Review Article

J. Med. Devices. 2017;11(4):040801-040801-11. doi:10.1115/1.4037258.

Cardiovascular disease (CVD), as the most prevalent human disease, incorporates a broad spectrum of cardiovascular system malfunctions/disorders. While cardiac transplantation is widely acknowledged as the optional treatment for patients suffering from end-stage heart failure (HF), due to its related drawbacks, such as the unavailability of heart donors, alternative treatments, i.e., implanting a ventricular assist device (VAD), it has been extensively utilized in recent years to recover heart function. However, this solution is thought problematic as it fails to satisfactorily provide lifelong support for patients at the end-stage of HF, nor does is solve the problem of their extensive postsurgery complications. In recent years, the huge technological advancements have enabled the manufacturing of a wide variety of reliable VAD devices, which provides a promising avenue for utilizing VAD implantation as the destination therapy (DT) in the future. Along with typical VAD systems, other innovative mechanical devices for cardiac support, as well as cell therapy and bioartificial cardiac tissue, have resulted in researchers proposing a new HF therapy. This paper aims to concisely review the current state of VAD technology, summarize recent advancements, discuss related complications, and argue for the development of the envisioned alternatives of HF therapy.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):040802-040802-14. doi:10.1115/1.4037053.

This paper deals with the survey of kinematic structures adapted to specific medical robots: minimally invasive surgery (MIS) and tele-echography. The large diversity of kinematic architectures that can be found in medical robotics leads us to perform a statistical analysis to inform and guide design of medical robots. Safety constraints and some considerations in design evolution of medical robots are presented in this paper. First, we describe the spectrum of medical robots in minimally invasive surgery and tele-echography applications and particularly the variety of kinematic architectures used. We present the robots and their kinematic architectures and highlight differences that occur in each medical application. We perform a statistical analysis which can serve as a resource in topological synthesis for each specific medical application. Safety is an important specification in medical robotics, and for that reason we show the means used to take into account this constraint. This study demonstrates that the nature of medical robots implies specific requirements leading to different kinematic structures. The statistical analysis gives information on choice of kinematic structures for medical applications (minimally invasive surgery and echography). The safety constraint as well as the interaction between doctor and robot leads to investigate new mechanical solutions to enhance medical robot safety and compliance. We expect that this paper will serve as a significant resource and help the design of future medical robots.

Commentary by Dr. Valentin Fuster

Research Papers

J. Med. Devices. 2017;11(4):041001-041001-9. doi:10.1115/1.4037259.

Three-dimensional (3D) bioprinting offers innovative research vectors for tissue engineering. However, commercially available bioprinting platforms can be cost prohibitive to small research facilities, especially in an academic setting. The goal is to design and fabricate a low-cost printing platform able to deliver cell-laden fluids with spatial accuracy along the X, Y, and Z axes of 0.1 mm. The bioprinter consists of three subassemblies: a base unit, a gantry, and a shuttle component. The platform utilizes four stepper motors to position along three axes and a fifth stepper motor actuating a pump. The shuttle and gantry are each driven along their respective horizontal axes via separate single stepper motor, while two coupled stepper motors are used to control location along the vertical axis. The current shuttle configuration allows for a 5 mL syringe to be extruded within a work envelope of 180 mm × 160 mm × 120 mm (X, Y, Z). The shuttle can easily be reconfigured to accommodate larger volume syringes. An attachment for a laser pen is located such that printing material may be light-activated pre-extrusion. Positional fidelity was established with calipers possessing a resolution to the nearest hundredth millimeter. The motors associated with the X and Y axes were calibrated to approximately 0.02 mm per motor impulse. The Z axis has a theoretical step distance of ∼51 nm, generating 0.04% error over a 10 mm travel distance. The A axis, or pump motor, has an impulse distance of 0.001 mm. The volume extruded by a single impulse is dictated by the diameter of the syringe used. With a 5 mL syringe possessing an inner diameter of 12.35 mm, the pump pushes as little as 0.119 μL. While the Z axis is tuned to the highest resolution settings for the motor driver, the X, Y, and A axes can obtain higher or lower resolution via physical switches on the motor drivers.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):041002-041002-10. doi:10.1115/1.4037441.

