The treatment of atlantoaxial instability with posterior hybrid fixation techniques

Abstract

Objective To evaluate the indications, safety and clinical outcomes of hybrid internal fixation techniques in the treatment of atlantoaxial instability. Methods From June 2010 to June 2013, a retrospective study was done on 19 patients (7 males and 12 females, with age range of 15 to 57 years, mean 40±13 years) with atlantoaxial instability who had undergone the treatments of atlantoaxial fusion operations with hybrid fixation techniques. All of 19 patients suffered from neck pain or limitations of cervical motion. Among them, 5 cases presented only the neck pain while 14 cases combined with spinal cord compression systems, including different degrees of sensory and motor disorders and increased reflex. The atlantoodontoid interval was larger than 3 mm in 8/19 cases with an average of 6.4±3.0 mm (3-10 mm). The distance from lateral mass of atlas burst fracture was 7-9 mm (mean, 7.7±0.9). CT scan was used to evaluate the height of the lateral arch above bilateral axial vertebral arteries, with 4 cases < 4 mm unilaterally. The atlantoaxial fusion was achieved using hybrid fixation techniques, including transarticular screw, C1 lateral mass screw, C2 pedicle screw, C2 translaminar screw and C1 laminar hook. The neck pain that all patients suffered was measured by Visual analogue scale (VAS), and the degree of cervical spinal cord injury of 14 patients who had neural symptoms and dysfunction was evaluated by Japanese Orthopedic Association score (JOA) and the rate of the improved JOA score (RIS). Cervical X-ray and CT scan after operation were used to observe the internal fixations and bone fusion during the follow-up. Results All the 19 patients got 12 to 24 months' follow-up, 15.3±4.2 months at average. In 3 months follow-up time, all patients got relief from the neck pain, the VAS of neck pain decreased to 1.2±0.97 after 3 months and to 0.63±0.76 at last follow-up postoperatively, comparing to 4.5±1.54 preoperatively. The JOA score increased to 14.5±1.8 after 3 months and to 16.1±1.2 postoperatively, comparing to 12.2±1.9 preoperatively. In 12 to 24 months (15.3±4.2 on average) follow-up there was no failure of internal fixations, pseudarthrosis or instability. No spinal cord injury or vascular complications occurred. Conclusion The evaluation about the anatomical structure of atlantoaxial region by radiographic examinations is essential to the appropriate options of internal fixations. The individual surgical procedures usinghybrid fixation techniques are safe and effective. Key words: Atlanto-axial joint; Joint instability; Spinal fusion; Treatment outcome