual control, resulting in a well-working prototype suitable for commercialization. The paper ends with a discussion on a number of cable-ring variants suitable for challenging new steerable designs in the future.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027518-027518-1. doi:10.1115/1.3443170.
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Otitis media is the most common bacterial illness in children, resulting in millions of office visits, antibiotic prescriptions, and surgical procedures annually in the United States. Antibiotics are commonly prescribed and has resulted in increased prevalence of antibiotic resistant strains of organisms. Additionally, patients with otitis media are candidates for tympanocentesis, myringotomy, and tympanostomy tube placement procedures. The ability to safely and efficiently perform these procedures to accurately diagnose, identify the bacterial organism, and treat otitis media with point of care therapy is needed. A shape-memory nitinol tympanostomy tube and an all-in-one introducer device (OtoStent tympanostomy device) currently under development will allow clinicians to safely and efficiently perform myringotomy, tympanocentesis, and tympanostomy tube placement with a single disposable device.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027519-027519-1. doi:10.1115/1.3443171.
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It is not easy to design an innovative and successful product in any field of engineering. Medical device design is further complicated by strict regulations. Current engineering design methods provide help in designing a good product, but the designer lacks tools that help him or her create an innovative, commercially successful product. In this study, we analyzed 51 innovative, award-winning medical devices against their competition to identify what made those products stand out from the competition. The method was focused on finding engineering-level characteristics that made the products successful and whether the characteristics of success in the medical device industry are similar to those of other industries. We used a set of innovation categories that have been shown to apply to mechanical engineering products. The results show that the most innovative medical devices were innovative in at least three categories. Overall, a majority (greater than 60%) of the award-winning medical devices exhibited enhanced user interactions, with a similar percentage displaying enhanced environmental interactions and architectural changes, compared with only 20% of devices offering an additional function. We conclude that designers of innovative medical devices need better design methods that extend beyond the functionality of the products.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027519-027519-1. doi:10.1115/1.3443172.
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Flexible endoscopes are used for diagnostic and therapeutic interventions in the human body for their ability to be advanced through tortuous trajectories. However, this very same property causes difficulties as well. For example, during surgery a rigid shaft would be more beneficial since it provides more stability and allows for better surgical accuracy. In order to keep the flexibility and obtain rigidity when needed, a shaft guide with controllable rigidity could be used. In this article we introduce the PlastoLock concept, which uses thermoplastics that are reversibly switched from rigid to compliant by changing their temperature from $5 °C$ to $43 °C$. These materials are used to make a shaft that can be rendered flexible to follow the flexible endoscope and rigid to guide it. To find polymers that are suitable for the PlastoLock concept an extensive database and internet search was performed. The results suggest that many suitable materials are available or can be custom synthesized to meet the requirements. The thermoplastic polymer Purasorb® PLC 7015 was obtained and a dynamic mechanical analysis showed that it is suitable for the PlastoLock concept. A simple production test indicated that this material is suitable for prototyping by molding. Overall, the results in this article show that the PlastoLock concept can offer simple, scalable solutions for medical situations that desire stiffness at one instance and flexibility at another.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027520-027520-1. doi:10.1115/1.3443173.
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Elasticity is an important physical attribute of biological tissue. Elasticity of normal tissue can differ significantly with pathological tissue in its stiffness. It is important to develop a clinical viable method to determine and visualize the elasticity of histological tissue. Magnetic resonance (MR) elastography is a promising noninvasive method to quantitatively measure the viscoelastic properties of biological tissue. We developed a new quasi-static actuation system with the spatial modulation of magnetization (SPAMM) imaging pulse sequence. The MR compatible actuation system consists of an ultrasonic motor, a force sensor, motion-transmission mechanism, ECG signal generation, and controller. The high torque ultrasonic motor, USR60-E3 by Shinsei Corporation, Japan, can function well in the magnetic environment. The simulated ECG signal is generated using function generator, and outputted to both MR scanner and controller respectively. SPAMM imaging sequence is utilized to acquire tagging images of the deformed tissue. The actuation is synchronized with the SPAMM sequence via simulated ECG signal. Indentation force is measured by MR compatible force sensor for the subsequent stiffness inversion procedure. Imaging experiments were conducted using this actuation system and a GE SIGNA 1.5T MR scanner. Clear tag-deformed images of agar gel phantom have been acquired. The results demonstrated the feasibility of utilizing SPAMM sequence and the proposed actuation system for tissue characterization. In comparison with dynamic method of MR elastography, this quasi-static method is relatively simple to implement since no motion sensitive gradient or gradient synchronization is required. A limitation of indentation method is the difficulty to obtain significant deformation of tumor inside the liver organ. Since radio frequency (RF) needle is inserted into liver organ during tumor ablation, the proposed system with needle-based actuation making use of this inevitable insertion will be able to intra-operatively image the liver tumor during ablation. The RF needle can directly vibrate the pathological tissue within the liver organ.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027520-027520-1. doi:10.1115/1.3443174.
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This paper elucidates the history, the design philosophy of innovation and the transformation of an old process-technology into a breakthrough, evidence-based therapy with international medical acceptance, verification of effectiveness as well as the strategic business model employed. Pulsed electromagnetic field therapy (PEMFT) was not medically acceptable and was, until recently in disrepute, professionally speaking. A revisiting of the technology with reference to the partially inconsistent, yet positive anecdotal results obtained, gave rise to in-depth analysis as well as scientific research conducted by independent institutions which resulted in the identification of the key physiological parameters which in turn could be related to a significant improvement of pathologies. By applying and promoting a systems approach as practiced by engineers who were involved in complex multidisciplinary projects for many years, a different perspective on the innovative development of PEMF therapy was established. The innovative process-based therapy working mainly at cellular and self-regulation level was a paradigmatic departure from the indication-based therapy as applied to pharmaceutical therapy. Over the past 10 years exceptional breakthroughs of the nonsymptom based therapy have been documented through clinical trials, scientific medical investigations and the publication of relevant literature. The turn-around of the old and insufficiently understood technology into an innovative, significant, scientific breakthrough-technology, requires a paradigm shift which is analogous to working in a different culture. It is surmised that this paradigm shift will strongly influence medical schools and practitioners over the next 5–10 years. The authors, as “outsiders” to the medical discipline, bring an engineering perspective to bear on the development of innovative but system-integrated medical devices which can promote the medical device industry and bring system engineering approaches into the realm of medical technology and therapy. Both authors have presented a number of papers at international conferences individually and in partnership on the topics of strategic business leadership and business transformation, system thinking and holistic management model development for high technology companies.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027521-027521-1. doi:10.1115/1.3443175.
