A Comparative Study of Machine Learning and Algorithmic Approaches to Automatically Identify the Yield Point in Normal and Aneurysmal Human Aortic Tissues.

The stress-strain curve of biological soft tissues helps characterize their mechanical behavior. The yield point on this curve is when a specimen breaches its elastic range due to irreversible microstructural damage. The yield point is easily found using the offset yield method in traditional engineering materials. However, correctly identifying the yield point in soft tissues can be subjective due to its nonlinear material behavior. The typical method for yield point identification is visual inspection, which is investigator-dependent and does not lend itself to automation of the analysis pipeline. An automated algorithm to identify the yield point objectively assesses soft tissues' biomechanical properties. This study aimed to analyze data from uniaxial extension testing on biological soft tissue specimens and create a machine learning (ML) model to determine a tissue sample's yield point. We present a trained machine learning model from 279 uniaxial extension curves from testing aneurysmal/nonaneurysmal and longitudinal/circumferential oriented tissue specimens that multiple experts labeled through an adjudication process. The ML model showed a median error of 5% in its estimated yield stress compared to the expert picks. The study found that an ML model could accurately identify the yield point (as defined) in various aortic tissues. Future studies will be performed to validate this approach by visually inspecting when damage occurs and adjusting the model using the ML-based approach.

Experimental Study of Rupture Pressure and Elasticity of Abdominal Aortic Aneurysms Found at Autopsy.

BACKGROUND: Resistance and elasticity of normal and aneurysmal aorta walls are directly associated with this vessel's growth and rupture. This study aims to experimentally analyze the biomechanical behavior of aneurysmal specimens found at autopsy, comparing them with normal diameter aortas removed from age-matched donors. METHODS: Thirty-eight human aortas (30 normal aortas; 8 infrarenal abdominal aortic aneurysms) were harvested during autopsy. An apparatus was built with a digital gauge, plastic tray, connections, and hoses that conducted fluid (air) from a pump through the system. Specimens were dissected, and a flexible balloon was introduced in each of them to avoid leakage. The specimens were fastened on the test tray, and activation of the air pump enhanced system pressure up to their rupture. RESULTS: All 8 aneurysms and all 30 normal aortas specimens evolved to rupture under inflation pressures above 590 mm Hg (mean ± standard deviation = 1,035 ± 375 mm Hg) and 840 mm Hg (mean ± SD = 1,405 ± 342 mm Hg), respectively. In the aneurysm group, 25% of specimens did not rupture in their most dilated region. Percentage of increment in diameter was higher in normal aortas (mean ± SD = 0.2106 ± 0.144) than in aneurysms (mean ± SD = 0.093 ± 0.070). CONCLUSIONS: In the present experiment, unruptured infrarenal abdominal aortic aneurysms could support high pressures nearly as much as nonaneurysmal abdominal aortas. In some specimens, the most dilated part of the aneurysm was not the most vulnerable under pressure. Normal aortas presented higher elasticity than aneurysms.

Investigation of the observed rupture lines in abdominal aortic aneurysms using crack propagation simulations.

OBJECTIVE: To use crack propagation simulation to study the rupture site characteristics in ruptured abdominal aortic aneurysms (AAA). METHODS: Rupture lines were precisely documented in four ruptured AAA harvested whole from cadavers. Wall thickness and material parameters were experimentally determined. Using subject-specific 3D geometry and subject-specific finite elastic model parameters, crack propagation simulations were conducted based on basic fracture mechanics principles to investigate if and how localized weak spots may have led to the observed rupture lines. RESULTS AND CONCLUSION: When an initial crack was imposed at the site of peak wall stress, the propagated path did not match the observed rupture line. This indicates that in this study population, the peak wall stress was unlikely to have caused the observed rupture. When cracks were initiated at random locations in the AAA along random orientations for random initial lengths, the orientation of the resulting propagated rupture line was consistently longitudinal. This suggests that the AAA morphology predisposes the AAA to rupture longitudinally, which is consistent with observations. It was found that, in this study population, rupture may have initiated at short segments of less than about 1 cm that then propagated to form the observed rupture lines. This suggests that ex vivo experimental and in vivo elastography studies should seek a spatial resolution (approx. 1 cm) to reliably identify weak spots in AAA. The small study population and lack of a reliable failure model for AAA tissue make these findings preliminary.

