Comparing machine learning algorithms for non-invasive detection and classification of failure in piezoresistive bone cement via electrical impedance tomography.

At an estimated cost of $8 billion annually in the United States, revision surgeries to total joint replacements represent a substantial financial burden to the health care system and a tremendous mental and physical burden on patients and their caretakers. Fixation failures, such as implant loosening, wear, and mechanical instability of the poly(methyl methacrylate) (PMMA) cement, which bonds the implant to the bone, are the main causes of long-term implant failure. Early and accurate diagnosis of cement failure is critical for developing novel therapeutic strategies and reducing the high risk of a misjudged revision. Unfortunately, prevailing imaging modalities, notably plain radiographs, struggle to detect the precursors of implant failure and are often interpreted incorrectly. Our prior work has shown that the modification of PMMA bone cement with low concentrations of conductive fillers makes it piezoresistive and therefore self-sensing. When combined with a conductivity imaging modality such as electrical impedance tomography (EIT), it is possible to monitor load transfer across the PMMA using cost-effective, physiologically benign, non-contact, and real-time electrical measurements. Despite the ability of EIT for monitoring load transfer across self-sensing PMMA bone cement, it is unable to accurately characterize failure mechanisms. Overcoming this challenge is critical to the success of this technology in practice. Therefore, we herein expand upon our previous results by integrating machine learning techniques with EIT for cement condition characterization with the goal of establishing the feasibility of even off-the-shelf machine learning algorithms to address this important problem. We survey a wide variety of different machine learning algorithms for application to this problem, including neural networks on voltage readings of an EIT phantom for tracking the spatial position of a sample, specifying defect orientation within a sample, and classifying defect types, including cracks and delaminations. In addition, we explore the utilization of principal component analysis (PCA) for pre-treating impedance signals in each of these problems. Within the tested algorithms, our results show clear advantages of neural networks, support vector machines, and K-nearest neighbor algorithms for interpreting EIT signals. We also show that PCA is an effective addition to machine learning. These preliminary results demonstrate that the combination of smart materials, EIT, and machine learning may be a powerful instrumentation tool for diagnosing the origin and evolution of mechanical failure in joint replacements.

Preparation of a pig experimental model of defective colon anastomosis - review.

Anastomotic leak is a serious complication in colorectal surgery. The problem of intestinal anastomosis healing disorders is dealt with by a number of experimental studies, especially in applied research. The design of animal models is diverse and the results of individual studies are difficult to compare. This paper summarizes the main issues of planning animal models of intestinal anastomoses, which are discussed individually. The main part of the text is a description of the defective intestinal anastomosis model of the pig. The anastomosis is constructed in the model with a localized mucosal protrusion. The animals are monitored for 3 weeks postoperatively, the clinical condition and changes in vital values and laboratory parameters are monitored, and CT examinations are performed at defined points. At the end of the observation period, samples are taken, macroscopic findings in the abdominal cavity are evaluated, adhesions are scored, and signs of leakage or passage disorders are assessed. The preparations are evaluated histologically both by standard methods analyzing vascularity, inflammatory infiltration and the proportion of collagen, and by methods developed de novo for the needs of the experiment, such as the analysis of the integrity of the intestinal wall at the site of the mucosal protrusion. We value the experimental model for the possibility of a systematic and detailed analysis of the healing state of the anastomosis in combination with a detailed observation protocol, which produces clinically relevant results.

Intestinal Anastomotic Healing: What do We Know About Processes Behind Anastomotic Complications.

Colorectal surgery has developed rapidly in the recent decades. Nevertheless, colorectal anastomotic leakage continues to appear postoperatively in unpleasant rates and leads to life-threatening conditions. The development of valid complication-preventing methods is inefficient in many aspects as we are still lacking knowledge about the basics of the process of anastomotic wound healing in the gastrointestinal tract. Without the proper understanding of the crucial mechanisms, research for prevention of anastomotic leakage is predestined to be unsuccessful. This review article discusses known pathophysiological mechanisms together with the most lately found processes to be further studied. The aim of the article is to facilitate the orientation in the topic, support the better understanding of known mechanisms and suggest promising possibilities and directions for further research.

