Accepted Manuscripts

Alexander H. Slocum Jr., Steven Reinitz, Shailly H. Jariwala and Douglas W. Van Citters
J. Med. Devices   doi: 10.1115/1.4037442
Intra-osseous (IO) needles are an easy and reliable alternative to intravenous (IV) access in the pre-hospital and emergency settings for treating patients in shock. The advantage of utilizing an IO is that secure, non-collapsible 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, pre-hospital trauma, or a mass-casualty incident, even trained providers can have trouble correctly placing IVs or IOs. The Tib-Finder™ is an intuitive drill guide that significantly improves efficiency with which IOs 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 intra-vascular 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.
TOPICS: Design, needles, Drills (Tools), Developing nations, Engineering prototypes, Shock (Mechanics), Chaos, Health care, Body systems and structures, Biomedicine, Emergencies
Peter S Walker and Ilya Borukhov
J. Med. Devices   doi: 10.1115/1.4037261
Background 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. Methods Stabilizing structures of the anatomic knee were identified under conditions of low and high axial loading. The upwards slope of the anterior medial tibial plateau and the anterior cruciate, were 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. Results The guided motion design showed much closer neutral path of motion and laxity in anterior-posterior an 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. Conclusions 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, Performance, Stability, Machinery, Biomechanics, ASTM International, Rotation
Review Article  
Laurence Nouaille, M. Amine Laribi, Carl A. Nelson, Said Zeghloul and Gerard Poisson
J. Med. Devices   doi: 10.1115/1.4037053
Introduction This paper deals with the survey of kinematic structures adapted to specific medical robots: minimally invasive surgery 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. Methods 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. Conclusion 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.
TOPICS: Kinematics, Robots, Surgery, Biomedicine, Safety, Design, Architecture, Statistical analysis, Robotics
Design Innovation Paper  
F. Mark Payne, Tony Connell and Jacob Rice
J. Med. Devices   doi: 10.1115/1.4030812
Background: Tissue expanders are used in breast reconstruction after mastectomy to create a space for placement of permanent breast implants. The AeroForm™ Tissue Expander, developed by AirXpanders™ Inc., utilizes carbon dioxide released from an internal reservoir to inflate the expander. The released gas is contained within a high barrier material pre-formed into a breast shaped shell of the desired volume. During patient travel to higher altitude, a partially inflated expander will increase in volume proportionately to the gas fill volume. At volume levels near full, expansion is governed by the compliance of the inner gas barrier and silicone shell. Therefore, the assessment of the expander performance at altitude consists of the analysis of two operating regimes. The first regime is fill levels < 70% full where the implant, when exposed to cabin pressure, expands without significantly stressing the inner gas barrier. The second is fill levels ~>70% where the response of the inner gas barrier is important, both in terms of structural capability and determination of the volume increase. We assessed the impact of pressurized flight on expander performance in both operating regimes. Findings: The volume increase associated with altitude increase to 8000 feet (maximum cabin altitude per FAA) is typically within the range administered during post-operative fills of saline expanders. Although assessment must be conducted by a clinician, a patient can be typically expected to tolerate the increased volume with some minor discomfort, such as a feeling of tightness. At higher fill levels, the structural capability of shell has been demonstrated to withstand the additional pressure loading. At these fill levels, the expander does not expand as much, due to the structural restraint of the shell. To date, 7 subjects have flown with the expander in situ during clinical trials. All subjects were required to temporarily cease dosing up to two weeks prior. Flight travel was completed uneventfully and they reported discomfort levels ranging from none to moderate. The recommendation to cease dosing two weeks prior to flying was made to allow the expected 1 cc per day of CO2 permeation to occur, which will result in slight deflation to accommodate for the expansion of the CO2 when flying. As expected, subjects reported a sensation of pressure upon ascent which subsided on descent.
TOPICS: Biological tissues, Carbon dioxide, Shells, Pressure, Flight, Reservoirs, Silicones

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