Cerebral Aneurysm Wall Stress After Coiling Depends on Morphology and Coil Packing Density.

Endovascular coil embolization is now widely used to treat cerebral aneurysms (CA) as an alternative to surgical clipping. It involves filling the aneurysmal sac with metallic coils to reduce flow, induce clotting, and promote the formation of a coil/thrombus mass which protects the aneurysm wall from hemodynamic forces and prevents rupture. However, a significant number of aneurysms are incompletely coiled leading to aneurysm regrowth and/or recanalization. Computational models of aneurysm coiling may provide important new insights into the effects of intrasaccular coil and thrombus on aneurysm wall stresses. Porcine blood and platinum coils were used to construct an in vitro coil thrombus mass (CTM) for mechanical testing. A uniaxial compression test was performed with whole blood clots and CTM, with coil packing densities (CPDs) of 10%, 20%, and 30% to obtain compressive stress/strain responses. A fourth-order polynomial mechanical response function was fit to the experimentally obtained stress/strain responses for each CPD in order to represent their mechanical properties for computational simulations. Patient-specific three-dimensional (3D) geometries of three aneurysms with simple geometry and four with complex geometry were reconstructed from digital subtraction angiography (DSA) images. The CPDs were digitally inserted in the aneurysm geometries and finite element modeling was used to determine transmural peak/mean wall stress (MWS) with and without coil packing. Reproducible stress/strain curves were obtained from compression testing of CTM and the polynomial mechanical response function was found to approximate the experimental stress/strain relationship obtained from mechanical testing to a high degree. An exponential increase in the CTM stiffness was observed with increasing CPD. Elevated wall stresses were found throughout the aneurysm dome, neck, and parent artery in simulations of the CAs with no filling. Complete, 100% filling of the aneurysms with whole blood clot and CPDs of 10%, 20%, and 30% significantly reduced MWS in simple and complex geometry aneurysms. Sequential increases in CPD resulted in significantly greater increases in MWS in simple but not complex geometry aneurysms. This study utilizes finite element analysis to demonstrate the reduction of transmural wall stress following coil embolization in patient-specific computational models of CAs. Our results provide a quantitative measure of the degree to which CPD impacts wall stress and suggest that complex aneurysmal geometries may be more resistant to coil embolization treatment. The computational modeling employed in this study serves as a first step in developing a tool to evaluate the patient-specific efficacy of coil embolization in treating CAs.

Housing First for older homeless adults with mental illness: a subgroup analysis of the At Home/Chez Soi randomized controlled trial.

OBJECTIVE: This study compares the effect of Housing First on older (≥50 years old) and younger (18-49 years old) homeless adults with mental illness participating in At Home/Chez Soi, a 24-month multisite randomized controlled trial of Housing First. METHOD: At Home/Chez Soi, participants (n = 2148) were randomized to receive rent supplements with intensive case management or assertive community treatment, based on their need level for mental health services, or usual care in their respective communities. A subgroup analysis compared older (n = 470) and younger (n = 1678) homeless participants across baseline characteristics and 24-month outcomes including housing stability (primary outcome), generic and condition-specific quality of life, community functioning, physical and mental health status, mental health symptom severity, psychological community integration, recovery, and substance use (secondary outcomes). RESULTS: At 24 months, Housing First significantly improved the percentage of days stably housed among older (+43.9%, 95% confidence interval [CI]: 38.4% to 49.5%) and younger homeless adults (+39.7%, 95% CI: 36.8% to 42.6%), compared with usual care, with no significant differences between age groups (difference of differences = +4.2%, 95% CI: -2.1% to 10.5%, p = 0.188). Improvements from baseline to 24 months in mental health and condition-specific quality of life were significantly greater among older homeless adults than among younger homeless adults. CONCLUSION: Housing First significantly improved housing stability among older and younger homeless adults with mental illness, resulting in superior mental health and quality of life outcomes in older homeless adults compared with younger homeless adults at 24 months. Copyright © 2017 John Wiley & Sons, Ltd.