Spontaneous retroperitoneal bleeding in COVID-19 patients - two case reports.

INTRODUCTION: COVID-19 disease is associated with a high risk of thromboembolic events, especially in patients with a severe course of the disease. At the same time, however, there is a risk of bleeding. These complications have a significant impact on patient morbidity and mortality. Thus, determining an optimal approach to thromboembolic disease prophylaxis can be challenging. CASE REPORTS: This paper presents two cases of polymorbid female patients suffering from COVID-19. Both patients experienced retroperitoneal hemorrhage while on low molecular weight heparins in the process of deintensification of the treatment of their moderate to severe disease. Although both patients were treated surgically with a good local effect on the hemorrhage, their deterioration progressed, finally resulting in death in both the cases. CONCLUSION: Despite the proven benefit of prophylaxis of thromboembolic events using low molecular weight heparins in patients with COVID-19, care should be taken to monitor coagulation laboratory parameters in proper time intervals. The risk of a fatal course of bleeding complications is extremely high in critically ill patients and patients with multiple comorbidities.

Tumor mimicking gastric ulcer penetrating asymptomatically into the pancreas.

Gastroduodenal ulcer disease is characterized by ulceration of the stomach or duodenum, with ulcer lesions occurring more frequently in the duodenum. Serious complications of this disease include bleeding, perforation of the ulcer and penetration into surrounding organ. Our report presents the case of an older man who had a gastric ulcer penetrating into the pancreas. This was not diagnosed at the time of the penetration. The patient came to our care for recurrent hematemesis without a proven source of bleeding. During the diagnostic process, the presence of an intramural gastric tumor was suspected. An excision of the suspected lesion was successfully performed at our clinic, followed by histological confirmation of perforated ulcer. The postoperative course was complicated by the development of a pancreatic fistula. However, conservative treatment resulted in complete recovery of the patient.

Permanent intravenous access in experimental surgery ­ our experience

Introduction: Permanent intravenous access is usually required in pigs used for surgical experiments, not only to enable repeated blood sample collections. The aim of this study was to evaluate the patency and complications of vascular access ports (VAP) implanted in pigs included in different surgical experiments. Methods: VAPs were implanted via the external jugular vein in a total of 211 pigs from 7 different experiments. All observed complications were retrospectively evaluated. Results: No complications were observed in 157 animals (74.4%). Complications of the least severity were edema or seroma around the port which were observed in 12 (5.7%) and 3 (1.4%) animals, respectively. Temporary problems with aspiration of blood via the port occurred in 13 animals (6.2%). The most severe complications which prevented the use of the VAP for aspiration and application were recorded in 26 animals (12.3%). These complications included: abscess formation around the port (12 animals), skin necrosis over the port (2 animals), partial wound dehiscence (2 animals) and loss of the VAP function due to an unspecified cause (10 animals). Removal of the VAP was not needed in any of the animals and none of the animals had to be excluded from the experiment due to the complications. The VAP can also be used for safe administration of iodine contrast agent during CT examination. Conclusion: Despite the observed complications the VAP is suitable as permanent intravenous access in pigs used for surgical experiments. This method helps to minimize the stress of the animals in the postoperative period and to reduce the number of experimental animals.

Benign liver angiomyolipoma: a case study.

