Observation on the long-term efficacy of posterior atlantoaxial fixation without fusion for the treatment of fresh type Ⅱ odontoid fractures

English Keywords:Odontoid fracture  Atlantoaxial fixation  Without fusion  Long-term efficacy  Range of motion of the atlantoaxial joint

English Abstract:

  【Abstract】 Objectives: To observe the long-term efficacy of posterior atlantoaxial fixation without fusion for the treatment of fresh type II odontoid fractures. Methods: Retrospective analysis of the clinical data of 22 patients with fresh type II odontoid fractures who underwent posterior atlantoaxial fixation without fusion at the Affiliated Hospital of Southwest Medical University from June 2006 to December 2017 and were followed up for more than 5 years was conducted. Among the patients, there were 19 males and 3 females, aged 19-58 years old(average of 40.9±10.5 years old) at the time of fracture; 17 cases were with no displacement or mild displacement(displacement≤2mm), and 5 cases were with obvious displacement(displacement>2mm). The visual analog scale(VAS) of neck pain, neck disability index(NDI), and grade of American Spinal Injury Association(ASIA) were compared between before operation, before removal of fixations, and at final follow-up, respectively. The neck stiffness severity of the patients was compared between before removal of fixations and at final follow-up using the method proposed by Landells et al. X-ray, multiplanar reconstruction CT, and functional CT were used to evaluate postoperative fracture healing, stability of atlantoaxial joint, degeneration grade of atlanto-odontoid and lateral atlantoaxial joints, and range of motion of the atlantoaxial joint. Correlation analysis was further performed to explore the factors that affect the rotational motion of atlantoaxial joint at final follow-up. Results: All the patients were removed for implants at 11.0±2.7 months after fixation surgery, and were followed up for 7.9±2.0 years. The median VAS scores before surgery, before removal of fixations, and at final follow-up were 6.5(6.0, 7.0) points, 1.0(1.0, 2.0) points, and 1.0(1.0, 1.0) points, respectively. The VAS score before the removal of fixations was significantly lower than that before surgery(P<0.05), which was not statistically different from that at the final follow-up(P>0.05). The median NDI before surgery, before the removal of fixations, and at final follow-up were 28.5(26.5, 32.0), 3.5(3.0, 5.0), and 2.0(2.0, 3.0), respectively. The NDI before the removal of fixations was significantly reduced compared with before surgery(P<0.05), and it further decreased at the final follow-up(P<0.05). Before the removal of fixations and at final follow-up, 3 patients who had spinal cord injury achieved 1 level improvement of ASIA grade compared to before surgery. There was no statistically significant difference in ASIA grade between before surgery, before the removal of fixations, and at final follow-up(P>0.05). At final follow-up, the proportion of patients with severe neck stiffness was significantly lower than that before the removal of fixations(36.4% vs. 77.3%, P<0.05). All the patients had fracture healing before the removal of fixations, and no implants breakage or fixation displacement was found. And at the final follow-up, no atlantoaxial instability was observed. At the final follow-up, the degeneration of the atlanto-odontoid joint worsened compared with before removal of fixations(P<0.05), and there was no statistically significant difference in the degeneration grade of the lateral atlantoaxial joints compared with before removal of fixations(P>0.05). At the final follow-up, the range of motions in flexion-extension and rotation of the atlantoaxial joint were 2.0°(0.9°, 3.0°) and 5.4°(3.7°, 9.5°), respectively. The correlation analysis showed that there was negative correlations between the degree of fracture displacement and the degeneration grade of the atlanto-odontoid joint and the rotational activity of the atlantoaxial joint in long-term follow-up(r=-0.381, P=0.038; r=-0.584, P=0.001). Conclusions: The treatment of fresh type II odontoid process fractures using posterior atlantoaxial fixation without fusion can achieve satisfactory long-term clinical results, but the range of motion of the atlantoaxial joint cannot be preserved well in the long term, which is related to the severe fracture displacement and progressive degeneration of the atlanto-odontoid joint.