Orthostatic intolerance in patients can occur secondary to concomitant venous pooling and enhanced capillary filtration when standing upright, and is one of the principle causes of syncope or fainting. Compression therapy is commonly recommended for the management of syncope based on the assumption that it increases venous return. Technologies currently used include compression stockings, whose efficacy has, however, been challenged, and intermittent pneumatic pressure devices, which highly restrict the patients' mobility. This paper therefore investigates a novel active compression brace (ACB), which could potentially provide intermittent pressure while not restricting movements. The ACB, actuated by shape memory alloy (SMA) wires, in this work was tested with twelve healthy individuals in a seated position. The experimental observation showed that the ACB can apply a constant initial pressure to the leg similar to commercial compression stockings and also produce intermittent pressure exceeding 30 mmHg. A comparison between analytical and experimental results showed a maximum of 2.08 mmHg absolute averaged difference among all the participants. A correlation analysis showed that the normalized root-mean-square deviation (NRMSD) between the experimental and analytical results had a significant negative correlation with the estimated total calf circumference minus the calf fat cross-sectional area (CSA). A calibration formula, accounting for fat and circumference of the leg, was introduced to account for these two parameters. The comfort of the ACB was also compared to two other available compression devices using questionnaires. No participants reported discomfort in terms of pressure, skin irritation, or heat generated by the ACB.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):041003-041003-10. doi:10.1115/1.4037349.

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of morbidity in aging populations worldwide. One of the most debilitating effects of COPD is hyperinflation, which restricts the function of healthier portions of the lung, diaphragm, and heart. Bronchoscopic lung volume reduction (BLVR) is a minimally invasive technique to reduce hyperinflation, consisting of one-way valves inserted bronchoscopically that slowly drain the diseased lobe of its accumulated air. Presented here is a novel redesign of current BLVR devices using pop-up microelectromechanical systems (MEMS) manufacturing to create microscale check valves. These operate more reliably than current polymer valves and allow tunable airflow to accommodate widely varying patient physiologies. Analysis and ex vivo testing of the redesigned valve predicted the valve should outlast current valves with a lifetime of well over 8 yr and showed airflow controllability within desired physiological ranges of up to 1.2 SLM. The valve resists backflow twice as well as the current standard valves while permitting comparable forward flow.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):041004-041004-6. doi:10.1115/1.4037257.

Improperly designed medical devices can induce unwanted biomechanical stressors on their users, impacting health and career longevity. Despite this, manufacturers struggle to balance device design with the growing female surgeon population. We have applied anthropometry to a population of surgeon hands as an alternative to preferred glove size. Correlations to physical dimensions of two laparoscopic staplers were assessed. Five anthropometric measurements were taken from dominant hands of surgeons. These measurements were selected with the goal of comparing resulting data to published anthropometry studies and assessing correlation to preferred glove size and instrument design. The trigger reach of the two laparoscopic staplers were measured to assess suitability among the surgeon population surveyed. Fifty eight surgeons (50 male, 8 female), average glove size 7.5 and 6.0, were measured. Data indicate that male surgeons had significantly larger hands than female. Hand circumference displayed a relatively strong positive correlation with preferred glove size (0.799, R2 = 63.9%); other measurements did not. The trigger span of one stapler was found suitable for only 78.2% of male and 30.9% of female surgeons, based on comparisons with anthropometry of the surveyed population. Anthropometry should be used to characterize surgeon hands instead of preferred glove size. Also, from the limited scope of this research, discrepancies exist between the size of the surgeon hand and the devices designed for their use. The use of inappropriately designed instrumentation can cause musculoskeletal injury, decreased productivity, and shortened careers. Manufacturers would benefit by consulting anthropometry databases to develop products.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):041005-041005-5. doi:10.1115/1.4037261.

While the majority of the total knees used today are of the cruciate retaining (CR) and cruciate substituting (PS) types, the results are not ideal in terms of satisfaction, function, and biomechanical parameters. It is proposed that a design which specifically substituted for the structures which provided stability could produce normal laxity behavior, which may be a path forward to improved outcomes. Stabilizing structures of the anatomic knee were identified under conditions of low and high axial loading. The upward slope of the anterior medial tibial plateau and the anterior cruciate was particularly important under all loading conditions. A guided motion design was formulated based on this data, and then tested in a simulating machine which performed an enhanced ASTM constraint test to determine stability and laxity. The guided motion design showed much closer neutral path of motion and laxity in anterior–posterior (AP) and internal–external rotation, compared with the PS design. Particular features included absence of paradoxical anterior sliding in early flexion, and lateral rollback in higher flexion. A total knee design which replicated the stabilizing structures of the anatomical knee is likely to provide more anatomical motion and may result in improved clinical outcomes.

