Development of a synchronous motion-tracking and video capture tool for flexible ureteroscopy.

INTRODUCTION: Hand/instrument motion-tracking in surgical simulation provides valuable data to improve psychomotor skills and can serve as a formative evaluation tool. Motion analysis has been well-studied in laparoscopic surgery; however, there are essentially no studies looking at motion-tracking for flexible ureteroscopy (fURS ), a common surgical procedure requiring hand dexterity and 3D spatial awareness. We aimed to design a synchronized motion-tracking and video capture system for fURS capable of collecting objective metrics for use in surgical skills training. METHODS: Motion tracking of the ureteroscope was performed using a motion-tracking platform, inertial measurement units (IMUs), and an optical sensor. Position (x, y, z) and orientation (roll, pitch, yaw) of the ureteroscope handle, lever deflection, and translation of the scope insertion point were collected. Video capture of the operator's hands was collected with a Raspberry Pi camera. All peripherals were controlled on a Raspberry Pi 4 and synchronized to its system clock. RESULTS: Our system demonstrated good accuracy in detecting translation of the ureteroscope in the x- and y-axes, and yaw, pitch and roll of the ureteroscope at discrete orientations of 0, ±30, ±60, and ±90 degrees. Unique to fURS, deflection of the lever was captured by the difference in IMU static accelerations with good accuracy. The optical sensor detected translation of the ureteroscope at the insertion point with good precision and an average error of 5.51%. CONCLUSIONS: We successfully developed a motion-tracking and video-capture system capable of collecting motion-analysis parameters unique to fURS . Future studies will focus on establishing the construct validity of this tool.

An Autonomous Continuous Bladder Irrigation System.

Introduction and Objective: Continuous bladder irrigation (CBI) is used in a variety of clinical settings, including post-transurethral surgery and the emergency department. Currently, CBI administration relies on nurses to diligently monitor and switch irrigation bags, as well as titrate the inflow rate based on effluent color. Inappropriate administration can result in discomfort to patients, clot urinary retention, repeat injury to the pathologic or surgical site, extended hospital stays, and even operative management. Our objective was to create an autonomous CBI system that decreases the incidence of disrupted irrigation flow and monitors the outflow to alert clinicians of critical events. Methods: 3D printing and off-the-shelf microcontrollers were used to design a device to fit the needs identified by stakeholders at our institution. An in vitro model of the bladder was created to test our design. The mechanical, electrical, and software subsystems were adjusted accordingly to meet our design requirements. Results: Our in vitro CBI model was able to simulate routine CBI administration with sudden bleeding. Bovine blood was used to simulate the bleeding events. A device was created that met identified stakeholder needs. Accurate detection of critical bleeding events, catheter blockage, and empty irrigation bags were achieved. The device responds to bleeding appropriately by increasing the irrigation rate. When the catheter is blocked, it stops the irrigation and alerts the nurse. Our system accurately titrated the irrigation rate to match a set outflow blood level parameter, conserving irrigation and minimizing nursing workload. Continuous monitoring of CBI effluent was recorded. Conclusions: We anticipate our device will decrease the cognitive load on nurses in busy clinical settings and improve workflow. Moreover, the detection of critical events will likely decrease patient morbidity. Continuous monitoring of the CBI outflow may prove to be a new clinical decision-making tool for ongoing hematuria. Clinical trial is pending.

A Novel Ureteroscopy Training Platform That Utilizes CT Urograms to Replicate Complex Renal Collecting System Anatomies.

Introduction: Flexible ureteroscopy (fURS) is a one-person surgical technique, limiting trainees' ability to practice intraoperatively. Although well suited for simulation training, few existing fURS simulators can accurately reproduce complex renal collecting system anatomies. We developed an anatomically accurate fURS simulator using three-dimensional (3D) reconstruction of CT urograms and 3D printing technology to address this need. Materials and Methods: Patient-specific CT urograms were used to create 3D reconstruction of the renal collecting system using Slicer™. 3D models were modified using Blender™. Hollow, elastomer kidney models were created using an Objet 3D™ printer. To test and evaluate the new fURS simulator, 25 volunteers were recruited (5 novices, 13 residents, and 7 urologists). Participants were asked to explore the model with fURS and were evaluated on their ability to deduce its 3D anatomy, their ability to navigate to prespecified calices, and their time to task completion. Furthermore, participants were asked to compare the anatomical model with existing fURS benchtop models (Cook Medical™ and Limbs & Things™) on several criteria, including internal visualization, tactile feedback, and overall functional and teaching fidelity, in a survey. Results: We were able to create a fURS simulator that accurately replicates anatomically complex renal collecting systems. In exploring the model, we noted that unlike staff urologists, novices and residents often completely missed lower pole calices. A survey comparison between our simulator and comparable benchtop simulators revealed consistently better ratings of our simulator on all criteria (p < 0.05). Conclusions: We were able to create an anatomically accurate fURS simulator that provides a more realistic scoping experience. Preliminary testing revealed that trainees will benefit from this simulator, particularly with respect to learning how to navigate challenging collecting systems.

