| OBJECTIVE: To analyze the biostress changes of internal fixation screws and vertebral bodies under different loading conditions by using finite element method(FEM),and to find the maximum risk of pedicle screw placement in long segment fixation.At the same time,it can maintain a reasonable three-dimensional orthopedic surgery.Methods A TPV-L5 spine of a degenerative scoliosis patient with posterior spinal fixation was performed by a 64-slice CT scanner.The thickness of the T12-L5 spine was 1 mm.260 CT images were obtained and burned in DICOM format.Save the file and import it into mimics17.0 software to obtain the full-segment fixed 3D model of the spine and nail rod system after degenerative scoliosis in T12-L5 segment,and then establish the intermittent nail according to the designed model.Three sets of 3D models of vertebral nails and key position nails were converted into finite element mesh models,and the specific material properties of the spine model of degenerative scoliosis patients were given.Finally,4 groups of regressions were established.A three-dimensional finite element model of scoliosis.The above model was introduced into the Ansys software to apply a 400 N load to the model in the initial state of simulating upright,flexion,extension,left flexion,and right flexion(ie,the initial state of each motion did not produce displacement).Apply 10N/M load under rotating and right rotating conditions.The stress changes of the post-nail system under different working conditions were analyzed.RESULTS: We completely established four sets of finite element models,in which the total segment fixed group totaled 1125627 units and 1708211 nodes,the discontinuous nail group totaled 1021934 units and 1548315 nodes,and the key vertebral nail group totaled1021948 units and 1548464.For each node,the key group location nail group has a total of997,735 units and 1511042 nodes.Precursor,extension,lateral flexion,and rotating conditions will greatly increase the force of the nail system.The force is more concentrated on the ends ofthe nail rod system.The comparison of the four kinds of nailing schemes: the whole section of the nailing rod system has the least stress,the vertebral body is also relatively balanced,and the key vertebra nailing scheme is slightly stressed.More than the full segment of the nail,and the vertebral body force is similar to the full segmental nailing procedure.The force of the intermittent nailing rod system is similar to that of the key vertebral nailing procedure,but the force of the vertebral body is too concentrated,presenting a In the unbalanced state,the key position is the least affected by the nail,but the nail system is the most stressed,and it also presents an imbalance.Conclusion 1.It is especially important to wear the protective gear in the early postoperative period,and pay special attention to reduce the above action in the life of the patient.During the operation,special attention should be paid to the success rate of the nail placement during the nail placement at the ends of the nail rod system.If necessary,the thicker pedicle screw can be used when the nail is placed at both ends of the head and tail.The rear screw break can also play a positive role.2.For the surgical nailing program of patients with degenerative scoliosis,under the premise of good physical condition and economic conditions,the whole-segment nailing program is the most secure,taking into account the risk of surgical nailing,operation time,and bleeding.In terms of volume,complications,and affordability,the key vertebral nailing program is also a reasonable surgical alternative.In clinical work,we can choose a reasonable nailing solution according to the actual situation of the patient. |
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