Publications by authors named "Frank Meyer"

165 Publications

Management of a postoperative fistula after pancreatic left resection using percutaneous endoscopy-assisted transpapillary pancreatic duct drainage via its stump.

VideoGIE 2021 Apr 27;6(4):172-175. Epub 2021 Jan 27.

Department of General, Abdominal, Vascular and Transplant Surgery, University Hospital, Magdeburg, Germany.

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http://dx.doi.org/10.1016/j.vgie.2020.12.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8058273PMC
April 2021

Dynamic Effects and Hydrogen Bonding in Mixed-Halide Perovskite Solar Cell Absorbers.

J Phys Chem Lett 2021 Apr 15;12(16):3885-3890. Epub 2021 Apr 15.

Renewable Energy, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH (HZB), 14109 Berlin, Germany.

The organic component (methylammonium) of CHNHPbICl-based perovskites shows electronic hybridization with the inorganic framework via H-bonding between N and I sites. Femtosecond dynamics induced by core excitation are shown to strongly influence the measured X-ray emission spectra and the resonant inelastic soft X-ray scattering of the organic components. The N core excitation leads to a greatly increased N-H bond length that modifies and strengthens the interaction with the inorganic framework compared to that in the ground state. The study indicates that excited-state dynamics must be accounted for in spectroscopic studies of this perovskite solar cell material, and the organic-inorganic hybridization interaction suggests new avenues for probing the electronic structure of this class of materials. It is incidentally shown that beam damage to the methylamine component can be avoided by moving the sample under the soft X-ray beam to minimize exposure and that this procedure is necessary to prevent the creation of experimental artifacts.
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http://dx.doi.org/10.1021/acs.jpclett.1c00745DOI Listing
April 2021

[The role of postdoctoral qualification candidates in surgical teaching].

Chirurg 2021 Apr 14. Epub 2021 Apr 14.

Klinik für Allgemein‑, Viszeral-, Gefäß- und Transplantationschirurgie, Universitätsklinikum Magdeburg A.ö.R., Leipziger Str. 44, 39120, Magdeburg, Deutschland.

Objective: This compact overview outlines the responsibilities and broad field of tasks of a post-doctoral fellow in surgical teaching within the framework of studies in human medicine.

Method: Narrative short review based on own individual and institutional teaching experiences.

Results: Role of the post-doctoral fellow (selection): (i) due to the planned (sub)specialization by the respective habilitation project and because of the accumulated (administrative and scientific as well as teaching) experience within the framework of this scientific graduation, the post-doctoral fellow appears to be a more suitable, motivated and competent doctoral manager and supervisor compared to colleagues who do not intend to get the habilitation. (ii) Dependence of medical disciplines: the role that can be taken in teaching is highly dependent on the subject matter and discipline. Thus, there is the possibility and the duty to always mediate competent practical skills in surgical subjects in addition to theoretical knowledge and to pay strict attention to their ready to use acquisition in preparation for clinical/surgical practice. (iii) In nonuniversity (teaching) hospitals, the surgical post-doctoral fellow can fulfill the tasks of surgical teaching through a complete internship and clerkship care. In university clinics the focus is more on holding lectures in addition to internship and clerkship tutorials.

Conclusion: The post-doctoral fellow plays a central role in surgical teaching. A wide range of tasks with holding and construction of lectures, seminars and block internships up to direct student support within the framework of the clerkship, the practical year and the support of a dissertation can be sufficiently fulfilled by the post-doctoral fellow in addition to the development of facultative teaching concepts full of ideas.
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http://dx.doi.org/10.1007/s00104-021-01406-9DOI Listing
April 2021

[Intraoperative angiography in carotid artery reconstruction-Pathological findings, reliability and importance of the procedure].

Chirurg 2021 Apr 14. Epub 2021 Apr 14.

Klinik für Neurologie, Universitätsklinikum Magdeburg A.ö.R., Leipziger Straße 44, 39120, Magdeburg, Deutschland.

Aim: To investigate the value of intraoperative angiography and its ad hoc evaluation with respect to cases of surgical technical inaccessibility.

Methods: Overall, 523 consecutive carotid artery thrombendarterectomy (TEA) patients with intraoperative control angiography, postoperative color-coded duplex sonography and retrospective re-evaluation of documented angiographic images were included in the evaluation.

Results: In the retrospective angiographic re-evaluation 23 (4.4%) occlusions or high-grade stenoses of the common carotid artery (CCA) or internal carotid artery (ICA) in the surgical field (12, 2.3%) or of downstream ICA or middle cerebral artery (MCA, 11, 2.1%) were detected. The detection rate was significantly lower in the intraoperative ad hoc evaluation with overall only 13 (2.5%) detected pathologies (7, 1.3% in the surgical field, 6, 1.1% in large downstream arteries, p=0.002). Postoperative duplex sonography performed in 505 patients detected 50 cases (10.1%) of local surgical technical inaccessibility, which was significantly more than in the angiography (p<0.001). In most cases these were nonocclusive, low-grade stenosing detachments of the intima media (n=19), 13 suture contractions, and 14 kinking/abrupt diameter changes at the distal end of the patch. Suture contractions and kinking/diameter changes were associated with a left-sided TEA (adjusted odds ratio, OR 2.4, 95% confidence interval, CI 1.1-5.1), an operation without a patch (adjusted OR, 16.6, 95% CI 1.3-215.0), and using Dacron patches in contrast to PTFE patches (adjusted OR 3.0, 95% CI 1.4-6.6).

Conclusion: The ad hoc evaluation of intraoperative completion angiography by surgeons missed a substantial number also of occluding and severely stenosing pathologies. Angiography is not suitable for the detection of nonocclusive and low-grade stenosing cases of operative inaccessibility. Postoperative color-coded duplex sonography is an adequate tool for surgical quality control.
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http://dx.doi.org/10.1007/s00104-021-01403-yDOI Listing
April 2021

Post-exercise pulsatility index indicates treatment effects in peripheral arterial occlusive disease (PAOD).

Wien Klin Wochenschr 2021 Mar 11. Epub 2021 Mar 11.

Division of Vascular Surgery, Dept. of General, Abdominal, Vascular and Transplant Surgery, Magdeburg University Hospital, Magdeburg, Germany.

Background: Hypothesis: Post-exercise measurements better discriminate PAOD-patients from healthy persons and they more sensitively detect hemodynamic improvements after treatment procedures than resting measurements.

Methods: A total of 19 healthy volunteers and 23 consecutive PAOD-patients underwent measurements of peak systolic velocity (PSV), end-diastolic velocity (EDV), minimal diastolic velocity (MDV), time-averaged maximum velocities (TAMAX), resistance index (RI) and pulsatility index (PI) before and after a standard exercise test (at 1, 2, 3, 4 and 5 min) before and after treatment (incl. epidemiological data, PAOD risk factors and comorbidities).