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Dental implants are generally used in edentulous patients. The key issue of this dental surgery is the effective osseointegration of implants with spongy bone and cortical bone and then they become a part of loading structure. Current osseointegration detection devices only offer overall evaluation without the information of location and orientation of bone defects. This study is to develop detection techniques to measure the quantity as well as to locate the orientation of imperfection around bone-implant interface based on resonance frequency analysis (RFA). A noncontact measurement technique is performed with acoustic excitation through a loud-speaker and displacement response via a capacity-type pick-up. In the first and second series experiments, RFA is applied to estimate the orientation and quantity of irregular bone defects on various in-vitro faulty models. The variation in RF not only locates the orientation and depth of defects but also reflects the change of boundary conditions surrounding the defective models. According to these results, the detection technique to locate irregular osseointegration is established. Furthermore, the detection device to this end is proposed as well. The proposed examining approach and device are promising and able to assist dentists in dental implant surgery.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027521-027521-1. doi:10.1115/1.3443176.
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When an infant is born prematurely, there are a number of health risks. Among these are underdeveloped lungs, which can lead to abnormal gas exchange of oxygen or hypoxemia. Hypoxemia is treated through oxygen therapy, which involves the delivery of supplemental oxygen to the patient but there are risks associated with this method. Risks include retinopathy, which can cause eye damage when oxygen concentration is too high, and brain damage, when the concentration is too low [1]. Supplemental oxygen concentration must be controlled rigorously. Currently healthcare staff monitors infants’ blood oxygen saturation level using a pulse oximeter. They manually adjust the oxygen concentration using an air-oxygen blender. Inconsistent manual adjustments can produce excessive fluctuations and cause the actual oxygen saturation level to deviate from the target value. Precision and accuracy are compromised. This project develops an automatic oxygen delivery system that regulates the supplemental oxygen concentration to obtain a target blood oxygen saturation level. A microprocessor uses a LABVIEW ® program to analyze pulse oximeter and analyzer readings and control electronic valves in a redesigned air-oxygen blender. A user panel receives a target saturation level, displays patient data, and signals alarms when necessary. The prototype construction and testing began February 2010.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027522-027522-1. doi:10.1115/1.3443177.
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To design a smart ankle-foot orthosis (SAFO) that improves upon current ankle-foot orthoses used to treat steppage gait. Current ankle-foot orthoses are subjected to significant stresses on the ankle region of the structure, causing discomfort and the possible failure of the AFO. Although these AFOs have a constant stiffness, they do not reduce the occurrence of slap foot, where the foot slaps on the ground rather than gradually lowering it. The SAFO is an active ankle-foot orthosis that allows the user’s foot to follow a normal gait cycle. It is designed to reduce stress at the ankle by allowing for movement of the foot beyond a 90 deg angle for plantarflexion. The hinged ankle-foot orthosis is incorporated with a novel dual hydraulic-cylinder system, two tension springs, and force sensitive resistors. The force sensors are placed at the hallux, first metatarsal head, fifth metatarsal base, and heel. The foot movement actuation follows the force applied to the plantar surface of the foot during gait. The sensor outputs are fed to a signal processor and control interface to coordinate the motor actuation with the forces exerted by the user. The motor turns the screw attached to the hydraulic cylinders, which, thereby, control the orifice size by moving a plate in the cylinder, thus, changing the resistance. The cylinder filled with air will be pressurized during the lean phase, as the orifices will be closed and will provide power just as a spring would during the heel-off phase. After the heel strike, the resistance of the fluid-filled cylinder is decreased to slowly lower the foot. Once the foot is flat, the resistance of the fluid-filled cylinder is increased to keep the foot in a position to allow for toe clearance. During the heel-off event, the air-filled cylinder will assist the user with the power to push off. When toe-off occurs, the fluid-filled cylinder will decrease the resistance to allow the tension springs to bring the foot back to neutral position. To power the motor and sensors, a rechargeable battery pack is placed in a waist bag. The SAFO’s flexible design uses a novel combination of hydraulic-pneumatic cylinders to prevent foot drop, and restore the user’s sense of normalcy by providing late stance plantarflexion and a return to neutral position in early swing phase.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027522-027522-1. doi:10.1115/1.3443178.
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Lower extremity weakness is a serious problem afflicting people all over the world. Until recently, the mobility options for people with this condition have been confining and limit the individual’s functionality. Walking assist devices are presently in development to restore hands-free walking to people with lower extremity weakness. These devices provide the necessary support and power to enable the individual to restore normal ambulation. The proposed design of exoleg, a single leg external walking assist device, addresses the demographic of people with lower extremity weakness. The design includes replication of the gait cycle utilizing mechanical links and user control interface with emphasis on safety. The design couples the actuation of the knee and hip through the use of linkages connected to a single motor. The actuation of the hip is controlled by a 4 bars crank-rocker linkage system while the knee is actuated by corresponding linkages (designed in WORKING MODEL 2D , a commercial simulation software) that generates the knee kinematic profile. The angular profiles of the knee and hip actuations are compared with the actual knee and hip angular trajectories. The frame of the device incorporates a passive ankle stabilization system to compensate for the effects of foot drop. The system utilizes feedback from trigger points from pressure sensors on the foot and goniometers at the hip and knee joints to measure the angulations in gait to keep the device in synchronization with natural ambulation. An on-board microprocessor receives the feedback from the trigger points and sends the actuation signal to the motor. A conceptual design of electrostatic actuator motor is also proposed to keep the device light weight and compact.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027523-027523-1. doi:10.1115/1.3443219.
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An intravascular optical coherence tomography probe is integrated in a computerized angioplasty balloon deployment system. The resulting setup can be useful in many applications. In this paper, based on the acquired intraluminal images, we achieve a detailed assessment of the diameter and wall thickness of the inflated balloon at different pressures. Such analysis is helpful in testing the balloon quality, in assessing deformation model, or in validating new balloon designs.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027523-027523-1. doi:10.1115/1.3443227.
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In this paper, the authors report in-vitro tests of an ultrasound system and method of wirelessly transmitting significant amounts of energy into the human body for the purpose of recharging implantable batteries. We demonstrate the complete charging of Li-ion batteries with energy capacities of $35 mA h$, $200 mA h$, and $600 mA h$ through several types of animal tissue while keeping the temperature rise of the tissue and piezoelectric receiver below the desired $2°C$ human safety limit recommended by FDA medical device guidelines. Given these encouraging results, it is logical to conclude that the rapidly growing neurostimulator market is a desirable and appropriate target for introduction of this novel recharging method.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027524-027524-1. doi:10.1115/1.3443233.
