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BACKGROUND:Vertebroplasty and kyphoplasty can effectively repair osteoporotic vertebral compression fractures, but bone cement injection can cause the change of stress in the fractured vertebrae and adjacent vertebrae after surgery, leading to new fractures. OBJECTIVE: To analyze the stress changes of the fractured vertebrae and adjacent vertebrae after vertebroplasty with different elastic modulus bone cement by a three-dimensional finite element method. METHODS: One healthy adult male volunteer was selected for lumbar spine CT scan. The acquired images were imported for three-dimensional reconstruction using Mimics. The three-dimensional model was smoothed, polished and denoised by Geomagic software, and then the solid mode was built under Workbench Ansys. An osteoporotic vertebral compression fracture model in L2-4 segments was established after assignment. Bone cement (4 mL) with different elastic moduli (8 000, 4 000, 2 000 and 1 000 MPa) injected into the L3 segment distributed in the middle of the vertebrae as spherical shape. 500 N pre-load was applied on the L2 surface with an additional bending moment of 50 N?m. The lower surface free degree of L4 was restrained. The L2-4 forward flexion, posterior extension, right flexion and axial rotation on the right side were stimulated. The stress changes of the fractured vertebrae and the upper and lower adjacent vertebrae before and after bone cement injection with different elastic moduli were compared. RESULTS AND CONCLUSION:The stress of the fractured vertebrae and adjacent vertebrae were significantly increased compared with that before operation. With the increase of elastic modulus, the stress of the fractured vertebrae increased, but there were no changes in the stress of adjacent vertebrae. These findings indicate that the elastic modulus of bone cement may be a method to reduce new fractures of the fractured and adjacent vertebrae after bone cement injection.
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BACKGROUND:Fisher-Lewis rat kidney transplant models are the international common chronic renal alograft rejection models, but their application is greatly limited because of difficulty in model preparation and high costs. OBJECTIVE:To explore a new method of establishing SD-Wistar rat models of chronic renal alograft rejection. METHODS: Fifty-six pairs of SD-Wistar rats were subjected to left kidney orthotopic transplantation. The right kidneys of the recipients were intact and used as internal controls. 23 rat recipients were randomly divided into model group (n=15) and control group (n=8). The rats in the model group were injected with cyclosporine microemulsion for 10 days (2 mg/kg/day,i.p.) after kidney transplantation. The rats in the control group were not treated with immunosuppressive therapy. RESULTS AND CONCLUSION:The irreversible acute rejection occurred in al the transplanted kidneys of rats in the control group within 4 weeks, leading to the necrosis of transplanted kidney. Moderate inflammatory cel infiltration appeared in the transplanted kidneys of rats in the model group at 4, 8 and 12 weeks after transplantation. Typical histopathological changes of chronic rejection were observed within 12 weeks after transplantation. The Banff total scores were increased with time after transplantation. Al these histopathological changes were not observed in the intact right kidneys of rat recipients in both groups. The valey value of
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BACKGROUND:Vertebroplasty and kyphoplasty can effectively repair osteoporotic vertebral compression fractures, but postoperative change of stress in the fractured vertebrae and adjacent vertebrae can lead to new fractures. OBJECTIVE:To analyze the stress changes of the fractured and adjacent vertebrae with different bone cement injection volume by three-dimensional finite element method. METHODS:One healthy adult male volunteer was selected for lumbar spine CT scan. The acquired images were imported for three-dimensional reconstruction using Mimics. The three-dimensional model was smoothed, polished and denoised by Geomagic software, and then the solid mode was built under Workbench Ansys. The osteoporotic vertebral compression fracture model in L2-L4 segments was established after assignment. Bone cement of 1, 2, 4, 6 mL was injected into the L3 vertebrae respectively and distributed in the middle of the vertebrae as spherical shape. 500 N pre-load was applied on L2 surface with an additional moment of 50 N·m. The lower surface free degree of L4 was restrainted. The L2-L4 forward flexion, extension, right flexion and axial rotation on the right side were stimulated to compare the stress changes of fractured vertebrae and adjacent vertebrae before and after the bone cement injection with different volume. RESULTS AND CONCLUSION:The stresses of fractured and adjacent vertebrae after the bone cement injection were significantly increased; meanwhile, the stresses of fractured and adjacent vertebrae increased with the increase of bone cement injection volume, which may be one of the factors leading to the compression fractures of adjacent vertebrae.