Results: In resting values, healthy persons and PAOD-patients did not differ significantly in any of the hemodynamic parameters. PSV increased after treatment in PAOD-patients by 5 cm/s (paired t‑test, p: 0.025); however, when the amplitude of autoregulatory changes related to the resting values were calculated, PAOD-patients showed clearly less hemodynamic changes after exercise than healthy persons (p: 0.04; 0.002; <0.001 for PSV, TAMAX and PI, resp.). The time course after exercise was compared by repeated measures of ANOVA. Healthy persons differed significantly in PI, RI and PSV from PAOD patients before and after treatment (p<0.001 each). The PAOD-patients revealed a significantly improved PI after treatment (p: 0.042). The only factor contributing significantly to PI independently from grouping was direct arterial vascularization as compared to discontinuous effects by an obstructed arterial tree.

Conclusion: Healthy persons cannot be well differentiated from PAOD-patients solely by hemodynamics at rest but by characteristic changes after standard exercise. Treatment effects are reflected by higher PI-values after exercise.
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http://dx.doi.org/10.1007/s00508-021-01818-xDOI Listing
March 2021

Transition of care in a case of obesity with metabolic surgery.

Z Gastroenterol 2021 Mar 8;59(3):250-254. Epub 2021 Mar 8.

Dept. of General, Abdomina, Vascular and Transplant Surgery, Otto-von-Guericke University with University Hospital, Magdeburg, Germany.

The World Health Summit 2011 confirmed the epidemic-like occurrence of diabetes mellitus and obesity. In Germany, 62.7 % and 21.9 % of the population have a BMI of more than 25 kg/m² and more than 30 kg/m, respectively. Currently, 10.5 obese people per 100 000 German inhabitants undergo bariatric surgery, while 86 and 114.8 per 100 000 in France and in Sweden, respectively, favor bariatric surgical interventions.

Aim: By means of a scientific case report, the instructive case of a young patient with morbid obesity is illustrated based on 1) selective references from the medical literature and 2) insights from the daily clinical practice in the case-specific medical and perioperative management after successful surgery for malformation in his childhood and, thus, the limited therapeutic options of metabolic surgery.

Case Report (case-, Diagnostic-, And Treatment-specific Aspects): 35-year-old patient with morbid obesity. : Status after surgical intervention for gastroschisis as a newborn (surgery report not available). : Super obesity characterized by 234 kg and 174 cm (→ BMI: 77.3 kg/m²), hypogonadotrophic hypogonadism. : · Initial treatment with gastric balloon followed by a weight reduction of 46 kg within the first 6 months; however, despite weight reduction, development of an insulin-dependent diabetes with insulin resistance from a diet-based diabetes;. · Repeat gastric balloon therapy for "bridging" but with no further weight reduction despite additional administration of GLP-1 analogues.. · Surgical intervention: Removal of the balloon - termination because of excessive adhesions to the liver and spleen as well as filiforme hepatic lesions (histopathology: liver hamartoma). Open surgery: extensive adhesiolysis because of previous pediatric surgery for gastroschisis, including associated non-rotation of the intestine with complete right-sided position of the intestine (left side: colon; right flexure: at infralienal position) prompting single-anastomosis duodeno-ileostomy (SADI)-procedure, leaving the stomach in situ with simultaneous cholecystectomy and herniotomy in sublay technique.. (early postoperative and mid- to long-term): The patient tolerated the intervention well. Postoperative course was uneventful with regard to mobilization, beginning of oral nutrition, and wound healing; there was a subsequent weight reduction due to a "common channel" of 250 cm.

Conclusion: While the increase of obesity prevalence in adults has currently stopped, incidence in children and teenagers is rapidly rising. The consequence might be that children and young adults who have undergone bariatric surgery in childhood and adolescence can develop complications from these former interventions as adults. Therefore, it is reasonable to recommend follow-up investigations within specialized centers according to well-established standards. On the other hand, the increasing prevalence of obesity in childhood leads to the possibility that adults who underwent pediatric surgery because of embryonal malformations may require an appointment with a bariatric surgeon at some point. For these patients (as a representative example of the transition of care phenomenon), the risk of metabolic surgical intervention is increased; such operations require the appropriate knowledge and expertise of the bariatric surgeon on embryonal malformations and their approach by pediatric surgery.
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http://dx.doi.org/10.1055/a-1348-2378DOI Listing
March 2021

Development of a detailed human neck finite element model and injury risk curves under lateral impact.

J Mech Behav Biomed Mater 2021 04 19;116:104318. Epub 2021 Jan 19.

Strasbourg University, ICUBE UMR 7357 CNRS, 2 Rue Boussingault, 67000, Strasbourg, France.

Advanced neck finite element modeling and development of neck injury criteria are important for the design of optimal neck protection systems in automotive and other environments. They are also important in virtual tests. The objectives of the present study were to develop a detailed finite element model (FEM) of the human neck and couple it to the existing head model, validate the model with kinematic data from legacy human volunteer and human cadaver impact datasets, and derive lateral impact neck injury risk curves using survival analysis from the upper and lower neck forces and moments. The detailed model represented the anatomy of a young adult mid-size male. It included all the cervical and first thoracic vertebrae, intervening discs, upper and lower spinal ligaments, bilateral facet joints, and passive musculature. Material properties were obtained from literature. Frontal, oblique, and lateral impacts to the distal end of the model was applied based on human volunteer and human cadaver experimental data. Corridor and cross-correlation methods were used for validation. The CORrelation and Analysis (CORA) score was used for objective assessments. Forces and moments were obtained at the occipital condyles (OC) and T1, and parametric survival analysis was used to derive injury risk curves to define human neck injury tolerance to lateral impact. The Brier Score Metric (BSM) was used to determine the hierarchical sequence among the injury metrics. The CORA scores for the lateral, frontal, and oblique impact loading conditions were 0.80, 0.91, and 0.87, respectively, for human volunteer data, and the mean score was 0.7 for human cadaver lateral impacts. Injury risk curves along with ±95% confidence intervals are given for all the four biomechanical metrics. The OC shear force was the optimal metric based on the BSM. A force of 1.5 kN was associated with the 50% probability level of AIS3+ neck injury. As a first step, the presented risk curves serve as human tolerance criteria under lateral impact, hitherto not available in published literatures, and they can be used in virtual testing and advancing restraint systems for improving human safety.
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http://dx.doi.org/10.1016/j.jmbbm.2021.104318DOI Listing
April 2021

[Jejunojejunostomy by Interventional Endosonography (EUS) using "Lumen-apposing Metal Stent" (LAMS) in a Case of Obstructed Jejunal Loop after Former Gastrectomy: Video-Paper on a Typical Case].

Zentralbl Chir 2020 Dec 17. Epub 2020 Dec 17.

Klinik für Innere Medizin III (Gastroenterologie, Hepatologie und Allg. Innere Medizin), SRH Wald-Klinikum Gera gGmbH, Gera, Deutschland.

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http://dx.doi.org/10.1055/a-1263-1648DOI Listing
December 2020

[EUS-guided therapy of cholangiolithiasis in surgically altered anatomy of the upper GI tract - a unicenter case study].

Z Gastroenterol 2020 Nov 16;58(11):1081-1090. Epub 2020 Nov 16.

