| In recent years,anterior approach surgery has been increasingly used in the treatment of cervical and lumbar degenerative diseases,reducing the risk of surgery and post-operative complications,fascilitating rehabiliation,and its internal fixation concept of maintaining lordosis have been adopted by more and more clinicians.At the same time,a large number of implants that are more consistent with the anterior approach surgery and the anatomical characteristics of the cervical and lumbar spine have also appeared;implants that adopt this concept The clinical application in the cervical and lumbar spine surgeries of the Chinese has achieved promising results,but there are still aspects that can be further optimized for its design:First,most of the anatomical intervertebral fusion cages put into clinical use in China are used for reference for the designing.If the anatomical parameter settings of the European and American populations are directly shifted for the Chinese,there may be a problem of poor matching in the cervical and lumbar endplates,which will affect the biomechanical properties of the endophytes,thereby affecting its clinical efficacy;secondly,the original Some researches on neck and lumbar endplate morphology mainly focus on the measurement of parameters in a few planes such as the median sagittal plane.The obtained endplate shape information is relatively limited,and more sufficient data is needed to express the endplate shape;The purpose of this study is to initiate the shape analyisis through multiple reference planes established based on anatomical markers to obtain a stable measurement area for different genders and segments of the cervical and lumbar endplates.to establish and verify the mean shape models of the sub-axial cervical spine and lumbar endplates;based on the average endplate models,design and verify the cervical and lumbar intervertebral instuments.Part One:Sub-axial cervical endplate shape statistics and the establishment of the average model[Objective]To obtain the anatomical characteristics of the middle and lower cervical spine(C3-7)of adult Chinese by selecting the corresponding shape expressions,and to analyze the shape changes statistically to compare the different shapes of the middle and lower cervical spine.The change rule of side,gender,and segment;establish the average model of the middle and lower cervical spine endplates and verify it.[Methods]The shape statistics of the middle and lower cervical spine was initiated over 56 normal adult Chinese cervical spine CT data,using Mimics 20.0 software to reconstruct the C3-7 vertebral body surface model segmentally,and employing the engineering software 3-Matics 12.0 in each vertebra Establish 6 reference planes on the body,namely the median sagittal plane,the left and right quarter parasagittal planes,the median coronal plane,the anterior and posterior quarter coronal planes.By intersecting the reference plane with the surface of the vertebral body,obtaining the curves in the above planes,import it into the three-dimensional curve processing software Rhinoceros 6.0,and measured the parameters of the curves on the above six planes to obtain the end plate width,depth and curve fitting arc angle and other parameters,and obtain them through the parameter ratio Secondary parameters are used to describe the local shape changes of the endplates;the endplate parameters of different sides,genders,and segments are statistically analyzed to compare their shape changes.The establishment and verification of the average curve model of the middle and lower cervical spine:import the three-dimensional surface model of the vertebral body into the engineering software 3-matics 12.0,establish the median sagittal plane,median coronal plane and median cross section,and establish the vertebral body through the intersection of the three planes Coordinate system;through the previous method,the median sagittal plane,left and right quarter parasagittal plane,median coronal plane,anterior and posterior quartercoronal plane curves of the upper and lower endplates were established respectively,and imported into the software Rhinoceros In 6.0,use this vertebral body coordinate system to re-align the curves of different individuals in space,and after trimming and modifying the curves,the average curves of the upper and lower endplates are generated respectively;Measured the parameters of the average curve of the end plate of different segments,compared with the results of the end plate parameter measurement in the previous part,to verify the validity of the average curve of the end plate;[Results]There was no statistical difference between the ratio of the depth of the quarter sagittal plane to the median sagittal plane and the ratio of the width of the quarter coronal plane to the median coronal plane for men and women(t-test).The ratio of the depth of the quarter sagittal plane to the median sagittal plane and the ratio of the width of the quarter coronal plane to the median coronal plane between the C3-7 vertebral body.There was no significant difference between the ratio of the depth of the quarter sagittal plane to the median sagittal plane and the ratio of the width of the quarter coronal plane to the median coronal plane between C3-C6 vertebral bodies(P<0.05);C7 and C3,C4,The ratio of the depth between the 1/4 sagittal plane and the median sagittal plane between C5 and C6 vertebral bodies was statistically different(P>0.05).The measured value of the average end plate curve is close to the average value of the shape statistical results,and the change trend is similar.