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BACKGROUND:Percutaneous vertebroplasty and kyphoplasty are both effective in the treatment of osteoporotic vertebral compression fractures, but different in the distribution and dispersion of bone cement. ＜br> OBJECTIVE:To analyze the factors affecting the bone cement dispersion within the vertebral body in treatment of osteoporotic vertebral compression fracture with vertebroplasty or kyphoplasty. ＜br> METHODS:A total of 41 patients with osteoporotic vertebral compression fractures were included, and divided into three groups:group A (22 cases receiving high viscosity bone cement vertebroplasty treatment), group B (5 cases receiving high viscosity bone cement kyphoplasty), group C (14 cases receiving low viscosity bone cement vertebroplasty treatment). The groups A and C were divided into subgroups according to bone cement injection volume, time from fracture to operation, preoperative degree of vertebral compression. The distribution and dispersion of bone cement in the vertebra were reconstructed by the CT three-dimensional imaging and volume rendering analysis. ＜br> RESULTS AND CONCLUSION:In the three groups, after operation, relative dispersion area and relative dispersion volume in the vertebrae had no obvious difference, and the bone cement could al diffuse to upper and lower lamina cross the vertebral midline. There was no significant difference in bone cement diffusion coefficient among the three groups. In a certain range, the bone cement injection volume and bone cement dispersion volume was positively correlated. In groups A and C, bone cement diffusion coefficient decreased with the increasing of bone cement injection volume, time from fracture to operation, and the compression degree of the fractured vertebrae, but showed no significant correlation with bone cement viscosity.
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Objective To retrospectively describe the technique and review the surgical results of OsteoMed M3 titanium plate and screws used to secure the posterior elements in the open position after expansive unilateral opendoor laminoplasty.Methods Twenty-six patients with multilevel cervical disc herniation and canal stenosis were treated with an expansive unilateral open-door laminoplasty with OsteoMed M3 plate and screws.The follow-up period was over 1 year.The improvement of spinal function after surgeries under JOA was evaluated to analyse the effects and releated factors.Results All of 26 cases' follow-up period was over 1 year.The mean JOA score increased significantly from 9.40 ± 1.658 ( range,5 to 13 ) points before surgery to 13.80 ± 1.958 ( range,7 to 16) points at final follow- up ( t =- 21.137,P =0.000 ).Mean recovery rate was 57.9％.Postoperative radiography,magnetic resonance imaging and computed tomography scan demonstrated significantly increased sagittal diameter and canal expansion.Two cases without relief of nurological symptoms underwent an additional anterior multilevel corpectomy.One case with ossification of the posterior longitudinal ligament had not good enough neurologic improvement after surgery.No neurologic deterioration owing to hinge reclosure or major surgery-related complications were observed.It would reduce the recovery for those with old age,long history,worse symptoms,cervical kyphosis and abnormal signal in MR imaging.It was good for patients to do early active cervical exercises after surgery.Conclusion Unilateral open- door laminoplasty with OsteoMed M3 titanium plate and screws fixation effectively maintains expansion of the spinal canal and resists closure while preserving alignment and stability.This modified technique is easy to perform with a low complication,is and economic,and is good for clinical application.
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ObjectiveTo investigate the biomechanical characteristics of different types of fixation with bioactive cervical fusion cage made of hydroxyapatite and poly L-lactic acid in cervical spinal fusion.MethodsIliac crest bone,bioactive cervical fusion cage and bioactive cervical fusion cage with plate fixation were used for anterior interbody implants after anterior discectomy across C5-6 in six fresh human cervical spine specimens respectively,and the range of motion of the cervical vertebrae interbody fusion were measured through the motional stability test.Results After discectomy,Bioactive Cervical Fusion Cage with plate fixation exhibited a significant increase in stability and a decrease of range of motion in angular motion than others in all motional directions ( P ＜ 0.005 ). Bioactive cervical fusion cage exhibited a decrease in stability and an increase of range of motion (6.25 ± 0.29) in angular motion than the intact spine (5.76 ± 0.40) in extension,but the difference was not significantly ( P ＞ 0.05 ).Bioactive cervical fusion cage exhibited a decrease in angular motion than iliac crest bone and a significant increase in stability in all motional directions except extension (P ＜ 0.005).ConclusionsBioactive cervical fusion cage' s biomechanical performance was excellent and bioactive cervical fusion cage with plate fixation was excellent in stability in all motional direction,and could remain initial stability of cervical vertebrae.