Accepted Manuscripts

Technical Brief  
Shuchen Ge, Liaoyuan Ai, Arthur Erdman and Chengli Song
J. Med. Devices   doi: 10.1115/1.4039753
Endoscopic closure is an essential procedure in gastrointestinal (GI) surgery, but currently it is difficult to close large defects endoscopically because of lacking appropriate device. Previously we developed a novel endoscopic clipping device, which has multi-firing function and is equipped with an independent clamp. The goal of this study is to provide a new closure method with this device and 4S-Modified Roeder (4SMR) slipknot. The mechanical strengths of the slipknot as regards to tensioning forces is also evaluated. The feasibility of the closure method is examined by deploying two clips during one insertion onto the 4SMR slipknot to close a 5 cm full-thickness linear defect of an ex-vivo porcine stomach from the center. The mechanical strength of the 4SMR slipknot is verified by mean peak forces to failure, while the knot is tensioning by 2.5, 5, 7.5 and 10 Newton force (n=20 for each group) respectively. Experimental results indicate tensioning force has a great influence on the mechanical strength of slipknot, with the mean peak force (tensioning force) being 7.1± 6.5, 16.3±9.3, 18.9±10.4 and 24.2±12.0 Newtons respectively. In conclusion, the proposed closure method can be used for large defects. Tensioning force higher than five Newtons is suitable to ensure a stronger 4SMR slipknot.
TOPICS: Endoscopic devices, Strength (Materials), Clamps (Tools), Surgery, Failure, Firing
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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