Standardized Reporting of Machine Learning Applications in Urology: The STREAM-URO Framework.

The Standardized Reporting of Machine Learning Applications in Urology (STREAM-URO) framework was developed to provide a set of recommendations to help standardize how machine learning studies in urology are reported. This framework serves three purposes: (1) to promote high-quality studies and streamline the peer review process; (2) to enhance reproducibility, comparability, and interpretability of results; and (3) to improve engagement and literacy of machine learning within the urological community.

The role of bariatric surgery on kidney transplantation: A systematic review and meta-analysis.

INTRODUCTION: Obesity (body mass index [BMI] >35 kg/m2) remains a relative contraindication for kidney transplant, while patients after kidney transplantation (KTX) are predisposed to obesity. The present study aims to investigate the role of bariatric surgery in improving transplant candidacy in patients prior to KTX, as well its safety and efficacy in KTX patients postoperatively. METHODS: A systematic search was conducted up to March 2020. Both comparative and non-comparative studies investigating the role of bariatric surgery before or after KTX were considered. Outcomes included change in BMI, rates of mortality and complications, and the rate of patients who underwent KTX following bariatric surgery. Pooled estimates were calculated using the random effects meta-analysis of proportions. RESULTS: Twenty-one studies were eligible for final review; 11 studies investigated the role of bariatric surgery before KTX. The weighted mean BMI was 43.4 (5.7) kg/m2 at baseline and 33.9 (6.3) kg/m2 at 29.1 months followup. After bariatric surgery, 83% (95% confidence interval [CI] 57-99) were successfully listed for KTX and 83% (95% CI 65-97) of patients subsequently received successful KTX. Ten studies investigated the role of bariatric surgery after kidney transplant. Weighted mean baseline BMI was 43.8 (2.2) kg/m2 and mean BMI at 19.5 months followup was 34.2 (6.7) kg/m2. Overall, all-cause 30-day mortality was 0.5% for both those who underwent bariatric surgery before or after receiving a KTX. The results of this study are limited by the inclusion of only non-randomized studies, limited followup, and high heterogeneity. CONCLUSIONS: Bariatric surgery may be safe and effective in reducing weight to improve KTX candidacy in patients with severe obesity and can also be used safely following KTX.

Simulation-Based Percutaneous Renal Access Training: Evaluating a Novel 3D Immersive Virtual Reality Platform.

Introduction: Percutaneous nephrolithotomy (PCNL) is the gold standard treatment for patients with a large stone burden. There are a variety of methods to teach this important endourologic procedure, including simulation. We evaluated three different PCNL simulation platforms for potential use in teaching and assessing percutaneous renal access skills. Materials and Methods: Urology residents, fellows, and faculty were recruited to participate in this study, which included completing standardized tasks on three PCNL simulation platforms: a virtual reality (VR) simulator (PercMentor, 3D Systems™), a porcine tissue simulator (Cook™ Medical), and a new 3D immersive VR simulator-Marion K181 (Marion Surgical™). Participants were asked to complete a standardized task-gaining prone percutaneous renal access using a fluoroscopic-guided technique. Participants were asked to rate the simulators, and performance data were recorded for analysis. Results: A total of 18 participants with varying levels of PCNL experience completed the study. The Marion K181 had higher ratings by participants in all domains (realism, tactile feedback, instrument movement, renal anatomy, fidelity of simulation, utility as teaching tool) compared with the PercMentor (p < 0.05) but did not differ in any domain when compared with the porcine PCNL model. Participants felt that the Marion K181 was comparable with the porcine PCNL model as a teaching tool, but had the advantage of not requiring radiation exposure. Fluoroscopy time was the variable that most consistently correlated with participant PCNL experience and level of training, across all three PCNL simulation platforms. Conclusions: There are a variety of PCNL simulation platforms available for teaching percutaneous renal access skills. Based on our initial comparative study, there is validity evidence to support the use of the novel Marion K181 PCNL simulator as a training tool rather than higher fidelity models requiring real radiation exposure. However, evidence is yet lacking for its use as an assessment tool.