AML cells have low spare reserve capacity in their respiratory chain that renders them susceptible to oxidative metabolic stress.

Mitochondrial respiration is a crucial component of cellular metabolism that can become dysregulated in cancer. Compared with normal hematopoietic cells, acute myeloid leukemia (AML) cells and patient samples have higher mitochondrial mass, without a concomitant increase in respiratory chain complex activity. Hence these cells have a lower spare reserve capacity in the respiratory chain and are more susceptible to oxidative stress. We therefore tested the effects of increasing the electron flux through the respiratory chain as a strategy to induce oxidative stress and cell death preferentially in AML cells. Treatment with the fatty acid palmitate induced oxidative stress and cell death in AML cells, and it suppressed tumor burden in leukemic cell lines and primary patient sample xenografts in the absence of overt toxicity to normal cells and organs. These data highlight a unique metabolic vulnerability in AML, and identify a new therapeutic strategy that targets abnormal oxidative metabolism in this malignancy.

Mapping the playing field-a novel web-based strategy to identify non-governmental actors in global surgery.

BACKGROUND: In the face of staggering global unmet need for surgical care, non-governmental organisations (NGOs) play a substantial part in the surgical workforce, providing surgical care for those who are without it. The number of NGOs providing surgical care in low-income and middle-income countries (LMICs) is unknown. This information is needed to determine the scope of such care, its contributions to global surgical case volume, to improve collaboration in an effort to maximise efficiency, and to inform national surgical workforce planning. We aimed to create a comprehensive, publicly available catalogue of NGOs providing surgery in LMICs. METHODS: We used the United Nations Rule Of Law definition to define NGOs. We included low-income, lower-middle- income, and upper-middle-income countries as defined by World Bank lending groups. Delivery of surgical care by an NGO was defined as the therapeutic manipulation of tissues taking place within an operating room, and was distinguished from the financial or logistical support of such care. We screened an online humanitarian clearing house (ReliefWeb), a large public NGO database (Idealist.org), two surgical volunteerism databases (Operation Giving Back and the Society for Pediatric Anesthesia), and the US State Department Private Volunteer Organizations database, did a review of the literature, and used a social media outlet (Twitter) to identify organisations meeting criteria for inclusion. A complementary analysis additionally provided a list of organisations delivering exclusively surgical care from a search of the OmniMed database, the Foundation Center Online Directory, UK Charity Commission, Australia Charity Commission, New Zealand Charity Commission, and the Canada Revenue Agency Charity Search. FINDINGS: We identified 313 unique organisations, working in all 139 LMICs. Organisations often used more than one model of care and engaged in several surgical specialties. Both short-term surgical missions (206 organisations, 66%) and long-term partnerships (213, 68%) were common models, with 40 organisations (13%) engaging in humanitarian interventions in crisis settings. The most commonly represented specialty was general surgery (120, 38%), but subspecialty surgery such as ophthalmology (88, 28%) and cleft lip and palate surgery (70, 22%) were also frequently performed. INTERPRETATION: To our knowledge, this is the most complete directory of NGOs undertaking surgery in resource-limited settings in existence. However, it is difficult to determine whether this review is exhaustive. Further work is needed to determine the total and relative contributions of these organisations to global surgical volume. This database will be made available for public use and should be maintained and updated to further coordinate global efforts and maximise impact. FUNDING: None.

Adlayer-mediated antibody immobilization to stainless steel for potential application to endothelial progenitor cell capture.

This work describes the straightforward surface modification of 316L stainless steel with BTS, S-(11-trichlorosilylundecanyl)-benzenethiosulfonate, a thiol-reactive trichlorosilane cross-linker molecule designed to form intermediary coatings with subsequent biofunctionalization capability. The strategy is more specifically exemplified with the immobilization of intact antibodies and their Fab' fragments. Both surface derivatization steps are thoroughly characterized by means of X-ray photoelectron spectroscopy. The antigen binding capability of both types of biofunctionalized surfaces is subsequently assessed by fluorescence microscopy. It was determined that BTS adlayers achieve robust immobilization of both intact and fragmented antibodies, while preserving antigen binding activity. Another key finding was the observation that the Fab' fragment immobilization strategy would constitute a preferential option over that involving intact antibodies in the context of in vivo capture of endothelial progenitor cells in stent applications.

