Objective To investigate the biological and biomechanical characteristics of acellular porcine aortic valve with dye mediated photo oxidation so that a new and better bioprosthetic valve materials can be obtained. Methods Thirty porcine aortic valves were divided into three groups with random number table. Acellular valves (n=10) were stabilized by dye mediated photo oxidation in dye mediated photo oxidation group; acellular valves (n=10) were stabilized by glutaraldehyde in glutaraldehyde group; and acellular valves (n=10) were acellularized only in acellular valves group. Thickness, appearance, histology, water content, shrinkage temperature, breaking strength and soluble protein level of acellular porcine aortic in three groups were tested respectively. Results There were light blue, soft, flexible and unshrinking valves in dye mediated photo oxidation group. Compared to valves in glutaraldehyde group, valves in dye mediated photo oxidation group had lighter thickness（0.26±0.09mm vs. 0.38±0.08mm，Plt;0.05）, more water content（86.30%±4.03% vs. 71.10%±3.23%，Plt;0.05）, and lower shrinkage temperature （76.30±0.70℃ vs. 87.70±0.30℃，Plt;0.05）; while these indexes had no statistically significant differences compared to those in acellular valves group. At the same time, compared to valves in acellular valves group, valves in dye mediated photo oxidation group had more breaking strength（17.33±2.65 mPa vs. 9.11±0.95 mPa，Plt;0.05） and lower soluble protein level（0.039%±0.013% vs. 0.107%±0.024%，Plt;0.05）; while these indexes had no statistically significant differences compared to those in glutaraldehyde group. Conclusion Acellular porcine aortic valve stabilized by dye mediated photo oxidation has nice biological and biomechanical characteristics.
Objective To compare the biomechanical stability of Kirschner wire and tension band wiring, reconstruction plate combined with tension band wiring, and olecranon anatomical plate in fixing proximal ulna combined with olecranon fracture, so as to provide the theoretical evidence for clinical selection of internal fixation. Methods Eight specimens of elbow joints and ligaments were taken from eight fresh male adult cadaveric elbows (aged 26-43 years, mean 34.8 years) donated voluntarily. The model of proximal ulna combined with olecranon fracture was made by an osteotomy in each specimen. Fracture end was fixed successively by Kirschner wire and tension band wiring (group A), reconstruction plate combined with tension band wiring (group B), and olecranon anatomical plate (group C), respectively. The biomechanical test was performed for monopodium compression experiments, and load-displacement curves were obtained. The stability of the fixation was evaluated according to the load value when the compression displacement of fracture segment was 2 mm. Results No Kirschner wire withdrawal, broken plate and screw, loosening and specimens destruction were observed. The load-displacement curves of 3 groups showed that the displacement increased gradually with increasing load, while the curve slope of groups B and C was significantly higher than that of group A. When the compression displacement was 2 mm, the load values of groups A, B, and C were (218.6 ± 66.9), (560.3 ± 116.1), and (577.2 ± 137.6) N, respectively; the load values of groups B and C were significantly higher than that of group A (P lt; 0.05), but no significant difference was observed between groups B and C (t=0.305, P=0.763). Conclusion The proximal ulna combined with olecranon fracture is unstable. Reconstruction plate combined with tension band wiring and olecranon anatomical plate can meet the requirement of fracture fixation, so they are favorable options for proximal ulna combined with olecranon fracture. Kirschner wire and tension band wiring is not a stable fixation, therefore, it should not be only used for proximal ulna combined with olecranon fracture.
Objective To observe the changes of force bearing area and pressures of the rabbit tibiofemoral contact area and the biomechanical reconstruction level of joint after meniscal allograft. Methods A total of 28 Japanese rabbits were involved, weighing 3.0-3.5 kg, male or female. Of 28 rabbits, 7 were selected as meniscus donors, the remaining 21 rabbits were randomized into group A (n=7), group B (n=7), and group C (n=7). Group A underwent single knee opening and suturing, group B underwent medial meniscus excision and suturing, and group C underwent medial meniscus allograft after medial meniscus excision and suturing. The rabbits were sacrified at 12 weeks after operation for biomechanical observation through biomechanical machine and color imaging system. The meniscus tissue specimens were harvested from groups A and C to perform histological and immunohistochemical staining. Results After operation, all rabbits in 3 groups survived to the end of experiment. There were significant differences in the force bearing area and pressures at 0-90° flexion between group B and groups A, C (P lt; 0.05) at 12 weeks, showing no significant difference between group A and group C (P gt; 0.05); and there were significant differences in the force bearing area and pressures at 120° flexion among 3 groups (P lt; 0.05). The histological observation showed that the number of cartilage cells and collagen fibers returned to normal in group C, and the immunohistochemical staining showed that transplanted meniscus of group C contained large amounts of collagen fibers consisting of collagen type I and collagen type II. After 12 weeks of operation, the collagen type I contents were 0.612 5 ± 0.059 8 in group A and 0.587 2 ± 0.063 9 in group C, showing no significant difference (t=0.765, P=0.465); the collagen type II contents were 0.772 4 ± 0.081 5 and 0.814 3 ± 0.051 7, respectively, showing no significant difference (t= —0.136, P=0.894). Conclusion The allograft of rabbit meniscus can significantly increase the force bearing area of the tibiofemoral contact area and reduce the average pressure. Therefore, biomechanically speaking, the meniscus allograft can protect the articular cartilage and reconstruct the biomechanical balance.
