DESIGN AND STUDY OF DIFFERENT PVDF STRUCTURES

Introduction

Tissue engineering (TE) is a promising technology that can develop structures very similar to native tissues to improve or replace their biological functions. Polyvinylidene fluoride (PVDF) is a new thermoplastic polymer widely used in biomedical applications. Each structure of PVDF has different mechanical and biological characteristics depending on its morphology and the methodology employed.

Methods

Doctor blade, salt leaching, and electrospinning methodologies were used to design different PVDF structures, including films, porous membranes, and electrospun membranes, respectively. Furthermore, electrospun PVDF membranes were developed according to the direction of the strands, obtaining membranes that were oriented as well as with random orientation. All these morphologies were subjected to mechanical, cytotoxicity and degradation studies.

Results

All PVDF morphologies underwent a minimum modification of 16% with respect to their original size. The porous membranes were the most fragile structures, and the electrospun membranes were the most resistant. According to ISO standard 10993–5, a material is considered to be biocompatible when the values are higher than 70%, and all PVDF morphologies had cell viability values above the 70% threshold. Finally, results showed that there was no degradability, regardless of the method or structure designed.

Conclusions

PVDF is a material with good mechanical characteristics, given that structures designed with electrospinning can withstand more stress. In addition, this material is non-degradable and biocompatible, broadening the range of biomedical and TE applications.

INITIAL EVALUATION OF A REAL-TIME ERGONOMIC POSTURE ASSESSMENT SYSTEM IN LAPAROSCOPIC SURGERY

Introduction

The objective of this study is to perform an initial evaluation of a system for assessment and visual feedback of the surgeon's posture during laparoscopic practice.

Methods

In order to monitor the surgeon's posture, we used the XSens motion tracking system. The neck, shoulder, elbow, and wrist joints were analyzed during laparoscopic practice. A visual feedback method was designed using Unity3D which indicates in real time if any of the analyzed joints suffers from an inadequate posture, allowing for its possible correction. The system was evaluated with a group of seven novice laparoscopic surgeons who performed several repetitions of two basic training tasks (eye-hand coordination and transfer). The participants were randomly organized into group A (4 subjects), who received visual feedback, and group B (3 subjects), as a control group.

Results

Regarding the coordination task, group A exhibited lower ergonomically inappropriate posture time for the left shoulder and elbow, being significant for the left shoulder posture. Similarly, this group showed a positive evolution during the training process for the different joints. Regarding the transfer task, both groups presented a positive evolution.

Conclusions

Preliminary results show that the presented method allows novice surgeons to improve their posture during laparoscopic practice. The use of the non-dominant hand and the complexity of the task seem to be conditioning aspects in the surgeon's ergonomics.

ROBOTIC PLATFORMS FOR MICROSURGERY: A SYSTEMATIC REVIEW

Introduction

Microsurgery involves procedures that demand maximum precision and dexterity, as well as the absence of tremor. In this regard, new robotic-assisted microsurgery solutions have emerged in recent years. The objective of this review is to analyze the current status of the robotic platforms in microsurgery.

Methods

This systematic review has been focused on the PubMed database over the last seven years (2015–2022), using keywords related to robotic platforms for microsurgery. Articles including clinical/preclinical studies were considered, and non-English language articles, abstracts, conference proceedings, reviews and letters were excluded.

Results

A total of 324 articles were identified, 27 of which passed the eligibility criteria.

Of the 14 platforms analyzed, da Vinci, MM3 and the easyMicro prototype incorporate their own vision system. The majority of the systems have tremor filtering and provide haptic feedback. The da Vinci system is the most widely used system in vascular and nerve microsurgery, reconstructive and lymph node dissection, eye surgery and urology. The MUSA and Symani systems have been used in reconstructive supermicrosurgery, the neuroarm in neurosurgery, the Surgical Robotic System and the easyMicro prototype in reconstructive and ocular surgery. The MM-3 (vascular), SMART (ocular) and smartARM (neurosurgery) have been tested in artificial models.

Conclusions

Among the platforms analyzed, da Vinci was the most widely used, specifically in ocular and reconstructive surgery. MUSA and neuroARM are rapidly progressing in reconstructive microsurgery and neurosurgery, respectively.