INTRODUCTION: Hepatic angiomyolipoma is a rare mesenchymal tumor. It consists of vessels, fatty tissue and muscle tissue. These can appear in various ratios. While the kidney is the most common localization of angiomyolipoma, only about 300 cases have been described in the liver so far. It is a tumor of uncertain behavior. Most of the patients suffering from the lesion is asymptomatic. It is often preoperatively misdiagnosed using various imaging methods given its similarity to other hepatic tumors. CASE REPORT: Our 64 years old female patient was being examined for dull abdominal pains with no other symptoms. Her close relatives suffered from no malignancies. Imaging exams showed a liver lesion highly suspicious for hepatocellular carcinoma. However, the patient showed no elevation of typical oncomarkers. We performed left lateral sectionectomy. A grey solid focal lesion was found in the resected tissue. Histological and immunohistochemical evaluation determined the diagnosis of angiomyolipoma. The postoperative period was uncomplicated. The patient has been followed at an office for hepato-pancreato-biliary diseases, with no signs of recurrence until the present. CONCLUSION: Hepatic angiomyolipoma is a rare disease. The diagnostic process can be challenging as illustrated by the presented case. Even though the working diagnosis proved false, the chosen treatment was appropriate and delivered good results. Long-term postoperative follow-up is required.

Acute abdomen in pregnancy: a retrospective study of pregnant patients hospitalised for abdominal pain.

INTRODUCTION: Abdominal emergencies occur in pregnant women with the rate of 1:500635 pregnancies. Such conditions usually develop from full health and worsen rapidly. Symptoms are often similar to those in physiological pregnancy (abdominal pain, vomiting, constipation). The diagnostic process is thus difficult and both the mother and her child are at risk. Our aim was to evaluate the frequency of abdominal emergencies in the Department of Surgery, University Hospital in Pilsen and to consider their impact on pregnancy and on the newborn. METHODS: We acquired a set of patients by retrograde collection of data. We searched for pregnant patients suspected of developing an abdominal emergency admitted to the Department of Surgery, Faculty of Medicine, Pilsen between 2004 and 2015. We evaluated a number of clinical signs to statistically describe the set. RESULTS: The set included 121 patients; 42 of the patients underwent a surgical procedure and 79 received conservative treatment. 38 patients underwent appendectomy; 6 appendixes were with no pathologies. McBurneys incision was an approach of choice in most cases. The most frequent symptom was pain in the right lower abdominal quadrant. The foetus has been lost in none of the cases. CONCLUSION: Acute appendicitis was the most frequent abdominal emergency in our set and also the most frequent reason for surgical intervention. The most specific sign was pain in the right lower abdominal quadrant. No impact of appendicitis or appendectomy on the health of the newborn has been observed. Even though abdominal emergencies in pregnancy are relatively rare, the results of the department are very good.

Repopulation of decellularized pig scaffolds: Promising approach for liver tissue engineering.

Repopulation of decellularized tissue with cells is a very promising approach in tissue engineering, with liver tissue engineering not being an exception. Decellularized liver scaffolds can serve as an excellent 3D environment for recellularization as it maintain tissue-specific microarchitecture of ECM proteins with important spatial cues for cell adhesion, migration, growth and differentiation. Moreover, by using autologous cells the newly constructed graft should lack immunogenicity in the host organism and thus eliminate the need for immunosuppressive therapy in the post-transplant period. This review provides an overview of liver decellularization and repopulation experiments done so far while highlighting the advances as well as pin-pointing the challenges that remain to be solved.

Injuries of the small and large intestine.

INTRODUCTION: Patients with abdominal trauma appear frequently. The most vulnerable organs in these patients are the liver and the spleen. Injuries of the small and large intestines are relatively less frequent. The diagnostic process of these injuries is complex and requires an analysis of all results. Therefore it is highly probable that the final diagnosis can be delayed and so can be delayed an indication of surgical exploration of the abdominal cavity, which can have serious consequences on the morbidity and mortality of these patients with intestinal trauma. METHODS: We collected our data using the WinMedicalc 2000 software. We searched for patients hospitalised in years 20082017 in the Department of Surgery, Faculty of Medicine in Pilsen subjected to surgical revision of the abdominal cavity for intestinal trauma. RESULTS: Our set comprised 41 patients, including 30 men and 11 women. The mean age of the patients was 41 years, 4 of the patients were children. Twenty-three of the patients suffered from polytrauma, while 9 of the patients had a relatively isolated injury of either the small intestine or the colon. Six of the patients died. The small intestine was injured in 17 patients, the colon was injured in 14 patients and both were injured in 10 patients. The intestinal injury was diagnosed in 17 cases based on CT imaging (performed 31 times in total); 23 cases were diagnosed in the peroperative period. CONCLUSIONS: We assessed a set of patients with an intestinal injury in terms of specific diagnosis, severity of trauma, diagnostic process and treatment. The results are similar to the results of studies in large sets of patients. Even though imaging methods can help to reach the right diagnosis, they are insufficient as a sole diagnostic method, and physical examination plays a major role.

