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Foreword

J. Med. Devices. 2013;7(2):020501-020501-2. doi:10.1115/1.4024810.

The following technical briefs were submitted, peer-reviewed, and accepted for presentation at the 2013 University of Minnesota's Design of Medical Devices (DMD) Conference (www.dmd.umn.edu) held April 9–11, 2013 at The Commons Hotel in Minneapolis, MN. We especially wish to acknowledge Dr. Just Herder, who tirelessly chaired the review process, recruited appropriate paper reviewers, and kept us on schedule.

Commentary by Dr. Valentin Fuster

Technical Briefs

J. Med. Devices. 2013;7(2):020902-020902-2. doi:10.1115/1.4024321.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020906-020906-2. doi:10.1115/1.4024307.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020912-020912-2. doi:10.1115/1.4024320.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020915-020915-2. doi:10.1115/1.4024327.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020918-020918-3. doi:10.1115/1.4024329.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020922-020922-2. doi:10.1115/1.4024330.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020926-020926-2. doi:10.1115/1.4024323.
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020930-020930-2. doi:10.1115/1.4024306.
Topics: needles , Testing
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020931-020931-3. doi:10.1115/1.4024336.

In this paper a method is presented for using value stream mapping for improving the development process of medical devices. Two examples are shown to demonstrate the utility of this approach.

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020937-020937-3. doi:10.1115/1.4024378.

Despite recognized as one key component for establishing a functional electrical connection with nerves, neural invasive peripheral interfaces are still not optimal for long-term applications in humans. An improvement in the field of biocompatible and non-toxic materials is necessary to overcome the issues of interface/tissue mismatch and physiological reactions. The present work aimed to study, implement and characterize a novel approach to modify the surface of neural mi-crolectrodes basedon polyimide thin films. The purpose was to improve biocompatibility and to promote neuronal migration, growth and differentiation by increasing the surface roughness and endowing the surface with structure-reactivity for thiol-containing amino acids or peptides. L-Cysteine-Rhodamine B, used as a model biomolecule, was successfully grafted on samples surface via the introduction of cross-linkable vinyl groups on polyimide foils. Preliminary in vitro biological analysis allowed to evaluate the tendency of PC12 cells to adhere and to proliferate.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020938-020938-3. doi:10.1115/1.4024379.

This article illustrates the development and preliminary results of SELINE, a self-opening neural interface. The advantages of this innovative neural interface are: higher selectivity due to its three-dimensional structure and efficient anchorage system to the nervous tissue. The device is made of polyimide that is a lightweight, flexible and biocompatible polymer. The electrode has been microfabricated using lithographic techniques; electrical and mechanical tests have been performed to evaluate the integrity of the device. Successful results have been obtained in the development of the electrode with excellent mechanical and electrical properties.

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020943-020943-2. doi:10.1115/1.4024311.

Flexible carbon nanotube composite sensors for medical device applications have been developed using small loadings of multi-walled carbon nanotubes dispersed into medical grade liquid silicone rubber for the purpose of measuring stress, strain and load placed on or by a medical device. The sensors may be attached to a medical device or molded within a medical device, such as an expandable balloon.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020945-020945-2. doi:10.1115/1.4024304.

Medical simulation is a developing field used in the education of medical students, doctors, residents, and many other medical professionals. Despite emerging simulation tools, little has been done to address surgeries in congenital patients, specifically with regards to the spinal cord. The objective of this project was to design, fabricate, and functionally evaluate a medical simulator to address the challenge of teaching the spinal detethering surgical procedure to neurosurgery residents. This simulator was designed to mimic anatomical and physiological characteristics of the lower lumbar region. Pressure sensors were used to quantify the forces that were applied to the spinal cord during the surgical procedure and a LabVIEW program was developed to monitor the pressure profile. The simulator was functionally evaluated by six residents, one fellow, one doctor, and two medical students. A conclusive, quantitative method for scoring these surgeries has not yet been developed, however, the residents and medical students were able to compare their procedures with those of more experienced doctors and fellows via qualitative methods. Future developments will include incorporating quantitative scoring methods as well as noise elimination hardware into the design.

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):020947-020947-2. doi:10.1115/1.4024792.
Topics: Surgery , Cavities
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):024501-024501-4. doi:10.1115/1.4023995.

Microfluidic fluorescence assay devices show great promise as preclinical and clinical diagnostic instruments. Normally, fluorescence signals from microfluidic chips are quantified by analysis of images obtained with a commercial fluorescence microscope. This method is unnecessarily expensive, time consuming, and requires significant operator training, particularly when considering future clinical translation of the technology. In this work, we developed a dedicated low cost fluorescence microfluidic device reader (FMDR) to read sandwich immunofluorescence assay (sIFA) devices configured to detect vascular endothelial growth factor ligand concentrations in ocular fluid samples. Using a series of sIFA calibration standards and a limited set of human ocular fluid samples, we demonstrated that our FMDR reader has similar sensitivity and accuracy to a fluorescence microscope for this task, with significantly lower total cost and reduced reading time. We anticipate that the reader could be used with minor modifications for virtually any fluorescence microfluidic device.

