RESUMO
Objective Construct the finite element model of vertebral pedicle screw fixation in thoracolumbar fractures can obtain the intuitive systematic mechanical effects under different motion conditions, it has a very important significance to the patients' rehabilitation, evaluation of system stability and prognosis.In this study, the biomechanical effects of different motion states of thoracic and lumbar spine fracture models were analyzed by the finite element analysis method.Methods We selected 1 orthopedic health volunteers from Nanjing General Hospital of Nanjing Military Region in June 2014, established the finite element model by the CT scan data of the healthy volunteer, used the geometric cutting method for fracture simulation and replacement, assembled posterior orthopedic internal fixation system of vertebral pedicle screw, simulated the different motion states and obtained the stress nephogram and displacement graph of the nail-stick system..Results For the six-nail and two-rod internal fixation system of posterior nail-stick system which set nails through injured vertebrae, we used the finite element operation method to simulate the biomechanical characteristics of different modes of motion in space, it combined by the movement of six directions(flexion, dorsiflexion, left side bend, right side bend, left twist, right twist).The maximum stress(94.99±1.72MPa) and the maximum displacement(0.1854±0.0052mm) and the of the dorsiflexion were significantly lower than that of flexion[(126.82±5.56)MPa、(0.2502±0.0050)mm]、left side bend[(152.18±9.13)Mpa、(0.3172±0.0048)mm]、right side bend[(159.58±13.54)Mpa、(0.3315±0.0051)mm](P<0.05).Conclusion The method of finite element analysis can obtain clear and intuitive biomechanical data, which provides effective evidence for the evaluation of surgical efficacy, the development of postoperative rehabilitation methods and the evaluation of the stability of thoracolumbar spinal system.
RESUMO
Objective:To analyze risk factors that were associated with loss of correction curvature after short-segment restoration and fixation in cases who had single-segment thoracolumbar fracture.Methods:87 Cases who had experienced single-segment thoracolumbar fracture and had underwent short-segment restoration and fixation in our department from Jan 2008 to Jan 2011,and had complete follow-up imaging were included.Cobb angles were measured on lateral thoracolumbar X-ray preoperatively,postoperatively and before removal of internal fixation.And these included the angle formed by vertebras that located above and below injured vertebrae (α angle),superior endplate of injured vertebrae and its superior vertebrae (β angle),inferior endplate of injured vertebrae and its inferior vertebrae (γ angle),inferior and superior endplate of injured vertebrae (δ angle).T-test was used to analyze these angles and their changes.And correlation analysis was used to analyze relationships between α angle change and other risk factors.Results:When compared with preoperative angles,the mean α angle,β angle,γ angle and δ angle were all significantly increased (p＜0.05) after the operation.The mean α angle and δ angle before the removal of internal fixation were both significantly smaller than those after the operation (p＜0.05),and the mean change ofα angle was-2.85 degrees.After the correlation analysis,we found significant correlations between the change ofα angle and postoperative correction curvature(-0.342,p=0.026),injured region in endplate(0.374,p=0.015),and change of the δ angle(0.231,p=0.041).Conclusion:There was significant loss in the correction curvature before the removal of internal fixation.And the loss was significantly associated with postoperative correction curvature,injured region in endplate,and change of the δ angle.