[Conclusions]1.The average shape model of the upper and lower endplates of the C3-C7 vertebrae was successfully established by calculating the average curve;2.There was no significant difference in the shapes of the upper and lower endplates of the C3-C7 vertebrae between men and women;there are no significant differences in the shape of the upper and lower endplates between the C6 vertebral bodies;differences exist in the shape of the endplates between the C7 and C3,C4,C5,and C6 vertebral bodies..Part Two:Design and verification of the interbody fusion cage based on the average endplate model[Objective]Based on the mean curve model of the C3-C7 vertebral endplate obtained in the previous part of the study,and the measured depth and width of the C3-C7 vertebral endplate,design an anatomical cervical intervertebral fusion cage and initiate the cadaveric cervical spine matching test and finite element analysis to verify the design.[Methods]The curved surface fitted by the average curve of the cervical endplate was used as the interface between the intervertebral fusion cage and the upper and lower endplates,and 7° was set as the lordosis angle.The height was set as the height,and the footprint boundary is based on the uncinate process of the average curve model as the left and right boundary,and 2/3 of the endplate is used as the front and back boundary.Set according to the statistical results of the parameters,size and model(large,small),design The results were exported in STL format;the intervertebral fusion cage was verified through the cadaver cervical spine matching test and the finite element test.Four different intervertebral fusion cages were compared,and they were designed based on the staged endplate average curve model.The fusion cage is an intervertebral fusion cage designed based on the average curve model of all cervical vertebrae endplates,and a certain type of anterior cervical intervertebral fusion cage that is put into clinical use and a patient specific intervertebral cage designed based on the anatomical features of the cadaver’s cervical endplate for contrast,the intervertebral fusion cage was 3D printed using light-curing molding technology,and the surface was pretreated to make the boundary visible on X-ray;the processed intervertebral fusion cage was implanted into the corresponding segment of the cadaver’s cervical spine,and CT examination was performed afterwards,the software Mimics 20.0 was imported to measure the remaining area to evaluate the fit between the fusion cage and the endplate;establish a finite element model of the cervical spine C5-6 discectomy to simulate the flexion,extension,lateral flexion and rotation of the intervertebral fusion cage after implantation The stress distribution in the state,the four kinds of intervertebral fusion cages are compared and analyzed.[Results]The results of the matching test suggest that the remaining area of the interbody fusion cage designed based on the mean curve models and the average curve model of all segments of the cervical spine,and patient specific design were significantly smaller than that of commercial fusion cages;and based on the segmented average curve There is no significant difference between the model and the interbody fusion cage designed based on the average curve model of the final cervical spine of all segments,and both are smaller than the patient specific intervertebral cage;the finite element analysis results of the C5-6 segment suggest that the personalized design and the final version are based on The stress distribution of the intervertebral fusion cage designed by the version average curve model and the patient specific intervertebral cage were more uniform;[Conclusions]The interbody fusion cage designed based on the average model of the endplate of the vertebral body,compared with the existing cervical interbody fusion cages which have been put into clinical application,the endplate stress distribution is more even during the flexion and extension of the cervical spine segment.Part Three:Analysis of the shape of the lumbosacral endplate and establishment of the average model[Objective]To compare the shape similarities and differences of the lumbosacral endplates(L1-S1)of the lumbosacral(L1-S1)endplates between different sides,genders,and segments;establish and verify the mean curve model of the lumbosacral endplates.