Commentary by Dr. Valentin Fuster

Research Papers

J. Med. Devices. 2013;7(2):020940-020940-2. doi:10.1115/1.4024432.

Transcutaneous energy transmission systems (TETS) wirelessly transmit power through the skin. TETS is particularly desirable for ventricular assist devices (VAD), which currently require cables through the skin to power the implanted pump. Current implantable TETS systems are not optimized for high power VAD applications. Optimizing the inductive link of the TET system is a multi-parameter problem. Most current techniques to optimize the design simplify the problem by combining parameters leading to sub-optimal solutions. In this paper we present an optimization method using a genetic algorithm to handle a larger set of parameters, which leads to a more optimal design.

Commentary by Dr. Valentin Fuster

Research Paper

J. Med. Devices. 2013;7(2):021001-021001-8. doi:10.1115/1.4024644.

The present paper presents an integrated computer-aided engineering (CAE) approach combining digital imaging, solid modeling, robust design methodology, and finite element analysis in order to conduct a parametric investigation of the design of locked plating systems. The present study allows for understanding the contributions of different design parameters on the biomechanics and reliability of these systems. Furthermore, the present approach will lead to exploration of optimum design parameters that will result in robust system performance. Three-dimensional surface models of cortical and cancellous femoral bone were derived via digital computed tomography (CT) image processing techniques and a medical imaging analysis program. A nine orthogonal array matrix simulation (L9) was conducted using finite element methods to study the effects of the various design parameters on plate performance. The introduced technique was demonstrated and experimentally verified on a case study using a Smith & Nephew PERI- LOC distal femur locking plate and a Synthes Less Invasive Stabilization System (LISS).

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):021002-021002-7. doi:10.1115/1.4024157.

This paper presents the design and experimental characterization of a binary jet valve, specifically developed to control an all-polymer needle manipulator during intramagnetic resonance imaging (MRI) prostate interventions (biopsies and brachytherapies). The key feature of the MRI-compatible valve is its compact dual-stage configuration. The first stage is composed of a low-friction jet nozzle, driven by a small rotary dielectric elastomer actuator (DEA). The second stage provides sufficient air flow and stability for the binary robotic application through an independent air supply, activated by a bistable spool. A hyperelastic stress-strain model is used to optimize the geometrical dimensions of the DEA jet assembly. Fully functional valve prototypes, made with 3M's VHB 4905 films, are monitored with a high-speed camera in order to quantify the system's shifting dynamics. The impact of nozzle clearance, dielectric elastomer film viscoelasticity, mechanical friction, and actuator torque generation on overall dynamic behavior of two different valve setups is discussed. Results show an overall shifting time of 200–300 ms when the friction of the nozzle and DEA actuation stretches are minimized. Low shifting time combined with compactness, simplicity, and low cost suggest that the low friction DEA-driven jet valves have great potential for switching a large number of pneumatic circuits in an MRI environment as well as in traditional pneumatic applications.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):021003-021003-5. doi:10.1115/1.4023131.

The FDA 510(k) clearance process is the most common regulatory pathway for medical devices. Since 2010, it has been at the forefront of regulatory policy discussion, with a multitude of stakeholders involved in a substantive exchange of ideas about the need and opportunities for improving the process and its implementation. This article is the second in a two-part series reporting the findings of a questionnaire-based assessment of recent industry experience with the 510(k) process. While the first article focused on findings directly relating to the medical device innovation process, this article reports more broadly on the findings and implications of interest to the medical community and policymakers. We discuss results in five key areas, ranging from the current performance of the 510(k) regulatory process to proposed changes and suggested performance metrics, and place identified challenges in perspective with ongoing and forthcoming FDA actions. Through the survey we also report on current trends in the amount of clinical evidence required by FDA for 510(k) devices and on the interactions between sponsors and the agency during various phases of clinical testing. The results suggest that significant opportunities exist for both industry and FDA to further improve the 510(k) process and the effectiveness of its implementation. Continued collection of process performance data can contribute to prioritizing suggested policy changes, and gauging their effects in a timely manner.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):021004-021004-9. doi:10.1115/1.4024158.