DESIGN AND STUDY OF DIFFERENT SILK FIBROIN STRUCTURES

Introduction

Tissue engineering (TE) has the capacity to design structures very similar to native tissues in order to restore, maintain or improve their biological functions. Silk fibroin (SF) is a natural protein that has been used in a wide variety of TE applications. Each SF structure has different mechanical and biological characteristics depending on the morphology and methodology employed.

Methods

Bombyx mori silkworm cocoons were extracted and processed to obtain SF. Subsequently, films, porous membranes, and electrospun membranes were designed using doctor blade, salt leaching, and electrospinning methodologies, respectively. Furthermore, electrospun SF membranes were developed according to the direction of the strands, obtaining membranes that were oriented as well as with random orientation. All these morphologies were subjected to mechanical, cytotoxicity and degradation studies.

Results

The most fragile SF structures were the films and the porous membranes, which underwent a maximum modification of approximately 5% with respect to their original size. However, electrospun membranes underwent a change in size of more than 20%. All SF morphologies had biocompatibility values close to 100%. Finally, there was a degradability between 3–5% at 4 weeks in all structures.

Conclusions

SF has very good mechanical characteristics when designed by electrospinning techniques. Although SF is biocompatible, there is a degradation of the material, which may affect the mechanical properties of the designed structure.

Development and assessment of an ex-vivo bench model aimed at laparoscopic ureteric reconstructive techniques

INTRODUCTION/BACKGROUND

Reconstructive and ablative urologic techniques require special technical mastery, especially the intracorporeal suturing.

OBJECTIVE

To report the subjective evaluation of a versatile ex-vivo model aimed to practice laparoscopic ureteric reconstructive techniques (LURT) on box-trainer.

STUDY DESIGN

The model is a continuous portion of porcine urinary bladder ("dilated pelvis"), the vesico-ureteral joint ("stenosis") and healthy ureter. All 127 participants (n = 119 urologists and n = 8 paediatric surgeons) performed on the model laparoscopic Anderson-Hynes dismembered pyeloplasty, and then, in the animal model, different LURT procedures (ureteroneocystostomy, ureteric reimplantation and/or dismembered pyeloplasty). The model was subjectively evaluated (face and content validity), through a 12 items questionnaire, based on a Likert scale (1-5 points) and a global question (1-10 points).

RESULTS

The total mean rating for 11/12 items was very high (>4points). Only one was rated under 3 points. The overall total mean rating from 1 to 10 points was very high (9.19 ± 0.82 points). In 10/12 items, expert's feedback (content validity) prevailed over non-experts (face validity).

DISCUSSION/CONCLUSION

The model was highly accepted for the practice of LURT techniques. Additionally, it is cost-effective, easy to assemble, ethically considerate, and realistic.

HEPARIN AS AN ANTIBACTERIAL COATING ON BIODEGRADABLE URETERAL STENTS: EXPERIMENTAL STUDY OF BRAIDSTENT®-H

INTRODUCTION

The aim of this study is to assess the effectiveness of heparin to inhibit the development of early bacteriuria as a coating for biodegradable ureteral stents.

MATERIAL AND METHODS

The BraidStent®-H biodegradable stent, whose heparin coating is incorporated by dip coating, was chosen for this study. Twenty-four swine were randomly divided into two groups: 12 animals underwent unilateral placement of the BraidStent®-H and 12 were fitted with a standard double-j stent (DJS). Bacteriuria is comparatively analyzed over time by consecutive urine sampling at 0, 1, 3, 6, 12, 24 and 48 hours. In addition, the concentration of heparin released in vitro in artificial urine at 0, 3, 6, 12, 24, 48, 72, 92 and 120 hours is determined via ELISA.

RESULTS

BraidStent®-H generates a significantly lower bacteriuria rate than a DJS at 6 and 12 hours. Heparin coating shows a significant delaying effect on the onset of bacteriuria, reaching 100% of the animals at 48 hours, compared to the DJS, which takes place at 6 hours. ELISA results reveal the presence of heparin in urine for a total of 72 hours. The coating does not affect the degradation of the device, which is completed at 6 weeks.