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Existing technologies and devices have facilitated the interaction of the blind or visually impaired (BVI) with their surroundings. However, reading remains an area where the potential of these technologies is not fully utilized. This work presents preliminary studies for the design of a finger-wearable E-Braille device that will allow the BVI to read electronic documents as they would read any document in Braille. The proposed device is wearable on a single finger on of the distal and middle phalanges (dorsal side). The main elements of the device are electrotactile display and force sensor. The electrotactile display is an electric board containing a matrix of electrodes that sends current to the fingertip for stimulating the touch feeling of a particular Braille character. By sending a sequence of Braille characters to this board, information can be sent to the user of the device through the generated electrotactile feeling. The force sensor is used in a feedback control loop to maintain steady contact pressure between the fingertip and the display board throughout the reading process. The entire finger-wearable E-Braille tactile display device is composed of a housing that can be customized to individual users, a miniature dc motor, mechanical components, and main elements. The initial testing of the proposed device is underway. Preliminary results indicate that the device can provide tactile sensation similar to that of reading a Braille document. The initial assessment of the device usability is underway.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027524-027524-1. doi:10.1115/1.3443234.
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The migration to modern information systems and advancement in noninvasive health monitoring devices enable highly mobile users to support increased efficiencies and improvements in delivery of healthcare. Users of these systems are likely to have different needs or views of information either because of organizational role or because of geographic location. In this distributed architecture, available resources must dynamically be able to be reassigned to respond to external factors such as changes in the environment, changes in short-term objectives, reallocation of responsibilities, and changes in resource consumption patterns. This paper describes a framework for healthcare decision making and management of healthcare operations through the application of dynamic resource management using information technology for what we call active management of healthcare operations.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027525-027525-1. doi:10.1115/1.3443260.
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Video capsule endoscopy (VCE) is a method used to wirelessly scan the gastrointestinal (GI) tract lumen. Despite the effectiveness of VCE in GI endoscopic procedures, VCE is limited because it lacks the capability to exactly locate itself as well as accurately detect bleeding or clotting within the GI tract. The unreliability of localization combined with inaccurate blood detection in VCE ultimately leads to wired endoscopy for additional diagnosis. In this paper, a method to address localization of the VCE device, also known as a pill camera or capsule, in conjunction with an accurate detection of active bleeding and clotting inside the small intestine, is introduced. The Texas Instruments, ZigBee® kit, which uses a 3D trilateration method will be used for accurate location detection and image transmission throughout the VCE procedure. The system will be interfaced with software providing end users with the path and total distance traveled by the pill capsule within the small intestine. The blood detection system is enhanced by using a minilow energy wireless Raman spectrometry to scan for active bleeding or clots along the small intestinal wall. The employed spectrometry method scans for wavelengths based on blood’s optical characteristics and records any image fitting the exact spectrum. Blood detection and localization data are coupled together and then transferred to an external receiver. These two improvements together will enhance capsule endoscopy procedures and fill the gap created by the existing capsule endoscopy technologies, therefore, meeting the needs of physicians and patients.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027525-027525-1. doi:10.1115/1.3443298.
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Meniscectomy is a medical procedure where ruptured meniscal tissue is removed within the knee joint. The conventional cutters fail to reach the entire meniscus. Therefore, the focus of this study is to create a steerable joint, which allows sideway steering of the tip to increase the reachability within the knee joint. Additionally, the steerable joint is required to be robust to transmit a cutting force of up to 190 N. The mechanism design is divided into the functions: steering and actuating cutting mechanism. The most promising solution of these functions was combined and resulted in the use of a crossed configuration of a compliant rolling-contact element for the instrument joint. Flexural steering beams actuate the rotation of the joint using the principle of a parallelogram mechanism. The prototype has a range of motion of $+25 deg$ and $−22 deg$ with a steering stiffness at the handle side of $33 N mm/rad$. An axial load of 200 N on the tip corresponded with a parasitic deflection of 4 deg. This unique type of steerable instrument shows potential to be functional in meniscectomy due to the great robustness of the joint.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027526-027526-1. doi:10.1115/1.3443317.
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This paper describes the development of an articulating endoscopic screw driver that can be used to place screws in osteosynthetic plates during thoracoscopic surgery. The device is small enough to be used with a 12 mm trocar sleeve and transmits sufficient torque to fully secure bone screws. The articulating joint enables correct screw alignment at obtuse angles of up to 60 deg from the tool axis. A novel articulating joint is presented, wherein a flexible shaft both transmits torque and actuates the joint; antagonist force is provided by a superelastic spring. Screws are secured against the driver blade during insertion and with a retention mechanism that can passively release the screw when it has been securely placed in the bone. The prototype has been fitted with a blade compatible with 2.0 mm and 2.3 mm self-drilling screws although a different driver blade or drill bit can easily be attached. Efficacy of the tool is demonstrated by securing an osteosynthetic plate to a rib in a mock surgical setup. This tool enables minimally invasive, thoracoscopic rib fixation.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027526-027526-1. doi:10.1115/1.3443318.
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Each year approximately 2000 children are born with a form of congenital heart disease that would benefit from mechanical restriction, or banding, of the pulmonary artery. [1,2] Installing or changing the setup of the banding requires an open chest surgery and during the first 6 months of the patient’s life, physiological parameters evolve rapidly, resulting in need for frequent reoperations. Mortality for those treated patients may be as high as 10–20%. [3] While many devices have been patented, none of them have been adopted due to size, adjustability, or reliability constraints with regard to implantation in newborns, especially below 6 months of age. Here we present the conception, design, and scale model testing of a novel pulmonary banding system for infants. This system features a hydraulic mechanical stepper actuator that offers great advantages in both reliability and compactness. As a proof of concept, we built a 5:1 scale working prototype that demonstrated the desired functionality of the device. Further steps involve scaling down the device so first porcine trials can be started.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027527-027527-1. doi:10.1115/1.3443321.
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Although hand prostheses with a cosmetic covering are commercially available for disabled people, the operating effort due to the stiffness of the mechanism is high. This results in high power requirements. This paper aims to present a new concept of mechanisms for the compensation of the nonlinear stiffness of hand prostheses by using statically balanced mechanisms with a nonlinear behavior. This concept was based on a combination of stability phases of snap-through buckling in bistable spring mechanisms to create the nonlinear balancing force. To demonstrate the efficiency of the concept, an optimized design for a case study of a child-sized hand prosthesis is also presented. A pattern search method was applied for the optimization. As a result, the calculated stiffness and, thereby, the operating effort was reduced by 96%. It can be concluded from the conceptual and numerical results that the presented concept provides a highly efficient solution to the discussed problem.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027527-027527-1. doi:10.1115/1.3443322.
