Mechanical Properties Of Graft Research Articles

Short-Term Postoperative Mechanical Properties of Graft in Anterior Cruciate Ligament Reconstruction

Short-Term Postoperative Mechanical Properties of Graft in Anterior Cruciate Ligament Reconstruction

HuBiogel incorporated fibro-porous hybrid nanomatrix graft for vascular tissue interfaces

Native extracellular matrix (ECM) possesses the biochemical cues to promote cell survival. However, decellularized, the ECM loses its cell supporting mechanical integrity. We report, here, a new biohybrid vascular graft fabricated from a blend of polycaprolactone (PCL), poliglecaprone (PGC), and incorporated with human biomatrix as functional materials for vascular tissue interfacing applications, thus harnessing the biochemical cues from the ECM and the mechanical integrity of the polymer blends. The fabricated fibro-porous tubular small diameter graft (i.d. = 4 mm) from electrospun polymer blend was coated with HuBiogeltm, a cocktail of collagenous matrix derived from human placenta called . The compositional, morphological, and mechanical properties of graft were measured, analyzed, and compared with a non-coated tubular PCL/PGC graft using Fourier Transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). BCA assay was used to calculate the protein content and coating-uniformity throughout the hybrid graft. Mechanical properties such as tensile strength (1.6 MPa), Young's modulus (2.4 MPa), burst pressure (>1900 mmHg), and suture retention strength (2.3 N) of hybrid graft were found to be comparable to native blood vessels. Protein coating has improved the hydrophilicity and the biocompatibility (cell viability and cell-attachment) enhanced with human umbilical vein endothelial cells (HUVECs) seeded in vitro onto the lumen layer of the graft over two weeks. The overall results promise this new biohybrid graft to be a potential candidate for vascular tissue interface and regeneration.

Mechanical Analysis of Extra-Articular Knee Ligaments. Part two: Tendon grafts used for knee ligament reconstruction

ObjectivesThe aim of this study was to provide information about the mechanical properties of grafts used for knee ligament reconstructions and to compare those results with the mechanical properties of native knee ligaments. MethodsEleven cadaveric knees were dissected for the semitendinosus, gracilis, iliotibial band (ITB), quadriceps and patellar tendon. Uniaxial testing to failure was performed using a standardized method and mechanical properties (elastic modulus, ultimate stress, ultimate strain, strain energy density) were determined. ResultsThe elastic modulus of the gracilis tendon (1458±476MPa) (P<0.001) and the semitendinosus tendon (1036±312MPa) (P<0.05) was significantly higher than the ITB (610±171MPa), quadriceps tendon (568±194MPa), and patellar tendon (417±107MPa). In addition, the ultimate stress of the hamstring tendons (gracilis 155.0±30.7MPa and semitendinosus 120.1±30.0MPa) was significantly higher (P<0.001, respectively P<0.05), relative to the ITB (75.0±11.8MPa), quadriceps tendon (81.0±27.6MPa), and patellar tendon (76.2±25.1MPa). A significant difference (P<0.05) could be noticed between the ultimate strain of the patellar tendon (24.6±5.9%) and the hamstrings (gracilis 14.5±3.1% and semitendinosus 17.0±4.0%). No significant difference in strain energy density between the grafts was observed. ConclusionsMaterial properties of common grafts used for knee ligament reconstructions often differ significantly from the original knee ligament which the graft is supposed to emulate.

Tissue-engineered stent-graft integrates with aortic wall by recruiting host tissue into graft scaffold

To prevent postoperative migration and endoleaks after endovascular aneurysm repair, we developed a tissue-engineered vascular graft that integrates with the aortic wall by recruiting the host tissue into the graft scaffold. In the present study, we assessed the mechanical properties of the new graft and evaluated the integration between the graft and aortic wall histologically and mechanically in canine models. The tissue-engineered vascular graft was woven to be partially degradable with a double-layered fiber (core; polyethylene terephthalate [PET], and sheath; polyglycolic acid [PGA]). The mechanical properties of the graft were assessed compared with a thin-walled woven polyester graft (control; 12 mm in diameter, 30 mm long). The stent-grafts, composed of a stainless Z stent (20 mm in diameter, 25 mm long) and a PET/PGA or control graft (n=5 in each group), were implanted in the descending thoracic aorta of mongrel dogs for 2 months. We assessed the histologic findings of the explants and the degree of adhesion between the graft and aortic wall. The PET/PGA graft achieved nearly the same mechanical properties as those of the control graft in tensile strength and flexibility, with slightly greater water permeability. At 2 months after implantation, in the PET/PGA group, the PGA component had degraded and been replaced by host tissue that contained a mixture of α-smooth muscle actin-positive cells and other host cells. The graft was a unified structure with the aorta. The adhesion strength between the graft and aortic wall was significantly enhanced in the PET/PGA group. The PET/PGA stent-graft demonstrated histologic and mechanical integration with the native aorta. This next-generation stent-graft might reduce the risk of migration and endoleaks, leading to preferable long-term results of endovascular aneurysm repair.