| Objective To discuss the relative parameters of the internal fixation of the cervical pedicle screw for the adult lower cervical vertebra,also providing the oretical reference for the placetnent of the screw during the operation,reference for the judgement of the restorement degree after the operation,and also reference for the choice of pedical screw diameter,length,and angulation.Methods Using electronic vernier caliper(accuracy 0.01mm),and angle guage (accuracy 1°)to measure(31 sets)the width and height of the dried specimens of C3～7 cervical vertebra's narrowest section,the relative pedical angle,axis length,the distance between 2 placement points of screws(left and right,upper and lower)and at the same time through Elscint CT Twin Flash to scan vertically the laminate surface of the narrowest section of pedicles and to measure the cortical bone's thickness,and the width and height of the cancellous bone.Average value and standard difference of the parametre in both sides of every vertebra were calculated.And to use indendenee T test to make a statistical analysis.Results(1)the width of pedical(PW,C＇D＇):C3～C7 PW,C＇D＇of both male and female have a trend of gradual expansion.There are no remarkable differences in the comparison of left and right side of the same level,and remarkable differences between female and male(P＞0.05),The value of C＇D＇/PW is near 60.0%.(2)The height of the narrowest part of the pedicle(PH,A＇B＇):C3～C7 the velue of both male and female has a trend of being big at two ends,small at middle(C5).Except A＇B＇of C7,the rest pedicles all have no remarkable difference in both male and female(P＜0.05),the value of A＇B＇/PH is near 50%.(3)the thickness of cortical bone in every side of the narrowest past of pedical:length of pedical(AB,CD,EF,GH):The external side of C3～C7 is extremely thin,about 1.01～1.22mm,the internal side is thicker than the external.The average value of AB/CD is 1.53,whereas the value of GH/EF is from 90.3%～100%,that is,the thickness of the upper and lower sides of cortical bone are almost same.(4)The average value of C＇D＇and A＇B＇show that of the same level, the value of C＇D＇is smaller than A＇B＇.(5)The osseous axial length of pedicle,and the length of pedicle(La,Lb):the variation of La and Lb is relatively small,the total average values of La and Lb are 31.17mm,16.31mm.the average value of Lb/La is 52.4%,Lb is about one half of La in length.(6)Angle A and Angle B of pedicle(A角,B角):(Angle A)C7 is the largest in both male and female,the average value of C3～C7 is 46.37°.In the comparison of male and female,except(C5)(P＜0.05)all the other pedicles have no remarkable difference(P＞0.05);Angle B,the value of C3～C7 becomes plus from minus,and it appears to have a trend of becoming larger gradudlly.(7)The distance between the left and right placement points on the same vertebra(OO):the average values of C3～C7 are highly close,among them,C5 is the largest,the total average is 41.04mm.(8)Of the consecutive vertebras,the distance of the upper and lower placement points(O'O'):the average value of 4 levels is between 14.37～14.92mm,The total average is 14.59mm.Conclusion The application of the screw for the pedicle of lower cervical vertebra must depend upon the width of cancellous bone,but attention must be paid to the individual difference on C3～C6,only screws of 3.0mm can be used.The range of the choice of the screw length is from 30～31 mm.The placement angle,has noticeable regularity.The distances between the left and right,upper and lower are the important references for the decision of the screw placement points during operation,and judgement of the restorement degree after operation... |
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