Objective To review the research and appl ication of functional tissue engineered tendons (FTETs). Methods Recent l iterature concerning the research of FTETs was reviewed and analyzed. Results Functional tissue engineering (FTE) was a new approach that placed an emphasis on the importance of mechanical stress in determining the success of tissue engineered constructs and the effect of tissue remodel ing in vivo. The concept of FTE was introduecd into the research of tissue engineered tendons; by measuring in vivo loads of normal tendon and using the information as a guidel ine, theappropriate tissue engineered tendon which can withstand in vivo loads was designed. It would be possible to solve the problems that the biomechanical function of the tissue engineered tendons could not meet the requirements of the loading environment in vivo. Conclusion FTETs have a more promising future for the treatment of tendon defects.
【Abstract】 Objective To investigate the feasibil ity of applying enzymatic method to prepare decellularizedporcine aorta and to evaluate its biomechanical properties, immunogenicity and cell compatibil ity. Methods 0.1% trypsin- 0.01% EDTA was appl ied to extract cells from porcine aorta under 37 continuously vibrating condition and its histology and microstructure were observed. The thickness, stress-strain curve, ultimate tension stress (UTS) and strain of failure (SOF) were compared before and after decellularization for 48, 96 and 120 hours under uniaxial tensile tests, respectively. The histological change was observed at 1, 3 and 6 weeks after the decellularized tissue was implanted subcutaneously in 3 dogs. According to the HE stains and a semi-quantitative Wakitani grading method, gross changes, category and amounts of infiltrated cells and neo-capillaries were compared between pre- and post-decellularization of porcine aortae. Endothel ial cells from canine external jugular vein were seeded onto the decellularized patches to observe the cell compatibil ity. Results Microscopy and electron microscopies examination identified that cell components was completely removed from the fresh porcine aorta and Masson’ strichrome showed that the structure of matrix (fibrins) was maintained intact at 96 hours using the decellularization method. There were no significant differences in the thickness, UTS and SOF between before and after decellularization (P gt; 0.05). However, The UTS values showed a decrease tendency and SOF showed an increase tendency. The stress-strain curve also verified a decrease tendency in mechanical intensity and an increase one in ductil ity after decellularization. After implanting the acellularized matrix subcutaneously in canine, moderately lymphocyte infiltration was seen at the 1st week and the infiltration was replaced by fibroblasts accompanied by neocapillary formation at the 6th week. A semi-quantity histological evaluation showed that there were differences in gross observation, category and the numbers of the infiltrated cells between decellularized and non-decellularized tissues（P lt; 0.05). A cell monolayer was identified by HE staining and scanning electron microscopywhen the endothel ial cells were seeded onto the inner luminal surface of the scaffold, al igned at the same direction on the whole. Conclusion The decellularized porcine aortic scaffold, prepared by trypsin-EDTA extraction under continuously vibrating condition, could meet the requirements of tissue-engineering graft in biomechanical properties, immunogenicity and cell compatibil ity.
Objective To discuss the method of constructingbiomechanical model of rabbit femur.Methods The sample of rabbit femur was prepared as follows:firstly，femur section images were obtained，then the image wasput into the computer and processed to get the boundary contour line; secondly, through programming the contour line coordinate for modeling was obtained, then the data were put into the model software to find the threedimensional entity model. Results Whole three-dimensional model of rabbit femur was constructed. It simulated actually dissection form of femur. Conclusion The establishment of the model lays a foundation for ascertaining optimal parameter of vibration improving bone minerydensity by finite element analysis.
