Effect of Surgical Expertise on Biomechanical Properties of Sutures After Abdominal Wall Closure.

BACKGROUND: Despite preventive methods and careful surgical technique, surgical site infection and incisional hernias are of main concern after the closure of surgical incisions and keep haunting abdominal wall wound healing. The aim of this study is to find how surgical expertise level modifies biomechanical properties of sutures commonly used in abdominal wall fascial closure (polypropylene, polyglactin 910, polydioxanone). MATERIALS AND METHODS: Surgery residents with different experience levels performed abdominal wall fascial closure in swine models with the previously mentioned suture materials. A standardized technique was used. Sutures were removed, and a tensile stress test was performed on the removed sutures. A total of 81 abdominal fascial closures were achieved. Time, extension, maximum tensile force (Ftmax), and maximum stress were measured and analyzed. RESULTS: The results of the polydioxanone stress test present a trend in three variables: extension, tensile force, and stress. The trend shows higher medians in the expert group and lower medians in the novice group. While using polypropylene sutures, medians in the expert group are the highest; however, a trend is not observed. Polyglactin 910 sutures have nonspecific behavior among the different experience groups and variables. Polypropylene is the material with the lowest Ftmax tested and fails at 42.64 (IQR 40.98-44.89) N. Regarding the elastic properties of the material, polyglactin demonstrates the least extension of all sutures tested, with a 14 (IQR 13.33-14.83) mm extension. This study demonstrates that polydioxanone has a superior Ftmax compared with polypropylene and has a superior extension at failure properties compared with polyglactin, confirming that polydioxanone could be the suture of choice used for abdominal wall fascial closure. CONCLUSIONS: Study results do not show statistically significant differences regarding the impact of the experience level of different general surgery residents in the biomechanical properties of sutures used in abdominal wall fascial closure.

Sheet-based extrusion bioprinting: a new multi-material paradigm providing mid-extrusion micropatterning control for microvascular applications.

As bioprinting advances into clinical relevance with patient-specific tissue and organ constructs, it must be capable of multi-material fabrication at high resolutions to accurately mimick the complex tissue structures found in the body. One of the most fundamental structures to regenerative medicine is microvasculature. Its continuous hierarchical branching vessel networks bridge surgically manipulatable arteries (∼1-6 mm) to capillary beds (∼10µm). Microvascular perfusion must be established quickly for autologous, allogeneic, or tissue engineered grafts to survive implantation and heal in place. However, traditional syringe-based bioprinting techniques have struggled to produce perfusable constructs with hierarchical branching at the resolution of the arterioles (∼100-10µm) found in microvascular tissues. This study introduces the novel CEVIC bioprinting device (i.e.ContinuouslyExtrudedVariableInternalChanneling), a multi-material technology that breaks the current extrusion-based bioprinting paradigm of pushing cell-laden hydrogels through a nozzle as filaments, instead, in the version explored here, extruding thin, wide cell-laden hydrogel sheets. The CEVIC device adapts the chaotic printing approach to control the width and number of microchannels within the construct as it is extruded (i.e. on-the-fly). Utilizing novel flow valve designs, this strategy can produce continuous gradients varying geometry and materials across the construct and hierarchical branching channels with average widths ranging from 621.5 ± 42.92%µm to 11.67 ± 14.99%µm, respectively, encompassing the resolution range of microvascular vessels. These constructs can also include fugitive/sacrificial ink that vacates to leave demonstrably perfusable channels. In a proof-of-concept experiment, a co-culture of two microvascular cell types, endothelial cells and pericytes, sustained over 90% viability throughout 1 week in microchannels within CEVIC-produced gelatin methacryloyl-sodium alginate hydrogel constructs. These results justify further exploration of generating CEVIC-bioprinted microvasculature, such as pre-culturing and implantation studies.

Influence of Controlled Cooling on Crystallinity of Poly (L-Lactic Acid) Scaffolds after Hydrolytic Degradation.

