Imaging Study Of Atlas Anatomical Parameters In Adult Patients With Os Odontoideum

Objective:1)Compare CT data of patients with Os odontoideum and those with normal odontoid process,and measure the anatomical parameters of the atlas;2)Calculate the surgical methods of patients with Os odontoideum,analyze the impact of atlas parameters on the method of surgical screw placement,and determine the conditions for the insertion of atlas screws;3)Provide some reference suggestions for the placement of atlas pedicle screws in patients with Os odontoideum.Method:1.Fifty patients were randomly selected from patients with Os odontoideum and those with normal odontoid process.Patients with Os odontoideum were defined as Group A,and patients with normal odontoid process were Group B.2.The three-dimensional CT reconstruction data of the atlas of the patients in Groups A and B were measured,and the measurement parameters included:(1)anteroposterior length of atlas(2)mediolateral width of atlas(3)the distance from the midline to the medial border of atlas pedicle(4)the distance from midline to the inner edge of transverse foramen(5)safe placement area(6)length of pedicle midpoint to front edge of lateral mass(7)width of atlas pedicle(8)lateral mass height(9)lateral mass width(10)medullary height of the atlas pedicle(11)height of atlas pedicle(12)height of posterior nodule(13)width of posterior nodule.3.According to the measurement results,the shape of the atlas pedicle is divided into three types:type Ⅰ(the pedicle has no pith cavity);type Ⅱ(the pedicle contains the pith and the height is less than 3.5mm);Type Ⅲ(the pedicle contains the medullary cavity and the height is greater than 3.5mm).4.Collect surgical screw placement methods,count atlas types and analyze their relationship.Result:Through statistical analysis,it was found that the height of the atlas pedicle of Group A was 3.09±1.11mm,the width of the pedicle was 5.48±1.23mm,medullary height of the atlas pedicle was 0.54±0.67mm,the safe placement area was 6.46± 1.9mm,and the mediolateral width of atlas was 73.52±5.07mm;the height of the atlas pedicle of Group B was 4.04± 1.02mm,the width of the pedicle was 7.34± 1.08mm,medullary height of the atlas pedicle was 1.39±0.88mm,the safe placement area was 7.6±1.48mm,and the mediolateral width of atlas was 76.42±5.72mm,the measurement average of Group A was significantly smaller than that of Group B(P<0.05),which was statistically different.There were 53(53%)type I(the pedicle has no pith cavity)in Group A,which were significantly higher than the 8 sides(8%)of Group B(P<0.05).Conclusion:Patients with Os odontoideum have smaller pedical height,width,and safe placement area than normal people.The rate without a medullary cavity(type Ⅰ)is significantly higher than that of normal people,so it is more difficult to successfully insert atlas pedicle screws.