CONCLUSIONS

Heparin evidences an effective inhibition of early bacteriuria, showing its potential as an antibacterial coating for biodegradable ureteral stents. Future studies should focus on the development of long-term heparin coatings for biodegradable materials.

EVALUATION OF THE RELEASE RATE OF A CHEMOTHERAPEUTIC AGENT INCORPORATED AS A COATING ON A BIODEGRADABLE URETERAL STENT. IN VITRO STUDY

INTRODUCTION

To assess the release rate of Mitomycin C (MMC) after its adherence to a biodegradable ureteral stent (BraidStent™-MMC) by dip coating in order to evaluate its potential application as an adjuvant treatment for upper tract urothelial carcinoma.

MATERIAL AND METHODS

The dip coating technique is applied to a total of 10 fragments of the BraidStent™ catheter which has a polymeric matrix as a coating. Each 3 cm fragment is immersed 10 times in pure MMC crystallising in methanol and finally obtaining the formation of microlayers on its surface. After drying, each fraction of the stent is immersed in 5 ml of artificial urine to study its interaction with this medium. The samples remain in an orbital shaker at 36ºC and the medium is exchanged under sterile conditions after 12, 24, 48, 48, 72, 96 and 120h. At each replacement, the remaining urine is analysed by HPLC-DAD to quantify the presence of the cytotoxic agent.   

RESULTS

During the first 12h, MMC is completely released reaching a mean concentration of 52.22 mg/L. Comparing this result with those previously obtained with the first BraidStent ™ -MMC formulation (10.82mg/L), it is determined that this technique allows to increase the release rate up to 5 times.

CONCLUSIONS

The release rate of Mitomycin C from a biodegradable ureteral stent is increased by integrating a polymeric matrix with microlayers in its coating. Further trials are needed to achieve the therapeutic dose for clinical application in oncology patients.

TOWARDS AN UNIFIED FRAMEWORK FOR VALIDATING DEEP LEARNING METHODS FOR COLORECTAL POLYPS: FIRST STEPS

INTRODUCTION

Deep learning techniques have significantly contributed to the field of medical imaging analysis. In case of colorectal cancer, they have shown a great utility for increasing the adenoma detection rate at colonoscopy, but a common validation methodology is still missing. In this study, we present preliminary efforts towards the definition of a validation framework.

MATERIAL AND METHODS

Different models based on different backbones and encoder-decoder architectures have been trained with a publicly available dataset that contains white light and NBI colonoscopy videos, with 76 different lesions from colonoscopy procedures in 48 human patients. A computer aided detection (CADe) demonstrator has been implemented to show the performance of the models.

RESULTS

This CADe demonstrator shows the areas detected as polyp by overlapping the predicted mask on the endoscopic image. It allows selecting the video to be used, among those from the test set. Although it only present basic features such as play, pause and moving to the next video, it easily loads the model and allows for visualization of results. The demonstrator is accompanied by a set of metrics to be used depending on the aimed task: polyp detection, localization and segmentation.

CONCLUSIONS

The use of this CADe demonstrator, together with a publicly available dataset and predefined metrics will allow for an easier and more fair comparison of methods. Further work is still required to validate the proposed framework.

Mimicking physiological O2 tension in the female reproductive tract improves assisted reproduction outcomes in pig

STUDY QUESTION

Is O2 tension in the pig oviduct and uterus affected by the estrous cycle stage and the animal's age, and can the outcome of in vitro embryo development be improved by mimicking these physiological values?

SUMMARY ANSWER

O2 tension within the pig reproductive organs is affected by the animal's age, and values close to those measured in vivo have a positive impact on embryo development and quality when used during IVF and embryo culture (EC).

WHAT IS KNOWN ALREADY

To obtain a healthy embryo in vitro, it is necessary to adopt a culture microenvironment that approximates physiological conditions. Despite advances in surgical procedures and sensitive probes that allow accurate assessment of in vivo O2 tension, few such studies have been conducted recently in mammals. In addition, no reference values of physiological O2 tension in the reproductive tract exist for large animal models such as pig, and the effect of O2 tension on ART outcomes is unknown.