Topics: Design , Knee
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):041006-041006-6. doi:10.1115/1.4037935.

We present a proof-of-concept design and preliminary data to demonstrate a novel syringe infusion pump that is low cost, nonelectric, reusable, and adjustable. This device addresses the need for infusion therapy in low- and middle-income countries (LMIC), where intermittent electrical power precludes the use of conventional electronic infusion pumps and limited financial resources make high costs of disposable infusion pumps impractical. Our design uses a pneumatically pressurized, hydraulic (air over oil) drive piston coupled to a closed-circuit flow restriction to drive a syringe plunger at a constant velocity, thus providing a constant volumetric flow rate to the patient. The device requires no proprietary or precision consumables, significantly reducing treatment costs compared with other methods. The highly adjustable device provides constant flow rates across the range of 0.5–8 mL/h when used with a 30-mL syringe. The user interface is simple and intuitive; the hardware is robust and portable. This novel technology platform has broad applications in addressing priority health needs in LMIC.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):041007-041007-10. doi:10.1115/1.4038017.

Intensity modulated radiation therapy (IMRT) is performed on a regular basis in the clinic to create complex radiation fields to treat cancer, but it has not been implemented in microradiotherapy (mRT) for preclinical systems. A multileaf collimator (MLC) is an integral part of a radiotherapy system that allows IMRT application. Presented here is the development of a key component of an open source mRT system for preclinical research. We have designed and fabricated a binary micro multileaf collimator (bmMLC) for mRT that can provide 1 mm or better resolution at isocenter and attenuate over 98% of a 250 kVp X-ray beam. This is the smallest collimator system designed for RT systems, with 20 brass leaves, each 0.5 mm thick, creating a physical field opening of 1 cm × 1 cm. The mode of actuation for the leaves was rotational, rather than linear, which is typical in larger clinical RT systems. The design presented here met the identified design requirements and represents a rigorous design process, during which several less successful designs were investigated and eventually discarded. After the fabrication of the design, dosimetric characteristics were tested and requirements were met. The final bmMLC designs and technical documents are made available as open-source.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):041008-041008-7. doi:10.1115/1.4038011.

Preclinical testing in rodent models is a ubiquitous part of modern biomedical research and commonly involves accessing the venous bloodstream for blood sampling and drug delivery. Manual tail vein cannulation is a time-consuming process and requires significant skill and training, particularly since improperly inserted needles can affect the experimental results and study outcomes. In this paper, we present a miniaturized, robotic medical device for automated, image-guided tail vein cannulations in rodent models. The device is composed of an actuated three degrees-of-freedom (DOFs) needle manipulator, three-dimensional (3D) near-infrared (NIR) stereo cameras, and an animal holding platform. Evaluating the system through a series of workspace simulations and free-space positioning tests, the device exhibited a sufficient work volume for the needle insertion task and submillimeter accuracy over the calibration targets. The results indicate that the device is capable of cannulating tail veins in rodent models as small as 0.3 mm in diameter, the smallest diameter vein required to target.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):041009-041009-8. doi:10.1115/1.4037442.

Intra-osseous (IO) needles are an easy and reliable alternative to intravenous (IV) access in the prehospital and emergency settings for treating patients in shock. The advantage of utilizing an IO is that secure, noncollapsible peripheral venous access can be obtained rapidly in critically ill patients. Placement of IO needles in the proximal tibia, humerus, or sternum, however, requires knowledge of human anatomy and the requisite skill to position, align, and place the device. In the developing world, this is not always available, and in the chaos of an in-hospital code, prehospital trauma, or a mass-casualty incident, even trained providers can have trouble correctly placing IV or IO needles. The Tib-Finder is an intuitive drill guide that significantly improves efficiency with which IO can be placed in the proximal tibia. Here, we present the conceptualization, design, and creation of an alpha-prototype Tib-Finder drill guide in less than 90 days; initial validation was achieved through analysis of anthropometric measurements of human skeletons, and usability studies were performed using untrained volunteers and mannequins. The Tib-Finder is intended to provide first responders and medical personnel, in the first world and the developing world, a way to accurately and repeatably locate the proximal tibia and achieve safe, rapid intravascular access in critically ill patients. Further, it eliminates the need for direct contact between patients and caregivers and improves the ease-of-use of IO devices by first responders and healthcare providers.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):041010-041010-10. doi:10.1115/1.4038145.