Real-time degradation studies of bioresorbable polymers can take weeks, months, and even years to conduct. For this reason, developing and validating mathematical models that describe and predict degradation can provide a means to accelerate the development of materials and devices for controlled drug release. This study aims to develop and experimentally validate a computer-aided model that simulates the hydrolytic degradation kinetics of bioresorbable polymeric micropatterned membranes for tissue engineering applications. Specifically, the model applies to circumstances that are conducive for the polymer to undergo surface erosion. The developed model provides a simulation tool enabling the prediction and visualization of the dynamic geometry of the degrading membrane. In order to validate the model, micropatterned polymeric membranes were hydrolytically degraded in vitro and the morphological changes were analyzed using optical microscopy. The model is then extended to predict spatiotemporal degradation kinetics of variational micropatterned architectures.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):021005-021005-5. doi:10.1115/1.4023705.

In this work, we modified the topography of commercial titanium orthopedic screws using electrochemical anodization in a 0.4 wt% hydrofluoric acid solution to produce titanium dioxide nanotube layers. The morphology of the nanotube layers were characterized using scanning electron microscopy. The mechanical properties of the nanotube layers were investigated by screwing and unscrewing an anodized screw into several different types of human bone while the torsional force applied to the screwdriver was measured using a torque screwdriver. The range of torsional force applied to the screwdriver was between 5 and 80cN·m. Independent assessment of the mechanical properties of the same surfaces was performed on simple anodized titanium foils using a triboindenter. Results showed that the fabricated nanotube layers can resist mechanical stresses close to those found in clinical situations.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2013;7(2):021006-021006-4. doi:10.1115/1.4024159.

Introduction. Osteonecrosis may be triggered by bone temperatures above 47 °C during routine orthopaedic bone cuts using power-driven saws with potentially negative impacts on bone healing. A new oscillating-tip saw blade design (Precision®; Stryker, Kalamazoo, USA) has been recently developed with a saw blade design that may influence the amount of heat generated. We have, therefore, sought to compare the bone temperature achieved using this new blade design with a standard oscillating saw during a standardized cutting task. Method. Six human cadaveric femora were obtained. Each femur was clamped and a distal femoral cutting jig was applied. An initial cut was performed to visualize the distal metaphyseal bone. The cutting block was then moved 2 mm proximal and a further cut performed, measuring the temperature of the bone with an infrared camera. This was repeated, moving the block 2 mm proximal with each cut, alternating between a standard oscillating saw blade (12 cuts) and the Precision® saw blade (12 cuts). The bone density at the level of each slice was established from a CT scan of each specimen which had been performed prior to the experiment. Results. The two blades did not differ with respect to the integrated mean temperature calculated for each cut (p = 0.89). The average peak temperatures were not significantly different between blades (p = 0.14). There was no significant difference between blades for peak heating rate (p = 0.7), although the area of bone heated above the 47 deg osteonecrotic threshold was significantly (p = 0.04) less for the standard saw blade. Conclusions. The Precision® blade may have advantages over standard oscillating blade, but reduced heat generation was not observed in this study. Indeed, the Precision® blade generated heat that exceeded the bony osteonecrosis threshold in a greater proportion of bone than the standard blade, questioning its use for osteotomy or uncemented knee arthroplasty. Further work should examine modifications to the blade design to better optimize the requirements of speed, accuracy and heat generation.

Commentary by Dr. Valentin Fuster

Design Innovation Paper

J. Med. Devices. 2013;7(2):025001-025001-6. doi:10.1115/1.4023704.

The currently available laparoscopic instruments are unable to manipulate and grasp the large intra-abdominal organs, such as spleen and kidney, with sufficient stability and safety. This paper describes a novel three-fingered endoscopic instrument, based on parallelogram mechanism, which can fully constrain the large organs and provide an effective grasping function. We first evaluated the efficacy of the design using a 3D model and finite element analysis. Then, a fully functional prototype was fabricated for experimental evaluations, including force propagation and pull force limitation characteristics. Finally, the instrument's capability for effective grasping was investigated on animal specimens in in vitro and in vivo examinations. The results of the force propagation analysis indicated a high amplification ratio of more than 1.2 for the actuating force when grasping large organs. The pull force experiments on a sheep heart specimen revealed a nearly linear relationship between the actuating force and the limit of the pulling force that could be attained without slippage. The resulting pinch force, however, was found to be injurious if the actuating force exceeded a limit of 8.6 N. The in vitro and in vivo examinations of the instrument indicated its capability to pass through a standard 10-mm trocar to enter the abdomen, open its fingers to a diameter of about 80 mm, and grasp and manipulate organs with different sizes, shapes, and properties. With further developments, the proposed design is expected to provide a practical and feasible solution for grasping of large organs during endoscopic operations. However, more preclinical examinations are needed to evaluate the potential risks of using rigid jaws against injury-prone soft organs.

Commentary by Dr. Valentin Fuster

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