The Preliminary Design And Related Experimental Research Of New Type Anterior Cervical Internal Fixation System For Chinese Feopie

Research BackgroundWith the widely use of Chinese cervical internal fixation system in clinic,the goodtherapeutic effect of it has been recognized by many scholars.The commonly used of anteriorcervical internal fixation steel plate system is the fixation of single cortical screws,forexample,AO's Morscher steel plate (cervical spine locking plate,CSLP) and Sofamor-Danek's Orion steel plate (anterior cervical locking plate system,ACLPS).Pose a QuestionWe found its problems during the long time clinical work:1.It is mainly suited to racesin European and American countries as their anatomical features of cervical vertebra notours.2.Relative to internal fixation system of extremities fractures which has variouschoices,at present,the appearance design of anterior cervical internal fixation is single andalso the choice of it is litter.The difference between steel plate and screw is only length whilewidth and appearance are almost the same.To children and special groups which suffer fromcervical vertebra diseases such as osteoporosis,dwarfism and so on,it still has no individual,personalized and diversificational anterior cervical internal fixation devices.3.The anteriorcervical internal fixation system still has many problems,such as complications which arehyperostosis,degenerative change,herniated disk,Stability down and so on that occur in fixedadjacent segments,and the weight different clinical symptoms which occur relevantly.ObjectiveThe paper design four different kinds of shape's new type of anterior cervical steelplates which are suitable for Chinese cervical vertebra's anatomical features (x-shaped,x-shaped middle-hole,工-shaped and H-shaped).Consulted and compared with Orionanterior cervical steel plate and screws internal fixation system,then through experimentalstudy of biomechanics, bone histomorphometry,pathology analysis of organization form and so on,to conclude corresponding statistics experimental data and do the statistical analysis inorder to design and screening a group of new type of anterior cervical internal fixationsystem which is more reasonable,scientific and suitable for Chinese people in clinicaltreatment of cervical vertebra diseases.MethodsCombining with Chinese people's anatomical features of cervical vertebra,design fourdifferent kinds of shape's new type of anterior cervical internal fixation system.The researchis divided into3parts:1.Design the shape of steel plate and be divided into groups.Make and prepare theexperimental model1)Get40samples of pigs' cervical vertebra (c2-c7) to be randomly divided into5groups,thatis the group of steel plate of Orion type,x-shaped steel plate,x-shaped middle-hole steel plate,工-shaped steel plate and H-shaped steel plate (n=8).2)Review literatures to obtain Chinese people's anatomical parameters of cervicalvertebra,and then design and make the4kinds of steel plates according to the appearancewith the skill of steel plate and single cortical screws.Do the internal fixation with the4newkinds of steel plates after c4,5herniated disc anterior interbody fusion seperately.Steelplates' material:00Cr18Ni14Mo3,plate height is32MM,the width of plate is17mm,the lengthof screw is12mm,the perimeter of screw is3.5mm,screw aperture is3.5mm,the thickness ofthe wall of hole is2.0mm,thickness of plating is19mm,the flutes pitch is1.75mm,the screwcore diameter is2.5mm.(Seeing in the chapter of designation of steel plate spesifically)3)Paste strain gauge on the6related measured sites in internal fixation specimens of groups(that is below four screw holes after plate's fixation and near the center of plate in the relatedvertebra after fixation).2.Biomechanics and other aspects' research in5kinds of steel plates'fixation1) Measure the Strain electric of c4,5segments of pigs'cervical vertebra before internalfixation.Based on the principle and technology of strain electric,set specimens of each groupto the electronic universal testing machine respectively to measure specimens' Strain electricof each group under the condition of compression, flexion, extension, left lateral bending,right lateral bending successively by resistance strain gauge. 2)Remove intervertebral disc and end plate in c4/5of each group,then implant bone pieces ofthe same,after that fix the steel plate.Paste strain gauge on the same6sites again,that ispasting sites of the two time are the same. Dynamically pressure on the electronic universaltesting machine to specimens, measure specimens' Strain electric of each group after internalfixation seperately under the condition of compression, flexion, extension, left lateralbending, right lateral bending by resistance strain gauge.Making the use of the one-wayHook's Law,calculate Strain of specimens in each group before and after fixation.Accordingto the stress shielding rate computational formula to calculate stress shielding rate of variousspecimens in various states.3)Do the stress relaxation and creep tests of5kinds of anterior cervical internal fixation ofsteel plate and screws system.The computer system collects100sets of experimental dataand automatically output data and curves after finishing. Deal experimental data withthree-parameter model at the end of the experiment to obtain stress relaxation equation ofeach group.3.Do the bone mineral density measurement,observation of bone histomorphometry andmeasurements of bone histomorphometry of5kinds of anterior cervical internal fixation ofsteel plate and screws system in Chinese people.Results1.The results of stress shielding rate show that the x-shaped steel plate and工-shapedsteel plate in the groups of compression, flexion, extension, left lateral bending, right lateralbending, have the litist stress shielding rate,which has significant difference (p＜0.05).2.The results of stress relaxation show that there is not significant different among withdown amount of the stress in7200s (p>0.05).The results of creep tests show that,in the samehorizontal stress,the difference was not significant in7200s' increased amount of thestrain(p>0.05).3.The results of bone mineral density measurement show that:1)The bone mineral density of the cancellous bone from the edge of fixed sites is