Animal models of liver diseases and their application in experimental surgery.

Both acute and chronic liver diseases are frequent and potentially lethal conditions. Development of new therapeutic strategies and drugs depends on understanding of liver injury pathogenesis and progression, which can be studied on suitable animal models. Due to the complexity of liver injury, the understanding of underlying mechanisms of liver diseases and their treatment has been limited by the lack of satisfactory animal models. SO far, a wide variety of animals has been used to mimic human liver disease, however, none of the models include all its clinical aspects seen in humans. Rodents, namely rats and mice, represent the largest group of liver disease models despite their limited resemblance to human. On the other hand, large animal models like pigs, previously used mostly in acute liver failure modeling, are now playing an important role in studying various acute and chronic liver diseases. Although significant progress has been made, the research in hepatology should continue to establish animal models anatomically and physiologically as close to human as possible to allow for translation of the experimental results to human medicine. This review presents various approaches to the study of acute and chronic liver diseases in animal models, with special emphasis on large animal models and their role in experimental surgery.

Hepatic pseudolymphoma: a surprising finding in a case with suspected generalisation of lung cancer.

INTRODUCTION: Pseudolymphoma is a rare focal lesion which occurs in different locations. Only about 50 cases of liver pseudolymphoma have been reported so far. The diagnostic process is challenging. The lesion can resemble different malignancies using various imaging methods. No typical laboratory markers are available. The right diagnosis is usually made on the basis of histological examination. CASE REPORT: A 67 years old female patient with lung fibrosis was undergoing assessments for a malignant-appearing focal lesion of the left lung and a focal liver lesion of unknown etiology. Upper lobectomy of the left lung proved lung carcinoma. The liver lesion was suspected for being metastatic, therefore a liver resection followed. The biopsy revealed hepatic pseudolymphoma. It took 150 days from the first positive CT scan until the liver resection. Currently, the patient shows no signs of recurrence. CONCLUSION: Hepatic pseudolymphoma is a rare disease and we have only little experience with it so far. The diagnostic process is challenging, which is clear from the presented case. Only histological and immunohistochemical examinations ruled out a malignancy. A long-term observation of the patient is indicated.

Treatment of liver injuries at the Trauma Centre of the University Hospital in Pilsen.

INTRODUCTION: Traumatic liver injury is the most frequent cause of death due to traumatic bleeding in the peritoneal cavity. The progress of pre-hospital emergency medical service, improved surgical techniques, and advanced post-operative care decreased the morbidity from 65% to 10% over the last 40 years. The management is either surgical or non-surgical. Operation is indicated in case of haemodynamic instability and failure of non-surgical treatment. The aim of the paper is to evaluate the aetiology of liver injury, the type of treatment, and therapeutic results in patients hospitalized between 2006 and 2018 at the Trauma Centre of the University Hospital in Pilsen. METHODS: Our retrospective study includes 322 patients. Assessed characteristics: Type of injury (polytraumatic or monotraumatic), cause of trauma, trauma grade according to The American Association for the Surgery of Trauma, type of treatment, complications, mortality and the length of stay. RESULTS: There were 191 male and 131 female patients included in the study; 18.9% of these were children below the age of 16. Polytraumata represented 53.1%, multiple traumata 35.4% and monotraumata 11.5% of all injuries; 94.7% of patients had a blunt trauma of the liver and the most common reason of injury was traffic accident (57.8%). Conservative management was applied in 66.1% of all patients. The following surgical procedures were performed: liver packing (34 cases), exploration and drainage (10), liver resection (5), laparoscopy (7), radiofrequency ablation (3), cholecystectomy (2), and one case of bile duct revision. Thirty-day mortality was 7.7%. One patient died of bilateral pneumonia; the other non-surviving patients died of decompensated hemorrhagic shock or due to craniocerebral injury. CONCLUSION: Complex and centralized medical care of patients with liver trauma not only allows appropriate primary therapy, but it is also a precondition for the management of further specific complications.

