| Part 1 Establishment and verification of the finite element model of healthy lumbar intervertebral disc and degenerative finite element model of aged lumbar intervertebral discObjective To explore a new method of establishing finite element model of lumbar intervertebral disc in healthy adults and degenerative finite element model of lumbar intervertebral disc in old people,and to verify and compare them.Method A male volunteer of healthy adult was selected and the LI vertebra to the middle femur was scanned by spiral CT.Medical image control and analysis software of Mimics 13.0,reverse engineering software of Geomagic 9.0,the finite element pre-processing software of Hypermesh 13.0 and the finite element analysis software of Abaqus were used to reverse reconstruction,geomagic cleaning of STL model,3 dimensional model reconstruction,grid processing and Simulation analysis,and then the finite element model of lumbar intervertebral disc of healthy adult was made.To establish the degenerated model of L4-5 in the elderly,the height of the intervertebral disc in healthy adults was reduced to 50%and the material properties of the intervertebral disc were changed to degenerate constitutive properties.Four hundred Newton of forces were applied evenly distributed on the surface of L3 vertebrae vertically to simulate the human body vertical load and eight N·m of torch load were also applied to the finite model.The movement of flexion,extension,lateral curvature and rotation were simulated respectively,and record,verify and compare the results of health model and elderly L4-5 degeneration model in various degree of deformation and stress distribution under the load.Result The finite element model of healthy lumbar intervertebral disc and degenerative finite element model of aged L4-5 intervertebral disc were established and their reliability were verified respectively.With the degeneration of L4-5 intervertebral disc,the overall stiffness of lumbar increases while the mobility decreases.At the same time,the stress of the intervertebral disc and the posterior structure of the adjacent segment increased,and the tension of the degenerative joint capsule ligament also increased.Conclusion 1.Based on the slice scanning data of spiral CT,the finite element model of healthy lumbar intervertebral disc and degenerative finite element model of aged L4-5 intervertebral disc were established using the slice scanning data of spiral CT,the Mimics 13.0 software,the Geomagic 9.0 software,Hypermesh 13.0 software and Abaqus 6.13-4 software.After verification,the above model is effective and reliable,and can be applied to finite element research.2.With the degeneration of L4-5 intervertebral disc,the overall stiffness of lumbar increases while the mobility decreases.At the same time,the stress of the intervertebral disc and the posterior structure of the adjacent segment increased,and the tension of the degenerative joint capsule ligament also increased.Part 2 Evaluation of lumbar biomechanical finite element analysis in the treatment of elderly lumbar disc degeneration by combined interventional therapyObjective To evaluate lumbar biomechanical finite element analysis in the treatment of elderly lumbar disc degeneration by combined interventional therapy.Method On the basis of the aged L4-5 intervertebral disc degeneration model,the treatment models of percutaneous lumbar discectomy(PLD),the combination of PLD and percutaneous disc cementoplasty(PDCP)(PLD+PDCP),the PLD,PDCP and percutaneous vertebraplasty(PVP)(PLD+PDCP+PVP)were established respectively.Different loads were applied on the above models,and the deformation degree and stress distribution were recorded and compared.Result The different treatment models of PLD,PLD+PDCP and PLD+PDCP+PVP were established respectively.When loads were applied to the PLD model,the mobility of the targeted lumbar,the fibrous ring stress,the posterior structural stress and the joint capsule ligament tension all showed an increasing trend in each direction.Inversely,when loads were applied to the PLD+PDCP model and PLD+PDCP+PVP model,the mobility of the targeted lumbar,the fibrous ring stress,the posterior structural stress and the joint capsule ligament tension all showed a decreasing trend in each direction.In contrast,PLD+PDCP+PVP model showed a higher lumbar stiffness.Conclusion When loads were applied to the PLD,PLD+PDCP and PLD+PDCP+PVP models,the mobility of the targeted lumbar and the stress of fibrous ring,the posterior structural and the joint capsule ligament all showed an increasing trend in PLD model,while the mobility of the targeted lumbar and the stress of fibrous ring,the posterior structural and the joint capsule ligament all showed an decreasing trend in PLD+PDCP and PLD+PDCP+PVP models in each direction.Part 3 Clinical application of combined interventional therapy in the treatment of elderly lumbar intervertebral disc degenerationObjective To determine the safety and efficacy of percutaneous lumbar discectomy(PLD)and percutaneous disc cementoplasty(PCP)for painful lumbar disc herniation(LDH)in elderly patients.Method Between January 2013 and December 2018,twenty-four older patients(11 male,13 female,and mean age,73.3±5.7 years)with painful LDH were treated with PLD and PDCP.The outcome data(the Macnab criteria,visual analog scale[VAS]score,and Oswestry disability index[ODI])were collected preoperatively;at 1 dan and lweek postoperatively;at post-treatment months 1,3,and 6;and every 6 months thereafter.In addition,treatment duration,injection volume of bone cement,distribution of bone cement,changes of the targeted disc;length of hospital stay,and complications were assessed.Result Treatment was successful in all patients,and the clinical improvement rate at the last follow-up was 87.5%.Ten,eleven,two and one patients showed excellent,good,fair and bad results,respectively.The average VAS score for back and leg pain decreased from6.95±0.95 and 7.21±0.83 before the procedure to 3.33±1.24 and 3.33±1.34 at 1 day,2.83±1.27 and 2.83±1.34 at 1 week,2.17±1.83 and 2.17±1.90 at 1 month,2.04±1.85 and 2.04±1.92 at 3 months,2.50±1.67 and2.37±1.38 at 6 months,and 2.77±1.59 and 2.77±1.64 at 1 year,respectively(P<0.001).The ODI also changed after the procedure,with significant differences between baseline scores and those at each follow-up(P<0.001).The excellent and good rate of postoperative bone cement distribution was 100%.The height of disc was increased from 8.55±1.43mm pre-operation to 12.43±2.47 post-operation.The mean procedure duration,injection volume of bone cement,and length of hospital stay were 59.29±9.00 min,2.71±0.46 ml,and 7.88±2.66 days,respectively.Major complications were observed in two patients,and one with aspiration pneumonia and the other with adjacent vertebral fracture.The both were recovered after positive treatment.Conclusion The combination of PLD and PDCP is feasible,safe,and effective for older patients with painful LDH. |
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