Safety and efficacy issues are associated with reprocessing of single-use electrosurgical pencils (EPs), requiring methods for assessing the reprocessing protocol before clinical reuse. This study aimed at monitoring the surface characteristics of single-use EPs subjected to multiple clinical use and in-hospital reprocessing. A total of 24 single-use-labeled EPs were divided in five test groups and one control group. The test groups were subjected to a different number of clinical uses, ranging from one to five. A multitechnique approach based on optical stereomicroscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) was applied. The silicon coating of the tip was significantly reduced, and foreign bodies were occasionally found on reprocessed EPs. The amount of biological debris and chemical residuals increased with the number of reprocessing cycles in critical areas. The degradation temperature of the EP handle polymer showed a progressive significant reduction. Cable cord showed no modification after reprocessing. EP tip could undergo major surface modifications that can affect functionality. The efficacy of the reprocessing protocol in removing debris from the EP handle should be carefully assessed. Surface and thermal characteristics have to be considered for validating a reprocessing protocol of single-use labeled EP.

Commentary by Dr. Valentin Fuster

Design Innovation Paper

J. Med. Devices. 2017;11(4):045001-045001-7. doi:10.1115/1.4037260.

An adjustable-length intramedullary (IM) nail may reduce both complications secondary to fracture fixation and manufacturing costs. We hypothesized that our novel nail would have suitable mechanical performance. To test this hypothesis, we manufactured three prototypes and evaluated them in quasi-static axial compression and torsion and quasi-static four-point bending. Prototypes were dynamically evaluated in both cyclic axial loading and four-point bending and torsion-to-failure. The prototypes exceeded expectations; they were comparable in both quasi-static axial stiffness (1.41 ± 0.37 N/m in cervine tibiae and 2.30 ± 0.63 in cadaver tibiae) and torsional stiffness (1.05 ± 0.26 N·m/deg in cervine tibiae) to currently used nails. The quasi-static four-point bending stiffness was 80.11 ± 09.360, greater than reported for currently used nails. A length-variance analysis indicates that moderate changes in length do not unacceptably alter bone-implant axial stiffness. After 103,000 cycles of axial loading, the prototype failed at the locking screws, comparable to locking screw failures seen clinically. The prototypes survived 1,000,000 cycles of four-point bend cyclic loading, as indicated by a consistent phase angle throughout cyclic loading. The torsion-to-failure test suggests that the prototype has adequate resistance to applied torques that might occur during the healing process. Together, these results suggest that our novel IM nail performs sufficiently well to merit further development. If brought to market, this adjustable-length IM nail could reduce both patient complications and healthcare costs.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(4):045002-045002-7. doi:10.1115/1.4037674.

Tremor, characterized by involuntary and rhythmical movements, is the most common movement disorder. Tremor can have peripheral and central oscillatory components which properly assessed may improve diagnostics. A magnetic resonance (MR)-safe haptic wrist manipulator enables simultaneous measurement of proprioceptive reflexes (peripheral components) and brain activations (central components) through functional magnetic resonance imaging (fMRI). The presented design for an MR-safe haptic wrist manipulator has electrohydraulic closed-circuit actuation, optical position and force sensing, and consists of exclusively nonconductive and magnetically compatible materials inside the MR-environment (Zone IV). The MR-safe hydraulic actuator, a custom-made plastic vane motor, is connected to the magnetic parts and electronics located in the shielded control room (Zone III) via hydraulic hoses and optical fibers. Deliberate internal leakage provides backdriveability, damping, and circumvents friction. The manipulator is completely MR-safe and therefore operates safely in any MR-environment while ensuring fMRI imaging quality. Undesired external leakage in the actuator prevented the use of prepressure, limiting the control bandwidth. The compact end effector design fits in the MR-scanner, is easily setup, and can be clamped to the MR-scanner bed. This enables use of the manipulator with the subject at the optimal fMRI location and allows it to be setup quickly, saving costly MR-scanner time. The actuation and sensor solutions performed well inside the MR-environment and did not deteriorate image quality, which allows for various motor control experiments. Enabling prepressure by carrying out the recommendations on fabrication and sealing should improve the bandwidth and fulfill the requirements for proprioceptive reflex identification.

Commentary by Dr. Valentin Fuster

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