Distribution of Connective Tissue in the Male and Female Porcine Liver: Histological Mapping and Recommendations for Sampling.

The pig is a large animal model that is often used in experimental medicine. The aim of this study was to assess, in normal pig livers, sexual dimorphism in the normal fraction of hepatic interlobular and intralobular connective tissue (CT) in six hepatic lobes and in three macroscopical regions of interest (ROIs) with different positions relative to the liver vasculature. Using stereological point grids, the fractions of CT were quantified in histological sections stained with aniline blue and nuclear fast red. Samples (415 tissue blocks) were collected from healthy piglets, representing paracaval, paraportal and peripheral ROIs. There was considerable variability in the CT fraction at all sampling levels. In males the mean fraction of interlobular CT was 4.7 ± 2.4% (mean ± SD) and ranged from 0% to 11.4%. In females the mean fraction of the interlobular CT was 3.6 ± 2.2% and ranged from 0% to 12.3%. The mean fraction of intralobular (perisinusoidal summed with pericentral) CT was <0.2% in both sexes. The interlobular CT represented >99.8% of the total hepatic CT and the fractions were highly correlated (Spearman r = 0.998, P <0.05). The smallest CT fraction was observed in the left medial lobe and in the paracaval ROI and the largest CT fraction was detected in the quadrate lobe and in the peripheral ROI. For planning experiments involving the histological quantification of liver fibrosis and requiring comparison between the liver lobes, these data facilitate the power analysis for sample size needed to detect the expected relative increase or decrease in the fraction of CT.

[Sinusoidal obstruction syndrome induced by monocrotaline in a large animal experiment - a pilot study]. / Sinusoidální obstrukcní syndrom indukovaný monokrotalinem v experimentu na velkém zvíreti - pilotní studie.

INTRODUCTION: Sinusoidal obstruction syndrome (SOS) is a disease which is caused by toxic injury to hepatic sinusoids. This syndrome is most frequently caused by myeloablative radiochemotherapy in patients before hematopoietic stem cells transplantation and also by oxaliplatin mainly in patients with colorectal liver metastases. The aim of this study was to establish a large animal model of SOS, which would enable further study of this disease and facilitate translation of experimental outcomes into human medicine. METHODS: A total of 27 domestic pigs (Prestice Black-Pied pig) were involved in this study (12 females). A group with a higher dose of monocrotaline (180 mg/kg) included 5 animals, and the remaining 22 pigs formed another group with a lower dose (36 mg/kg). Monocrotaline was administered via the portal vein and one week after the administration, partial hepatectomy of the left lateral liver lobe was performed. The animals were followed up for 3 weeks after monocrotaline administration. Regular ultrasound examinations were performed as well as examination of biochemical markers of liver and kidney functions and histological examination of liver parenchyma samples. RESULTS: The features of toxic liver injury which we observed in case of all animals were comparable with macroscopic and microscopic appearance of SOS. We recorded AST, ALT, bilirubin and ammonia elevation after monocrotaline administration. Echogenicity on ultrasound images of injured liver parenchyma was higher compared to echogenicity of healthy parenchyma. All the five animals from the first group with a higher monocrotaline dose had died before partial hepatectomy (1st-3rd day after monocrotaline administration). Death before partial hepatectomy occurred in 3 cases (6th and 7th day after monocrotaline administration) in the second group of 22 animals with a lower dose of monocrotaline. Death after partial hepatectomy occurred in 8 cases (7th-17th day after moncrotaline administration) in the same group. 11 animals survived the entire experimental period. The cause of death (in both groups) was metabolic failure in 10 animals and exsanguination in 4 animals, both due to severe hepatopathy. Death of 2 animals was not associated with monocrotaline intoxication (strangulation of small intestine, gastrectasis). CONCLUSIONS: We established a large animal model of SOS induced by monocrotaline administration (36 mg/kg via portal vein). This model can contribute to research of therapeutic modalities for this disease or to evaluation of surgical treatment of patients with SOS.Key words: sinusoidal obstruction syndrome monocrotaline oxaliplatin hepatotoxicity experimental model.