An artificial intelligence based abdominal aortic aneurysm prognosis classifier to predict patient outcomes.

Abdominal aortic aneurysms (AAA) have been rigorously investigated to understand when their clinically-estimated risk of rupture-an event that is the 13th leading cause of death in the US-exceeds the risk associated with repair. Yet the current clinical guideline remains a one-size-fits-all "maximum diameter criterion" whereby AAA exceeding a threshold diameter is thought to make the risk of rupture high enough to warrant intervention. However, between 7 and 23.4% of smaller-sized AAA have been reported to rupture with diameters below the threshold. In this study, we train and assess machine learning models using clinical, biomechanical, and morphological indices from 381 patients to develop an aneurysm prognosis classifier to predict one of three outcomes for a given AAA patient: their AAA will remain stable, their AAA will require repair based as currently indicated from the maximum diameter criterion, or their AAA will rupture. This study represents the largest cohort of AAA patients that utilizes the first available medical image and clinical data to classify patient outcomes. The APC model therefore represents a potential clinical tool to striate specific patient outcomes using machine learning models and patient-specific image-based (biomechanical and morphological) and clinical data as input. Such a tool could greatly assist clinicians in their management decisions for patients with AAA.

Aortic tissue stiffness and tensile strength are correlated with density changes following proteolytic treatment.

INTRODUCTION: Dissection or rupture of the aorta is accompanied by high mortality rates, and there is a pressing need for better prediction of these events for improved patient management and clinical outcomes. Biomechanically, these events represent a situation wherein the locally acting wall stress exceed the local tissue strength. Based on recent reports for polymers, we hypothesized that aortic tissue failure strength and stiffness are directly associated with tissue mass density. The objective of this work was to test this novel hypothesis for porcine thoracic aorta. METHODS: Three tissue specimens from freshly harvested porcine thoracic aorta were treated with either collagenase or elastase to selectively degrade structural proteins in the tissue, or with phosphate buffer saline (control). The tissue mass and volume of each specimen were measured before and after treatment to allow for density calculation, then mechanically tested to failure under uniaxial extension. RESULTS: Protease treatments resulted in statistically significant tissue density reduction (sham vs. collagenase p = 0.02 and sham vs elastase p = 0.003), which in turn was significantly and directly correlated with both ultimate tensile strength (sham vs. collagenase p = 0.02 and sham vs elastase p = 0.03) and tangent modulus (sham vs. collagenase p = 0.007 and sham vs elastase p = 0.03). CONCLUSIONS: This work demonstrates for the first time that tissue stiffness and tensile strength are directly correlated with tissue density in proteolytically-treated aorta. These findings constitute an important step towards understanding aortic tissue failure mechanisms and could potentially be leveraged for non-invasive aortic strength assessment through density measurements, which could have implications to clinical care.

Scanning the aged to minimize missed injury: An EAST multicenter study.

BACKGROUND: Despite the high incidence of blunt trauma in older adults, there is a lack of evidence-based guidance for computed tomography (CT) imaging in this population. We aimed to identify an algorithm to guide use of a Pan-Scan (Head/C-spine/Torso) or a Selective Scan (Head/C-spine ± Torso). We hypothesized that a patient's initial history and exam could be used to guide imaging. METHODS: We prospectively studied blunt trauma patients aged 65+ at 18 Level I/II trauma centers. Patients presenting >24 h after injury or who died upon arrival were excluded. We collected history and physical elements and final injury diagnoses. Injury diagnoses were categorized into CT body regions of Head/C-spine or Torso (chest, abdomen/pelvis, and T/L spine). Using machine learning and regression modeling as well as a priori clinical algorithms based, we tested various decision rules against our dataset. Our priority was to identify a simple rule which could be applied at the bedside, maximizing sensitivity (Sens) and negative predictive value (NPV) to minimize missed injuries. RESULTS: We enrolled 5,498 patients with 3,082 injuries. Nearly half (47.1%, n = 2,587) had an injury within the defined CT body regions. No rule to guide a Pan-Scan could be identified with suitable Sens/NPV for clinical use. A clinical algorithm to identify patients for Pan-Scan, using a combination of physical exam findings and specific high-risk criteria, was identified and had a Sens of 0.94 and NPV of 0.86 This rule would have identified injuries in all but 90 patients (1.6%) and would theoretically spare 11.9% (655) of blunt trauma patients a torso CT. CONCLUSIONS: Our findings advocate for Head/Cspine CT in all geriatric patients with the addition of torso CT in the setting of positive clinical findings and high-risk criteria. Prospective validation of this rule could lead to streamlined diagnostic care of this growing trauma population. LEVEL OF EVIDENCE: Level 2, Diagnostic Tests or Criteria.

