Review Article

J. Med. Devices. 2017;11(1):010801-010801-14. doi:10.1115/1.4035374.

Access to the left atrium is required for several minimally invasive cardiac interventions in the left heart. For this purpose, transseptal puncture (TSP) technique is often performed, perforating the atrial septum under fluoroscopic or/and ultrasound imaging guidance. Although this approach has been used for many years, complications/failures are not uncommon mainly in patients with abnormal atrial anatomy and repeated TSP. Thus, this study presents an overview of methods and techniques that have been proposed to increase the safety and feasibility of the TSP. A systematic review of literature was conducted through the analysis of the articles published between 2008 and 2015. The search was performed in PubMed, Scopus, and ISI Web of Knowledge using the expression “transseptal puncture.” A total of 354 articles were retrieved from the databases, and 64 articles were selected for this review. Moreover, these 64 articles were divided into four categories, namely: (1) incidence studies, (2) intraprocedural guidance techniques, (3) preprocedural planning methods, and (4) surgical instruments. A total of 36 articles focused on incidence studies, 24 articles suggested novel intraprocedural guidance techniques, 5 works focused on preprocedural planning strategies, and 21 works proposed surgical instruments. The novel 3D guidance techniques, radio-frequency surgical instruments, and pre-interventional planning approaches showed potential to overcome the main procedural limitations/complications, through the reduction of the intervention time, radiation, number of failures, and complications.

Commentary by Dr. Valentin Fuster

Research Papers

J. Med. Devices. 2016;11(1):011001-011001-10. doi:10.1115/1.4034880.

Stent geometries are obtained by topology optimization for minimized compliance under different stenosis levels and plaque material types. Three levels of stenosis by cross-sectional area, i.e., 30%, 40%, and 50% and three different plaque material properties, i.e., calcified, cellular, and hypocellular, were studied. The raw optimization results were converted to clear design concepts and their performance was evaluated by implanting them in their respective stenosed artery types using finite element analysis. The results were compared with a generic stent in similar arteries, which showed that the new designs showed less recoil. This work provides a concept that stents could be tailored to specific lesions in order to minimize recoil and maintain a patent lumen in stenotic arteries.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;11(1):011002-011002-6. doi:10.1115/1.4034881.

The ubiquitous nature of laparoscopic surgery and the decreased training time available for surgeons are driving an increased need for effective training systems to help surgeons learn different procedures. A cost-effective and user-friendly simulator has been designed to imitate specific training tasks for laparoscopic surgery in virtual environments via image processing and computer vision. The capability of using various actual surgical instruments suited for these specific procedures gives heightened fidelity to the simulator. Image processing via matlab software provides real-time mapping of the graspers in the workspace to the virtual reality (VR) environment (vizard software). Two different tasks (peg transfer and needle passing) were designed to evaluate trainees and compare their performance with characteristics of expert surgeons. Pilot testing of the system was carried out with 11 subjects to validate the similarity of this device with an existing surgical box trainer. Task completion time and muscle activity have been used as metrics for evaluation. The decrease in completion time for all subjects suggests similarity of skills transfer for both simulators. In addition, the p-value of muscle activity showed no significant differences for most muscles in the peg transfer task when using either the VR or physical analog environment and no significant differences for about half of the muscles in the needle passing task. Based on the results, the new proposed VR simulator appears to be a viable alternative to help trainees gain laparoscopic skills.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;11(1):011003-011003-8. doi:10.1115/1.4035005.

Fusion of robotics and minimally invasive surgery (MIS) has created new opportunities to develop diagnostic and therapeutic tools. Surgical robotics is advancing from externally actuated systems to miniature in-vivo robotics. However, with miniaturization of electric-motor-driven surgical robots, there comes a trade-off between the size of the robot and its capability. Slow actuation, low load capacity, sterilization difficulties, leaking electricity and transferring produced heat to tissues, and high cost are among the key limitations of the use of electric motors in in-vivo applications. Fluid power in the form of hydraulics or pneumatics has a long history in driving many industrial devices and could be exploited to circumvent these limitations. High power density and good compatibility with the in-vivo environment are the key advantages of fluid power over electric motors when it comes to in-vivo applications. However, fabrication of hydraulic/pneumatic actuators within the desired size and pressure range required for in-vivo surgical robotic applications poses new challenges. Sealing these types of miniature actuators at operating pressures requires obtaining very fine surface finishes which is difficult and costly. The research described here presents design, fabrication, and testing of a hydraulic/pneumatic double-acting cylinder, a limited-motion vane motor, and a balloon-actuated laparoscopic grasper. These actuators are small, seal-less, easy to fabricate, disposable, and inexpensive, thus ideal for single-use in-vivo applications. To demonstrate the ability of these actuators to drive robotic joints, they were modified and integrated in a robotic arm. The design and testing of this surgical robotic arm are presented to validate the concept of fluid-power actuators for in-vivo applications.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;11(1):011004-011004-7. doi:10.1115/1.4035083.