STUDY DESIGN, SIZE, DURATION

This study was conducted in pigs. We measured oviductal and uterine O2 tension (n = 29 and 13, respectively) and then examined how the use of the physiological values in pig IVF and EC affected pig ART output (n = 1447 oocytes).

PARTICIPANTS/MATERIALS, SETTING, METHODS

The oviductal and uterine O2 tension at the different stages of the estrous cycle was monitored using a laparo-endoscopic single-site surgery (LESS) assisted approach along with a flexible and thin miniaturized luminescent probe. Two groups of pigs, Large-white × Landrace breed, were used: for the first group, 16 pre-pubertal gilts (5 months old and 95 kg) were induced to ovulate with equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG); in the second group 13 mature sows (24-48 months and 185 kg) were used. IVF and EC were performed at two different O2 tensions: Atmospheric O2 (20%) and the mean in vivo value measured (7%). At 18-20 h post-insemination (hpi), a small sample of presumptive zygotes were fixed, stained and examined under epifluorescence microscopy to assess the fertilization rates. At 48 hpi, cleavage was evaluated under the stereomicroscope. Finally, at 180 hpi, development to the blastocyst stage was quantified, blastocyst morphology was assessed, and embryos were fixed and stained to count the mean cell number per blastocyst.

MAIN RESULTS AND THE ROLE OF CHANCE

The mean O2 content within the pig oviduct and uterus was always lower than in ambient air. The average O2 percentage was higher in gilts (10.0%) than in sows (7.6%) (P < 0.0001). The cleavage rate of porcine in vitro fertilized embryos maintained under 7% O2 during IVF and EC was significantly higher (60.0 ± 2.3) compared with those cultured under 20% O2 (32.0 ± 2.2) (P < 0.05). An increase in the number of cells in embryos cultured under the low O2 concentration (88.9 ± 5.9) was observed compared to those cultured under 20% O2 (59.0 ± 5.0) (P < 0.05).

LARGE SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

Although minimally invasive surgery was used the effect of anesthesia and manipulations on O2 tension within the organs are unknown.

WIDER IMPLICATIONS OF THE FINDINGS

Using physiological oxygen concentrations in IVF/EC could improve ART outcomes.

STUDY FUNDING AND COMPETING INTEREST(S)

This study was funded by Spanish Ministry of Economy and Competitiveness (MINECO) and European Regional Development Fund (FEDER). Grants AGL2012-40180-C03-01 and AGL2015-66341-R. The authors declare no conflict of interest.

[Proposed experimental model to provide training in the management of anesthesia in liver transplantation]

OBJECTIVE

To propose and evaluate the use of a porcine model for training in how to manage and improve the quality of anesthesia during liver transplantation.

MATERIAL AND METHODS

Five trained anesthesiologists who had no previous experience in managing anesthesia during liver transplantation and who did not work in hospitals where the procedure was performed volunteered for the training course and evaluated it. Each trainee anesthetized 5 animals. Surgery was performed under total balanced anesthesia with monitoring of hemodynamics, ventilation, biochemistry, arterial blood gases, and coagulation. Previously set criteria were used to evaluate the trainees' skill in maintaining patient stability. Their work was assessed 7 times: at baseline, 15 minutes into the preanhepatic phase, at the end of the preanhepatic stage, 15 minutes into the anhepatic phase, at the end of the anhepatic phase, 15 minutes into the postanhepatic phase, and at the end of the postanhepatic phase. After completing the course, the trainees filled in a questionnaire to evaluate its usefulness. Analysis of variance was applied to score changes in anesthetic quality criteria.

RESULTS

After implantation, changes in metabolic (acidosis) and cardiac (hypotension and bradycardia) status were the most critical abnormalities the trainees faced. Their skill in coping with hemodynamic and metabolic changes improved significantly (P<.05). All participants expressed a preference for receiving training in a porcine model before providing anesthesia in this surgical setting.

CONCLUSIONS

Under this training model, the anesthesiologists understood and were able to manage the hemodynamic and physiologic changes that develop during a liver transplant procedure. We believe that training using a porcine model allows an anesthesiologist to acquire experience and skill in this setting.