[Methods]A total of 40 adult lumbar CT scan data that met the inclusion criteria were enrolled in this part of the study.Among them,20 were male and female.The data included complete lumbosacral(L1-S1)data;based on the CT value,the three-dimensional modeling software Mimics 20.0 was used.Perform segmentation and reconstruction of the lumbar vertebral body to establish a three-dimensional surface model of a single vertebral body;import the three-dimensional surface model into the engineering software 3-Matics 12.0,and use point markers to establish 6 reference planes on the upper and lower endplates,including the median sagittal plane,Left and right quarter parasagittal plane,median coronal plane,anterior and posterior quarter coronal plane,through the reference plane intersects the surface of the vertebral body to generate the corresponding curve,import the curve into the software Rhinoceros 6.0,re-aligned in the space and perform the corresponding plane parameter measurement,and use the ratio of some parameters obtained through the measurement as secondary data for the local shape expression of the endplate;import the data into the statistical software Prism 9.0 to perform statistics on the measured parameters and secondary parameters Analyze,compare the similarities and differences between different sides,genders,and segments,analyze the trend of shape changes;establish the vertebral body coordinate system through the intersection of three planes(mid-sagittal plane,median coronal plane,and median cross-section);The upper and lower final curves of the body are imported into the software Rhinoceros 6.0,and the vertebral body coordinate system is used for spatial alignment,the curves are trimmed and reconstructed,and the average curve is generated;the average curve is verified by the results of parameter measurement;[Results]The sagittal depth of the endplate gradually increased at L1-3,reached the highest at L3,and then gradually decreased from L4-S1;there was no significant difference in the coronal width of the endplate at L1-4,and the upper and lower L5 The width of the lower endplate is significantly higher than that of the other segments;the width and depth of the lower endplate are higher than the upper endplate in the L1-4 segment,and lower than the lower endplate in the L5 segment;The secondary parameter results indicate that there is no significant difference in the ratio between the front 1/4 coronal plane and the median coronal plane of L1-3,but it is higher in L4-5;the posterior 1/4 coronal plane and the median coronal plane,left and right 1 There is no significant difference in the ratio of/4 sagittal plane to mid-sagittal plane in the endplates of each segment;the ratio of coronal plane width to sagittal plane depth has no significant difference in the L1-3 segment,and from L4 to L5 segment gradually riseThe measured values of endplate width and depth parameters are slightly larger for men than for women,but in most comparisons,there is no significant difference between the two.There is no statistically significant difference between men and women in the angle of the concave endplate arc;for bilateral endplate arcs,there is no significant difference between the arc depression angle and the end plate width and depth;there is no significant difference between the average model end plate measurement value and the parameter measurement mean value,and the change trend of the two is similar;[Conclusions]1.The lumbosacral endplate surface curve model was successfully established;2.the shape analysis of the endplate resulted as follows:1.The coronal parameters gradually increased between from L1 to L5;2.The sagittal parameters increase in the L1-3,and decreased since L4;3.The shape of the L1-4 is similar.The shape of men and women is similar,and there are differences in the shape of the L5 lower endplate and the upper S1.Part Four:Design and Biomechanical Test of Anterior Lumbar Interbody Fusion Cage[Objective]Based on the MEAN endplate curve model,to design a self-locking cage for L3-4 anterior interbody fusion surgery,and conducting a series of biomechanical testing to simulate the calf L3-4 lumbar spine fusion surgery,in order to verify the cage.[Methods]Based on the CT data of 40 adult lumbo and sacrum,the average human lumbar 3-4 endplate model was established as a reference for the shape of the intervertebral fusion cage-endplate interface;the intervertebral fusion cage footprint boundary was set based on the shape statistics;Using the intervertebral height and lordosis angle of the intervertebral fusion cage put into clinical application,a lumbar 3-4 self-locking anterolateral intervertebral fusion cage was designed,and the designed intervertebral fusion cage was metal 3D printed;Bovine lumbar spine L3-4 discectomy and interbody fusion model,using traditional nail and rod system and anterior fusion cage implantation as a control group;observe its range of motion under flexion,extension,lateral flexion,and rotation;[Results]There is no significant difference in the range of motion of the lumbar 3-4 vertebral body interbody fusion cage designed based on shape statistics compared with the traditional nail-rod fixation;[Conclusions]The anterior self-locking intervertebral fusion cage designed based on the mean model of the L3-4 endplate is manufactured using metal 3D printing technology and successfully assembled in the corresponding intervertebral segment of the calf.Biomechanical tests indicate its effectiveness. |
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