The areas of the most frequent cartilage loss in mild–moderate medial osteoarthritis (OA) were reviewed from previous studies. Implant components were designed to resurface these areas. The surface geometries of the components were based on an average femur and tibia produced from 20 magnetic resonance imaging (MRI) models of normal knees. Accuracy of fit of the components was determined on these 20 individual knees. The femoral surface was toroidal, covering a band on the distal end of the femur, angled inward anteriorly. For a five-size system, the average deviations between the implant surfaces and the intact cartilage surfaces of 20 femurs were only 0.3 mm. For the tibia, the deviations were 0.5–0.7 mm, but the errors were mainly around the tibial spine, with smaller deviations in the central bearing region. Hence, these small implant components would accurately restore the original bearing surfaces and allow for preservation of all the knee structures. Using a thin metal component for the tibia would preserve the strong cancellous bone near the surface, an advantage for fixation. In this case, the femoral component would have a plastic bearing surface, but still be less than 10 mm thickness. Such a design could have a useful place in the early treatment of medial OA of the knee.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;11(1):011005-011005-13. doi:10.1115/1.4034882.

Laparoscopic hysterectomy is a procedure that involves the removal of the uterus through an abdominal keyhole incision. Morcellators have been specifically designed for this task, but their use has been discouraged by the food and drug administration (FDA) since November 2014 because of risks of cancerous tissue spread. The use of laparoscopic bags to catch and contain tissue debris has been suggested, but this does not solve the root cause of tissue spread. The fundamental problem lies in the tendency of the tissue mass outside the morcellation tube to rotate along with the cutting blade, causing tissue to be spread through the abdomen. This paper presents a bio-inspired concept that constrains the tissue mass in the advent of its rotation in order to improve the overall morcellation efficacy and reduce tissue spread. A design of gripping teeth integrated into the inner diameter of the morcellation tube is proposed. Various tooth geometries were developed and evaluated through an iterative process in order to maximize the gripping forces of these teeth. The maximum gripping force was determined through the measurement of force–displacement curves during the gripping of gelatin and bovine tissue samples. The results indicate that a tooth ring with a diameter of 15 mm can provide a torque resistance of 1.9 Ncm. Finally, a full morcellation instrument concept design is provided.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;11(1):011006-011006-7. doi:10.1115/1.4035129.

Robotic total hip arthroplasty is a procedure in which a milling operation is performed on the femur followed by insertion of a prosthetic implant. Although surgeons operate the robots, they do not control the choice of robotic tools and cutting strategies of the robot. Toolpath parameters, such as feedrate, tool geometry, and spindle speeds, govern the cutting forces of the robot. This research covers a methodological approach for finding optimal parameters such that cutting forces and surgical times are reduced. Many different types of orthopedic surgical burs were retrofitted into an advanced computer numerically controlled (CNC) machine, and the characteristics of each tool were evaluated. A simulation cutting model was then developed to find the parameters that could remove the most material in the fastest amount of time without violating any of the safety constraints of surgery. The new methodology proposed not only finds the theoretical optimal parameters but also expedites the process of finding sufficient parameters for orthopedic surgery.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(1):011007-011007-12. doi:10.1115/1.4035375.