Modelos experimentales en la cirugía laparoscópica urológica

We present the experience of the Minimally Invasive Surgery Centre (MISC) in the development of a modular training model in laparoscopic surgery. The experience analysis includes the description of the training objectives, the learning process of simple and advance laparoscopic urologic techniques, as well as some current and future considerations before applying the laparoscopic techniques. This learning program pretends to optimize the knowledge of the surgeon and the clinical practice of these surgical techniques. The phases of the learning process have been classified in four levels, which include different modules and models and whose application will depend on the experience and surgical skills. This pyramidal training system permits the student to advance step by step through each level depending on her surgical skills. We have presented our experience in twelve courses about laparoscopic urology and four courses of laparoscopic radical prostatectomy, in which more than 300 urologists have assisted. Furthermore, some Spanish Urology Units have been developing special experimental training programs on laparoscopic radical prostatectomy, partial nephrectomy or laparoscopic dismembered pyeloplasty with Anderson-Hynes technique. It has been previously described that laparoscopic modular learning constitutes a very useful concept to avoid problems related to an incomplete and incorrect learning process. Also it seems clear that the laparoscopic training reduces the learning curve in laparoscopic urologic techniques.

Histopathologic features of the vagus nerve after electrical stimulation in swine

This paper describes the histological features of the vagus nerve after its stimulation with an electrostimulation system that is being developed for morbid obesity treatment. An electrostimulation system was implanted laparoscopically around the ventral vagal trunk of five Large White female pigs (49.63+/-1.94 kg.). Vagal nerve stimulation was performed by continuous constant voltage current pulses. Thoracic samples of both ventral and dorsal vagal trunks were obtained thoracoscopically one month after implantation. Animals were sacrificed one month after thoracoscopic vaguectomy. Tissue samples were then harvested from the vagal nerve at the implantation site, 1cm cranial to it, thoracic portion of ventral and dorsal vagal trunks, sub-diaphragmatic dorsal vagal trunk, left and right vagus nerves. Specimens were analysed with light microscope. The severity of the lesions was graded from 0 to 4 (0: no lesion, 1: mild, 2: moderate, 3: severe and 4: extremely severe), taking into account fibrosis, vascularization, necrosis, fiber degeneration and inflammation. Electrode implantation resulted in thickened epineurium and endoneural connective tissue. The greatest lesion score was evidenced at the leads implantation site in the ventral vagal trunk, followed by, in order of decreasing lesion severity, left vagus nerve, thoracic portion of ventral vagal trunk, subdiaphragmatic dorsal vagal trunk, thoracic portion of dorsal vagal trunk and right vagus nerve. The stimulation device used in this study caused connective tissue growth, greatest in the samples located closer to the implantation site. However, there was no sign of altered vascularization in any studied specimen.

[Diagnosis and follow up with endoluminal ultrasound in the endourologic treatment of experimental ureteral stenosis]

OBJECTIVES

The objective of this study is to determine the utility and reliability of endoluminal sonography transducer in the diagnosis and follow up after the treatment of partial ureteral obstruction.

MATERIAL AND METHODS

Ten healthy Large White female pigs, weighing 35-40 Kg, were induced a partial ureteral obstruction by laparoscopic approach. All the studied animals underwent the same three-phase procedure; inducement (phase 1), diagnosis (phase 2) and treatment of experimental strictures (phase 3), as well as, a month follow up. In all the stages of the study endoluminal sonography was used to diagnose the stricture and to assess the treatment, as well as, to measure the internal ureter diameter.

RESULTS

The endoluminal ultrasonography was able to assess, in all the cases, the affectation of all the ureteral layers. All the animals develop a ureteral stricture after a four weeks ligature and, except in one animal, they progress favourably after the treatment using the balloon rupture technique of the stricture ureter. The means of the ureteral diameter are: phase 1 (0.46 +/- 0.10 cm), phase 2 (0.30 +/- 0.17 cm), phase 3 (0.47 +/- 0.13 cm).

CONCLUSIONS

The use of the IVUS in the diagnosis of ureteral strictures results safe and useful, as well as, its application in the election and in the assessment of the treatment.