Klinik für Gastroenterologie, Hepatologie und Allgemeine Innere Medizin, SRH Wald-Klinikum Gera gGmbH, Gera.

Aim:  To investigate feasibility and outcome the novel and favorable option of an endoscopic ultrasonography(EUS)-guided antegrade or even retrograde gall stone extraction via a transhepatic route in patients (pats.) with no option for the usual gold standard, ERCP.

Material/methods:  All consecutive pats. with cholangiolithiasis and surgically altered anatomy of the upper GI tract with and without previous attempts of an ERCP were enrolled in this unicenter case study and were characterized with regard to the technical and clinical success of this approach.

Results:  From 2004 to 03/2020, overall 449 pats. underwent EUS-guided cholangiodrainage (n = 37 pats. with cholangiolithiasis). In 8 of these 37 pats., gall stone extraction was achieved using EUS-ERCP rendezvous technique (not included in the study since there was no surgically altered anatomy of the upper GI tract). In 13 of the remaining 29 subjects (45 %), there was a failure of previous attempts to reach the papilla of Vater or biliodigestive anastomosis using balloon-enteroscopy-guided ERCP. EUS-guided access to the biliary system was achieved in all 29 pats. Stone extraction was performed in 26 individuals (90 %) by means of antegrade push-technique after balloon dilatation of the papilla of Vater and biliodigestive anastomosis, respectively, before. In 11/29 cases (42 %), double pigtail prostheses were subsequently placed to track papilla of Vater/biliodigestive anastomosis ("ring drainage"), which were removed with gastroscopy three months later after previous ultrasound- and lab parameter-based follow-up control. In two pats. (7 %), gall stones were extracted via a retrograde route using a transhepatic access site; in one patient (3 %), stones were removed by means of a combined ante-/retrograde technique. In two subjects (7 %), cholangioscopy with electrohydraulic lithotripsy was used.Technical as well as clinical success rate was 100 % (29 of 29 pats.). Re-interventions became necessary in 6/29 cases (21 %), complications occurred in 6 individuals (21 %).

Conclusion:  EUS-guided stone extraction in antegrade or retrograde technique for pats. with surgically altered anatomy of the upper GI tract can be considered a favorable and safe but challenging approach of interventional endoscopy/EUS. It can provide high technical and clinical success and low complication rates; it has the potential to substitute the time-consuming balloon-enteroscopy-guided ERCP as well as, in particular, PTCD and, thus, secundary and tertiary therapeutic alternatives.
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http://dx.doi.org/10.1055/a-1250-8834DOI Listing
November 2020

Investigations of the Deuterium Permeability of As-Deposited and Oxidized TiAlN Coatings.

Materials (Basel) 2020 May 1;13(9). Epub 2020 May 1.

Department of Tribology, Fraunhofer-Institut für Werkstoffmechanik IWM, Woehlerstrasse 11, 79108 Freiburg, Germany.

Aluminum containing MAX (MAX) phase materials have attracted increasing attention due to their corrosion resistance, a pronounced self-healing effect and promising diffusion barrier properties for hydrogen. We synthesized TiAlN coatings on ferritic steel substrates by physical vapor deposition of alternating Ti- and AlN-layers followed by thermal annealing. The microstructure developed a {0001}-texture with platelet-like shaped grains. To investigate the oxidation behavior, the samples were exposed to a temperature of 700 °C in a muffle furnace. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) depth profiles revealed the formation of oxide scales, which consisted mainly of dense and stable α-AlO. The oxide layer thickness increased with a time dependency of ~t. Electron probe micro analysis (EPMA) scans revealed a diffusion of Al from the coating into the substrate. Steel membranes with as-deposited TiAlN and partially oxidized TiAlN coatings were used for permeation tests. The permeation of deuterium from the gas phase was measured in an ultra-high vacuum (UHV) permeation cell by mass spectrometry at temperatures of 30-400 °C. We obtained a permeation reduction factor (PRF) of 45 for a pure TiAlN coating and a PRF of ~3700 for the oxidized sample. Thus, protective coatings, which prevent hydrogen-induced corrosion, can be achieved by the proper design of TiAlN coatings with suitable oxide scale thicknesses.
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http://dx.doi.org/10.3390/ma13092085DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7254320PMC
May 2020

[Magdeburg Medical School - Logbook for Surgical Training of Final Year Medical Students - an Interdisciplinary, Medical School-Specific Concept Based on the Guidelines Issued by the Medical School Association ("Medizinischer Fakultätentag") in 2012].

Zentralbl Chir 2020 Dec 8;145(6):549-558. Epub 2020 Apr 8.

Klinik für Allgemein-, Viszeral-, Gefäß- und Transplantationschirurgie, Universitätsklinikum Magdeburg A. ö. R., Deutschland.

Background: The final year is the last part of the study of human medicine and can be regarded as an essential period, during which medical knowledge should be consequently converted into medical expertise. Since the amendment of the medical license policy ("Ärztliche Approbationsordnung" [ÄApprO]) from July 17, 2012, in particular, since April 01, 2013, German universities have been obliged to provide a training schedule such as a "logbook" for this final year, specifically for the mandatory time periods within surgery and internal medicine. In preparation for this innovation, the German Medical School Association ("Medizinischer Fakultätentag") presented basic logbooks as consensus documents in June 2012. The portfolio for each surgery discipline and the Magdeburg Medical School, had been developed on the basis of individual initiatives and used for years, and was revised, specified and further developed into a "logbook of the medical study's final year" - specific for daily practice and the Magdeburg Medical School, and to the guidelines of the Medical School Association ("Medizinischer Fakultätentag"). The aim of the present commentary is i) to present the Magdeburg Medical School logbook and its clinical planning for cases, diagnoses and (surgical) interventions, as a summary of institutional experience and ii) to describe the mandatory surgical part of the "Magdeburg's final year of the study of human medicine".

Method: Narrative short overview including individual teaching experiences and topic-related references from "PubMed" using terms for literature search such as "surgical logbook", "practical year" and "medical teaching". The background and aims of the document's modifications are explained for each surgical discipline.

Results: The "Logbook" is subdivided into 6 chapters: introduction, basics, statement of requirement, selected surgical diseases and interventions as well as information on final year-associated events and courses and instructions for creating the obligatory case report.

Conclusion: The presented "Magdeburg Medical School Final Year Logbook of the Surgical Disciplines" has been created according to the requirements of the German Medical School Association ("Medizinischer Fakultätentag") and has been simultaneously adapted to the conditions and established medical teaching at the presenting Medical School. In particular, the medical students are given a document related to daily clinical practice, which allows them, within an overall teaching concept, to acquire indispensable expertise.
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http://dx.doi.org/10.1055/a-1084-4127DOI Listing
December 2020

The Tumor Suppressor TFF1 Occurs in Different Forms and Interacts with Multiple Partners in the Human Gastric Mucus Barrier: Indications for Diverse Protective Functions.

Int J Mol Sci 2020 Apr 4;21(7). Epub 2020 Apr 4.

Institute of Molecular Biology and Medicinal Chemistry, Otto-von-Guericke University Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany.

