3D
printing of fiber-reinforced thermoset composites is desirable
for rapid fabrication of 3D composite objects with minimal tooling.
One of the main issues in 3D printing of thermoset composites is the
low cure rates of matrix resins, which prevents rapid curing and rigidization
of composite materials during the printing process and capturing the
desired print geometry. Here, we demonstrate a new technique for in situ printing and curing of carbon-fiber-reinforced thermoset
composites without any postcuring or postprocessing steps. Upon extrusion
and deposition of the composite ink from a printing nozzle, the ink
is cured via frontal polymerization, leading to rapid printing of
high-quality composites. Tailoring the processing conditions allows
for freeform or rapid, supported printing of 3D composite objects
with zero void content and highly oriented carbon fiber reinforcements.
An eight-year-old, male castrated basset hound presenting with a three-month history of lethargy was examined. Diagnostic tests including radiography and ultrasonography showed a right-sided renal mass. A 99mTc diethylenetriamine penta-acetic acid scan demonstrated that this kidney was non-functional. At surgery, invasion of the caudal vena cava was found, and the renal segment of the vena cava and the right kidney were resected. The left renal vein was anastomosed to the more proximal vena cava using a polytetrafluoroethylene graft, and the dog recovered well. Two days postsurgery, the dog suffered an acute episode of aspiration pneumonia and was euthanased. The renal mass was diagnosed as lymphoma on histopathology.
Background: The purpose of this study was to evaluate the mechanical, structural, and histologic quality of rotator cuff repairs augmented with an interposition electrospun nanofiber scaffold composed of polyglycolic acid (PGA) and poly-L-lactide-co-ε-caprolactone (PLCL) in an acute sheep model. Methods: Forty acute infraspinatus tendon detachment and repair procedures were performed in a sheep infraspinatus model using a double-row transosseous-equivalent anchor technique either with an interposition nanofiber scaffold composed of polyglycolic acid-poly-L-lactide-co-ε-caprolactone or with no scaffold. Animals were euthanized at the 6-week (20 samples) and 12-week (20 samples) postoperative time points to assess the biomechanical and histologic properties of the repairs and to compare differences within each group. Results: Within the scaffold-treated group, there was a significant increase in ultimate failure force (in newtons) from 6 to 12 weeks (P < .01), a significant increase in ultimate failure load from 6 to 12 weeks (P < .01), and a significant increase in ultimate failure stress (in megapascals) from 6 to 12 weeks (P < .01). At 6 weeks, the tendon-bone attachment was most consistent with an ''indirect'' type of insertion, whereas at 12 weeks, a visible difference in the progression and re-formation of the enthesis was observed. Compared with controls, animals in the scaffold-treated group displayed an insertion of the fibrous tendon with the humeral footprint that was beginning to be organized in a manner similar to the ''native'' direct/fibrocartilaginous insertion of the ovine infraspinatus tendon. In the majority of these animals treated with the scaffold, prominent perforating collagen fibers, similar to Sharpey fibers, were present and extending through a region of calcified fibrocartilage and attaching to the humeral footprint. No surgical complications occurred in any of the 40 sheep, including delayed wound healing or infection. Conclusions: In a sheep acute rotator cuff repair model, securing a nanofiber scaffold between the tendon and the bone using a doublerow transosseous-equivalent anchor fixation technique resulted in greater failure strength. Additionally, at the enthesis, Sharpey fiber-like attachments (ie, collagen fibers extending from the tendon into the calcified fibrocartilage of the humerus) were observed, which were not seen in the control group.Institutional review board approval was not required for this basic science study. This study was conducted under Institutional Animal Care and Use Committee approval by board-certified veterinary surgeons (Colorado State University no. 17-7154).
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