Performance assessment - The knowledge, skills and attitudes of surgical performance.

Pediatric surgical education has traditionally focused on the hard cognitive and psychomotor (technical) skills. While more and more attention is being paid to softer skills such as communication, collaboration, leadership, health advocacy, professionalism and scholarship, the bulk of curricula remain focused on the hard skills. An intricate part of education is the assessment of performance. This article reviews the current literature on the assessment of cognitive and psychomotor skills, focusing particularly on the assessment of technical skills in the realm of simulation.

Photoacoustic imaging of kidney fibrosis for assessing pretransplant organ quality.

Roughly 10% of the world's population has chronic kidney disease (CKD). In its advanced stages, CKD greatly increases the risk of hospitalization and death. Although kidney transplantation has revolutionized the care of advanced CKD, clinicians have limited ways of assessing donor kidney quality. Thus, optimal donor kidney-recipient matching cannot be performed, meaning that some patients receive damaged kidneys that function poorly. Fibrosis is a form of chronic damage often present in donor kidneys, and it is an important predictor of future renal function. Currently, no safe, easy-to-perform technique exists that accurately quantifies renal fibrosis. We describe a potentially novel photoacoustic (PA) imaging technique that directly images collagen, the principal component of fibrotic tissue. PA imaging noninvasively quantifies whole kidney fibrotic burden in mice, and cortical fibrosis in pig and human kidneys, with outstanding accuracy and speed. Remarkably, 3-dimensional PA imaging exhibited sufficiently high resolution to capture intrarenal variations in collagen content. We further show that PA imaging can be performed in a setting that mimics human kidney transplantation, suggesting the potential for rapid clinical translation. Taken together, our data suggest that PA collagen imaging is a major advance in fibrosis quantification that could have widespread preclinical and clinical impact.

Exploring the patterns of practice and satisfaction among female urologists in Canada.

INTRODUCTION: Our aim was to explore the satisfaction, personal and professional challenges, and practice barriers among female urologists in Canada. METHODS: A literature review was completed to design our survey. Trends with respect to career and personal satisfaction were identified, including academic advancement, mentorship, professional challenges, workplace discrimination, family satisfaction, and remuneration, among others. These key themes were formatted into 44 questions, translated into French, and distributed electronically as a survey to 80 female urology staff across Canada. RESULTS: Sixty (75.0%) women completed the survey. Many had been in practice <5 years (44.1%) and 72.9% completed a fellowship. Overall, 96.6% of women were very or somewhat satisfied with their career. Seeing more time-consuming patients and financial constraints within the healthcare system were the greatest source of dissatisfaction. Two-thirds of respondents reported that they received significant mentorship and 40% found it difficult to find a mentor during their training. Overall, 65.0% experienced gender discrimination, most commonly from a colleague or a patient. Women who practiced in the community were more likely to report experiencing discrimination compared to women practicing in an academic setting (78.1% vs. 51.9%; p=0.034). Mean time for maternity leave was 17.1 (±8.3) weeks, and 30.2% reported a pregnancy-related complication triggered by their work. Overall, 66.1% would choose urology again. CONCLUSIONS: It is important to advocate for the wellness of female urologists. To accomplish this, we need to address the challenges revealed in the survey, including supporting women on maternity leave, improving mentorship, and prioritizing female urology leadership initiatives. We have established a formal circle of support within the urology community in Canada to achieve these goals.

A Peritoneal Dialysis Access Quality Improvement Initiative: A Single-Center Experience.

