Composite Biosynthetic Graft for Repair of Long-Segment Tracheal Stenosis: A Pilot In Vivo and In Vitro Feasibility Study.

Pediatric patients who undergo surgery for long-segment congenital tracheal stenosis (LSCTS) have suboptimal outcomes and postsurgical complications. To address this, we propose a biosynthetic graft comprising (1) a porcine small intestinal submucosa extracellular matrix (SIS-ECM) patch for tracheal repair, and (2) a resorbable polymeric exostent for biomechanical support. The SIS-ECM patch was evaluated in vivo in an ovine trachea model over an 8 month period. Concurrently, the biosynthetic graft was evaluated in a benchtop lamb trachea model for biomechanical stability. In vivo results show that SIS-ECM performs better than bovine pericardium (control) by preventing granulation tissue/restenosis, restoring tracheal architecture, blood vessels, matrix components, pseudostratified columnar and stratified epithelium, ciliary structures, mucin production, and goblet cells. In vitro tests show that the biosynthetic graft can provide the desired axial and flexural stability, and biomechanical function approaching that of native trachea. These results encourage future studies to evaluate safety and efficacy, including biomechanics and collapse risk, biodegradation, and in vivo response enabling a stable long-term tracheal repair option for pediatric patients with LSCTS and other tracheal defects.

The ChorioAnchor: Design and Testing of a Novel Chorioamniotic Anchoring Device to Enable Percutaneous Fetoscopic Surgery.

INTRODUCTION: Percutaneous fetoscopic surgery is hampered by an increased risk of preterm prelabor rupture of membranes (PPROM). Recent surgical techniques have shown that suturing the chorioamniotic membranes following laparotomy and uterine exteriorization is associated with a lower risk of PPROM compared to percutaneous in utero surgery. This study presents the ChorioAnchor, a novel resorbable device that percutaneously anchors the chorioamniotic membranes to the uterine wall. METHODS: Human factors testing and peel tests were used to simulate the worst-case in-use loading conditions, establishing the device strength requirements. Tensile testing was used to measure the time-zero strength of the device. Porcine cadaver testing was used to examine ultrasound visibility and acute handling characteristics. Short-term host response was examined through an acute 7-day implantation study in a rabbit model. RESULTS: With a time-zero tensile strength of 47 N, the ChorioAnchor exceeded the established 4 N strength requirement. Both the ChorioAnchor and delivery device were seen to be clearly visible under ultrasound imaging. Short-term host response to the device was well within the range expected for this type of device. CONCLUSION: The ChorioAnchor meets its engineering requirements in the early stages of implantation. Future studies will examine the kinetics of degradation of the device in vitro and in vivo.

Advancing pediatric medical device development via non-dilutive NIH SBIR/STTR grant funding.

INTRODUCTION: A shortage of medical devices designed for children persists due to the smaller pediatric population and market factors. Furthermore, pediatric device development is challenging due to the limited available funding sources. We describe our experience with pediatric device projects that successfully received federal grant support towards commercializing the devices that can serve as a guide for future innovators. METHODS: The developmental pathways of pediatric device projects at a tertiary-care children's hospital that received NIH SBIR/STTR funding between 2016-2019 were reviewed. The clinical problems, designs, specific aims, and development phase were delineated. RESULTS: Pediatric faculty successfully secured NIH SBIR/STTR funding for five pediatric devices via qualified small business concerns (SBC's). Three projects were initiated in the capstone engineering design programs and developed further at two affiliated engineering schools, while the other two projects were developed in the faculty members' labs. Four projects received funding via established SBC's, while one was awarded funding via a newly established SBC. CONCLUSION: NIH SBIR/STTR grants are an essential source of external non-dilutive funding for pediatric device innovation and especially for academic-initiated projects. This funding can provide needed early-stage support to facilitate commercialization. In addition, these grants can serve as achievable accomplishments for pediatric faculty portfolios toward academic promotion. Our experience shows that it is possible to build a robust innovation ecosystem comprised of academic faculty (clinical/engineering) collaborating with local device development companies while jointly implementing a product development strategy leveraging NIH SBIR/STTR funding for critical translational research phases of pediatric device development.

Alternative measures of toe trajectory more accurately predict the probability of tripping than minimum toe clearance.

Tripping is responsible for a large percentage of falls. Minimum toe clearance (MTC) during the swing phase of gait is commonly used to infer the probability of tripping (POT). However, there is limited empirical evidence to support the relationship between these two variables, and other measures of toe trajectory may better predict POT than MTC. The goals of this study were to: 1) quantify the relationship between MTC and POT; and 2) explore alternative measures of toe trajectory that may predict POT more accurately than MTC. POT was estimated by comparing the distribution of tripping obstacles measured along heavily-used, paved sidewalks on a university campus, to the toe trajectory of 40 young adults obtained while walking over an obstacle-free walkway in a research laboratory. POT exhibited a curvilinear relationship with MTC, and regression equations were established to predict POT from MTC. POT was more accurately predicted when using virtual points on the bottom of the anterior edge of the shoe to determine MTC, compared to using a physical marker located on top of the toes to determine MTC. POT was also more accurately predicted when using a new measure of toe trajectory (the area below 40mm and above the toe trajectory, normalized by the swing length), compared to just MTC. These are the first empirical results supporting a direct, quantitative relationship between MTC and POT. These results may improve the ability to identify risk factors that influence POT, and aid in developing interventions to reduce POT.

Biomechanical Properties of Human Ascending Thoracic Aortic Dissections.

Thoracic aortic dissections are associated with a significant risk of morbidity and mortality, and currently challenge our understanding of the biomechanical factors leading to their initiation and propagation. We quantified the biaxial mechanical properties of human type A dissections (n = 16) and modeled the stress-strain data using a microstructurally motivated form of strain energy function. Our results show significantly higher stiffness for dissected tissues as compared to control aorta without arterial disease. Higher stiffness of dissected tissues did not, however, correlate with greater aortic diameter measured prior to surgery nor were there any age dependent differences in the tissue properties.

Regional variations in the nonlinearity and anisotropy of bovine aortic elastin.

Arterial walls have a regular and lamellar organization of elastin present as concentric fenestrated networks in the media. In contrast, elastin networks are longitudinally oriented in layers adjacent to the media. In a previous model exploring the biomechanics of arterial elastin, we had proposed a microstructurally motivated strain energy function modeled using orthotropic material symmetry. Using mechanical experiments, we showed that the neo-Hookean term had a dominant contribution to the overall form of the strain energy function. In contrast, invariants corresponding to the two fiber families had smaller contributions. To extend these investigations, we use biaxial force-controlled experiments to quantify regional variations in the anisotropy and nonlinearity of elastin isolated from bovine aortic tissues proximal and distal to the heart. Results from this study show that tissue nonlinearity significantly increases distal to the heart as compared to proximally located regions ([Formula: see text]). Distally located samples also have a trend for increased anisotropy ([Formula: see text]), with the circumferential direction stiffer than the longitudinal, as compared to an isotropic and relatively linear response for proximally located elastin samples. These results are consistent with the underlying tissue histology from proximally located samples that had higher optical density ([Formula: see text]), fiber thickness ([Formula: see text]), and trend for lower tortuosity ([Formula: see text]) in elastin fibers as compared to the thinner and highly undulating elastin fibers isolated from distally located samples. Our studies suggest that it is important to consider elastin fiber orientations in investigations that use microstructure-based models to describe the contributions of elastin and collagen to arterial mechanics.