TFF1 is a protective peptide of the Trefoil Factor Family (TFF), which is co-secreted with the mucin MUC5AC, gastrokine 2 (GKN2), and IgG Fc binding protein (FCGBP) from gastric surface mucous cells. -deficient mice obligatorily develop antropyloric adenoma and about 30% progress to carcinomas, indicating that Tff1 is a tumor suppressor. As a hallmark, TFF1 contains seven cysteine residues with three disulfide bonds stabilizing the conserved TFF domain. Here, we systematically investigated the molecular forms of TFF1 in the human gastric mucosa. TFF1 mainly occurs in an unusual monomeric form, but also as a homodimer. Furthermore, minor amounts of TFF1 form heterodimers with GKN2, FCGBP, and an unknown partner protein, respectively. TFF1 also binds to the mucin MUC6 in vitro, as shown by overlay assays with synthetic I-labeled TFF1 homodimer. The dominant presence of a monomeric form with a free thiol group at Cys-58 is in agreement with previous studies in and mouse. Cys-58 is likely highly reactive due to flanking acid residues (PPEEECEF) and might act as a scavenger for extracellular reactive oxygen/nitrogen species protecting the gastric mucosa from damage by oxidative stress, e.g., HO generated by dual oxidase (DUOX).
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http://dx.doi.org/10.3390/ijms21072508DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7177788PMC
April 2020

[Modern Finding-Specific and Patient-Adapted Management of Peripheral Pseudoaneurysms after Arterial Access].

Zentralbl Chir 2020 Oct 5;145(5):438-444. Epub 2020 Mar 5.

Klinik für Gefäßmedizin - Angiologie und Gefäß- und Endovascularchirurgie, Klinikum Darmstadt, Deutschland.

Aside from haematomas, pseudoaneurysms (PSA) are considered the most frequent complications after catheter-guided interventions.

Aim And Method: Narrative compact short overview to describe aetiopathogenesis and characteristics of pseudoaneurysms and the options for diagnostic measures, therapy and its complications.

Results: Aetiopathogenesis: via the closed access site, the puncture channel, there is continuous bleeding out of the vessel which forms a pseudoaneurysm-associated cavity within the perivascular tissue. This is not surrounded by a regular vascular wall as in true aneurysms but is only formed by the surrounding tissue structures. However, this border is not sufficient and the pseudoaneurysm may extend, with diffuse bleeding episodes into the tissue. Thus, surrounding structures such as nerves and veins can be compressed by the expanding pseudoaneurysm, which can lead to irreversible damage. Diagnostic measures: duplex ultra-sonography absolutely predominant. CT-A, MR-A and DSA for specific problems and clinical case characteristics (e.g., accompanying diseases etc.) - DSA is to be linked with the option of image-guided intervention during the same session.

Therapy: by manual compression and subsequent dressing with compression, ultrasound-guided compression, thrombin injection and surgical intervention, there are several therapeutic measures for appropriate selection according to the specific need. Ultrasound-guided compression should be immediately used since it is highly efficient and widely available. In addition to compression, thrombin can be injected into the pseudoaneurysm-preserving nerval structures and tissue from alterations. This provides much better occlusion rates but is more demanding. Surgical intervention is the most efficient approach to occlude a pseudoaneurysm but is demanding and can be associated with complications such as disturbances of wound healing in altered tissue and the longest hospital stay. Alternative approaches have not been established yet.

Conclusion: The diagnostic and therapeutic management of pseudoaneurysms for different findings and patients can be considered a great challenge, and requires an experienced angiologist or vascular surgeon.
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http://dx.doi.org/10.1055/a-1096-1327DOI Listing
October 2020

[What the (abdominal) surgeon needs to know on novel insights regarding cholic acids and their interaction with the intestinal microbioma].

Z Gastroenterol 2020 Mar 4;58(3):245-253. Epub 2020 Feb 4.

Klinik für Allgemein-, Viszeral-, Gefäß- und Transplantationschirurgie, Universitätsklinikum Magdeburg A. ö. R., Magdeburg, Germany.

The abdominal surgeon may have the opportunity to steadily learn on the (patho-)biochemical and (-)physiological consequences of his disease-related surgical activity (change of anatomy of the GI tract and its surrounding organs, medication and so on) if he refers closely to several medical disciplines as specifically indicated.

Aim & Method:  By means of a short compact overview based on (i) topic-related references from the scientific medical literature and (ii) own surgery-specific perceptions, interrelation of cholic acids (CA) with metabolism, in particular, with planned or performed (abdomino-)surgical procedures should be illustrated.

Results (corner Points):  1. Surgery and biochemistry have a common and traditionally matured matter of consideration with regard to the consequences of an altered portal vein circulation and liver cirrhosis. 2. CA are (i) natural detergents, (ii) components of cholesterol-associated gall stones and (iii) essential signal molecules of intestine-liver metabolic interaction. CA and chenodesoxycholic acid [CDCA] dominate the CA pool with approximately 35 %. By conjugation of CA with taurine und glycine, its solubility is increased. The enterohepatic circulation minimizes the excretion of CA. 3. The generation of CA out of cholesterol within the liver (turnover/day: 0.2-0.6 g cholesterol) is controlled by cholesterol-7α-hydroxylase (CYP7A1). A toxic CA accumulation is prevented by a CA-induced repression of CYP7A1 expression and sulfation of CA (resulting in an increase of urine solubility). 4. CA show regulatory activities in the energy, glucose, lipid and lipoprotein metabolism and connate immune system. By binding of the CA to the farnesoid X-nuclear receptor [FXR] and the membranous G-protein-coupled CA receptor-1 [GPBAR1, TGR5], mannifold effects within the fat and carbohydrate metabolism are induced. 5. CA trigger the expression of the iodothyronine-dejodinase (DIO2) within the brown fat tissue and skelet muscles by activation of the GPBAR1-MAPK signal pathways. Hence, thyroxine (T) is transformed to trijodthyronine (T) and, subsequently, fat oxidation and thermogenesis are increased. 6. CA change the intestinal microbioma by bacteriolytic activities and, on the other hand, the CA profile is modulated by the microbioma. Typical microbial effects of the CA pool are (i) separation of glycine and taurine residuals of conjugated CA by "bile salt hydrolases" and (ii) chemical modification of free, primary CA by re-amidation, oxidation-reduction, esterification and desulfation. 7. CA inhibit the endotoxin-based inflammatory response induced by lipopolysaccharides (LPS; membranous component of gram-negative bacteria). Via binding of CA to macrophages-associated receptors (GPBAR1 and FXR), (i) the LPS-induced proinflammatory cytokine generation is reduced and the expression of antiinflammatory IL-10 is promoted. In addition, (ii) white-blood cell "trafficking" is regulated and (iii) inflammasoma is activated by macrophages and neutrophil granulocytes. 8. The body weight-independent changes after bariatric surgery (e. g., in case of "Roux-en-Y gastric bypass" [RYGB]) correlate with an increased CA serum level and an altered intestinal CA profile. The latter leads secundarily to a modification of the microbioma. RYGB has - among others - positive effects onto the carbohydrate metabolism. Thus, insulin sensitivity of the liver is improved and the secretion of the glucagon-like peptide 1 is enhanced.