Background:Little evidence exists regarding optimal peritoneal dialysis (PD) access insertion pathways, benchmarking for patency targets, and definitions of access dysfunction.Methods:This quality improvement (QI) project evaluated patients with PD catheters inserted at a single center in Toronto, Canada, following: establishment of PD catheter insertion protocols, a PD access coordinator, PD access operator training, and outcomes reporting. We define primary vs secondary PD catheter dysfunction by presentation before/after initial home PD treatment. We report catheter dysfunction rates, interventions restoring PD catheter patency (interventional radiology [IR] vs advanced laparoscopic [AL]) (embedded vs non-embedded) between 2012 and 2017.Results:A total of 297 first PD catheters were inserted between January 2012 and December 2017. Interventional radiology PD catheters (n = 94) were placed in older patients with greater comorbidities and less prior abdominal surgery than AL-placed catheters. Indications for IR insertion included need for urgent dialysis given resource availability (36.2% [n = 34]) and prohibitive surgical risk (26.6% [n = 25]). Interventional radiology-inserted catheters had overall (primary and secondary) dysfunction rates of 17%. Non-embedded AL catheters had 16.1% overall dysfunction. Embedded AL-inserted PD catheters had a 24.6% overall dysfunction rate. Among all dysfunctional catheters, IR manipulation was successful in 31% (n = 11), and surgical revision was necessary in all unsuccessful cases with either lysis of adhesions or omentopexy to establish patency.Conclusion:Our PD catheter QI initiative involved tracking, outcome reporting, defining PD catheter dysfunction and PD access insertion pathway development, yielding important insights into opportunities for program improvement. Multicenter research initiatives are needed to further improve PD access dysfunction definitions and to establish the best benchmarks for these metrics.

Routine Preoperative Electrocardiograms in Patients at Low Risk for Cardiac Complications During Shockwave Lithotripsy: Are They Useful?

INTRODUCTION: Routine preoperative electrocardiogram (ECG) before shockwave lithotripsy (SWL) is frequently performed despite recommendations against its use in asymptomatic patients undergoing low-risk surgical procedures. This study assesses whether routine preoperative ECG before SWL is useful in patients at low risk for cardiac complications. MATERIALS AND METHODS: A retrospective study of SWL at our center (2003-2013) reviewed all cardiac-related preoperative cancellations, intraoperative complications, postoperative admissions, and emergency department presentations in patients at low risk for cardiac complications. Patients received SWL with sedation and continuous five-lead ECG monitoring. RESULTS: Of 30,892 referrals, preoperative ECG triggered 13 (0.04%) cancelations in low-risk patients (1 with new atrial fibrillation and 12 with ischemia/previous infarction). Of these patients, 1 had a subsequent abnormal cardiac work-up and 11 underwent uncomplicated SWL without cardiac intervention (2 had unknown history). Of 27,722 treatments, 5 (0.02%) were stopped prematurely in low-risk patients because of arrhythmia (3 had normal preoperative ECG, 1 had abnormal ECG, and 1 did not complete ECG). Three patients developed an arrhythmia with sedation and 2 patients were admitted postoperatively because of cardiac complications (1 for atrial fibrillation and 1 for hypertension), of whom all had normal preoperative ECG. No patients presented to our emergency department with cardiac complications after SWL. CONCLUSIONS: In patients at low risk for cardiac complications, preoperative ECG triggered very few cancellations and did not predict early termination of treatment or cardiac complications after SWL. These findings suggest that in low-risk patients, routine preoperative ECG has little effect on treatment or complication rate and should be omitted.

Refinement in the analysis of motion within low-cost laparoscopic simulators of differing size: Implications on assessing technical skills.

BACKGROUND: Simulation is becoming more important in the teaching and assessment of technical skills. The purpose of this study was to refine the use of motion analysis parameters (MAPs) to assess performance of a defined task in low-cost pediatric laparoscopic simulators of differing size. METHODS: 105 participants performed a defined intracorporeal suturing task in large and small pediatric laparoscopic simulators. Outcomes included MAPs - path length, extreme velocity events, and extreme acceleration events in all available degrees of freedom for novices, intermediates, and experts. ANOVA p <0.05 was judged significant. RESULTS: In the smaller simulator, all MAPs discriminated between expertise groups in all degrees of freedom. In the larger simulator, all but one MAP discriminated between expertise groups. Experts demonstrated the greatest variability in performance between the larger and smaller simulators. CONCLUSION: Analysis of motion in the performance of a defined intracorporeal suturing task allowed discrimination between novices, intermediates, and experts in large and small low-cost pediatric laparoscopic simulators. Further refinement in MAPs will determine their role in surgical education. LEVEL OF EVIDENCE: Not applicable.