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This paper describes the application of machine learning approaches for predictive modeling to improve the estimation of risks for complications of allogeneic hematopoietic cell transplantation (HCT) including relapse, graft-versus-host disease, and transplant-related mortality (TRM). Clinical disease and demographic factors known to impact the outcome of HCT include: recipient and donor age, type of donor (related/unrelated), donor-recipient gender, diagnosis and disease status pre-HCT, and stem cell source (peripheral blood, marrow, and umbilical cord blood). However, biostatistical analysis of risk has only limited accuracy in estimating a given patient’s risks of serous post-HCT complications. We describe the application of standard support vector machine (SVM) classifiers for data-analytic modeling of TRM. The goal is to predict the binary output TRM (alive or dead) from a set of genetic, demographic, and clinical inputs. Classification decision rule is estimated using SVM approach appropriate for such sparse multivariate data. This study compares several feature selection techniques for modeling TRM and objectively evaluates the quality of feature selection via prediction accuracy of the corresponding SVM classifiers. In addition, we discuss methods for interpretation of multivariate SVM models.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027528-027528-1. doi:10.1115/1.3443323.
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Endotracheal intubations are performed on thousands of patients each day. Intubation is achieved by inserting a small plastic tube down a patient’s trachea, allowing oxygen and anesthetics to be delivered directly to the lungs. The tube is held in place by inflating a small cuff on the distal tip, which also serves to seal the trachea. The use of a manometer to measure the pressure within the cuff is essential to keep the practice safe. Hyperinflation of the cuff can put too much pressure on the trachea, leading to tissue death and post-procedure patient discomfort. A hypo-inflated cuff results in a poor seal within the patient’s airway and can lead to ineffective positive pressure ventilation, or gastro-inflation, which can in turn lead to vomiting, putting the patient at risk for asphyxiation. The latter complication can cause hypoxia and death. Manometers used to measure cuff pressure are costly, cumbersome, and potentially inaccurate. A pressure measuring syringe has been designed, tested, and verified to meet physicians’ needs for a simple, low-cost pressure measurement device. New data suggest that overblown cuffs are very common during surgery (2009, Abstract 3AP1-1, presented at the European Society of Anaesthesiology, Milan, Italy). In fact, most are inflated to a pressure greater than the recommended 25 cm $H2O$, and past studies on patients in critical care settings corroborate these observations (Jaber, S., , 2007, “Endotracheal Tube Cuff Pressure in Intensive Care Unit: The Need for Pressure Monitoring,” Intensive Care Med., 33 , pp. 917–918). A pressure-sensing device that gives physicians a tool to help avoid over- and underinflation of the endotracheal tube (ETT) cuff was able to provide an accurate, repeatable measurement of the intracuff pressure. A deterministic design process was used to develop a set of functional requirements for a pressure measuring device that accomplishes both inflation of the cuff and a simultaneous measurement of the cuff pressure. A silicone bellow inside the body of the plunger acts as a single elastomechanical measurement device, permitting a highly repeatable measurement of the intracuff pressure. The design also maintains most of the traditional syringe design in that only the plunger is modified to accommodate the bellows. The components of the syringe are also scalable in order to allow the design to be utilized for other pressure sensitive procedures. The current iteration of the syringe can accurately measure pressure within a range of 0–40 cm $H2O$. Prototypes for the syringe were 3D printed and tested, and silicone rubber bellows were outsourced. In the final prototoype, the plunger is injection molded. The total estimated final cost of the syringe is about \$1.50, which is comparable to the cost of a typical syringe. Because of this, the pressure measuring syringe is a viable candidate for low-cost mass production. The calculated pressure-deflection relationship of the bellows was experimentally verified, further demonstrating the scalability of the design. In conclusion, a simple and cost-effective syringe manometer has been developed, which controls and measures air pressure in ETT cuffs.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027528-027528-1. doi:10.1115/1.3443324.
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A flexure-based ankle rehabilitation device utilizes the linear elastic force-deflection characteristics of certain types of flexure beams to measure the forces and torques output by the human ankle joint complex (AJC). Three sets of flexures, placed so as to allow rotation about the three primary rotational axes of the AJC, allow for a measurement of all three major rotations applied by the ankle joint and coupled motions essential for walking, balancing, and running. Currently, there is no method or universally accepted device used to measure and quantify the strength, speed, and stabilizing ability of the AJC. This is especially important when it is considered that ankle injuries are perhaps the most common type of musculoskeletal injury. Furthermore, AJC integrity is recognized as critical to the maintenance of balance and prevention of falls among older adults. We have developed a device that would primarily be used by physicians or rehabilitative professionals as part of a more standardized methodology of musculoskeletal care and to determine the extent of an ankle’s recovery after injury. It has potential to help researchers better understand the recovery process and the mechanics of ankle injuries. Additionally, it could be useful to the footwear and orthopedic industries as a means of evaluating products for AJC protection and recovery. The architecture of the device could also be modified to fit other multi-DOF joints, such as the wrist, shoulder, hip, or spine. Single-DOF devices could also be developed to potentially increase efficacy of rehabilitation practices for single-DOF joints such as the knee and the elbow. Upon fulfilling its initial functional requirements, this device still has a lot of potential for further development. The current design can be tuned fairly easily by exchanging different flexure modules of varying stiffness. This allows for testing of different materials, stiffness values, and flexure module designs. Furthermore, it would be possible to expand on the design so that it can be used as a training tool, instead of just as an evaluation device. A rehabilitation program utilizing such a device would serve to isolate the ankle much more than current recovery exercises, helping to reduce the chances of re-injury. Current technology used to evaluate ankle rehabilitation focuses solely either on the foot’s range of motion or on the joint’s ability to balance the rest of the body. While the former ignores the ankle strength, the latter disregards any information regarding the ankle beyond the standing configuration. The flexure-based ankle rehabilitation device measures ankle strength and power output through a range of motion that is anatomically similar to walking, running, etc. Also, measuring power output is not feasible with currently available devices and is believed to be very important for further injury prevention. Also, a wide range of foot configurations can be achieved, suggesting that regardless of the patient’s physical abilities, the device can still be used to safely and effectively rehabilitate a person’s injured joint and return it to a healthy state. Results from the initial prototype suggest that an ankle rehabilitation device utilizing compliant mechanisms can measure the expected torque outputs from the ankle joint. Use of compliant mechanisms allows for the design of a more cost-effective, compact device that can be handled by physicians even outside of a hospital setting. The final paper will present the second design iteration and the results of measurements that will be performed on patients’ rehabilitating ankles in the interim so as to determine what other adjustments need to be made in the system to account for the coupled motions of the ankle joint. A full working system including data acquisition equipment utilized to collect patient information and the final device iteration will be presented in the final technical paper.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027529-027529-1. doi:10.1115/1.3443723.
