| Background: vertebral fusion technology has become a surgeontreatment of lumbar spine degenerative disease as "gold standard". Alongwith the application of rigid internal fixation which rendered increasingof lumbar fusion rate, stress shielding effect emerge. The elastic modulusof the titanium alloy is4-10times the elastic modulus of the bone.Implant and bone elastic modulus difference is too large stress shieldingcan occur, leading to reabsorption of the bone around the implant. Withthe advent of non-fusion technology, the rapid popularization andapplication in the world, non-fusion devices are constantly developingand updating, so that is a non-fusion retain motor function, relying on theelasticity of the implant or movable Fretting functional components toachieve dynamic fixation. An elastic fixation system that is non-fusionlumbar K-rod, through the posterior lumbar pedicle screw placement jointelastic rods, can achieve effective decompression, improve clinicalsymptoms, but also to rebuild the structure and function of the spine,dynamic stabilization of the spine to achieve controlled, providing a nearnormal lumbar motion mode mechanical environment. Existing researchresults show that in the lumbar spine after fixation rigidity will accelerate the degeneration of adjacent segments, and because of the stress shieldingeffect causes vertebral osteoporosis, but the extent of the current researchon stress shielding after lumbar fixation K-rod elasticity is not clear.Objective: To stress shielding effect is inevitable within the lumbarfixation mechanical phenomenon, internal fixation due to stress shieldingeffect, bone suffered stress stimulation significantly reduced, resulting ina negative balance of bone remodeling, bone resorption occurs aroundinternal fixation. The fusion of different type do biomechanical testresults showed: All fusion surgery will increase the stress near theintervertebral; vivo animal experiments also confirmed: rigid internalfixation can cause stress shielding and osteoporosis. This experiment isthe use of porcine lumbar build resiliency within the k-rod fixed and rigidinternal fixation of the biomechanical model, and its biomechanicaltesting, comparative analysis within the lumbar elasticity k-rod fixationsystem with rigid internal fixation system in vitro stress shielding effect,provide a basis for clinical biomechanics.Methods: a rigid lumbar pedicle screw fixation system consists of atitanium alloy and titanium alloy composed of connecting rods; newlumbar dynamic elastic K-rod fixation system is a dynamic stabilizationsystem, this fixing system is made of titanium connecting rod bolt anduniversal cable PEEK materials and titanium alloy made components.Establish biomechanical model, selected1212-month-old male pig lumbar spine thoracic12-5specimens were randomly divided into afixed set of k-rod elasticity six specimens within the rigid fixation groupsix samples, two samples of Strain measured before fixation of pediclescrews in the lumbar4,5vertebrae below the specimen fixing screw holesoutside edge, on both sides of the transverse processes of lumbarvertebrae4,54,5lumbar vertebra in front in front of the middle as themeasuring point, Select10measuring points paste resistance straingauges, analog physiological function in the electronic universal testingmachine load applied150Nf flexion and extension in the state, the testspecimens were fixed strain values in each group before the staticresistance strain gauges. Then each group specimens posterior lumbar(L4-5) respectively in the k-rod holder elasticity and rigidity withinretainers, No.1-10measuring point with pedicle screw fixation pointbefore measuring samples in each group the same location, in order tomeasure strain within a fixed connection rod and pedicle screws at thejunction of the inner rod and pedicle screw fixation at the junction of fouradditional measuring point (measuring point No.11-14), the measuringpoint above resistance paste strain gauges, analog people in the electronicuniversal testing machine150Nf load applied physiological functions inflexion and extension state, static resistance strain gauge strain testspecimen after fixation. Using statistical analysis of the results, by usingSPSS software package16.0SPSS, chicago, ILUSA, data analysis, data was used to compare differences between groups ANOVA analysis andsceffe law, paired t-test were compared (P <0.05for the difference wassignificant).Results: k-rod elastic lumbar fixation system able to achieve the role ofintraoperative and immediate postoperative lumbar stability firmly fixedlumbar spine. Action by making its micro-surgery intervertebralsegmental retaining some active function. After fixation in flexion loadstress measurement points within1,2,5,6,9,10k-rod fixation specimenselasticity is less than rigid internal fixation group specimens stress valueswere significantly different (P <0.05);3,4,7,8-point k-rod fixationspecimens elastic stress value is greater than the stress of rigid internalfixation group specimens each measuring point, the difference wassignificant (P <0.05). Under the extension stress loads within1,2,5,6,9,10measuring point k-rod fixation elastic specimens less than rigid internalfixation group specimens stress values were significantly different (P<0.05);3, stress stress measurement points within4,7,8k-rod fixation ofspecimens larger than the elastic rigidity of internal fixation groupspecimens each measuring point, the difference was significant (P <0.05).Stress shielding effect of the elastic lumbar k-rod fixation systemproduces less than rigid fixation system.Conclusion: The lumbar k-rod fixation system inherited elastic elasticfixed ideas, connecting rods lower elastic modulus, stress shielding effect in the internal fixation after lowering, designed to meet the biomechanicalprinciples; and the ability to ensure the fixation of the lumbar spine Underthe premise of fixed lumbar segments retain a certain degree of motorfunction, is a simple, safe, effective and dynamic lumbar stabilizationsystem. |
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