The regulatory environment for artificial intelligence-enabled devices in the United States.

The regulatory environment in the United States has not kept pace with the rapidly developing market for artificial intelligence (AI)-enabled devices. The number of AI-enabled devices has increased year after year. All of these devices are registered or cleared by the US Food and Drug Administration through exempt or 510(k) premarket notification pathways, and the majority are related to the radiology or cardiovascular spaces. US Food and Drug Administration guidance has not yet addressed the unique challenges of AI-enabled devices, including development, comprehensibility, and continuously learning models. The liability aspects of AI-enabled devices deployed into use by clinicians in practice have yet to be addressed. Future guidance from government regulatory sources will be necessary as the field moves forward.

Lateral Lumbar Interbody Fusion Using Expandable vs Static Titanium Interbody Cages: A Prospective Cohort Study of Clinical and Radiographic Outcomes.

BACKGROUND: Expandable cages are a recent development employed to reduce subsidence and improve fusion compared with static cages as they alleviate the need for repeated trialing or overdistraction of the disc space. This study aimed to compare the radiographic and clinical outcomes in patients undergoing lateral lumbar interbody fusion (LLIF) with either an expandable or static titanium cage. METHODS: This was a prospective study of 98 consecutive patients undergoing LLIF performed over a 2-year period, with the first 50 patients receiving static cages and the following 48 receiving expandable cages. Radiographic evaluation included interbody fusion status, cage subsidence, and change in segmental lordosis and disc height. Clinical evaluation assessed patient-reported outcome measures (PROMs), including the Oswestry Disability Index, visual analog scale (VAS) for back and leg pain, and short form-12 physical and mental health survey scores collected at 3, 6, and 12 months postoperatively. RESULTS: The 98 patients had 169 cages impacted (84 expandable vs 85 static). Mean age was 69.2 years, and 53.1% were women. There was no significant difference between the 2 groups in terms of age, gender, body mass index, or smoking status. The expandable cage group had higher rates of interbody fusion (94.0% vs 82.9%, P = 0.039) at 12 months as well as significantly reduced implant subsidence rates at all follow-up timepoints (4% vs 18% at 3 months; 4% vs 20% at 6 and 12 months). Patients from the expandable cage group showed a mean 1.9 more points of reduction in VAS back pain (P = 0.006) and 2.49 points greater reduction in VAS leg pain (P = 0.023) at 12-month follow-up. CONCLUSIONS: Expandable lateral interbody spacers resulted in significantly improved fusion rates with reduced subsidence risks and statistically significant improvement in PROMs up to 12 months postoperatively compared with impacted lateral static cages. CLINICAL RELEVANCE: The data provide clinical relevance in favoring expandable cages over static cages for enhanced fusion outcomes in lumbar fusions.

The Effect of Tibial Tunnel Drilling Technique on Retained Intra-Articular Bone Debris Following Anterior Cruciate Ligament Reconstruction.