Recent advances in medical robotics have initiated a transition from rigid serial manipulators to flexible or continuum robots capable of navigating to confined anatomy within the body. A desire for further procedure minimization is a key accelerator for the development of these flexible systems where the end goal is to provide access to the previously inaccessible anatomical workspaces and enable new minimally invasive surgical (MIS) procedures. While sophisticated navigation and control capabilities have been demonstrated for such systems, existing manufacturing approaches have limited the capabilities of millimeter-scale end-effectors for these flexible systems to date and, to achieve next generation highly functional end-effectors for surgical robots, advanced manufacturing approaches are required. We address this challenge by utilizing a disruptive 2D layer-by-layer precision fabrication process (inspired by printed circuit board manufacturing) that can create functional 3D mechanisms by folding 2D layers of materials which may be structural, flexible, adhesive, or conductive. Such an approach enables actuation, sensing, and circuitry to be directly integrated with the articulating features by selecting the appropriate materials during the layer-by-layer manufacturing process. To demonstrate the efficacy of this technology, we use it to fabricate three modular robotic components at the millimeter-scale: (1) sensors, (2) mechanisms, and (3) actuators. These modules could potentially be implemented into transendoscopic systems, enabling bilateral grasping, retraction and cutting, and could potentially mitigate challenging MIS interventions performed via endoscopy or flexible means. This research lays the ground work for new mechanism, sensor and actuation technologies that can be readily integrated via new millimeter-scale layer-by-layer manufacturing approaches.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(1):011008-011008-6. doi:10.1115/1.4035548.

Natural orifice transluminal endoscopic surgery (NOTES) is a surgical technique to perform “scarless” abdominal operations. Robotic technology has been exploited to improve NOTES and circumvent its limitations. Lack of a multitasking platform is a major limitation. Manual tool exchange can be time consuming and may lead to complications such as bleeding. Previous multifunctional manipulator designs use electric motors. These designs are bulky, slow, and expensive. This paper presents design, prototyping, and testing of a hydraulic robotic tool changing manipulator. The manipulator is small, fast, low-cost, and capable of carrying four different types of laparoscopic instruments.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(1):011009-011009-9. doi:10.1115/1.4035547.

Highly porous, open-celled shape memory polymer (SMP) foams are being developed for a number of vascular occlusion devices. Applications include abdominal aortic and neurovascular aneurysm or peripheral vascular occlusion. A major concern with implanting these high surface area materials in the vasculature is the potential to generate unacceptable particulate burden, in terms of number, size, and composition. This study demonstrates that particulate numbers and sizes in SMP foams are in compliance with limits stated by the most relevant standard and guidance documents. Particulates were quantified in SMP foams as made, postreticulation, and after incorporating nanoparticles intended to increase material toughness and improve radiopacity. When concentrated particulate treatments were administered to fibroblasts, they exhibited high cell viability (100%). These results demonstrate that the SMP foams do not induce an unacceptable level of risk to potential vascular occlusion devices due to particulate generation.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(1):011010-011010-6. doi:10.1115/1.4035546.

Objective pulmonary function (PF) evaluation is essential for the diagnosis, monitoring, and management of many pediatric respiratory diseases as seen in the emergency room, intensive care, and outpatient settings. In this paper, the development and testing of a new noninvasive PF instrument, pneuRIPTM, which utilizes respiratory inductance plethysmography (RIP) are discussed. The pneuRIPTM hardware includes a small circuit board that connects to the RIP bands and measures and wirelessly transmits the band inductance data to any designated wirelessly connected tablet. The software provides indices of respiratory work presented instantaneously in a user-friendly graphical user interface on the tablet. The system was tested with ten normal children and compared with an existing system, Respitrace (Sensormedics, Yorba Linda, CA), under normal and loaded breathing conditions. Under normal breathing, the percentage differences between the two systems were 2.9% for labored breathing index (LBI), 31.8% for phase angle (Φ), 4.8% for percentage rib cage (RC%), and 26.7% for respiratory rate (BPM). Under loaded breathing, the percentage differences between the two systems were 1.6% for LBI, 4.1% for Φ, 8.5% for RC%, and 52.7% for BPM. For LBI, Φ, and RC%, the two systems were in general agreement. For BPM the pneuRIPTM is shown to be more accurate than the respitrace when compared to manually counting the breaths: 13.2% versus 36.4% accuracy for normal breathing and 16.9% versus 60.7% accuracy for breathing under load, respectively.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(1):011011-011011-10. doi:10.1115/1.4035563.