[Experimental promotion of liver regeneration after portal vein branch ligation]. / Moznosti experimentálního ovlivnení regenerace jaterního parenchymu v souvislosti s ligací vetví portální zíly.

INTRODUCTION: Portal vein embolization or ligation (PVE/PVL) is part of most multi-stage liver procedures in the case of low future liver remnant volume (FLRV). PVE initiates compensatory hypertrophy of non-occluded liver parenchyma. This hypertrophy is stimulated by an increased volume of portal blood in the non-occluded veins. PVE results in adequate FLRV growth necessary for resection only in 63-96% patients. The aim of this publication is to summarize the possibilities of influencing liver regeneration after PVE/PVL in an experiment using cytokines (TNF-α, IL-6), a monoclonal antibody against TGF-ß1 (MAB TGF-ß1) and mesenchymal stem cells (MSC). METHODS: The experimental model of PVE/PVL was chosen as best compatible for potential use in human medicine. 9 (control group), 9 (TNF-α group), 8 (IL-6 group), 6 (MSC group) and 7 piglets (MAB TGF-ß1 group) were enrolled in individual studies. We performed laparotomy with PVL of the right-sided liver lobes under general anaesthesia. The following amounts of substances were applied in the non-occluded portal vein branches immediately after PVL: physiological solution (control group), recombinant porcine TNF-α (5 µg/kg), recombinant porcine IL-6 (0.5 µg/kg) and MSC (8.75, 14.0, 17.0, 17.5, 43.0 and 61.0 x 106 MSC). MAB TGF-ß1 was applied 24 hours after PVL (40 µg/kg). Biochemical parameters were analysed repeatedly and FLRV ultrasound assessments were performed in the postoperative period. The experiments were ended on postoperative day 14 by sacryfiing the animals under general anaesthesia. Liver samples of hypertrophic and atrophic liver parenchyma were analysed. RESULTS: Repeated ultrasound assessments of the effects of MSC, TNF-α, IL-6 and MAB TGF-ß1 compared with the physiological solution in the control group demonstrated statistically significant acceleration of FLRV growth in the experimental groups. For MSC, maximum growth was observed between postoperative days 3 and 7, on day 7 for TNF-α, between days 3 and 7 for MAB TGF-ß1 and on day 7 for IL-6. Serum levels of AST and ALT increased after PVL and MSC whereas other biochemical parameters showed no statistically significant differences. We identified individual MSC using immunohistochemistry in the hypertrophic tissue of the MSC group. A statistically significant difference was observed in the number of binucleated hepatocytes, with their increased concentration in the IL-6 group. CONCLUSION: Application of IL-6, TNF-α, MAB TGF-ß1 and MSC seems to provide suitable stimulation for achieving faster FLRV growth. Nevertheless, many controversial questions still remain to be answered with respect to the mechanism of their respective effects.Key words: liver regeneration portal vein embolization large animal experiment mesenchymal stem cells cytokines.