Intraoperative Radiographic Determination of Ureteral Length as a Method of Determining Ideal Stent Length.

INTRODUCTION: Accurate determination of ureteral length (UL) and appropriate stent length remains a challenge. The objective of this study was to describe an intraoperative technique to measure UL and determine appropriate stent length, and to compare this technique with other methods of determining appropriate stent length. METHODS: Patients undergoing ureteroscopy requiring postoperative stenting and who had a preoperative CT were prospectively identified. Gender, age, height, body mass index, L1 to L5 lumbar height on CT, and surgeon's estimate of UL were recorded. UL was measured using four methods: direct measurement with a ureteral catheter, ureteropelvic junction (UPJ) to ureterovesical junction distance on axial and coronal CT, and using a novel intraoperative radiographic technique. Radiographic measurement was performed using a radiographic nipple marker affixed to the skin over the ureteral orifice (UO) and an angiographic catheter with radiopaque markings at 1 cm intervals. UL was the distance from the UPJ to the marker at the UO measured using the catheter markers. Correlation between direct measurement and the recorded variables and methods of ureteral measurement were calculated. Stent length was chosen based on radiographic measurement. Stents were deemed of appropriate length if they showed a proximal coil in the renal pelvis and a distal coil in the bladder without crossing midline. RESULTS: Twenty-five ureters from 23 patients were included. Radiographically measured UL was strongly correlated with direct measurement. (r = 0.873, p < 0.01). Coronal and axial CT ULs were significantly associated with direct measurement (p < 0.05). Height, lumbar height, and surgeon's estimate of UL were not. Stents were deemed of appropriate length in 23/25 cases (92%). CONCLUSIONS: This new method for radiographic UL measurement is strongly correlated with directly measured UL. A length of stent chosen based on radiographic UL resulted in an appropriate stent length.

Analysis of motion in laparoscopy: the deconstruction of an intra-corporeal suturing task.

BACKGROUND: This study analyzes instrument motion for segments of a defined intra-corporeal suturing task in a laparoscopic simulator. We describe a system providing real-time velocity and acceleration assessment in the performance of this task. Analysis of the deconstructed task segments allows targeted assessment and teaching. METHODS: A traditional box trainer was fitted with a custom-built motion-tracking system. Participants were stratified into novice, intermediate and expert groups. They performed a defined intra-corporeal suturing task. Real-time data were collected in four degrees of freedom (DOFs) (Roll, Surge, Pitch, Yaw). The task was then deconstructed into four segments: loading needle/pull-through, double-throw knot, first single-throw knot, and second single-throw knot. Motion analysis parameters (MAPs) were studied for each DOF. RESULTS: Sixty-four participants were tested (14 novices, 19 intermediates, 31 experts). The largest difference in MAPs was seen in the 'double-throw knot' segment. MAPs for the 'loading needle/pull-through' segment revealed differences between novices and experts in Roll and Pitch DOFs only. For the 'first single knot' segment, similar MAP trends were noted across all DOFs, with significant differences between novices versus experts and intermediates versus experts. For the 'second single knot' segment, the difference in MAPs was preserved only for novices versus experts. CONCLUSIONS: By analyzing motion for a defined suturing task in a laparoscopic simulator, we can gain insight into the specific hand motions distinguishing experts from non-experts. Such information may allow teaching in a more focused, effective and efficient manner.

[Fundamentals of laparoscopic surgery in Colombia using telesimulation: an effective educational tool for distance learning]. / Fundamentos de cirugía laparoscópica en Colombia con telesimulación: una herramienta adicional para la formación integral de cirujanos.

