Follow-up (3- 47 months, average of 15.96 ± 13.89 months) showed a significant improvement of all clinical symptoms in all patients (Table 1 and 2).
Vertico-horizontal Atlantoaxial Index
In patients with basilar invagination and atlantoaxial dislocation, the point of maximal neural compression is the odontoid process.6 Based on this pathological mechanism, neural compression can be divided into vertical displacement (along the long axis of the odontoid process) and horizontal displacement (parallel to the lower endplate of the axis). Wherefore, the evaluation of neural compression can be achieved by measuring the displacement of the odontoid process in the mid-sagittal plane of CT or MRI images.
Several atlantoaxial…show more content… Duraplasty was not performed. Bone bridge formation is demonstrated between the occiput and the C2 spinous process.
Patients with atlantoaxial dislocation often have different bony malformations like basilar invagination, atlanto-occipital fusion, atlas hypoplasia, Klippel-Feil syndrome, etc.4,10-13 In these cases, evaluating the neural compression is difficult. There are many measurements for the evaluation of basilar invagination with atlantoaxial dislocation, reflecting the fact that no single method is consistent.3
Chamberlain’s line, McRae’s line, McGregor’s line, Fischgold’s line, Redlund-Johnell method and Klaus height index are often used to observe the location of the odontoid process and the lower endplate of the axis. However, these methods are often interfered by the bony malformations like atlanto-occipital fusion. In Ranawat and modified Ranawat method, there are difficulties to precisely locate the midpoint of the anterior and posterior arch of the atlas. While, with hypoplasia of the posterior arch of the atlas, the Sakaguchi-Kauppi method is difficult to measure. Further, these methods are based on plain radiographs, hence precise localization of landmarks may not be possible. Also, these methods cannot be measured postoperatively especially after resecting the posterior margin of the foramen magnum.
Atlanto-dental Interval can clarify the extent of horizontal dislocation of occipitocervical and