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Objective To study thoracic re-remodeling and therapeutic effect after the bar removal for pectus excavatum corrected by minimal-invasive technique.Methods 145 cases with pectus excavatum,male 115,femal 30;adults in 59,children 86;corrected by minimal-invasive technique improved and performed by the same group surgeon.Bar removed 12-82 months after the procedure,appraising index of curative effects include in chest appearance,thoracic index,thoracic computer tomography(CT) and the distance between the behind of sternum to the anterior border of thoracic spine in the sagittal view.Results The chest shape was good.Thoracic index:before bar removal 2.36 ± 0.32 in children,2.60 ± 0.45 in adults;after that,2.77 ± 0.44 in children,3.04 ± 0.56 in adults.There was all subsidence on the each point of the sternum,descent the maximum at the inferior end of the midsternum,(15.18 ±7.95)mm in children,(14.93 ± 8.81) mm in adults,comparing with bar removal before and after.There was statistical significance.Not the signs of compressing the heart on the CT view.The time interval of the bar removed 3-year in children,5-year in adults without affecting the development of the patients' thorax.Conclusion The sternum descended slightly after bar removal when pectus excavatum corrected to expecting effects.After that,thoracic remodeling again,the chest shape well.
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BACKGROUND: Studies on the biomechanical properties in NUSS procedure have obtained some achievements, but the effect of scoliosis surgical correction of scoliosis on thoracic deformity remains unclear.OBJECTIVE: To explore the effect of simultaneous correction of pectus excavatum and scoliosis on thoracic deformity so as to provide reference for designing a rational orthopedic scheme.METHODS: The three-dimensional reconstruction model of the chest was established based on the CT data of the patients with pectus excavatum and scoliosis. The surgical correction of pectus excavatum and scoliosis was simulated by numerical simulation method.RESULTS AND CONCLUSION: (1) Results after correction showed that the bilateral spinous processes at T3-5 segments displaced to the left (X direction) about 1 mm, suggesting that the simultaneous correction is favorable for the correction of scoliosis. (2) Compared with the single NUSS procedure, the displacement at Y direction was increased by 13.358 mm in the simultaneous correction; meanwhile, there was significant difference in the shortest displacement between two methods.(3) In views of Von Mises stress distribution, the stress in the simultaneous correction was decreased by 24.6 MPa compared with the single Nuss procedure, indicating that the simultaneous correction can significantly reduce the Von Mises stress on the chest, which contributes to alleviate the postoperative pain. (4) Our results show that the simultaneous correction cannot only improve scoliosis, but also improve the symptoms of pectus excavatum.
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Objective To study the damage propagation and evolution mechanism of cartilage under compressive loads.Methods The fiber-reinforced porous elastic model of cartilage with micro-defect was established by using finite element method,and the process of damage evolution under compressive loads was simulated and analyzed with parameters.The patterns of stress and strain distributions on cartilage matrix and collagen fiber at different damage extension stages were obtained.Results The strain in the surface and forefront of cartilage damage increased significantly with the increase of compression displacement,and they were obviously in positive correlation;in the process of damage evolution,there was a trend that cartilage extended to the deep and both sides simultaneously;cracks and damage in cartilage extended preferentially along the fiber tangent direction.With the aggravation of cartilage damage,the lateral extension speed was significantly faster than the longitudinal extension speed.Conclusions The process of cartilage damage extension has a close relationship with the distribution of fibers.The damages in matrix and fiber promote each other.The evolution speed and degree of cartilage vary constantly in different layers and at different stages.These results can provide the qualitative reference for prediction and repair of cartilage damage,as well as the theoretical basis for explaining pathological phenomena of damage degeneration and its clinic treatment.
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BACKGROUND:As lumbar spine biomechanics research is unceasingly thorough and the constant development of related fusion and dynamic fixation device, the spine fusion technique which is represented by artificial disc replacement is a new choice to the spine surgeons. Therefore, it is particularly important to design reasonable artificial intervertebral disc. OBJECTIVE:To establish the finite element model of the new artificial disc replacement of the lumbar motion segment for further biomechanical study. METHODS:The L3-4 thin-section CT images of a healthy male volunteer was selected, combined with human anatomy data and applied the reverse engineering technology to rebuild the lumbar spine model with medical image software Mimics and tool software Geomagic Studio. The three-dimensional model of the silicone artificial disc was converted into a finite element model through software ANSYS12.0. RESULTS AND CONCLUSION:Through CT scanning, digital image processing and computer-aided design, the three-dimensional model of the lumbar motion segment and the finite element model of artificial disc replacement were successful y established. The finite element model contained 691 085 units and 1 008 913 nodes which could be applied constraint and load and could be used for spinal biomechanics and the further research of the new artificial intervertebral disc.
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There are many physical factors affecting the development of cartilage tissue,the mechanical con-dition is the main important one that particularly act.The mechanical conditions used in engineering cartilage tissue,such as compressive and shear force,fluid flow,hydrostatic pressure and tissue deformation or with some of them combined,were reviewed.From the standpoint of bionics,the mechanical environments ap-plied on tissue engineering should work in three aspects:providing adequately mechanical stimuli to the cells seeded in 3-D scaffold;ensuring the efficient mass-transport of the nutrients and waste products in the cells:promoting the development of functionally extracellular matrix in 3-D scaffold.The mechanical environments currently used only represented the part of mechanical conditions of in vive articular cartilage will be reviewed.In our view that rolling depression load may achieve the fit mechanical environment for cultivation of functional cartilage constructs in vitro.