Conclusion:  CA are a parade example for metabolic regulators, the interactions of which have an impact onto various (patho-)biochemical and (-)physiological processes, (abdomino-)surgically relevant diseases and (abdomino-)surgical measures. Their biochemical/physiological activities and insight into associated molecular processes should be part of the medical and scientific skills of a modern (abdominal) surgeon with a developed pathophysiological expertise.
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http://dx.doi.org/10.1055/a-1071-8219DOI Listing
March 2020

Protection performance of bicycle helmets.

J Safety Res 2019 12 13;71:67-77. Epub 2019 Nov 13.

University of Strasbourg, Icube, UMR 7357 Multiscale Materials and Biomechanics, 2 rue Boussingault, Strasbourg 67000, France. Electronic address:

Introduction: The evaluation of head protection systems needs proper knowledge of the head impact conditions in terms of impact speed and angle, as well as a realistic estimation of brain tolerance limits. In current bicycle helmet test procedures, both of these aspects should be improved.

Method: The present paper suggests a bicycle helmet evaluation methodology based on realistic impact conditions and consideration of tissue level brain injury risk, in addition to well known headform kinematic parameters. The method is then applied to a set of 32 existing helmets, leading to a total of 576 experimental impact tests followed by 576 numerical simulations of the brain response.

Results: It is shown that the most critical impacts are the linear-lateral ones as well as the oblique impact leading to rotation around the vertical axis (ZRot), leading both to around 50% risks of moderate neurological injuries. Based on this test method, the study enables us to compare the protection capability of a given helmet and eventually to compare helmets via a dedicated rating system.
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http://dx.doi.org/10.1016/j.jsr.2019.09.003DOI Listing
December 2019

[Importance of splenectomy in the operative treatment of gastric cancer].

Chirurg 2020 Jun;91(6):502-510

AN-Institut für Qualitätssicherung in der Operativen Medizin, Otto-von-Guericke-Universität Magdeburg, Magdeburg, Deutschland.

Background: The value of simultaneous splenectomy as part of an oncologically adequate resection for gastric cancer has been controversially discussed over the last decades.

Methods: As part of a prospective multicenter observational study data were obtained from patients admitted to hospital with histologically diagnosed primary gastric cancer or adenocarcinoma of the esophagogastric junction (AEG). The profiles of care of patients who had undergone surgical treatment in 141 surgical departments from 1 January 2007 to 31 December 2009 were collated. Overall, 2897 patients were enrolled in the study (tumor resection, n = 2545).

Results: The overall splenectomy rate was 11.1% (n = 283) and the highest proportion was found in AEG tumor lesions (19.4%). In the whole group of patients as well as depending on the tumor site, there was a higher preoperative comorbidity in splenectomized patients. While the rate of general postoperative complications after splenectomy was significantly increased in all patients and also depending on various tumor sites, there were no differences in the rate of specific postoperative complications. A significantly higher hospital mortality comparing the splenectomy group of patients with those in whom the spleen could be preserved, was only observed in AEG-associated tumor lesions (15.2% vs. 5.0%). All splenectomized patients showed a shorter long-term survival (p < 0.001) compared to resections with a preserved spleen (18 months vs. 36 months).

Conclusion: In the surgical treatment of gastric cancer, splenectomy can be considered a negative predictor for a worse perioperative outcome and a worse long-term survival.
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http://dx.doi.org/10.1007/s00104-019-01075-9DOI Listing
June 2020

Different Forms of TFF2, A Lectin of the Human Gastric Mucus Barrier: Binding Studies.

Int J Mol Sci 2019 Nov 22;20(23). Epub 2019 Nov 22.

Institute of Molecular Biology and Medicinal Chemistry, Otto-von-Guericke University Magdeburg, Leipziger Str. 44, 39120 Magdeburg, Germany.

Trefoil factor family 2 (TFF2) and the mucin MUC6 are co-secreted from human gastric and duodenal glands. TFF2 binds MUC6 as a lectin and is a constituent of the gastric mucus. Herein, we investigated human gastric extracts by FPLC and identified mainly high- but also low-molecular-mass forms of TFF2. From the high-molecular-mass forms, TFF2 can be completely released by boiling in SDS or by harsh denaturing extraction. The low-molecular-mass form representing monomeric TFF2 can be washed out in part from gastric mucosa specimens with buffer. Overlay assays with radioactively labeled TFF2 revealed binding to the mucin MUC6 and not MUC5AC. This binding is modulated by Ca and can be blocked by the lectin GSA-II and the monoclonal antibody HIK1083. TFF2 binding was also inhibited by Me-β-Gal, but not the α anomer. Thus, both the α1,4GlcNAc as well as the juxtaperipheral β-galactoside residues of the characteristic GlcNAcα1→4Galβ1→R moiety of human MUC6 are essential for TFF2 binding. Furthermore, there are major differences in the TFF2 binding characteristics when human is compared with the porcine system. Taken together, TFF2 appears to fulfill an important role in stabilizing the inner insoluble gastric mucus barrier layer, particularly by its binding to the mucin MUC6.
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http://dx.doi.org/10.3390/ijms20235871DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6928932PMC
November 2019

["Drug Interaction Stewardship" (DIS) and Therapeutic Drug Monitoring for Anti-infective Treatment in Intensive Care, a Single Centre Observational Study].

Zentralbl Chir 2020 Apr 11;145(2):176-187. Epub 2019 Nov 11.

Klinik für Allgemein-, Viszeral-, Gefäß- und Transplantationschirurgie, Universitätsklinikum Magdeburg, Deutschland.

Introduction: Appropriate medication of intensive care patients is complicated by disturbed organ functions and organ failure, pathophysiological changes in severely ill patients as well as possible sepsis, ongoing haemodialysis for renal and hepatic insufficiency, varying pharmacokinetics/-dynamics (PK/PD) of drugs as well as numerous drug interactions.

Aim: Illustration of an interdisciplinary approach in daily clinical practice to optimise regular "polymedication" as well as the ongoing medication of patients prior to surgical interventions as indicated and as part of the appropriate peri- and postoperative intensive care management.

Method: A so-called "drug interaction stewardship" (DIS) is very similar to the already established "antibiotic stewardship" (ABS) during daily clinical routine of an intensive care unit and has been implemented. In addition, therapeutic drug monitoring (TDM) has been extended to antibiotics/antimycotics (such as meropenem, piperacillin-tazobactam, ceftazidime, linezolide, voriconazole, fluconazole, caspofungin), for which TDM had not yet been established. This was in a consecutive cohort of patients with abdominal surgery over a defined time period and was part of a systematic clinical single centre observational study (tertiary centre).

Results: From 01 - 2012 to 08 - 2016, 1,454 single drug patient consultations led to 385 (26.5%) changes in medical treatment, which had been previously initiated by an experienced intensive care physician. Most frequently in 156 cases (10.7%) this was due to newly calculated PK/PD. Analysis of 2,333 TDM samples resulted in a minimum serum level within the adequate range in 1,130 cases (48.4%). In 427 cases (18.3%), the drug serum level was too low and in 776 subjects (33.3%), prompting a change in the type, dose, dose interval and application route.