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A novel EMG feedback device has been designed and developed. The device exists in two forms: a trainer version to be used by the general consumer and a stethoscope version that is tailored to be used by a therapist or a clinician. The trainer version was designed and built to have a small form factor for direct placement of the device on a disposable electrode patch, thus eliminating the need for electrode wires. The unique design allows for vibrotactile feedback in addition to standard auditory feedback. The stethoscope version provides a stethoscopelike form factor. The audio output can be either a pure tone or the sound of the EMG signal itself. The electrodes in this version consist of a reusable bar electrode containing two fixed electrodes and a reusable grounding electrode. The stethoscope version allows the user to quickly and easily hear EMG information from various locations of the body. Each of the devices provides users with capabilities and functions not previously available from traditional EMG feedback devices.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027529-027529-1. doi:10.1115/1.3443730.
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X-ray mammography has been used in the early detection of breast tumors for decades. Related techniques to enhance preventive screenings are still demanding. Since the 1990s, near infrared diffuse optical tomography (NIR DOT), a functional medical imaging modality, is being exploited and developed to reconstruct optical-coefficient images of tissues. Much endeavor to improve the spatial resolution and contrast of DOT images has been exerted for clinic applications in the diagnosis of breast tumors. The study aims at the design, implementation, and verification of a mammography based NIR DOT. This multimodality imaging method is able to provide information that neither X-ray nor diffuse optical tomography can give alone. To this end, a device with multiple-channel switching of NIR sources and translational scanning of out-emitted intensity constructed on a commercialized mammography system is being designed and built up. We employ the mammography image as structure information that is used as an initial guess for the image reconstruction of optical properties of tissues. Preliminary numerical trials are performed using heterogeneous phantoms made of high-scattering Intralipid. Promising results are obtained with various spatial resolutions due to partial NIR detected intensity.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027530-027530-1. doi:10.1115/1.3443732.
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The design of medical technologies for developing countries is a multidisciplinary process. We describe a model process for an appropriate medical device design. D-Lab Health combines real world projects and partners with a diverse student team to provide experiential educational opportunities in a developing country health care setting; in turn, the partners benefit from student medical device designs. In order to effectively communicate practical design strategies toward an appropriate design for medical technology, a series of accelerated technology learning modules was developed using commercially available and customized medical devices. Each module included a formal framework for the students to think about the competing priorities of the user, chooser, payer, and approver of such global health technologies, christened the “global health innovation compass.” These modules provided a hands-on laboratory experience that demystified the design process. This was particularly useful for nonengineering students who were able to add value to the project through their life-sciences background. An essential component of the course was a week-long visit to our field partners in Nicaragua to enable the students to get first hand experience and to identify a health need they could address with a technology solution. Subsequently, the students utilized their hands-on training to develop medical device prototypes within an abbreviated production schedule of 3 weeks. We describe the design process for one such prototype “a low cost glucometer.”

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027530-027530-1. doi:10.1115/1.3443733.
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The current methodologies of clinical heart transplantation limit the ischemic window to 4–6 h. Periods longer than this can induce dysfunction in the organ and can lead to increased patient morbidity and mortality. An alternative to the current methods of static cold storage (CS) is continuous hypothermic perfusion (CHP), where a hypothermic oxygenated crystalloid solution is mechanically perfused through the coronary arteries. This has been shown to preserve the function for up to 72 h, but the techniques have yet to be optimized. We have developed an apparatus and methodology for performing CHP on large mammalian hearts, followed by reanimation in our in vitro Langendorff apparatus (The Visible HeartTM ). We are also investigating the utility of the cardioprotective agents docosahexaenoic acid and [D-Ala2, D-Leu5] enkephalin, both of which have shown cardioprotective effects in our laboratory, and we believe that their addition to the preservation solution can further extend the transplant window. A series of pilot studies has been performed to date, with modestly successful results. Hearts preserved with CHP seem to show better functionality than CS hearts but far worse functionality than hearts reanimated immediately after explant. We hope to use this system to optimize CHP methodology and eventually develop a system for prolonging the window for heart transplantation.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027531-027531-1. doi:10.1115/1.3443736.
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The development of OpenFES hardware presented in this paper involved a closed-loop functional electrical stimulation (FES) system that could be assembled from off-the-shelf parts in India. The state-of-the-art biosignal-based control strategies could be evaluated in a clinical research setting using the familiar development environment of MATLAB/SIMULINK (The Mathworks). This hardware was developed primarily for a rehabilitation research center where students from an engineering and medical school could use it as a testbed for clinical research. It is envisioned that the design of a working prototype would be available after thorough testing at http://robo4rehab.wikispaces.com/OpenFES so that it can be further enhanced in an open-source setting. The command source selected for modulating/triggering the electrical stimulation was electromyogram (EMG), which is the recording of the bioelectrical signal generated at the cell membrane of contracting muscle fibers. The FES controller was implemented in an xPC target (The Mathworks) real-time kernel, running on a single board computer where the stimulation pattern, i.e., the temporal pattern of current pulses, was computed online based on the surface EMG patterns. The stimulation parameters were passed to a dsPIC33F microcontroller (Microchip, India) driven voltage controlled current source (VCCS) via a universal asynchronous receiver/transmitter (UART). The VCCS consisted of a coupled transconductance amplifier in series with precharged capacitors. The biphasic stimulation waveform was obtained with an analog switch that switched to reverse the polarity of the surface electrodes. The input stage for surface EMG consisted of an instrumentation amplifier with an anti-aliasing filter made of switched-capacitor (recording capacitor) banks. The dry surface EMG electrodes had buffer op-amps to provide high input impedance. A dsPIC33F microcontroller (Microchip, India) in the input/output (I/O) stage coordinated the switching of the stimulating capacitors with the recording capacitors in order to reject the stimulation artifact. The control software ran on the xPC target and delivered the stimulation parameters via UART to the dsPIC33F microcontroller (Microchip, India). The controller specifications are as follows: (1) Communications: xPC target is a battery powered stand-alone FES controller, communicating with the slave microprocessor in the input/output stages via UART. (2) FES controller: PC/104 single board computer (Advantech Co., PCM-3355) running xPC target kernel (The Mathworks). (3) PC/104 CPU: 366 MHz ×86 (AMD Geode processor). (4) Display: LCD ($1024×768$ at 18 bpp TFT) or CRT ($1024×768$ at 24 noninterlaced). (5) Stimulation pulse-width range: 1–255 ms. (6) Stimulation amplitude range: 0–100 mA (16 bit analog output with voltage controlled current source). (7) Stimulation frequency range: up to 30 Hz. (8) I/O channels (Sensoray, model 526): 4 AO (16 bit), 8 DIO, and 8 AI (16 bit). (9) Channel offset: 1000 Hz. (10) Analog to digital conversion for EMG: 16 bit. (11) Maximum signal amplitude: about 10 mV (peak to peak). (12) Minimum signal amplitude: about 1 mV (peak to peak), i.e., the noise floor should preferably be lower. (13) Signal to noise ratio.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027531-027531-1. doi:10.1115/1.3443737.