Purpose: To assess the effect of tibial tunnel drilling technique (retro-drilled bone socket vs full tibial tunnel) on the presence and grade of postoperative, intra-articular bone debris following primary hamstring anterior cruciate ligament (ACL) reconstruction. Methods: This was a retrospective cohort study of primary hamstring autograft ACL reconstructions performed by 2 surgeons. Two blinded independent reviewers assessed the presence and length of retained intra-articular bone debris on the immediate postoperative lateral radiograph. Debris was graded according to a predefined 5-point ordinal grading system: grade 0 (no debris) to IV (severe debris). Results were analyzed according to the type of tibial tunnel; retro-drilled socket or full tibial tunnel using Kappa statistics and the Mann-Whitney U test. Results: Sixty-five patients undergoing primary hamstring ACL were included (39 tibial socket: 26 full tibial tunnel). Bone debris was observed among the tibial socket technique in 29 of 39 instances (74.3%), compared with 14 of 26 (53.8%) instances for the full tibial tunnel technique (P = .09). Where there was measurable debris present, the tibial socket group had a mean length of bone debris of 13.7 ± 6.2 mm as compared with the full tibial tunnel, 10.0 ± 4.7 mm (P = .165). There were significant differences in bone debris gradings between the 2 treatment groups, with tibial sockets having an overall greater grade (P = .04). Conclusions: A difference in the presence of, or length of, retained bone debris on the postoperative lateral radiograph was not demonstrated between the retro-drilled bone socket and full tibial tunnel techniques. However, when bone debris was present, greater grades of debris were seen in the retro-drilled socket group. Level of Evidence: III, retrospective, comparative study.

Mechanical and matrix effects of short and long-duration exposure to beta-aminopropionitrile in elastase-induced model abdominal aortic aneurysm in mice.

Objective: Evaluate the mechanical and matrix effects on abdominal aortic aneurysms (AAA) during the initial aortic dilation and after prolonged exposure to beta-aminopropionitrile (BAPN) in a topical elastase AAA model. Methods: Abdominal aortae of C57/BL6 mice were exposed to topical elastase with or without BAPN in the drinking water starting 4 days before elastase exposure. For the standard AAA model, animals were harvested at 2 weeks after active elastase (STD2) or heat-inactivated elastase (SHAM2). For the enhanced elastase model, BAPN treatment continued for either 4 days (ENH2b) or until harvest (ENH2) at 2 weeks; BAPN was continued until harvest at 8 weeks in one group (ENH8). Each group underwent assessment of aortic diameter, mechanical testing (tangent modulus and ultimate tensile strength [UTS]), and quantification of insoluble elastin and bulk collagen in both the elastase exposed aorta as well as the descending thoracic aorta. Results: BAPN treatment did not increase aortic dilation compared with the standard model after 2 weeks (ENH2, 1.65 ± 0.23 mm; ENH2b, 1.49 ± 0.39 mm; STD2, 1.67 ± 0.29 mm; and SHAM2, 0.73 ± 0.10 mm), but did result in increased dilation after 8 weeks (4.3 ± 2.0 mm; P = .005). After 2 weeks, compared with the standard model, continuous therapy with BAPN did not have an effect on UTS (24.84 ± 7.62 N/cm2; 18.05 ± 4.95 N/cm2), tangent modulus (32.60 ± 9.83 N/cm2; 26.13 ± 9.10 N/cm2), elastin (7.41 ± 2.43%; 7.37 ± 4.00%), or collagen (4.25 ± 0.79%; 5.86 ± 1.19%) content. The brief treatment, EHN2b, resulted in increased aortic collagen content compared with STD2 (7.55 ± 2.48%; P = .006) and an increase in UTS compared with ENH2 (35.18 ± 18.60 N/cm2; P = .03). The ENH8 group had the lowest tangent modulus (3.71 ± 3.10 N/cm2; P = .005) compared with all aortas harvested at 2 weeks and a lower UTS (2.18 ± 2.18 N/cm2) compared with both the STD2 (24.84 ± 7.62 N/cm2; P = .008) and ENH2b (35.18 ± 18.60 N/cm2; P = .001) groups. No differences in the mechanical properties or matrix protein concentrations were associated with abdominal elastase exposure or BAPN treatment for the thoracic aorta. The tangent modulus was higher in the STD2 group (32.60 ± 9.83 N/cm2; P = .0456) vs the SHAM2 group (17.99 ± 5.76 N/cm2), and the UTS was lower in the ENH2 group (18.05 ± 4.95 N/cm2; P = .0292) compared with the ENH2b group (35.18 ± 18.60 N/cm2). The ENH8 group had the lowest tangent modulus (3.71 ± 3.10 N/cm2; P = .005) compared with all aortas harvested at 2 weeks and a lower UTS (2.18 ± 2.18 N/cm2) compared with both the STD2 (24.84 ± 7.62 N/cm2; P = .008) and ENH2b (35.18 ± 18.60 N/cm2; P = .001) groups. Abdominal aortic elastin in the STD2 group (7.41 ± 2.43%; P = .035) was lower compared with the SHAM2 group (15.29 ± 7.66%). Aortic collagen was lower in the STD2 group (4.25 ± 0.79%; P = .007) compared with the SHAM2 group (12.44 ± 6.02%) and higher for the ENH2b (7.55 ± 2.48%; P = .006) compared with the STD2 group. Conclusions: Enhancing an elastase AAA model with BAPN does not affect the initial (2-week) dilation phase substantially, either mechanically or by altering the matrix content. Late mechanical and matrix effects of prolonged BAPN treatment are limited to the elastase-exposed segment of the aorta. Clinical Relevance: This paper explores the use of short- and long-term exposure to beta-aminopropionitrile to create an enhanced topical elastase abdominal aortic aneurysm model in mice. Readouts of aneurysm severity included loss of mechanical stability and vascular extracellular matrix composition reminiscent of what is seen in the course of human disease. Additionally, we show that the thoracic aorta, unlike the findings below the renal arteries, is not damaged in our animal model.