Conclusion: DIS and TDM provide a high rate of detection of unwanted drug interactions and inappropriate drug levels in surgical intensive care patients and help to assure targeted therapy changes.
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http://dx.doi.org/10.1055/a-1014-3451DOI Listing
April 2020

What does a (general and abdominal) surgeon need to know on plastic surgery?

Pol Przegl Chir 2019 Jun;91(5):41-50

Dept. of General, Abdominal and Vascular Surgery, University Hospital at Magdeburg, Magdeburg (Germany).

Background: Plastic surgery was first introduced as a sub-specialty of general surgery in Germany in 1978. Since then, this surgical subspecialty/discipline has evolved enormous potential, e.g. in collaboration with other disciplines such as general andabdominal surgery.

Aim: To highlight and summarize the basic potential, technical options and novel aspects of plastic surgery, which are relevant for the common interdisciplinary surgical strategies of plastic and general as well as abdominal surgery in clinical practice.

Method: Short and compact narrative review based on 1) a selection of relevant references from the medical scientific literature and 2) surgical experiences obtained in daily practice. R esults (selected corner points): 1) Biological protection procedures in vascular surgery by flap coverage after meticulous debridement with or without autogenic vascular reconstruction are used to overcome infection of a vascular prosthesis, a serious problem, associated with the risk of anastomotic rupture and bleeding by transfer of immunological competence due to tissue coverage and finally to induce healing in the area of an infected vascular prosthesis. 2) Fistula treatment for aorto-tracheal or aorto-duodenal fistulas, a big challenge for the referring general surgeon, can be treated by flap coverage, i.e. interposition of the pectoralis-major flap and the omentum-majus flap, respectively. 3) With regard to nerve surgery, encouraging results have been reported after early microsurgical recurrent laryngeal nerve repair, i.e. improved subjective voice quality or reconstitution of respiratory capacity in diaphragmatic. 4) Lymphatic surgery for lymphedema occurring either primarily due to an absence or lack of lymphatic vessels or secondarily due to infection, trauma, radiation therapy or surgery can be indicated in specialized microsurgical centers, e.g. for surgical repair of the lymphatic pathway: I) the interrupted lymphatic system can be reconstructed by an interposition, or II) the lymphatic fluid can be drained extraanatomically (e.g. by a lymphatic-venous anastomosis). Further techniques are the following: free lymph node transplantation included in a free vascularized groin flap or autologous lymphatic vessel transfer or vein graft interposition (used for lymphatic vessel interposition). 5) Mass reduction such as dermolipectomy with subsequent split-thickness is a valuable option, which provides excellent volume reduction. 6) Defect coverage: A. Split- or full-thickness skin grafts are a common method of defect coverage (in cases of clean and well-vascularized wound bed and lacking donor skin, or if the graft bed is of questionable quality) using various allogenic or xenogenic skin substitute materials. B. Further methods offer a wide-range armamentarium of local and free fasciocutaneous and musculocutaneous flaps, e.g. after abdomino-perineal rectum extirpation using the vertical rectus-abdominis myocutaneous flap (VRAM) or propeller flaps according to the "angiosome". 7) Abdominal wall hernia closure with instable skin coverage, flap closure, either alone or in combination with mesh is superior to mesh closure only. 8) Free flaps: If there is no option for a local or pedicled flap available, free flaps can be well used for abdominal wall defect closure (complication rate in experienced hands is low).

Conclusion: Plastic surgery is an indispensable partner for specific surgical problems and clinical situations of general and abdominal surgery, which indicates that each general and abdominal surgeon should be well notified on great options and surgical techniques offered by modern plastic surgery to achieve best outcomes and quality of life for patients and should combine the expertise of these two surgical disciplines.
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http://dx.doi.org/10.5604/01.3001.0013.2365DOI Listing
June 2019

[Modern Management of Arterio-Visceral/Arterio-Lumenal Fistulas - Selection of Representative Clinical Situations and Cases].

Zentralbl Chir 2019 Oct 21;144(5):471-481. Epub 2019 Oct 21.

Klinik für Allgemein-, Viszeral-, Gefäß- und Transplantationschirurgie, Universitätsklinikum Magdeburg A. ö. R., Magdeburg, Deutschland.

Introduction: Circuits of abdominal arteries to adjoining lumenal organs, especially in triggering circumstances, are rare diseases that are increasingly evident in endovascular therapies and complex viscero-/tumor-surgical procedures with subsequent lengthy adjuvant therapies. Their care is a challenge and involves frequent complications and mortality.

Method: Narrative overview on the basis of current scientific references and our clinical and surgical experience.

Results: Uretero-arterial fistulas are usually associated with recurrent and intermittent gross haematuria. The diagnostic test of choice continues to be angiography with the potential for endovascular therapy, which has displaced open surgical procedures due to minimal invasiveness, low morbidity and mortality. Aorto-oesophageal fistulas may result from underlying infectious and malignant diseases as well as open and endovascular therapies of the aorta. Multi-line contrast CT of the thorax/abdomen and gastroscopy have priority in diagnostic testing. Endovascular procedures can only be understood as bridging procedures, and only the removal of prostheses with aortic and gastrointestinal reconstruction are curative. Aorto-enteric fistulas are secondary complications of open and endovascular aortic surgery. Contrast enhanced multi-line CT has high sensitivity and specificity. In contrast, open surgical therapy involves in-situ reconstruction of extra-anatomical reconstructions with aortic ligature. Endovascular therapy is reserved for exceptional cases. Inflammatory aneurysms of visceral arteries may be associated with adjacent inflammatory processes, most commonly pseudoaneurysms. The most suitable diagnostic procedure is contrast-enhanced thin-film CT angiography. The treatment of choice is endovascular ablation using covered stents or embolisation.

Conclusion: Arterio-visceral/arterio-lumenal fistulas are similar in pathogenesis, predisposing factors and clinical symptoms. An interdisciplinary consultation is employed to identify individualised therapy. Endovascular/interventional procedures are safe and effective, and open surgical rehabilitation is mostly curative.
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http://dx.doi.org/10.1055/a-1011-4342DOI Listing
October 2019

Efficient nonlinear compression of a mode-locked thin-disk oscillator to 27  fs at 98  W average power.

Opt Lett 2019 Sep;44(17):4115-4118

We demonstrate efficient pulse compression of a 13.4 MHz, 534 fs, 123 W, Yb:YAG thin-disk oscillator down to 27 fs at 98 W average power, resulting in a record-high 166 MW peak power from an amplifier-free oscillator-driven setup. Our compressor is based on two stages: one multipass cell allowing us to reduce the pulse duration to sub-90 fs and, subsequently, a multiple-plate compressor, allowing us to reach 27 fs. The overall average power compression efficiency is 80%, and the beam has excellent beam quality and homogeneity. In addition, we demonstrate further spectral broadening that supports a transform limit of 5 fs in a second multiple-plate stage, demonstrating the potential for reaching a 100 W class, amplifier-free, few-cycle source in the near future. The performance of this unique source is very promising for applications previously restricted to amplified sources, such as efficient generation of extreme ultraviolet light at high repetition rate, and the generation of high-power broadband THz radiation.
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http://dx.doi.org/10.1364/OL.44.004115DOI Listing
September 2019

Depressing Conclusion.

