Analysis on 3D CT imaging of lateral atlantoaxial joints in patients with old odontoid fracture and atlantoaxial dislocation

English Keywords:Old odontoid fracture  Lateral atlantoaxial joint  Obliquity  Atlantoaxial dislocation  CT

English Abstract:

  【Abstract】 Objectives: To observe the three-dimensional CT imaging of lateral atlantoaxial joints in patients with old odontoid fracture and atlantoaxial dislocation, and to explore its clinical significance. Methods: Retrospective analysis on the patients with old odontoid fracture and atlantoaxial dislocation admitted from June 2013 to April 2020 in our hospital. 21 patients were included in this study(group A). Twenty-one volunteers matched by age and sex without occipitocervical lesions were selected as control group(group B). The coronal and sagittal inclination angles of atlantoaxial lateral mass joints in group A and group B were measured and compared on two-dimensional CT, which were used as quantitative evaluation indexes of lateral mass joint morphological changes. The measurement was performed by two spinal surgeons independently, and was repeated at an interval of one week. The inter-observer reliability of group B was tested. The course of fracture and sagittal inclination angle of atlantoaxial lateral mass joints were recorded in group A, and Pearson correlation analysis was used to analyze the correlation in between. According to the reduction condition of atlantoaxial dislocation under cervical hyperextension or skull traction under general anesthesia, patients in group A were defined as reducible(reduction≥50%) and irreducible(reduction<50%). The proportion of irreducible patients in group A with or without lateral mass joint morphological changes was calculated to analyze the correlation between the changes of lateral mass joint morphology and the difficulty of atlantoaxial dislocation reduction. The atlantodental interval(ADI) value and JOA score were compared between patients with and without lateral mass joint morphological changes in group A. Results: In group B, the inter-observer reliability was 0.923 and 0.902, and the intra-observer reliability was 0.934 and 0.909. The obliquity in coronal and sagittal plane of 42 sides of lateral atlantoaxial joints in patients in group B were 24.6°±3.9° and 14.8°±2.7°. The obliquity in coronal plane of 41 sides of lateral atlantoaxial joints in patients in group A was 25.2°±4.1°(One case with unilateral lateral mass fusion could not be measured). There was no significant difference of obliquity in coronal plane between group A and group B(P>0.05). The obliquity in sagittal plane of 41 sides of lateral atlantoaxial joints in patients in group A was 8.2°±4.9°, which was less than that of group B(P<0.05). Pearson correlation analysis showed that the duration of fracture was negatively correlated with the sagittal inclination angle of bilateral atlantoaxial mass joints (left: r=-0.702, P<0.01; right: r=-0.605, P<0.05). In group A, 12 patients had lateral mass joint collapse, fornix like and fish lip like morphological changes (unilateral 6 cases, bilateral 6 cases). According to the evaluation of skull traction under general anesthesia, 10 cases were reversible and 11 cases were irreducible. The proportion of irreducible atlantoaxial dislocation was 75%(9/12) in patients with morphological changes of lateral atlantoaxial joint, which was significantly higher than that of patients without morphological changes of lateral atlantoaxial joint 22.2%(2/9)(P<0.05). In group A, the ADI value and JOA score of patients with lateral mass joint morphological change were 10.3±1.6mm and 9.6±3.2, respectively, which were significantly different from those without lateral mass joint morphology change(7.2±3.1mm, 14.6±3.3)(P<0.05). Conclusions: Some patients with old odontoid fracture and atlantoaxial dislocation had morphological changes of atlantoaxial lateral mass joint, and the morphological changes of lateral mass joint were related to the occurrence and development of atlantoaxial dislocation and the reducibility of the atlantoaxial dislocation. For the patients with old odontoid process fracture and atlantoaxial dislocation, three dimensional CT evaluation of atlantoaxial lateral mass joint shape has a certain guiding value for surgical decision-making and intraoperative operation.