Individualized strategy for upper cervical surgery based on the identification of atlantoaxial anatomic variation

English Keywords:Atlantoaxial dislocation  Anatomic variation  Individual surgery

English Abstract:

  【Abstract】 Objectives: To explore the individualized strategy for posterior atlantoaxial surgery based on the identification of atlantoaxial anatomic variation. Methods: Clinical data of 86 patients with upper cervical disorders who underwent posterior approach instrumentation from March 2012 to October 2015 in Guangzhou General Hospital of Guangzhou Military Command were analyzed retrospectively. There were 33 cases of atantoaxial dislocation with cranial-cervical junction malformation, 18 cases of traumatic atlantoaxial dislocation, 14 cases of atlantoaxial intraspinal tumor, 9 cases of atlantoaxial dislocation with upper cervical tuberculosis and 12 cases of atlantoaxial dislocation with rheumatoid arthritis. According to the height of posterior atlas arch(HPAA) in lateral X-ray radiography, atlas transpedicle screws were determined to place whether on not. When it was referred as type A atlas(HPAA≥3.5mm), atlantal pedicle screw fixation could be chosen, while atlas lamina hook could be used in patients with type B atlas(HPAA<3.5mm). Types of axial vertebral artery foramen were determined by value a(distance between the entrance of vertebral artery foramen and inner wall of axial canal) and value e(slice number when the bulb of vertebral artery foramen occurred × slice thickness) which obtained in thin slice CT scan. a>4.5mm and e≥4.5mm was type Ⅰ; a≤4.5mm and e＜4.5mm was type Ⅱ; a≤4.5mm and e≥4.5mm was type Ⅲ; a＞4.5mm and e＜4.5mm was type Ⅳ. Type Ⅱ axis chose lamina screws and other types of Ⅰ/Ⅲ/Ⅳ axis chose transpedicle screws. Results: There were 146 sides of type A and 26 sides of type B in atlas, 32 sides of type Ⅱ, 140 sides of type Ⅰ/Ⅲ/Ⅳ in axis. Then 26 atlas hooks, 146 atlas transpedicle screws, 32 axis lamina screws and 140 axis transpedicle screws were used. Therefore 3 types of instrumentation were performed in the study: atlas pedicle screw-rod-axis pedicle screw, atlas pedicle screw-rod-axis lamina screw, atlas hooks-rod-axis pedicle screw. The operation time was 95-156mins(average, 130±25mins), blood loss was 105-188ml(average, 150±35ml). Postoperative X-ray showed that all the patients got ideal reduction. The patients were followed up for 8 to 18 months(average, 13±5.5 months). The latest CT scan showed good bone fusion in 85 patients, except 1 patient with atlas hook loosening. Conclusions: For atlantoaxial dislocation, individualized strategy based on atlantoaxial anatomic variation in modern image techniques will be helpful to reduce surgical risk and improve the success rate of procedure.