Authors:
Frank P Meyer

Dtsch Arztebl Int 2019 05;116(19):346

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http://dx.doi.org/10.3238/arztebl.2019.0346aDOI Listing
May 2019

[Options and Management of Vascular Reconstruction in the Context of Abdominal Surgery and its Perioperative Care - Selection of Typical Clinical Situations and Cases].

Zentralbl Chir 2019 Oct 3;144(5):460-470. Epub 2019 Jul 3.

Arbeitsbereich Gefäßchirurgie, Klinik für Allgemein-, Viszeral-, Gefäß- und Transplantationschirurgie, Universitätsklinikum Magdeburg A. ö. R., Deutschland.

Introduction: Interdisciplinary cooperation between surgeons can help to optimise outcome in the management of complex surgical diseases. The indication for surgical intervention has gradually expanded in advanced multivisceral tumour growth, with iatrogenic vascular injuries in the field of abdominal and oncological surgery and mesenteric ischemia. Appropriate expertise in vascular surgery is then essential, although this is not always available or in all hospitals.

Aim: Narrative review based on current scientific references in the relevant literature and our own clinical and surgical experiences in decision making, the approach in clinical management and various options of vascular reconstruction in abdominal surgery.

Results: Prognosis is still limited in pancreatic cancer. R0 resection is the only curative therapeutic option - thus, the surgeon has to provide specific intraoperative expertise. Arterial reconstruction is still controversial, due to increased postoperative morbidity and limited evidence. But in specific cases, venous reconstruction has been established in clinical practice. In addition, in retroperitoneal sarcoma with advanced/extended tumour growth, reconstruction of the infiltrated inferior V. cava or common iliac artery by means of patch plasty or autologous bypass/segmental vascular prosthesis can become necessary as part of multivisceral resections. During inflammatory processes or with tumour adhesions/infiltrations to surrounding anatomical structures, intraoperative vascular injuries or postoperative vascular alterations can occur, further complicated by anatomical variants. The extremely strict demands on the abdominal surgeons, in particular in mesenteric ischemia, are influenced by i) a competent assessment of the mesenteric vessels based on ii) adequate imaging as well as iii) appropriate time management. Prompt recanalisation can play a decisive role for the prognosis.

Conclusion: Vascular reconstructions in abdominal surgery, in particular, in oncological surgery, require great expertise of the surgeon. In this context, competent preoperative diagnostic testing, extensive specific experience in vascular surgery/interventions, appropriate interdisciplinary case management, adequate surgical tactic and technique are all important.
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http://dx.doi.org/10.1055/a-0862-0807DOI Listing
October 2019

Alternative Mobilization by Means of a Novel Orthesis in Patients after Amputation.

Z Orthop Unfall 2020 Feb 4;158(1):75-80. Epub 2019 Jun 4.

Vascular Surgery Division, Department of General, Visceral, Vascular and Transplantation Surgery, Magdeburg University Hospital.

Introduction: The mobilization of patients with diabetic foot syndrome after surgical treatment by debridement or partial amputation is usually difficult in daily practice and in inpatient care.

Aim And Method: A case report - with a representative case showing the innovative possibilities of an alternative mobilization option by means of a new orthesis ("iWALK 2.0"; IWALKFree Inc., Mansfield, Ontario, Canada) after surgical therapy of diabetic gangrene, exemplified by the successful clinical course.

Results: The inpatient admission of a 59-year-old male patient revealed septic gangrene of the right foot in insulin-dependent diabetes mellitus. After admission and initial diagnosis, the calculated antibiotics therapy and initial surgical rehabilitation of the right foot took place. After stabilization and control of the infection, the minor amputation was performed at the Bona-Jäger line without primary wound closure, wound care was provided by vacuum sealing. Complicated by pre-existing peroneal paralysis of the contralateral leg following herniated disc, mobilization could be accomplished out of the wheelchair using a novel "free-hand" orthesis "iWALK 2.0" and a walker with physiotherapeutic support. Thus, while simultaneously relieving the operated foot, self-sufficient mobilization at a later time was possible. This gave the patient a positive attitude to life in addition to more independence.

Conclusion: The successful application of the "free-hand" site "iWALK 2.0" under the listed clinical constellation thus suggests that it is a clear alternative of "postoperative rehabilitation" in the diagnosis of a surgically treated diabetic foot gangrene after minor amputation with a consolidated wound while ultimately serving to achieve a more comprehensive level of experience for targeted use with a clearly defined indication.
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http://dx.doi.org/10.1055/a-0871-2612DOI Listing
February 2020

First report on extended distance between tumor lesion and adjacent organs at risk using interventionally applied balloon catheters: a simple procedure to optimize clinical target volume covering effective isodose in interstitial high-dose-rate brachytherapy of liver malignomas.

J Contemp Brachytherapy 2019 Apr 29;11(2):152-161. Epub 2019 Apr 29.

International School of Image-Guided Interventions, Magdeburg, Germany.

Purpose: Organs at risk (OARs), which are very close to a clinical target volume (CTV), can compromise effective tumor irradiation. The present study investigated the feasibility and safety of a novel approach, in particular, the extent of the dosimetric effect of distancing CTV from adjacent OARs by means of interventionally applied balloon catheters.

Material And Methods: Patients with peripheral hepatic malignancies, in whom the critical proximity of an OAR to the CTV in the assessment by contrast-enhanced magnetic resonance imaging (MRI) scans and the preplanning process were included. Additionally, patients underwent placement of an interventional balloon catheter during computed tomography (CT)-guided application of interstitial brachytherapy (iBT) catheters inserted into the tissue between hepatic capsule and adjacent OAR. The virtual position of an OAR without balloon catheter was anticipated and contoured in addition to contouring of CTV and OAR. The calculated dose values for CTV as well as 1 cc of the relevant OAR (D) with and without balloon were recorded. The D of the realized irradiation plan was statistically compared to the D of the virtually contoured OARs.

Results: In 31 cases, at least one balloon catheter was administered. The mean D of the OAR in the group with balloon(s) was 12.6 Gy compared with 16 Gy in the virtual cohort without the device, therefore significantly lower ( < 0.001). Overall, there were no acute complications. Severe (> 2 CTCAEv4.03) late complications observed in 3/31 (9.6%) patients during follow-up period after brachytherapy were most certainly not due to the balloon application. Side effects were probably associated with pre-existing serious diseases and potentially additional local late effects of the irradiation in general rather than with the balloon catheters.

Conclusions: The distancing of the adjacent OARs allows a higher D value of CTV, therefore allowing for more efficient local control.
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http://dx.doi.org/10.5114/jcb.2019.84798DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6536139PMC
April 2019

Forces and moments in cervical spinal column segments in frontal impacts using finite element modeling and human cadaver tests.