INTRODUCTION: The Fundamentals of Laparoscopic Surgery program is an educational program developed by the Society of American Gastrointestinal Endoscopic Surgeons, which includes a handson skills training component, a cognitive component, and an assessment component for laparoscopic surgery. Its main objective is to provide surgical residents and practicing surgeons with the opportunity to learn fundamental skills and obtain the theoretical knowledge required to perform laparoscopic surgery, guaranteeing a better performance in the operating room, and thus, improving patient security. OBJECTIVE: The purpose of this study was to evaluate the effectiveness of telesimulation for teaching the Fundamentals of Laparosopic Surgery program in Colombia. MATERIALS AND METHODS: Twenty participants (ten general surgeons and ten general surgery residents) in two cities in Colombia participated in eight weekly telesimulation sessions. Fundamentals of Laparoscopic Surgery scores were obtained for each participant before the telesimulation sessions (pre-test scores) and after telesimulation training was completed (post-test scores). RESULTS: Using scoring parameters developed by the Society of American Gastrointestinal Endoscopic Surgeons, we found a significant improvement between pre-test and post-test scores. All the participants passed the skills component of the course. CONCLUSION: This study evidences the effectiveness of telesimulation to improve the laparoscopic skills of the participants who had no previous knowledge of the Fundamentals of Laparoscopic Surgery program, which guaranteed obtaining the necessary score for approving the practical component of the program.

Fundamentos de cirugía laparoscópica en Colombia con telesimulación: una herramienta adicional para la formación integral de cirujanos / Fundamentals of laparoscopic surgery in Colombia using telesimulation: an effective educational tool for distance learning

Introducción. El programa "Fundamentos de Cirugía Laparoscópica" es un módulo educativo desarrollado por la Society of American Gastrointestinal Endoscopic Surgeons, que incluye el desarrollo de habilidades prácticas y conocimientos teóricos en cirugía laparoscópica. Su misión principal es brindar a los residentes de las áreas quirúrgicas, y a los cirujanos en general, una herramienta adicional en su formación, para aprender los fundamentos y el conocimiento teórico necesario para la práctica de la cirugía laparoscópica, lo que garantizará un mejor desempeño en las salas de cirugía y, por ende, mayor seguridad para los pacientes. Objetivo. Evaluar la efectividad de la telesimulación para enseñar el componente práctico del programa "Fundamentos de Cirugía Laparoscópica" en Colombia. Materiales y métodos. Veinte participantes (10 cirujanos generales y 10 residentes de cirugía general) de dos ciudades de Colombia, participaron en ocho sesiones (una semanal) de entrenamiento en "Fundamentos de Cirugía Laparoscópica" mediante telesimulación. Se les hizo un examen práctico antes de las telesimulaciones, y un examen teórico y práctico, al final de las ocho sesiones. Resultados. Utilizando parámetros numéricos definidos por la Society of American Gastrointestinal Endoscopic Surgeons, se encontró diferencias significativas el examen previo y el posterior. El 100 % de los participantes aprobaron el componente práctico del programa. Conclusiones. Este estudio demuestra la efectividad de la telesimulación para mejorar las habilidades laparoscópicas de participantes sin conocimiento previo del programa "Fundamentos de Cirugía Laparoscópica", lo que garantizó obtener el puntaje necesario para aprobar la sección práctica del programa.

Introduction: The Fundamentals of Laparoscopic Surgery program is an educational program developed by the Society of American Gastrointestinal Endoscopic Surgeons, which includes a hands-on skills training component, a cognitive component, and an assessment component for laparoscopic surgery. Its main objective is to provide surgical residents and practicing surgeons with the opportunity to learn fundamental skills and obtain the theoretical knowledge required to perform laparoscopic surgery, guaranteeing a better performance in the operating room, and thus, improving patient security. Objective: The purpose of this study was to evaluate the effectiveness of telesimulation for teaching the Fundamentals of Laparosopic Surgery program in Colombia. Materials and methods: Twenty participants (ten general surgeons and ten general surgery residents) in two cities in Colombia participated in eight weekly telesimulation sessions. Fundamentals of Laparoscopic Surgery scores were obtained for each participant before the telesimulation sessions (pre-test scores) and after telesimulation training was completed (post-test scores). Results: Using scoring parameters developed by the Society of American Gastrointestinal Endoscopic Surgeons, we found a significant improvement between pre-test and post-test scores. All the participants passed the skills component of the course. Conclusion: This study evidences the effectiveness of telesimulation to improve the laparoscopic skills of the participants who had no previous knowledge of the Fundamentals of Laparoscopic Surgery program, which guaranteed obtaining the necessary score for approving the practical component of the program.

Development and validation of a pediatric laparoscopic surgery simulator.