ObjectiveTo completely establish a three-dimensional (3D) simulation model of degenerative lumbar scoliosis (DLS) with the whole lumbar segments, then to analyze the biomechanical changes of the scoliosis segments by finite element analysis.MethodsA case of DLS patient was selected with L1-5 segments of CT scanning data, which was imported into MIMICS 15, SolidWorks, Hyper-Mesh software to establish a 3D simulation model, and ANSYS 15 was used to analyze the model. At the same time, different material properties and boundary loading conditions were assigned to various structures to simulate the actual human body conditions.ResultsThe 3D model built a total of 856 154 units and 232 850 nodes, including the reconstruction of fine vertebral bodies, intervertebral disc tissue, structure of various ligaments and joint cartilages. Under the load and torque, the range of whole lumbar segments was decreased, in the stress distribution on the four discs: the L2/3 intervertebral disc stress value (3.320 MPa) > L 4/5 intervertebral disc stress value (0.783 MPa) > L 3/4 intervertebral disc stress value (0.551 MPa) > L 1/2 intervertebral disc stress value (0.462 MPa). The stress distribution of the vertebral body showed that, L5 vertebral stress (34.0 MPa) > L 4 (33.6 MPa) >L 3 (30.0 MPa) > L 1 (23.3 MPa) > L 2 (22.4 MPa).ConclusionThe range of motion of the six degrees of freedom of the lumbar spine in DLS is decreased, the local stress distribution of the lumbar spine is abnormal, and the abnormal stress changes of the apical vertebral body and the top intervertebral disc may be the biomechanical basis for the occurrence or progression of DLS.
ObjectiveTo explore the feasibility of the clinical application of individualized simulated S1 pedicle screw.MethodsThe data of patients with lumbar disease diagnosed and treated in the Fourth People’s Hospital of Zigong from May 2017 to April 2019 were retrospectively analyzed. According to the preoperative individualized design of the S1 pedicle screw placement path, the patients were divided into individualized screw placement group and traditional screw placement group. The distance D between the screw tip and the endplate of the S1, the angle α of the screw in the plane of the dysplasia and the lumbar pedicle of the L5, the angle of oblique angle β, the number of screws of 35 and 40 mm in length, and the screw loosening rate (followed-up within 1 year) in the two groups were analyzed.ResultsA total of 59 patients were enrolled in this study, 31 in the individualized screw placement group and 28 in the traditional screw placement group. The differences in the distance D between the screw tip and the endplate of the S1 [(2.61±0.82) vs.(4.13±1.51) mm; t=-5.718, P<0.001], the angle α of the screw in the plane of the dysplasia and the lumbar pedicle of the L5 [(9.31±3.52) vs. (13.53±4.78)°; t=-5.646, P<0.001], the angle of oblique angle β [(15.73±6.04) vs. (10.65±5.09)°; t=3.022, P=0.004], the proportion of using screw models [40 mm in length: 56 vs. 8; 35 mm in length: 6 vs. 48; χ2=68.539, P<0.001], and the screw loosening rate followed-up within 1 year [3.22% vs. 16.07%; χ2=5.774, P<0.001] were statistically significant between the individualized screw placement group and the traditional screw placement group.ConclusionsPreoperative individualized design of the pedicle screw of the S1 pedicle screw can be used in clinical practice. The biomechanical stability of the S1 pedicle screw can be improved and the sagittal balance can be achieved.
Idiopathic pulmonary fibrosis (IPF) is a progressive scar-forming disease with a high mortality rate that has received widespread attention. Epithelial mesenchymal transition (EMT) is an important part of the pulmonary fibrosis process, and changes in the biomechanical properties of lung tissue have an important impact on it. In this paper, we summarize the changes in the biomechanical microenvironment of lung tissue in IPF-EMT in recent years, and provide a systematic review on the effects of alterations in the mechanical microenvironment in pulmonary fibrosis on the process of EMT, the effects of mechanical factors on the behavior of alveolar epithelial cells in EMT and the biomechanical signaling in EMT, in order to provide new references for the research on the prevention and treatment of IPF.
In order to understand how the biomechanical properties of rabbit cornea change over time after corneal ablation, 21 healthy adult rabbits were used in this study, with the left eye as experimental side and the right eye as the control side. Firstly, a lamellar knife was used to remove a portion of the anterior corneal surface tissue (30%~50% of the original corneal thickness) from the left eye of each rabbit, as an animal model simulating corneal refractive surgery. Secondly, postoperative experimental rabbits were kept for one, three, or six months until being euthanized. Strip specimens were produced using their corneas in vitro to perform a uniaxial tensile test with an average loading-unloading rate of approximately 0.16 mm/s. Finally, the visco-hyperelastic material constitutive model was used to fit the data. The results showed that there was a significant difference in the viscoelastic parameters of the corneas between the experimental and the control eyes at the first and third postoperative months. There was a difference in tangential modulus between the experimental and the control eyes at strain levels of 0.02 and 0.05 at the third postoperative month. There was no significant difference in biomechanical parameters between the experimental and the control eyes at the sixth postoperative month. These results indicate that compared with the control eyes, the biomechanical properties of the experimental eyes vary over postoperative time. At the third postoperative month, the ratio of corneal tangential modulus between the experimental and the control eyes significantly increased, and then decreased. This work lays a preliminary foundation for understanding the biomechanical properties of the cornea after corneal refractive surgery based on rapid testing data obtained clinically.