ObjectiveTo clarify the structure and biomechanical characteristics of the dura mater of the cervical, thoracic, and lumbar segments of sheep, in order to provide a theoretical reference for the study of artificial dura mater.MethodsFive adult male white sheep were sacrificed. The dura mater of C5, T10, and L3 planes were obtained. The histological HE staining was used to observe the internal structure and the thickness of dura mater; the inner and outer surfaces morphology of the dura was observed by scanning electron microscopy (SEM); transmission electron microscopy (TEM) was used to observe the internal structure of dura mater and to measure the diameter of collagen fibers in each part of dura mater. The dura mater of C6, C7, T11, T12, L4, and L5 planes were taken for uniaxial biomechanical test, and modulus of elasticity, tensile strength, and elongation at break were measured.ResultsHE staining showed that the thickness of the cervical, thoracic, and lumbar dura mater gradually decreased, and the thickness of the dura mater was (268.19±15.91), (198.16±27.25), (103.74±21.54) μm, respectively, and the differences were significant (P<0.05). SEM observation showed that there were more collagen fibers and fewer cells on the inner surface of the dura mater, while more cells were distributed on the outer surface, and the cells on the inner and outer surface were stretched along the longitudinal axis. TEM observation showed that the collagen fibers in the dura mater were interlaced and arranged in layers. The collagen fibers in the lamina were arranged in the same direction, and the collagen fibers between the lamina were arranged vertically. The diameters of collagen fibers in the cervical, thoracic, and lumbar dura mater were (68.04±21.00), (64.54±20.64), (60.36±19.65) nm, respectively, and the differences were not significant (P>0.05). Uniaxial biomechanical tests results showed that there was no significant difference in modulus of elasticity, tensile strength, and elongation at break between the axial and transverse dura mater of the cervical dura mater (P>0.05); the axial data of thoracic and lumbar segments were significantly larger than the transverse data (P<0.05). The axial modulus of elasticity, tensile strength, and elongation at break of the dura mater of the cervical, thoracic, and lumbar dura mater were significantly different (P<0.05) from the transverse ones, and showing a decreasing trend. Among them, the ratio of axial and transverse modulus of elasticity of cervical and thoracic dura were significantly smaller than that of lumbar segment (P<0.05), and there was no significant difference between cervical segments and thoracic segments (P>0.05).ConclusionThe thickness of dura mater in sheep decreased gradually from head to tail. There are more collagen fibers and fewer cells on the inner surface of dura mater, while the outer surface of dura mater is covered by cells. The collagen fiberboard layers in the dura mater are arranged alternately, and have obvious anisotropic biomechanical characteristics, and the anisotropic biomechanical characteristics get more significant from the head to the tail.
ObjectiveTo investigate the feasibility and mechanical properties of polymethyl methacrylate (PMMA) bone cement and allogeneic bone mixture to strengthen sheep vertebrae with osteoporotic compression fracture.MethodsA total of 75 lumbar vertebrae (L1-L5) of adult goats was harvested to prepare the osteoporotic vertebral body model by decalcification. The volume of vertebral body and the weight and bone density before and after decalcification were measured. And the failure strength, failure displacement, and stiffness were tested by using a mechanical tester. Then the vertebral compression fracture models were prepared and divided into 3 groups (n=25). The vertebral bodies were injected with allogeneic bone in group A, PMMA bone cement in group B, and mixture of allogeneic bone and PMMA bone cement in a ratio of 1∶1 in group C. After CT observation of the implant distribution in the vertebral body, the failure strength, failure displacement, and stiffness of the vertebral body were measured again.ResultsThere was no significant difference in weight, bone density, and volume of vertebral bodies before decalcification between groups (P>0.05). After decalcification, there was no significant difference in bone density, decreasing rate, and weight between groups (P>0.05). There were significant differences in vertebral body weight and bone mineral density between pre- and post-decalcification in 3 groups (P<0.05). CT showed that the implants in each group were evenly distributed in the vertebral body with no leakage. Before fracture, the differences in vertebral body failure strength, failure displacement, and stiffness between groups were not significant (P>0.05). After augmentation, the failure displacement of group A was significantly greater than that of groups B and C, and the failure strength and stiffness were less than those of groups B and C, the failure displacement of group C was greater than that of group B, and the failure strength and stiffness were less than those of group B, the differences between groups were significant (P<0.05). Except for the failure strength of group A (P>0.05), the differences in the failure strength, failure displacement, and stiffness before fracture and after augmentation in the other groups were significant (P<0.05).ConclusionThe mixture of allogeneic bone and PMMA bone cement in a ratio of 1∶1 can improve the strength of the vertebral body of sheep osteoporotic compression fractures and restore the initial stiffness of the vertebral body. It has good mechanical properties and can be used as one of the filling materials in percutaneous vertebroplasty.
ObjectiveTo explore the safety and feasibility of the establishment method and management strategy of prolonged support model with veno-venous extracorporeal membrane oxygenation (V-V ECMO) under dual lumen cannula (DLC) in conscious sheep.MethodsThree adult male sheep were selected. An Avalon Elite DLC was inserted into the superior vena cava, right atrium, and inferior vena cava through the right jugular vein and was connected with centrifugal pump and oxygenator to establish the extracorporeal membrane oxygenation circuit. All the 3 sheep were transferred into the monitoring cage after operation and were ambulatory after anesthesia recovery. Hemodynamic parameters and extracorporeal membrane oxygenation performance were measured every day.ResultsAll three sheep survived to the end of the experiment (7 days). In the whole process of the experiment, the basic vital signs of the experimental sheep were stable, and no serious bleeding or thrombotic events occurred. During the experiment, hemoglobin concentration and platelet count were relatively stable, plasma free hemoglobin was maintained at a low level, extracorporeal membrane oxygenation flow rate was stable, and oxygenation performance of oxygenator was good.ConclusionProlonged V-V ECMO model in conscious sheep under DLC is feasible and stable.