Digital Research On The Human Atlantoaxial Complex Using Micro-CT And Its Significance In Traditional Chinese Medicine Developmen

The atlantoaxial complex is a unique "conjugate" structure of the cervical vertebra,and it is the most active and weakest segment in the whole spine,which is a difficulty in the treatment of cervical vertebra diseases.In this study,the Micro CT technique was used to study the micro-structure of the atlantoaxial complex and the regional differences in the distribution of trabecular bone,and to explore its fracture mechanism and the optimal treatment plan of internal fixation technology and the significance of TCM Auxologye.Objective:This thesis is to describe the micro structure characteristics and then explore the micro-injury mechanism of the vertebral fracture of the atlantoaxial complex by using the three-dimensional digital reconstruction and Micro CT scanning.The characteristics of the posterior nail placement channel and the relevant parameters in pedicle and lamina screws are studied to provide a digital basis for screw fixation.Based on standard CT images of the axis,the occurrence rate and characteristics of the non-fusion ossification centre structure with incomplete absorption and closure of the base of the odontoid were studied,the possible influencing factors of this structure on adult odontoid fractures were analyzed and preliminary study on this structure in TCM Auxology.Methods:Micro CT scans were obtained from five normal the atlantoaxial complex.The scanned data were three-dimensionally reconstructed with Micro CT software to observe the micro structure.The volume fraction was calculated to acquire trabeculae of regions of interest and measure the relevant data of nail channel and pedicle and lamina of various parameters analyzed statistically.The standard CT scan images of 50 cases of axis were selected to calculate the incidence of incomplete absorption and closure of the non-fusion ossification centre structure at the base of the odontoid and the related anatomical structure indicators.Combined with Micro CT scan images of the odontoid process,the clear structural characteristics of bone trabeculae in the incomplete absorption and the non-fusion ossification centre structure were analyzed.Results:High-resolution Micro CT images of the micro-structures were obtained from the atlantoaxial complex.The 3D images clearly show the micro-structure of the various parts of the atlantoaxial complex.The rod-shaped trabecular bone is adapted to the bending of the mechanical environment at the junction of the anterior or posterior atlas arch.The lamellar-like trabecular bone rich in the marrow cavity of the anterior and posterior arch with the most prominent in the medial portion.The posterior arch at the junction and the lateral mass of the vertebral artery groove were the thinnest,but the cortical bone was good and the micro-structure of the odontoid ossification center were observed.There was a statistically significant difference between the bone structure fraction and the region of interest in the top of the trabeculae and the bottom of the lateral mass(P<0.05).The average length of pedicle screw length(PSL)was 24.89 ± 2.79 mm,the average length of lateral mass(LML)was 18.12 ± 2.07 mm,the average height of lateral mass(LMH)is 13.54 ± 1.47mm,the average height of vertebral artery groove(VAGH)was 3.36 ± 0.29 mm.There were also significant differences among anterior arch cavity width(AACW),posterior arch cavity height(PACH)and posterior arch cortical thickness(PACT)(P<0.05).However,there were no significant differences in anterior arch cavity height(AACH),posterior arch cavity width(PACW)and anterior arch cortical thickness(AACT)(P>0.05).Compared with the same position,there were statistical differences in the parameters of the middle interior anterior and exterior arch cortical thickness(MIAACT and MEAACT)and the middlc/posterior posterior arch cavity width and height(MPACW/MPACH and PPACW/PPACH)(P<0.05).There was a statistically significant difference in the bone structure fraction compared with the region of interest in the fourth part of the trabeculae and the first part of the odontoid(P<0.05).There was a statistically significant difference in the bone structure fraction compared with the region of interest in the top and bottom parts of the trabeculae and the center part of the axis vertebral(P<0.05).The average length of pedicle screw length(PSL)was 21.74 ± 1.93mm,the average length of pedicle cavity height(PCH)was 6.04 ± 1.11m.There are no significant differences among pedicle cavity width(PCW),pedicle cortical thickness(PCT)and exterior lamina cortical thickness(UELCT)(P>0.05).There were significant differences in axis laminacavity width(LCW)and interior lamina cortical thickness(ILCT)(P<0.05).Compared to the same position,there are statistical differences in the parameters of the middle pedicle cortical thickness and posterior pedicle cortical thickness(MPCT and PPCT)(P<0.05).Compared to the same position,there are statistical differences in the parameters of the upper interior lamina cortical thickness and upper exterior lamina cortical thickness(UILCT and UELCT)(P<0.05).Incidence of variation of the non-fusion ossification centre structure in the base of the odontoid was 28%.Micro CT revealed the micro-structure of trabecular bone in the non-fusion ossification centre structure and the close relationship between the trabecular bone and the odontoid.The trabecular bone indexes chosen in the target area of the ossification centre were weaker than those in other areas.In the non-ossification centre structure group,the mean sagittal diameter of the base of odontoid(SDBO,mm)was 7.64 ±1.29 mm,the mean transverse diameter of the base of odontoid(TDBO,mm)was 7.14 ± 1.55 mm,and the SDBO:TDBO ratio was 1.1 ± 0.22.In the ossification centre structure group,the mean SDBO was 7.7 ± 1.15 mm,the mean TDBO was 7.38 ± 1.32 mm,and the SDBO:TDBO ratio was 1.07 ± 0.21.There was no significant difference in the associated indexes between the ossification and non-ossification groups(P>0.05).In the non-ossification centre structure group,the mean SDOC was 5.34±0.97 mm,the mean TDOC was 8.02 ± 1.64 mm,the mean DBOOC was 8.05 ± 1.57 mm,the mean DBAO was 11.85 ± 1.48 mm,and the ratio of SDOC/TDOC and DBCOC/DBAOC was 0.68.Conclusions:Evaluation of the micro-structures of the normal the atlantoaxial complex can be obtained with high-resolution images of Micro CT.The micro-injury mechanism of the atlas fracture may be to transmit energy of the trabecular bone to the weak part of anatomical structure.It is verified that the use of pedicle exposed nailing technique can complete the placement of the vertebral artery groove.It is due to adequate massive purchased bones and good screw holding force.The rod trabecular bone plays an important role in energy transmission in the mechanism of axis fracture.The structural parameters of trabecula are weak and the existence of the basal ossification center of the odontoid may be the crucial reason for the Anderson type Ⅱ and Ⅲ fracture.The average width of any part of the pedicle is greater than 5.5 mm,which can fully accommodate 3.5-4.0 mm diameter screws.The upper part of lamina should be carefully handled with 3.5mm diameter screws.3.5-4.0mm diameter screw insertion can be safely selected in the middle and lower parts of the lamina.The occurrence rate of the non-fusion ossification centre structure in the base of the odontoid is relatively high and the weakening of the trabecular bone in its structure is the main reason for the aetiology of type II and III odontoid fractures in adults and to provide a method and way for guiding clinical application of TCM Auxology.