Artificial intelligence framework to predict wall stress in abdominal aortic aneurysm.

Abdominal aortic aneurysms (AAA) have been rigorously investigated to understand when their risk of rupture - which is the 13th leading cause of death in the US - exceeds the risks associated with repair. Clinical intervention occurs when an aneurysm diameter exceeds 5.5 cm, but this "one-size fits all" criterion is insufficient, as it has been reported thatup to a quarter of AAA smaller than 5.5 cm do rupture. Therefore, there is a need for a more reliable, patient-specific, clinical tool to aide in the management of AAA. Biomechanical assessment of AAA is thought to provide critical physical insights to rupture risk, but clinical translataion of biomechanics-based tools has been limited due to the expertise, time, and computational requirements. It was estimated that through 2015, only 348 individual AAA cases have had biomechanical stress analysis performed, suggesting a deficient sample size to make such analysis relevant in the clinic. Artificial intelligence (AI) algorithms offer the potential to increase the throughput of AAA biomechanical analyses by reducing the overall time required to assess the wall stresses in these complex structures using traditional methods. This can be achieved by automatically segmenting regions of interest from medical images and using machine learning models to predict wall stresses of AAA. In this study, we present an automated AI-based methodology to predict the biomechanical wall stresses for individual AAA. The predictions using this approach were completed in a significantly less amount of time compared to a more traditional approach (~4 hours vs 20 seconds).

An Objective and Repeatable Sac Isolation Technique for Comparing Biomechanical Metrics in Abdominal Aortic Aneurysms.

(1) Abdominal aortic aneurysm (AAA) biomechanics-based metrics often reported may be over/under-estimated by including non-aneurysmal regions in the analyses, which is typical, rather than isolating the dilated sac region. We demonstrate the utility of a novel sac-isolation algorithm by comparing peak/mean wall stress (PWS, MWS), with/without sac isolation, for AAA that were categorized as stable or unstable in 245 patient CT image sets. (2) 245 patient computed tomography images were collected, segmented, meshed, and had subsequent finite element analysis performed in preparation of our novel sac isolation technique. Sac isolation was initiated by rotating 3D surfaces incrementally, extracting 2D projections, curve fitting a Fourier series, and taking the local extrema as superior/inferior boundaries for the aneurysmal sac. The PWS/MWS were compared pairwise using the entire aneurysm and the isolated sac alone. (3) MWS, not PWS, was significantly different between the sac alone and the entire aneurysm. We found no statistically significant difference in wall stress measures between stable (n = 222) and unstable (n = 23) groups using the entire aneurysm. However, using sac-isolation, PWS (24.6 ± 7.06 vs. 20.5 ± 8.04 N/cm2; p = 0.003) and MWS (12.0 ± 3.63 vs. 10.5 ± 4.11 N/cm2; p = 0.022) were both significantly higher in unstable vs. stable groups. (4) Our results suggest that evaluating only the AAA sac can influence wall stress metrics and may reveal differences in stable and unstable groups of aneurysms that may not otherwise be detected when the entire aneurysm is used.