Currently, most of commercial needle-free jet injectors generate the liquid jet by a method called “driving object method” (DOM); however, the reliability and efficiency are still questioned. This paper proposes a new concept of jet generation method, known as “impact driven method” (IDM). A prototype of an IDM jet injector is designed, built, tested, and compared to a commercial device (Cool.click, Tigard, OR). Fundamental characteristics, i.e., the exit jet velocity and impact pressure, are measured. Jet injection processes are visualized both in air and in 20% polyacrylamide by high speed photography. In this study, from the prototype of the IDM jet injector, a maximum jet velocity of 400 m/s and impact peak pressure of 68 MPa can be obtained. It is clear that the IDM jet injector provides a double pulsed liquid jet, which is a major advantage over the commercial jet injector. Because, the first pulse gives a shorter erosion stage, and then, immediately the second pulse follows and provides a better penetration, wider lateral dispersion, and considerably less back splash. Hence, lower pain level and higher delivery efficiency should be achieved. It can be concluded that the IDM concept is highly feasible for implementation in real applications, either for human or animal injection. However, the control and accuracy of IDM still needs to be carefully investigated.

Topics: Pressure , Ejectors , Jets , needles
Commentary by Dr. Valentin Fuster
J. Med. Devices. 2017;11(1):011012-011012-9. doi:10.1115/1.4035688.

Needle biopsy procedures, such as fine-needle aspiration and core needle biopsy, are used to extract tissue samples for diagnosis, and collection of larger samples allows for more accurate diagnosis of cancers. The combination of lower needle insertion force, less needle deflection, and reduced friction between the tissue and needle surface also leads to a more efficient biopsy procedure. In this research, a new end-cut-type coaxial needle with a modified aspiration mechanism has been developed to extract large tissue with minimal damage. The study shows that the clearance between the inner stylette and external needle and the insertion speed are the key factors affecting the biopsy performance including syringe friction force and amount of tissue extracted. Larger tissue samples (gelatin and chicken breast are used as samples here) can be obtained when inserting at lower speeds and using coaxial needles with smaller clearances between the external needles and inner stylettes. For solid samples (gelatin), the space inside the external needle is nearly filled with the solid sample. For samples consisting of both solid (chicken meat) and liquid components, a slower needle insertion results in extraction of more liquid than solid. To extract larger solid samples, high-speed needle insertion is required. This paper presents the design and manufacture of the system, protocol to evaluate the needle biopsy, and evaluation of the needle biopsy performance using gelatin and chicken breast as tissue samples.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Med. Devices. 2016;11(1):014501-014501-9. doi:10.1115/1.4034575.

This paper presents a miniature wrist that can be integrated into needle-sized surgical instruments. The wrist consists of a nitinol tube with asymmetric cutouts that is actuated by a single tendon to provide high distal curvature. We derive and experimentally validate kinematic and static models for the wrist and describe several prototype wrists, illustrating the straightforward fabrication and scalability of the design. We experimentally investigate fatigue life, the concept of tip-first bending, and practical use of the wrist with a concentric tube robot in an endonasal surgical scenario.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;11(1):014502-014502-3. doi:10.1115/1.4034879.

A novel monobloc design of a two degree-of-freedom (DOF) compliant tool tip for a handheld powered surgical tool is presented in this paper. The monobloc tool tip can pitch and yaw using corner-filleted flexure hinge-based compliant joints and has an integrated compliant grasper. The 2DOF of the tool tip is realized by six compliant joints placed in an alternating fashion, orthogonal to each other. The tool is externally powered and consists of a drive box, a stainless steel tube, and a compliant tool tip at the distal end. The drive box houses a thumb joystick for command input, three servo actuators, and a microcontroller. The microcontroller maps surgeon's command input to the tool tip orientation and grasper actuation. By design, the graspers of the tool tip are actuated by tensile forces conveyed by the tethers, which exert a compressive load on the 2DOF compliant joints. Since the compressive load-carrying capacity of slender flexure-based compliant joints is limited, a design to enhance the compressive load-carrying capacity of the compliant joints with a circular guide is presented. A finite-element simulation was done to verify the design of the compliant joints. Experiments were carried out to assess the relationship between the force input by the servo actuators and joint deflection. Additional experiments were carried out to determine the maximum pinching force that can be exerted by the compliant graspers. A prototype of the complete surgical tool was built to demonstrate the utility of the proposed compliant tool tip as an alternative to traditional tool tip for a handheld powered surgical tool.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;11(1):014503-014503-6. doi:10.1115/1.4035127.

