| Background and ObjectiveBasilar invagination is a deformity of the occipital-cervical junction characterized by the upward protrusion of the axial odontoid into the foramen magnum.Often accompanied by atlantooccipital fusion,C2-C3 fusion,short clivus,other bony malformations and vertebral artery course variation,and other soft tissue developmental malformations.In addition to symptoms caused by compression of the medulla oblongata and spinal cord,patients with indentation of the skull base often present with symptoms such as limb weakness and numbness,as well as torticollis,short neck,and neck pain.The sagittal balance of the cervical spine is crucial for maintaining a healthy biomechanical environment of the cervical spine.The deterioration of the cervical spine biomechanical environment may lead to the occurrence of various types of cervical spondylosis.In patients with a depressed basilar deformity,the deformity at the occipital-cervical junction alters the biomechanical environment of the entire cervical spine.Therefore,studying the biomechanical environment of the cervical spine in patients with basilar depression is of great significance for understanding this disease.Based on the imaging data obtained in clinical practice,this topic will carry out imaging measurement analysis to clarify the sagittal arrangement of the cervical spine and the degeneration of the intervertebral disc in patients with basilar invagination,and analyze the biomechanical environment of the cervical spine in patients with basilar invagination.The possible causative mechanism,in addition,based on imaging data,this subject also analyzed the anatomical characteristics of the axial pedicle in patients with basilar invagination to guide the surgical screw placement strategy in this patient population with common bony deformity variants.To further explore the molecular mechanism of cervical intervertebral disc degeneration in patients with basilar invagination,this topic finally studied the role of autophagy in the process of intervertebral disc degeneration by analyzing the single-cell sequencing data of degenerated intervertebral disc.Part Ⅰ:Study of the cervical sagittal alignment in patients with basilar invaginationMethods:This part of the study retrospectively analyzed some measured values of 87 patients with basilar invagination and 98 asymptomatic subjects based on lateral X-ray films,including(1)Cranial parameters:Cranial slope(CS),Cranial tilt(CT),Cranial Incidence angle(CI),SVA CGH-C7;(2)Cervical spine parameters:C0-C2 angle,C2-C7 angle,Cervical lordosis(CL),SVA C2-C7,Cervical tilt,Spine tilt,Spino-cranial angle(SCA);(3)Thoracic inlet parameters:Thoracic inlet angle(TIA),T1 slope(T1S),and Neck tilt(NT).These parameters were compared between experimental and control groups,and between subgroups of patients with basilar depression with or without atlantooccipital fusion or C2-C3 fusion.In addition,correlation analysis was performed on these measurement indicators.Results:There were no differences in age and gender between the basilar invagination group and the control group.These measured values of patients with basilar invagination were greater than those of the control group:cranial inclination(CT),cranial incidence angle(CI),SVA CGH-C7,C2-C7 angles,cervical inclination,and spinal cranial angle(SCA).The patients with basilar invagination were smaller than controls in the measured values:Cranial slope(CS),C0-C2 angle,C0-C7 angle,SVA C2-C7,spine tilt(ST),thoracic incidence angle(TIA),Neck tilt(NT).In basilar invagination group,SVA CGH-C7 and SVA C2-C7(r=0.76),C0-C2 angle and SVA C2-C7(r=0.50),C2-C7 angle and SVA C2-C7(r=-0.26),C0-C2 angle and C2-C7 angle(r=-0.59),T1S and C2-C7 angle(r=0.55),TIA and C2-C7 angle(r=0.43),skull tilt angle and C0-C2 angle(r=0.35),CI and C0-C2 angle(r=-0.31)were significantly correlated.Conclusion:In patients with basilar invagination,the overall head tilts forward and downward,the upper cervical lordosis is smaller,the lower cervical lordosis is larger,and the thoracic entrance angle is smaller.To reduce the adverse effects of occipital-cervical junction deformity on cervical sagittal balance and cervical biomechanical environment,patients with basilar depression may require early treatment.Part Ⅱ:Study of cervical disc degeneration in patients with basilar invaginationMethods:Totally 75 patients diagnosed BI from February 2009 to October 2017 and 76 normal adults treated at hospital clinic or physical examination center from January 2017 to April 2021 were selected as the research object.Two groups were divided into 5 age groups:18-27years、28-37 years、38-47 years、48-57 years and≥58 years.OC2A and C2-7 Cobb angle was measured in neutral neck lateral radiograph.According to the modified Pfirrmann eight-level grading system,cervical intervertebral disc was assessed by preoperative cervical MRI examination.Cervical curvature and intervertebral disc degeneration between the two groups were compared using variance analysis and nonparametric rank-sum test.Results:(1)No differences were found between two groups of age and gender.(2)The OC2A of each age group in BI group was significantly smaller than those in the normal group(P<0.05).The C2-7 Cobb angle in BI patients was greater than those in normal adults,but there was no significant difference in C2-C7 Cobb angle between 18-27 and 28-37 years old(P>0.05).(3)Degeneration of cervical intervertebral disc in BI group was more serious than that in normal group.Conclusion:This study found disc degeneration with past anterior cervical flexion in patients with Basilar invagination,which may be the result of long-term abnormal cervical spine biomechanics and cervical muscle group strength effects.This suggests that the treatment of patients with basilar invagination needs to consider the restoration of the entire cervical spine biomechanical environment.Part Ⅲ:Anatomical study of C2 pedicle morphology in patients with basilar invaginationMethods:The present study was based on CT images.100 patients with BI were included in this retrospective study denoted as the BI group.100 cases without cervical lesions or abnormalities were served as the control group.Radiographic parameters including the pedicle width,pedicle length,pedicle height,pedicle transverse angle,pedicle lamina angle and pedicle superior angle were measured and analyzed.In addition,the effect of C2-3 fusion on C2 pedicle deformity in patients with BI was investigated as well.Results:No significant differences were in age or sex between BI and control groups.The width,length,and height of the C2 pedicle of BI patients were smaller than those of the control group.The pedicle cancellous bone was smaller in BI patients while no significant difference in cortical bone was observed between BI and control groups.44%of pedicles were smaller than 4.5 mm in the BI group.Patients with C2-3 fusion presented smaller pedicle transverse angles and larger pedicle superior angles than that in the non-C2-3 fusion group.In the BI group with atlantoaxial dislocation or atlantooccipital fusion,inconsistency in the left and right angles of the pedicle was observed.Conclusion:The C2 pedicle in the BI group was thinner than that in the control group,representing the general population,because of the smaller cortical bone.C2-3 fusion,atlantoaxial dislocation,and atlantooccipital fusion result in changes in the angle of the C2 pedicle. |
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