Digital Anatomy And Histomorphology Of The Ossification Center Of The Base Of Odontoid Process In Children

Objectives:1.To study the developmental features of the anatomical structure of the ossification center of the base of odontoid process in normal children aged 1 to 6years,to analyze the factors affecting its fusion,and provide basic data for its evolution law and clinical application in the diagnosis and treatment of disease.2.To investigate the structural features and distribution characteristics of bone trabecular in the ossification center of the base of odontoid process and its surrounding areas in normal children,and to analyze its evolution process and its impact on the odontoid process fractures.3.The morphological staining of the ossification center of the base of odontoid process in normal children was used to observe and explore its structural features.Methods:1.Normal cervical vertebrae imaging data of 160 children aged 1 to 6years were collected and divided into 6 groups according to the age of 1-year-old,including 20 cases in each of 1-year-old and 2-year-old groups,and 30 cases in each of the other four groups.The raw data of cervical tomographic images scanned continuously were imported into Mimics21.0 software for measurement in DICOM format.The measurement indicators are divided into four categories:the indicators of itself and position of the ossification center,the indicators of the relationship with the odontoid process and the surrounding structure.2.The whole cervical vertebrae specimens of 3 normal children aged 3 years were selected and scanned by Micro-CT.The DICOM images data obtained were imported into Hiscan Analyzer software for three-dimensional reconstruction,which fully displayed the ossification center of the base of odontoid process.The area of interest was selected in and around the ossification center of odontoid base.The microstructure features of the trabeculae bone were observed,and the structural parameters of the trabecular bone were measured.A total of 8 measurement indicators of the trabecular bone volume fraction,the bone surface density,the trabecula bone number,the trabecula bone thickness,the trabecula bone surface area/volume,the trabecula bone separation degree,the trabecula bone module factor and degree of anisotropy.3.The cervical vertebra specimen of a child after Micro-CT scanning was made into tissue thin sections by hard tissue embedding and slicing technology,and hematoxylin-eosin,toluidine blue and safranine O-solid green staining were respectively performed to observe the histomorphological structure of the ossification center.The observed indicators were the morphology and cell features of ossification center of the base of the odontoid process,the intervertebral disc,and the bone tissue.Results:1.Developmental features of the anatomical structure of the ossification center:（1）The indicators of itself of the ossification center:The transverse and sagittal diameters gradually decreased with age,which were 6.34±0.96 mm and 2.15±0.51 mm in the 6 to 7-year-old group respectively.The area decreased with the decrease of the transverse diameter from 2-year-old group.There were significant differences in the sagittal diameter of 1-year-old group among all age groups except 2-year-old group（P<0.05）.The transverse diameter and area of the 6 to 7-year-old group was significantly different from other age groups（P<0.05）.（2）The indicators of position of the ossification center:The distance of inferior border of ossification centre and the bottom of the axis and the distance of left border of ossification centre and left transverse process increased with age.（3）The indicators of the relationship with the odontoid process of the ossification center:The transverse diameter of the base of odontoid process in the 1-year-old and 2-year-old groups was significantly different from that in the 3-year-old group to the 6 to 7-year-old group（P<0.05）.（4）The indicators of the relationship with the surrounding structure of the ossification center:The distance between the base of the axis and the ossification center in the 1-year-old group was only significantly different from that in the 6 to 7-year-old group（P<0.05）.The left declination angle of ossification centre and the base of odontoid in the1-year-old group was only significantly different from that in the 2-year-old group（P<0.05）,and there was no statistical difference compared with other age groups（P>0.05）.（5）The correlation analysis showed that the correlation between the transverse diameter of the ossification center and the sagittal diameter,the area and the circumference was relatively high.（6）Multiple linear regression analysis showed that the transverse diameter of the ossification center was affected by age and sagittal diameter.The sagittal diameter was influenced by age,transverse diameter,the transverse diameter of the base of odontoid and the left declination angle of ossification centre and the base of odontoid.2.Comparison of the trabecular bone parameters between the area of the ossification central and its surrounding areas:（1）The trabecular bone volume fraction,the trabecular bone surface area/trabecular bone volume,and the trabecular bone module factor between the area of the ossification central and its upper and lower border areas have statistical（P<0.05）.（2）The trabecular bone surface area/volume value of C₂vertebral body area and each C_3⁵vertebral body area was statistically different（P<0.05）,which was significantly different from that of C_4⁵vertebral body the bone surface density（P<0.05）.The trabecular bonevolume value was statistically different（P<0.05）,which was significantly different from the trabecular bone separation value in the C₇vertebral body region（P<0.05）,and was significantly different from the trabecular bone volume in the C₃,C₆,and C₇vertebral body regions.The value of module factor was statistically different（P<0.05）.（3）There was no statistical difference from the trabecular bone number,the trabecular bone thickness and degree of anisotropy in different regions（P>0.05）.3.Histomorphological observation results of the ossification center:（1）hematoxylin-eosin,toluidine blue and safranine O-solid green staining were clear,It was observed that the cartilage nuclei at the base of odontoid process were blue purple,blue and red respectively.The chondrocytes at the intervertebral disc were scattered and arranged between the fiber bundles,and the cartilage tissue was in sharp contrast with the bone tissue.（2）The chondrocytes in the central area are evenly arranged under the three staining methods,and the chondrocytes in the peripheral area are hypertrophic than those in the central area.（3）Compared with the three staining methods,the chondrocytes the base of odontoid process were most clearly observed by aniline blue staining.Conclusions:1.The transverse and sagittal diameter of the ossification center of the base of odontoid process decreased with age.The distance between protrusions increased with age.The distance of inferior border of ossification centre and the bottom of the axis,left border and left transverse process and right border and righr transverse process increased with age.2.The decrease of transverse diameter is related to the increase of age and the decrease of sagittal diameter.The decrease of sagittal diameter is related to the increase of age,the transverse diameter of the base of odontoid,the left declination angle of ossification centre and the base of odontoid and the decrease of transverse diameter.3.The measurement results of relevant indicators of the ossification center supplement the basic anatomical and morphological data for the growth and development features of the ossification center of the base of odontoid process in children.4.The area around the ossification center of the base of odontoid process in children has its unique distribution features of the trabecular bone.The volume fraction,surface area/volume,and the trabecula bone module factor reflect the healing degree of the ossification center.5.The histomorphological analysis of this experiment showed that the cartilage at the base of odontoid process belongs to hyaline cartilage.