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Valvular heart disease is a significant problem. The primary care physician initially does assessment through auscultation. Accuracy in classification of sounds is suboptimal (20–40%). Technological advances have paralleled an increase in referral for Doppler echocardiography and a decrease in auscultatory skill. An increase in the referral of functionally innocent heart murmurs has contributed to the increasing cost of care. A computer-aided analysis has been shown to improve the accuracy of primary care physicians. A remote centralized computer-aided analysis could provide physicians with an additional tool in the assessment of heart murmurs, especially in settings without access to echocardiography. iStethoscopePro is an application for the iPhone and iPod Touch capable of recording and emailing sounds. We developed a device, which interfaces with iStethoscopePro and any acoustic stethoscope. We used this device to capture heart sounds from a conventional acoustic stethoscope and email them using iStethoscopePro for analysis with an artificial neural network (ANN). Hypothesis: It is possible to record heart sounds from an acoustic stethoscope, email them, and classify them with an ANN. Our device recorded heart sounds with insignificant intersample variation. After training the ANN with representations of four heart murmurs (aortic regurgitation, aortic stenosis, mitral regurgitation, and mitral stenosis) and normal, we achieved an overall accuracy of 45% with sensitivities of 50–75%. A remote centralized analysis of sound captured from an acoustic stethoscope is possible and could augment traditional auscultatory exams by offering an objective classification. Improving the accuracy and specificity of the ANN is necessary. This collection modality offers a method for the collection of a great deal of sounds for further development of artificial intelligence systems.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027532-027532-1. doi:10.1115/1.3443738.
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Previous studies have shown that many S-nitrosothiols (RSNOs) rapidly degrade, with half-lives from minutes to seconds in aqueous solution [1]. The research presented in this paper presents data that the RSNO 1,3-benzenedinitrosothiol has been relatively stable for over 1 year. This RSNO still releases nitric oxide (NO) when subjected to ultraviolet light and has the same characteristic absorbance peak as a freshly made RSNO. Developing this stable RSNO potentially provides a venue for further investigation into using this NO donor to improve the biocompatibility of implanted optical sensors.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027532-027532-1. doi:10.1115/1.3443739.
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Trauma is the leading cause of death in persons younger than 44 years old in America; half of the deaths occur within the first hour following the incident. The likelihood of survival for such critical trauma patients is significantly increased if an Emergency Department Thoracotomy (EDT) is performed. EDT entails the surgeon performing large and rapid incisions into the pleural space of the thoracic cavity to resuscitate patients who have suffered penetrating chest trauma. This procedure is highly invasive and rare and is typically conducted outside the operating theater in the absence of a trained cardiothoracic surgeon. Since most emergency clinicians are not trained to perform EDT and are often hesitant to perform it, poor outcomes are common. The use of clinical simulators offers the potential to eliminate these concerns; however, current medical simulators are not dedicated to the training of EDT. The goal of this work was to design and build a mechanical simulator to mimic the functionality of the rib cage and the components within the thoracic cavity to serve as a learning and assessment tool for conducting EDT. This design paper presents the user requirements and engineering specifications for the simulator, explains the materials selection approach employed for the thoracic components, and describes the iterative approach for designing, fabricating, and validating the EDT simulator.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027533-027533-1. doi:10.1115/1.3443741.
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Percutaneous cochlear implantation (PCI) is a recently developed minimally invasive technique that utilizes image guidance and a custom-made microstereotactic frame to guide a drill directly to the cochlea. It enables cochlear access through a single drill port, reducing invasiveness in comparison to mastoidectomy. With the reduction in invasiveness, PCI enables a corresponding reduction in visualization and space in which to work at the cochlear entry point. This precludes standard cochlear implant deployment techniques and necessitates a new insertion tool that can deploy a cochlear implant into the cochlea while working down a deep, narrow channel. In this paper, we describe a manual insertion tool that we have developed for this purpose. The tool is capable of inserting an electrode array into the cochlea using the advance off-stylet technique, using simple manual controls on its handle.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027533-027533-1. doi:10.1115/1.3443740.
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We propose a simple, robust, and linear method to control the spike timing of a periodically firing neuron. The control scheme uses the neuron’s phase response curve to identify an area of optimal sensitivity for the chosen stimulation parameters. The spike advance as a function of current pulse amplitude is characterized at the optimal phase, and a linear least-squares regression is fit to the data. The inverted regression is used as the control function for this method. The efficacy of this method is demonstrated through numerical simulations of a Hodgkin–Huxley style neuron model as well as in real neurons from rat hippocampal slice preparations. The study shows a proof of concept for the application of a linear control scheme to control neuron spike timing in vitro. This study was done on an individual cell level, but translation to a tissue or network level is possible. Control schemes of this type could be implemented in a closed loop implantable device to treat neuromotor disorders involving pathologically neuronal activity such as epilepsy or Parkinson’s disease.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027534-027534-1. doi:10.1115/1.3443743.
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In diseases such as hydrocephalus, the cerebral ventricles enlarge. The treatment options for these patients are presently based on pressure, which has limited capabilities. We present the design of a volume sensor as an alternative monitoring option. Through the use of computer aided design and simulation, we optimized a sensor in silico with fewer resources. Specifically, we designed a sensor for animal experimentation with a scalable procedure for human sensors. In this paper, we present a rational design approach for a sensor that integrates advances in medical imaging. Magnetic resonance data sets of both normal and diseased subjects were used as a virtual laboratory. Finite element simulations were performed under pathological disease states of the brain as a contribution toward an accelerated device design. An optimized sensor was then fabricated for these subjects based on the outcome of the simulations. In this paper, we explain how a computer aided subject-specific design was used to help fabricate and test our sensor.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027534-027534-1. doi:10.1115/1.3443744.