A Multidisciplinary Approach to Penetrating Neck Trauma in a Patient with Self-Inflicted Gunshot Injuries to Zones 1-3 of the Neck.

Penetrating neck trauma comprises 5%-10% of all traumatic injuries in adults and carries up to a 10% mortality rate for those affected. Management of penetrating neck trauma can be challenging and often requires a multidisciplinary approach. A case of penetrating neck trauma via self-inflicted gunshot wound to zones 1-3 of the neck in an intoxicated, suicidal 60-year-old man is presented. Immediately after stabilization by the trauma surgery team, surgical reconstruction using a pectoralis major pedicled myocutaneous flap was completed by the plastic and reconstructive surgery team. The patient's hospital course was complicated by injury to the left phrenic nerve, oropharyngeal swallowing dysfunction, and left diaphragmatic dysfunction. The trauma team initiated prompt multidisciplinary responses to each of these complications as they arose by involving the plastic and reconstructive surgery, otolaryngology, gastroenterology, and speech language pathology teams. Early involvement of the physical medicine and rehabilitation, psychiatry, dietary, and pharmacy teams allowed for early optimization and monitoring of the patient's mobility, psychological, and nutritional statuses. The timely initiation of multidisciplinary care in this patient's case allowed for the patient to not only to survive a potentially fatal penetrating neck trauma, but to be discharged to a rehabilitation facility with an independent level of function. Given the complications due to severe penetrating neck trauma of zones 1-3 in this case, it is essential for early involvement of the appropriate subspecialty teams in order to achieve the best possible outcome for the patient.

Bronchoscopy Decreases Ventilator-Associated Pneumonia in Trauma Patients.

Health care-associated pneumonias (HAPs) are a significant comorbidity seen in hospitalized patients. Traumatic injury is a known independent risk factor for the development of HAP. Trauma-related injuries also contribute to an increase in the rate of pneumonia in mechanically ventilated patients requiring intensive care unit (ICU) treatment. In 2011, the ventilator-associated pneumonia (VAP) rate among ICU patients at our institution (CMMC) increased dramatically. As a result, our infection control specialists performed a focused review of these patients and found a likely association between these infections and patients requiring pre-hospital intubation. Their determination prompted a July 2012 revision of the CMMC Trauma/Surgery Admission ICU protocol for ventilated patients to include bronchoscopy for all patients who have been intubated pre-hospital providing no contraindications were present. Our aim was to ascertain any influence of the protocol change on the rate of VAP. We conducted a retrospective medical record review of trauma patients who were intubated in the field or ED and seen at our institution (an accredited Level 1 trauma center) from 2012 to 2018. Applying the current definition of VAP from the Centers for Disease Control and Prevention (CDC) to data collected from the CMMC trauma registry, we observed a 13% lower VAP rate in the bronchoscopy group (YB) as compared to the group that did not receive bronchoscopy (NB) (P < .025). Based on our results, we determined that bronchoscopy performed in this setting does support a statistically significant decrease in the rate of ventilator-associated pneumonia.

Functionally Silent, Giant Pheochromocytoma Presenting With Varicocele.

Adrenal incidentalomas are a known entity that have been increasing in commonality with the advent of improved diagnostic and imaging techniques. There are a vast variety of causative pathologies to which this diagnosis can be attributed. Some of these pathologies are more common than others, while many remain extremely rare. One of the distinct entities that is a unique cause of incidentalomas is the diagnosis presented herein: pheochromocytoma. Pheochromocytomas are often an exceptional subset of incidentalomas that can certainly play a major role in treatment and management plans. However, the exclusivity of a pheochromocytoma diagnosis alone is not where the uniqueness of this case rests. The uniqueness in this patient is paramount to report due to 2 additional significant factors. The first was that the patient was entirely asymptomatic aside from complaints related to scrotal swelling due to a varicocele, for which this presentation of pheochromocytoma has been scarcely reported in the literature. Second, the patient had a pathology proven diagnosis of pheochromocytoma, while lacking both symptoms and biochemical findings to support the diagnosis, making it truly a silent pheochromocytoma.