Molecular weight characterization of virgin and explanted polyester arterial prostheses.
The macromolecular properties of 17 virgin commercial arterial prostheses and a series of explanted prostheses, both manufactured from poly(ethylene terephthalate) (PET) yarns, have been studied by gel permeation chromatography (GPC) and by differential scanning calorimetry (DSC). Only small differences were found between the average molecular weights and the degree of crystallinity of the unused reference grafts. A broadening of the DSC curves was observed for the prostheses containing texturized yarns compared with those made solely from flat, untexturized yarns. This broadening may be due to greater heterogeneity of the crystal sizes caused by the texturizing process and to the use of two or more different yarns with dissimilar thermal histories in the same prosthesis. Average molecular weights of the explant series were significantly lower than those of the corresponding reference grafts but almost time independent. The polydispersity index and the degree of crystallinity of the explants remained constant as a function of time. These results are discussed in regard to others available in the literature.
Retromuskuläre Netzplastik in Deutschland
ZusammenfassungAusgehend von den enttäuschenden Ergebnissen der primären Nahtreparation von Narbenhernien und neueren Forschungsergebnissen, die eine gestörte Narbenbildung als wesentliche Ursache nahe legen, ist die Netzplastik heute als Methode der Wahl zur Reparation von Narbenhernien anzusehen. Eine konsequente Weiterentwicklung der seit über 40 Jahren eingesetzten Polypropylennetze führte zu den von uns favorisierten großporigen, materialreduzierten Prothesen, die den physiologischen Bedürfnissen der Bauchwand angepasst sind und eine optimale Gewebsintegration sicherstellen. Dabei ließen sich mit der retromuskulären “Sublay-Position” die auch reproduzierbar besten Ergebnisse erzielen. Als wesentlicher Vorteil ist hierbei die Fixierung der Prothese durch den intraabdominellen Druck anzusehen. Im Langzeitverlauf lassen sich hiermit Rezidivraten von unter 10% realisieren. Analysiert man die nach vermeintlich korrekt durchgeführter “Sublay-Reparation” möglichen Rezidivhernien, so ist im Wesentlichen eine inadäquate Überlappung der Prothese meist am kranialen oder kaudalen Ende der Inzision für das Versagen der Operation verantwortlich zu machen. Aus unserer Sicht stellt daher eine Überlappung von mindestens 5–6 cm in allen Richtungen eine zwingend einzuhaltende Voraussetzung für eine erfolgreiche Operation dar. Insbesondere mit den modernen leichtgewichtigen Netzen lassen sich mit der retromuskulären “Sublay-Netzplastik” exzellente Ergebnisse bezüglich Rezidivraten, Komplikationen und Patientenkomfort erzielen.AbstractSince the onset of an incisional hernia is caused by the biological problem of forming stable scar tissue, the mesh techniques are now the methods of choice for incisional hernia repair. Polypropylene is the material most widely used for open mesh repair. New developments have led to low-weight, large-pore polypropylene prostheses, which have been adapted to the physiological requirements of the abdominal wall and permit a reliable tissue integration. These meshes make it possible for a scar net to form rather than a stiff scar plate, thus helping to avoid the complications encountered with the use of earlier meshes. The ideal position for the mesh seems to be the retromuscular underlay position, in which the force of abdominal pressure holds the prosthesis tightly against the deep surface of the muscles. The retromuscular underlay repair technique has yielded the lowest incidence rates for recurrence: around 10% even after long-term follow up. Analysis of the failures after open mesh repair suggests that inadequate size of the mesh with insufficient overlap at the edges is the main reason for recurrence. An overlap of at least 5–6 cm all round must therefore be considered mandatory for successful reinforcement of the abdominal wall. Open mesh repair, particularly with modern low-weight polypropylene meshes applied by the retromuscular underlay technique, offers excellent results in the treatment of incision hernias, even in long-term follow-up studies.
Measuring Sheet Resistances of Dielectrics Using Co‐Planar Hydrogel Electrochemical Cells with Practical Applications to Characterize the Protective Quality of Paints on Sculptures
Electrical properties of thin dielectric films at the solid-liquid phase boundary are an important performance characteristic of many devices, coatings and sensors. In this paper, co-polymeric hydrogels of polyacrylic acid co-sulfonic acid, swollen with a salt solution to act as the solid electrolyte, were used to assess interfaces using electrochemical impedance spectroscopy (EIS) in a co-planar geometry. Silane-modified glasses were characterized by the co-planar hydrogel EIS cell and found to be distinguishable based on their surface monolayer chemistry. EIS measurements were also made on primed and painted metal substrates, using both test panels and an outdoor sculpture, Tony Smith's Stinger. The panels were then exposed to accelerated and outdoor weathering and showed degradation on the surface paint layers, which was observable electrochemically using EIS and confirmed visually by SEM. Electrochemical spectral features were compared between data from a standard paint-test cell versus this co-planar hydrogel cell; both cell types were able to measure coating capacitance, providing useful information about the condition of the bulk coating. Yet, sheet resistance (Rs) was a spectral feature seen only by the co-planar hydrogel cell. Thus, it can be concluded that the use of such co-planar hydrogel cells can provide an earlier warning sign to coating degradation and such cells provide a new type of spectral information that is not assessable by the standard geometry.