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In this paper, we describe a method for automatically building a statistical shape model by applying a morphing method and a principal component analysis (PCA) to a large database of femurs. One of the major challenges in building a shape model from a training data set of 3D objects is the determination of the correspondence between different shapes. In our work, we solve this problem by using a morphing method. The morphing method consists of deforming the same template mesh over a large database of femur geometries, which results in isotopological meshes and one to one correspondences; i.e., the resulting meshes have the same number of nodes, the same number of elements, and the same connectivity in all morphed meshes. By applying the morphing-based registration followed by PCA to a large database of femurs, we demonstrate that the method can be used to derive a low dimensional representation of the main variabilities of the femur geometry.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027535-027535-1. doi:10.1115/1.3443745.
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Pressurized metered-dose inhalers (pMDIs) have been the most effective therapeutic treatment for controlling lung diseases such as asthma and COPD. The flow through a two-orifice system of pMDI is very complex and poorly understood. Previous experimental work has shown that metastability may play a significant role in determining the flow conditions inside pMDIs. In this paper, we present the findings of a homogeneous equilibrium model with those of a delayed equilibrium model (DEM) accounting for propellant metastability. These results are compared with the available experimental and numerical predictions Further, the DEM was applied with HFA propellants R134A and R227, and the results were compared with traditional propellant R12.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027535-027535-1. doi:10.1115/1.3443751.
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Steerable needles offer the potential to turn corners during insertion, thereby avoiding obstacles, reducing tip placement error and enabling a less invasive access to challenging anatomical locations. In this paper, we describe an experimental testbed designed to facilitate experiments with several popular steering mechanisms. One such mechanism makes use of asymmetric forces generated by a bevel tip for actuating steerable needles, and another uses multiple concentric precurved tubes that can change the needle shaft shape by rotating within one another and extending telescopically. The experimental testbed consists of a new robotic actuation unit for controlling axial rotation and linear translation of multiple tubes. It also includes stereo-optical cameras and a magnetic tracking system for the feedback of needle shape and tip location. The setup can be used in future work for model validation and closed-loop feedback control of steerable needles and cannulae.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027536-027536-1. doi:10.1115/1.3443756.
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Precurved needles are used in a variety of medical applications for both passive and active control of instrument position. In one application, the deployment of a precurved stylet from a concentric outer cannula can be used to achieve lateral positioning of the distal tip of the stylet. This paper outlines how the material and geometry of the stylet can be chosen to ensure that it will not yield and thus repeatedly return to its precurved shape when deployed from a cannula. Using this methodology, we calculate the maximum strain for a range of stylet geometries and show that nitinol is required for the stylet material so that it will not plastically deform. Then, 16 stylets of varying diameters (0.508 mm, 0.635 mm, 0.838 mm, and 0.990 mm) and radii of curvature (10 mm, 20 mm, 30 mm, and 40 mm) were manufactured. Experiments were performed with four different diameter cannulas (20, 18, 16, and 14 gauges) to measure the forces required to deploy the stylets from and retract them back inside the cannulas. Retraction forces were measured between 0.3 N and 13.9 N, and deployment forces were measured between 0.2 N and 7.0 N. For a given cannula, it was found that force increases as the stylet diameter increases and as the bend radius decreases.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027536-027536-1. doi:10.1115/1.3443759.
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In the design of medical devices, the use of numerical simulation, either with or without complementary experimentation, may lead to a more competent product. The experimentation in question may either be performed in vitro or in vivo. This paper conveys a case study in which the two methodologies, numerical simulation and in vitro experimentation used in tandem, enabled the evaluation of safety issues related to a heat-generating implant. The numerical simulation was implemented by means of ANSYS finite-element software employed in the transient mode. The experimental work provided information necessary for the execution of the simulation and, therefore, was performed as the first phase of the research. The implant is of the type that is equipped with a short-lived battery that requires intermittent recharging. The recharging is accomplished by means of an antenna that is externally mounted on the skin surface. The antenna is the primary of a transformer, and the implant contains the secondary of the transformer. During the recharging period of the battery, heat is generated in both the antenna and the implant. By the symbiotic use of the experimental results and the numerical simulation, time-dependent temperatures were determined in the tissue that is situated in the neighborhood of the implant and the antenna. These temperatures were evaluated from the standpoint of possible tissue damage.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027537-027537-1. doi:10.1115/1.3443765.
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Creating product innovations involves the need to understand the social context in which the innovation is created and ultimately the context in which it is to be used. The use of globally distributed teams (GDTs) in engineering education to understand and enhance the social and technological interaction could catalyze the process of creating innovation. This paper proposes a framework for the analysis and support of the GDT setting. The proposed framework builds on the standardized open system interconnection model for network communication consisting of seven interconnected layers. As it has been suggested in prior studies, a successful collaboration in a GDT relies on several critical factors that build on each other. Organizing and supporting these factors in an interconnected layered scheme could better clarify the interaction between social and technological aspects. A case study of a student medical device project is analyzed using the proposed framework. The project involved students from University of Minnesota, MN and KTH Royal Institute of Technology, Stockholm, Sweden.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027537-027537-1. doi:10.1115/1.3443769.
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The purpose of this project is to develop a modular architecture framework for the design and manufacture of medical devices. This modular framework aims to incorporate design variables and criteria that are unique to the medical domain to facilitate reliable operation, easier maintenance, and faster product development time. Central to this research effort is the need for inputs from the range of stakeholders. The specific goals for this effort are to determine design criteria by collaborating with users and manufacturers of medical equipment and literature search, to translate user inputs to specific design targets, to develop a preliminary modular design framework using multicriteria optimization methods, and to test a preliminary modular architecture using a simple medical device such as a glucometer. The importance of the research with respect to its application in the medical arena can be very significant. With the product interaction with humans, both on the manufacturing level and the user level, the issue of safety is paramount. Some of the other significant contributions are in the improvement of the following: product quality and reliability, product life cycle issues, and an enabler for the medical community.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027538-027538-1. doi:10.1115/1.3443776.
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This paper proposes the conceptual design of a mechanical stimulator that uses a tissue engineering strategy to develop a diarthrosislike structure in vivo. The adopted design approach is based on a function analysis. The approach has resulted in the design of a stimulator consisting of four components: cages, a compliant four-bar mechanism, a transmission mechanism, and a fixation component. The implanted stimulator is driven by internal body power, particularly by the longitudinal deformation of a skeletal muscle. The compliant mechanism is designed to impose controlled shear and compressive strain to the growing joint construct in order to initiate cartilage formation. The paper emphasizes the conceptual design and its rationale. Evaluation using finite element analysis was performed, which showed that the design meets the technical demands. Titanium prototypes were fabricated for stiffness and endurance testing.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027538-027538-1. doi:10.1115/1.3443779.