BACKGROUND: Although a validated simulator exists for adult laparoscopy, there is no pediatric counterpart. The objective of this study is to develop and validate a pediatric laparoscopic surgery (PLS) simulator. METHODS: A PLS simulator was developed. Participants were stratified according to level of expertise and tested on the fundamentals of laparoscopic surgery (FLS) and PLS simulators. A subsequent group was tested exclusively on the PLS simulator. RESULTS: The PLS intracorporeal suturing score was lower than its adult counterpart (P = .02). The PLS pattern-cutting score was higher than in the FLS simulator (P < .001). If the latter was eliminated from the calculation, the revised total FLS score was significantly better than the revised PLS score. When all participants were combined, total PLS scores as well as performance on 3 of 5 tasks allowed differentiation between novice, intermediate, and expert. CONCLUSIONS: The PLS simulator was able to discriminate between the novice, intermediate, and expert using the total PLS score and the performance on 3 of the 5 tasks, thus providing evidence for construct validity. The other 2 tasks will require formal modification or a change in the scoring metrics to establish their independent construct validity.

Endothelial cell morphologic response to asymmetric stenosis hemodynamics: effects of spatial wall shear stress gradients.

Endothelial cells are known to respond to hemodynamic forces. Their phenotype has been suggested to differ between atheroprone and atheroprotective regions of the vasculature, which are characterized by the local hemodynamic environment. Once an atherosclerotic plaque has formed in a vessel, the obstruction creates complex spatial gradients in wall shear stress. Endothelial cell response to wall shear stress may be linked to the stability of coronary plaques. Unfortunately, in vitro studies of the endothelial cell involvement in plaque stability have been limited by unrealistic and simplified geometries, which cannot reproduce accurately the hemodynamics created by a coronary stenosis. Hence, in an attempt to better replicate the spatial wall shear stress gradient patterns in an atherosclerotic region, a three dimensional asymmetric stenosis model was created. Human abdominal aortic endothelial cells were exposed to steady flow (Re=50, 100, and 200 and tau=4.5 dyn/cm(2), 9 dyn/cm(2), and 18 dyn/cm(2)) in idealized 50% asymmetric stenosis and straight/tubular in vitro models. Local morphological changes that occur due to magnitude, duration, and spatial gradients were quantified to identify differences in cell response. In the one dimensional flow regions, where flow is fully developed and uniform wall shear stress is observed, cells aligned in flow direction and had a spindlelike shape when compared with static controls. Morphological changes were progressive and a function of time and magnitude in these regions. Cells were more randomly oriented and had a more cobblestone shape in regions of spatial wall shear stress gradients. These regions were present, both proximal and distal, at the stenosis and on the wall opposite to the stenosis. The response of endothelial cells to spatial wall shear stress gradients both in regions of acceleration and deceleration and without flow recirculation has not been previously reported. This study shows the dependence of endothelial cell morphology on spatial wall shear stress gradients and demonstrates that care must be taken to account for altered phenotype due to geometric features. These results may help explain plaque stability, as cells in shoulder regions near an atherosclerotic plaque had a cobblestone morphology indicating that they may be more permeable to subendothelial transport and express prothrombotic factors, which would increase the risk of atherothrombosis.

The development of 3-D, in vitro, endothelial culture models for the study of coronary artery disease.

The response of the vascular endothelium to wall shear stress plays a central role in the development and progression of atherosclerosis. Current studies have investigated endothelial response using idealized in vitro flow chambers. Such cell culture models are unable to accurately replicate the complex in vivo wall shear stress patterns arising from anatomical geometries. To better understand this implication, we have created both simplified/tubular and anatomically realistic in vitro endothelial flow models of the human right coronary artery. A post-mortem vascular cast of the human left ventricular outflow tract was used to create geometrically accurate silicone elastomer models. Straight, tubular models were created using a custom made mold. Following the culture of human abdominal aortic endothelial cells within the inner lumen, cells were exposed to steady flow (Re = 233) for varying time periods. The resulting cell morphology was analyzed in terms of shape index and angle of orientation relative to the flow direction. In both models a progressive elongation and alignment of the endothelium in the flow direction was observed following 8, 12, and 24 hours. This change, however, was significantly less pronounced in the anatomical model (as observed from morphological variations indicative of localized flow features). Differences were also observed between the inner and outer walls at the disease-prone proximal region. Since morphological adaptation is a visual indication of endothelial shear stress activation, the use of anatomical models in endothelial genetic and biochemical studies may offer better insight into the disease process.