notablylower than that of the non-fixed sites,which has a statistics difference (P<0.05);2)The bone mineral density of the cancellous bone of cervical vertebra in the screw holeedge of X-shaped steel plate is higher than that of other groups,which has a statistics difference (P<0.05);3)The bone mineral density in the screw hole edge of工-shaped steel plate is higher thanthat of x-shaped with middle-hole,H-shaped and Orion-type (P<0.05);4)The bone mineral density in the screw hole edge of x-shaped with middle-hole is higherthan that of H-shaped and Orion-type,which has a statistics difference (P<0.05);5)The bone mineral density in the screw hole edge of H-shaped is higher than that ofOrion-type,which has a statistics difference (P<0.05);6)The bone mineral density of the cancellous bone from the screw hole edge of fixed sites isalmost the same between X-shaped and工-shaped,which has no statistics difference(P>0.05);7)The bone mineral density of the cancellous bone from the screw hole edge of fixed sites inthe X-shaped and工-shaped are notably higher than that in the other groups,which has astatistics difference (P<0.05).4.The results of the observation of bone histomorphometry show that:1)The trabecular bone of vertebral cancellous bone in the non-fixed sites are arranged indense and neatly;2)The trabecular bone of vertebral cancellous bone in the fixed sites are arrangeddisorderly,even some of the trabecular bone fracture;3)The bone tissue form of the cancellous bone from the edge of screw-fixed sites in theX-shaped is better than that in the other groups;4)The trabecular bone in the screw hole edge of X-shaped with middle-hole and工-shapedare arranged much more disorderly,the fracture are more seriousyl;5)The trabecular bone in the screw hole edge of H-shaped and Orion-type are arranged mostdisorderly,the fracture are most seriously.5.The results of measurements of bone histomorphometry show that:1)&2)The values of the non-fixed control group are greater than those of the other groupsbesides trabecular seperating degree, whose values are less than the other fixation groups,both of which has a statistics differences (p＜0.05);3)While the values of the X-shaped steel plate fixation group and工-shaped steel platefixation group are greater than the average of the other groups besides trabecular seperating degree, whose values are less than the other internal fixation groups,both of which has astatistics differences (p＜0.05);4)There is no statistics difference in the values of the screw hole edge between X-shaped and工-shaped(P>0.05);5)There is no statistics difference in the values of the screw hole edge between H-shaped andOrion-type besides trabecular seperating degree(P>0.05);6)The values of trabecular seperating degree in the screw hole edge of X-shaped are lower tothat in other groups,which has a statistics difference (P<0.05);7)There is no statistics difference in the values of trabecular seperating degree in the screwhole edge between H-shaped and Orion-type(P>0.05),which is also right between X-shapedand I-shaped(P>0.05).ConclusionThe research results indicate:The new type of X-shaped and工-shaped steel plate haveadvantages after internal fixation,for example,stress shielding rate is minor,the down amountof bone mineral density in the screw hole edge is minor,the changes of index or parameterssuch as the measurement of bone tissue are minor,and so on.They can reduce stress shieldingafter internal fixation to some extent,they could reduce the happening of vertebralosteoporosis in fixed segments relatively,at the same time,they could prevent that the stressof interface between screws and bone is too centralized caused by the fixation of steelplate,as well as that reduce bone destruction of interface between screws and bone andenhance intensity of screws in resistance to dial out.All of facts above prompt that the newtype of X-shaped and工-shaped steel plate could ease the happening of regression inadjacent segments of fixation fusion segments in long term to some extent,the designation ofwhich is more suitable for ideas of elastic fixation,biological osteosynthesis(BO) and theoryof biomechanics.Among them,工-shaped steel plate still has a larger development space inimprovement of diversified models and has certain advantages of aspects such asmorphology,biomechanics,improvement of model and so on.The research results couldprovide scientific basis at the aspect of the design and improvement in morphology for thenew type of cervical anterior internal fixation steel plate,also they have certainenlightenment significance to the improvement of steel plate.While the results of the other groups are lager accordingly.Innovations point1.The paper is different from previous similar research. Previous research mostly basedon simulation regression,fracture,dislocation and so on of lower segments of cervicalvertebra,then do the experiments of stability and viscoelasticity under the condition ofanteflexion,extension,left lateral bending, right lateral bending and so on by transplantingbones or cervical anterior internal fixation system after Titanium nets fusion,such as anteriorsteel plate and screws,posterior lateral mass screws, pedicle screw(PS) and so on.Thisexperiment uses steel plates of different geometric shape,that is X-shaped,X-shapedmiddle-hole,工-shaped, H-shaped and Orion-type after simulation c4,5herniated diskinterbody fusion to do the internal fixation,then study the comparation of each group instress shielding rate,bone histomorphometry,bone mineral density and other aspects. It hasbeen proved that this experiment have not been reported in the previous literature by noveltychecking.2.The designation of steel plate and screws for the new type of anterior cervical internalfixation system change the situation that instruments of anterior cervical internal fixation aresingleness so that the choices are little in clinic.Also it provides steel plate and screws whichare diversified and more selective for the new type of anterior cervical internal fixationsystem to be more suited to children and special groups which suffer from cervical vertebradiseases such as osteoporosis,dwarfism and so on in China.Its operation is relatively easy,atthe same time,it exposes relatively small trauma,and also it easy to be clamped,placed andfixed.