The use of hybrid manufacturing to produce bimodal scaffolds has represented a great advancement in tissue engineering. These scaffolds provide a favorable environment in which cells can adhere and produce new tissue. However, there are several areas of opportunity to manufacture structures that provide enough strength and rigidity, while also improving chemical integrity. As an advancement in the manufacturing process of scaffolds, a cooling system was introduced in a fused deposition modeling (FDM) machine to vary the temperature on the printing bed. Two groups of polylactic acid (PLA) scaffolds were then printed at two different bed temperatures. The rate of degradation was evaluated during eight weeks in Hank's Balanced Salt Solution (HBSS) in a controlled environment (37 °C-120 rpm) to assess crystallinity. Results showed the influence of the cooling system on the degradation rate of printed scaffolds after the immersion period. This phenomenon was attributable to the mechanism associated with alkaline hydrolysis, where a higher degree of crystallinity obtained in one group induced greater rates of mass loss. The overall crystallinity was observed, through differential scanning calorimetry (DSC), thermo gravimetric analysis (TGA), and Fourier transformed infrared spectroscopy (FTIR) analysis, to increase with time because of the erosion of some amorphous parts after immersion.

Parenteral nutrition-associated liver disease and lipid emulsions.

Parenteral nutrition-associated liver disease (PNALD) is a particularly important problem in patients who need this type of nutritional support for a long time. Prevalence of the condition is highly variable depending on the series, and its clinical presentation is different in adults and children. The etiology of PNALD is not well defined, and participation of several factors at the same time has been suggested. When a bilirubin level >2 mg/dl is detected for a long time, other causes of liver disease should be ruled out and risk factors should be minimized. The composition of lipid emulsions used in parenteral nutrition is one of the factors related to PNALD. This article reviews the different types of lipid emulsions and the potential benefits of emulsions enriched with omega-3 fatty acids.

HDDD2 is a familial frontotemporal lobar degeneration with ubiquitin-positive, tau-negative inclusions caused by a missense mutation in the signal peptide of progranulin.

OBJECTIVE: Familial autosomal dominant frontotemporal dementia with ubiquitin-positive, tau-negative inclusions in the brain linked to 17q21-22 recently has been reported to carry null mutations in the progranulin gene (PGRN). Hereditary dysphasic disinhibition dementia (HDDD) is a frontotemporal dementia with prominent changes in behavior and language deficits. A previous study found significant linkage to chromosome 17 in a HDDD family (HDDD2), but no mutation in the MAPT gene. Longitudinal follow-up has enabled us to identify new cases and to further characterize the dementia in this family. The goals of this study were to develop research criteria to classify the different clinical expressions of dementia observed in this large kindred, to identify the causal mutation in affected individuals and correlate this with phenotypic characteristics in this pedigree, and to assess the neuropathological characteristics using immunohistochemical techniques. METHODS: In this study we describe a detailed clinical, pathological and mutation analysis of the HDDD2 kindred. RESULTS: Neuropathologically, HDDD2 represents a familial frontotemporal lobar degeneration with ubiquitin-positive, tau-negative inclusions (FTLD-U). We developed research classification criteria and identified three distinct diagnostic thresholds, which helped localize the disease locus. The chromosomal region with the strongest evidence of linkage lies within the minimum critical region for FTLD-U. Sequencing of each exon of the PGRN gene led to the identification of a novel missense mutation, Ala-9 Asp, within the signal peptide. INTERPRETATION: HDDD2 is an FTLD-U caused by a missense mutation in the PGRN gene that cosegregates with the disease and with the disease haplotype in at-risk individuals. This mutation is the first reported pathogenic missense mutation in the signal peptide of the PGRN gene causing FTLD-U. In light of the previous reports of null mutations and its position in the gene, two possible pathological mechanisms are proposed: (1) the protein may accumulate within the endoplasmic reticulum due to inefficient secretion; and (2) mutant RNA may have a lower expression because of degradation via nonsense-mediated decay.