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Measuring the blood gases of patients in the intensive care unit or undergoing major surgical procedures in real time would help healthcare providers diagnose and manage base excess and base deficient disorders. Optical fibers provide a platform upon which an intravascular blood gas sensor may be built and has been by various companies. Unfortunately, thrombosis on the sensor surface interferes with the blood gas measurements and also poses the risk of creating emboli. Nitric oxide inhibits platelet adhesion and activation, which can reduce thrombus formation on the sensor surface. An optically based pH sensor is fabricated as a first step to show that nitric oxide can be used with blood gas sensors to reduce thrombosis and not interfere with the measurements. pH sensors fabricated using glass microscope slides suffered from leaching of the dye from the sol-gel matrix. The dye readily leached out when the dye was in its appropriate protonated or deprotonated form. To reduce the leaching of the dye, methods of covalently linking the dye to fumed silica have been investigated, and one is presented here.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027539-027539-1. doi:10.1115/1.3443783.
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Impedance incorporated implanted device provides a unique approach to monitor hemodynamics. The challenge of the use of this method is the optimization of electrode configurations. To alleviate this issue, a 3D thorax model is presented in this study. The model was developed from CT images of a patient, covering from the neck to the lower abdomen. A MATLAB -based program was developed and used to delineate different tissues/organs. The model contains 467 layers and 37 different types of tissues. Each layer had 262,144 pixels with a resolution of $1.0×1.0 mm2$, approximately $122×106 pixels$ (voxels) in total. This high-resolution model can be used as a virtual phantom to optimize electrode configuration for the monitoring of hemodynamics by an implanted device.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027539-027539-1. doi:10.1115/1.3443789.
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Feedback-control has been proved to be advantageous in various technical fields and is likely to increase the performance of electrical neural interface devices. The control algorithms in such a device will rely on metrics of neural activity, thereby necessitating their differentiation from artifacts caused by electrical stimulation. We demonstrate an efficient algorithm for determining the relationship between the electrical stimulus current waveform and the recorded artifact potential, or transfer function. This facilitates online stimulus artifact subtraction and concurrent neural recordings during electrical stimulation. Furthermore, we demonstrate significant changes in this transfer function, in vivo, that occur on time scales of hours and are indicative of changes in the electrical properties of neural tissue. Tracking these variations is paramount for the successful implementation of a feedback-enabled neural control system.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027540-027540-1. doi:10.1115/1.3454859.
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Obstructive sleep apnea is a common sleep disorder in which throat muscles relax during sleep, causing the upper airway to close. As a result, breathing ceases until a brief awakening restores the muscle tone and reopens the airway. Untreated sleep apnea contributes to cognitive, cardiovascular, and metabolic morbidity and has substantial negative impact on an individual’s quality of life. Treatment most commonly consists of nightly use of a nasal mask connected to a continuous positive airway pressure (CPAP) machine. The CPAP machine splints the upper airway open by supplying positive air pressure. However, the machine is expensive, requires electricity, and has suboptimal portability, noise, and aesthetics. The aim of this work was to develop a low-cost, lightweight, quiet, and mechanical CPAP machine that would function without an external energy source in resource-limited settings.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027540-027540-1. doi:10.1115/1.3454860.
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An actuated handheld force-feedback controlled ultrasound probe has been developed. The controller maintains a prescribed contact force between the probe and a patient’s body. The device will enhance the diagnostic capability of free-hand elastography, swept-force compound imaging and make it easier for a technician to acquire repeatable (i.e., directly comparable) images over time. The mechanical system consists of an ultrasound probe, a ball-screw-driven linear actuator, and a force/torque sensor. The feedback controller commands the motor to rotate the ball screw to translate the ultrasound probe in order to maintain a desired contact force. In preliminary user studies, it was found that the control system maintained a constant contact force with 1.7 times less variation than human subjects provided with a visual force display. Users without a visual force display were only able to maintain a constant force with 20 times worse variation than the automatic controller. The system was also used to determine the viscoelastic properties of soft tissues.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027541-027541-1. doi:10.1115/1.3454861.
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This paper is concerned with the feasibility and design of a low-cost prosthetic knee joint that uses a compliant member for stance-phase control. A mechanical locking mechanism was used in conjunction with a compliant control axis to achieve automatic stance-phase locking. The concept was developed with the aid of computer-aided engineering software and was validated through the fabrication and testing of a simplified prototype made of an injection moldable polymer. A prosthetic knee joint was then designed, incorporating the compliant member concept. After modeling, fabrication, and laboratory testing, a pilot study was conducted in a clinical setting. A simple gait analysis showed asymmetric gait patterns that demonstrated the need for improved swing-phase control and damping, while qualitative feedback indicated the desire to reduce the noise produced by the knee. The knee provided the automatic stance-phase control for which it was designed and shows significant potential to evolve into a highly functioning, low-cost knee.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027541-027541-1. doi:10.1115/1.3454862.
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Surgical robots have greatly facilitated numerous challenging medical procedures such as totally endoscopic coronary artery bypass grafting. Despite the initial success of some classical robotic mechanisms (e.g., the da Vinci robot from Intuitive Surgical), limitations in the fundamental hardware impose constraints on the system capabilities and ease of use. While sensing, control, and computation hardware for robotically assisted surgery continue to improve, actuator technology remains relatively unchanged. This paper reviews the state of the art in actuators for surgical robotic devices and therefore elucidates the need for further actuator technology development. A physics-based actuator taxonomy is presented followed by a classification of the prominent research areas in surgical robotics. Using this taxonomic framework, we review the present role of actuator technology in surgical robotic devices.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027542-027542-1. doi:10.1115/1.3455144.
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A patient-specific seizure prediction algorithm is proposed using a classifier to differentiate pre-ictal from inter-ictal EEG signals. The spectral power of EEG processed in four different fashions is used as features: raw, time-differential, space-differential, and time/space-differential EEG. The features are classified using cost-sensitive support vector machines by the double cross-validation methodology. The proposed algorithm has been applied to EEG recordings of 18 patients in the Freiburg EEG database, totaling 80 seizures and 437 h long inter-ictal recordings. Classification with the feature obtained from time/space-differential ECoG demonstrates the performance of 86.25% sensitivity and 0.1281 false positives per hour in out-of-sample testing.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2010;4(2):027542-027542-1. doi:10.1115/1.3454863.
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