Stroke is one of the leading causes of adult physical disability, and rehabilitation and hospitalization costs for stroke are among the highest for all injuries. Current rehabilitation techniques are labor intensive and time consuming for therapists and difficult to perform effectively. Research suggests that starting rehabilitation during the acute or subacute stage of recovery results in better outcomes than therapy delivered in the chronic stage. To improve the gait rehabilitation process, robot-assisted gait rehabilitation has gained much interest over the past years. However, many robot-assisted rehabilitation devices have limitations; one of which is being bulky and complex to handle. Large and expensive devices that require special training to operate are less attractive to clinics and therapists, and ultimately less likely to be available to patients especially at the early stage of stroke. To address these limitations, this research proposes a new gait rehabilitation device called the linkage design gait trainer (LGT). The device is based on a walking frame design with a simple four-bar linkage “end-effector” mechanism to generate normal gait trajectories during general walking and exercise. The design of the four-bar linkage mechanism was optimized for a particular gait pattern. A prototype of the device was developed and tested. The kinematics of the device itself and gait kinematics with and without assistance from the device were recorded and analyzed using an optical motion capture system. The results show the linkage mechanism is able to guide the leg of the user during over ground walking. There were some differences in the hip (20.5 deg RMS) and knee (14.8 deg RMS) trajectory between the person walking with and without the device assistance. The study demonstrated the concept and feasibility of this novel gait training device.

Commentary by Dr. Valentin Fuster
J. Med. Devices. 2016;11(1):014504-014504-3. doi:10.1115/1.4035128.

Medical drains frequently become obstructed requiring removal or re-intervention. Currently, there is no widely accepted practice for maintaining drain patency. A simple device to remove obstructions from medical drains may have significant benefit. We manufactured a prototype drain clot extractor (DCE) for extracting obstructions. Fresh nonanticoagulated swine blood was instilled within drainage tubes of 16, 20, and 32 French (n = 2 for each size) to generate a 4 cm blood clot. The operator was then equipped with a 0.035 in. guidewire (GW) and given 2.5 min to attempt removal while blinded. Similarly, the operator was equipped with the DCE. Volumes removed were determined by volume displacement and by drain size and method of removal. Comparison of DCE to GW by analysis of variance and means comparison using Tukey were used for statistical analysis. The DCE facilitated mechanical removal of obstructions for 16, 20, and 32 French drainage tubes. Volumes removed: 16 French (GW mean 10% volume, DCE mean 70% volume p = 0.02); 20 French (GW mean 12.5% volume, DCE mean 75% volume p = 0.01); 32 French (GW mean 37.5% volume, DCE mean 100% volume p = 0.01). DCE volume removal had no dependence on drain size (p > 0.05). This device may have utility for reducing morbidity from early drain discontinuation or replacement. Further in vivo and clinical studies are needed to determine the safety, feasibility, and efficacy of this device as tool for removing medical drainage obstructions.

Topics: Drainage , Biomedicine , Blood
Commentary by Dr. Valentin Fuster

Design Innovation Paper

J. Med. Devices. 2017;11(1):015001-015001-8. doi:10.1115/1.4035689.

Acupoint catgut-embedding (ACE) therapy is a type of acupuncture surgery that combines concepts of traditional Chinese medicine with modern medical instruments. The therapy involves using a hypodermic needle and an acupuncture needle to embed 1-cm long catgut segments in an acupoint, enabling the catgut to perform long-term stimulation of the acupoint and achieve the effects of acupuncture treatment. Each therapy process requires numerous repetitions of the same steps, and each needle set can only be used to embed one catgut segment. Additionally, doctors must perform this surgical procedure by hand; no automatic auxiliary instrument has been developed to date. To address these problems, this paper proposes an innovative design of the first automatic ACE auxiliary instrument in the world. The instrument could assist doctors to complete the ACE steps. And it neither requires a battery or external electric power nor changes needles during therapy. The study first involved designing the mechanism and embodiment for the instrument, enabling it to perform one catgut-embedding procedure in only two steps with the repeated use of one needle set. We then created the prototype and tested its functionality in terms of the success rate of catgut cutting, average length of catgut segments, the success rate of needle insertion and acupoint range, and the success rates of catgut insertion and catgut embedding. The results showed that the prototype did conform to our design goals, but the success rates of catgut cutting and catgut insertion could be further enhanced.

Commentary by Dr. Valentin Fuster

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