J Mech Behav Biomed Mater 2019 02 2;90:681-688. Epub 2018 Oct 2.

Cemter for NeuroTrauma Research, Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, United States; Department of Orthopaedic Surgery,Medical College of Wisconsin, Milwaukee, WI, United States. Electronic address:

Experiments have been conducted using isolated tissues of the spine such as ligaments, functional units, and subaxial cervical spine columns. Forces and or moments under external loading can be obtained at the ends of these isolated/segmented preparations; however, these models require fixations at the end(s). To understand the response of the entire cervical spine without the artificial boundary/end conditions, it is necessary to use the whole body human cadaver in the experimental model. This model can be used to obtain the overall kinematics of the head and neck. The forces and moments at each vertebral level of the cervical column segments cannot be directly obtained using the kinematic and mass property data. The objective of this study was to determine such local loads under simulated frontal impact loading using a validated head-neck finite element model and experiments from whole body human cadaver tests, at velocities ranging from 3.9 to 16 m/s. The specimens were prepared with a nine linear accelerometer package on the head, and a triaxial accelerometer with a triaxial angular rate sensor on T1, and a set of three non-collinear retroreflective targets were secured to the T1 using the accelerometer mount. A similar array of targets was attached to the skull. Head accelerations were computed at the center of gravity of the head using specimen-specific physical properties. Upper and lower neck forces were computed using center of gravity acceleration data. This dataset was used to verify a previously validated finite element model of the head-neck model by inputting the mean T1 accelerations at different velocities. The model was parametrically exercised from 4 to 16 m/s in increments of 3 m/s to determine the forces and moments in the local anatomical system at all spinal levels. Results indicated that, with increasing velocities, the axial loading was found to be level-invariant, while the shear force and moment responses depended on the level. The nonuniform developments of the segmental forces and moments across different spinal levels suggest a shift in instantaneous axis of rotations between the across different spinal levels. Such differential changes between contiguous levels may lead to local spinal instability, resulting in long-term effects such as accelerated degeneration and spondylosis. The study underscored the need to conduct additional research to include effects of posture and geometrical variations that exist between males and females for a more comprehensive understanding of the local load-sharing in frontal impacts.
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http://dx.doi.org/10.1016/j.jmbbm.2018.09.043DOI Listing
February 2019

Broadband terahertz pulse generation driven by an ultrafast thin-disk laser oscillator.

Opt Express 2018 Oct;26(20):26377-26384

We demonstrate broadband THz generation driven by an ultrafast thin-disk laser (TDL) oscillator. By optical rectification of 50-fs pulses at 61 MHz repetition rate in a collinear geometry in crystalline GaP, THz radiation with a central frequency at around 3.4 THz and a spectrum extending from below 1 THz to nearly 7 THz are generated. We realized a spectroscopic characterization of a GaP crystal and a benchmark measurement of the water-vapor absorption spectrum in the THz range. Sub-50-GHz resolution is achieved within a 5 THz bandwidth. Our experiments show the potential of ultrafast TDL oscillators for driving MHz-repetition-rate broadband THz systems.
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http://dx.doi.org/10.1364/OE.26.026377DOI Listing
October 2018

[Pitfalls of Differential Diagnosis in Dermatologic Surgery].

Dtsch Med Wochenschr 2018 11 15;143(23):1682-1689. Epub 2018 Nov 15.

Evaluation of skin diseases can be challenging for non-dermatologists. Even obvious well-characterized skin pathologies might be misleading and thus treatment can fail. Particularly the differentiation of surgical treated entities is important, for example the management of a wound healing disturbance profoundly differs from that of a pyoderma gangrenosum. This article outlines several easily mistaken pairs of dermatologic entities on one hand and surgical on the other. For example, a livedo vasculopathy can be confused with a leg ulcer, a nail melanoma with a simple hematoma and finally a hidradenitis suppurativa with an axillary abscess. Typical clinical signs and anamnestic data may often lead to the right diagnosis also assisted by the simple fact to "keep it in mind".
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http://dx.doi.org/10.1055/a-0655-7103DOI Listing
November 2018

Vacuum-assisted closure (VAC) for postoperative secondary peritonitis: Effect on bacterial load as well as local and systemic cytokine response (initial results).

Pol Przegl Chir 2018 Aug;90(5):27-35

Municipal Hospital ("Klinikum") at Magdeburg (Germany) Dept. of Vascular Surgery.

Background: It is still a matter of debate what the best management of peritonitis is following eliminating the source of infection. This particularly concerns the amplitude of local and systemic inflammatory response as well as bacterial clearence at the infectious site.

Aim: To investigate the effects of vacuum-assisted closure (VAC) vs. relaparotomy on demand (ROD) onto the i) severity and course of disease, ii) surgical outcome, iii) intraperitoneal bacterial load as well as iv) local and systemic inflammatory and immune response in postoperative secondary peritonitis.

Methods: Over a defined time period, all consecutive patients of the reporting surgical department with a secondary peritonitis (assessed by Mannheim's Peritonitis Index [MPI] and APPACHE II score) were enrolled in this systematic unicenter clinical prospective observational pilot study reflecting daily surgical practice and as a contribution to internal quality assurance. Patients were subclassified into VAC or ROD group according to surgeon's individual decision at the time point of primary surgical intervention with the intent to sanitize the source of infection. Early postoperative result was assessed by 30-d and in-hospital mortality. Bacterial load was characterized by microbiological culture of intraperitoneal fluid collection obtained on postoperative days (POD) 0 (primary surgical intervention), 1, 4, 7, 10, 13 and following description of the microbial spectrum including semiquantitative assessment of bacterial load. Local and systemic inflammatory and immune response was determined by ELISA-based analysis of CrP, PCT and the representative cytokines such as TNF-α, IL-1β, IL-6, IL-8, and IL-10 of serum and peritoneal fluid samples.

Results: Over a 26-months investigation period, 18 patients (sex ratio, male:female=9:9) were eligible for study criteria: n=8 were enrolled in the VAC (m:f=4:4) and n=10 in the ROD group (m:f=5:5). With regard to early postoperative results represented by mortality, there is no significant difference between both patients groups. Despite the relatively low number of cases enrolled in this study, a trend for more severe findings associated with the VAC group could be detected based on MPI score. There was also a trend of higher APACHE II scores in the VAC group from the 7th POD on and, in addition, patients of this group had a longer hospital stay. For patients with persisting infection, there were no relevant differences comparing VAC therapy and ROD. Cytokines released, in particular, at the beginning of the inflammation cascade with proinflammatory characteristics, showed higher values within the peritoneal fluid whereas CrP and PCT were found to be higher within the serum samples. Summary & Conclusion: Comparing data of various local and systemic inflammatory and immune parameters, there were only a few correlations. This may indicate a compartimentation of the inflammatory process within the abdominal cavity. Based on the observed inter-individual variation of this pilot study data, the clinically applicable benefit appears questionable. In this context, a reliable effect of VAC therapy onto reduction of bacterial burden within the abdominal cavity could not clearly be detected.
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http://dx.doi.org/10.5604/01.3001.0012.1751DOI Listing
August 2018