Intraoperative three-dimensional fluoroscopy based navigation assisted C1, 2 transarticular screw placement for the treatment of atlantoaxia instability

Abstract

Objective To evaluate the accuracy of transarticular screw fixation using intraoperative three-dimensional fluoroscopy-based navigation (ITFN) and to evaluate the clinical outcomes of this treatment method. Methods Data of 56 patients(26 males and 30 females) with atlantoaxial instability who were treated by C1, 2 transarticular screw fixation using ITFN from November 2005 to October 2015 were retrospectively analyzed. The mean age of the patients was 44.5 years (range, 9-68 years). There were 44 cases with congenital malformation, 4 with old odontoid fracture, 7 with spontaneous dislocation, and 1 with rheumatoid arthritis. C2 isthmus width and height were measured on preoperatively obtained CT scans, and screw positioning was evaluated on postoperatively obtained CT scans, and classified into three types: ideal position (type I), acceptable position (type II) and unacceptable position (type III). A novel grading system is proposed based on previous study and grading system, and the difficulty of placing C1, 2 transarticular screw using ITFN was classified into three types: easy (total score 0), median (total score 1) and hard (total score 2, 3). Pain scores were assessed using the visual analogue scale. Myelopathy was assessed using the Nurick scale and Odom’s criteria. Results The isthmus width was 5.46±1.86 mm on the right side and 5.38±1.36 mm on the left side. The isthmus height was 4.89±1.33 mm on the right side and 4.97±1.17 mm on the left side. According to the grading system, 78, 11, and 23 of the sides were classified into easy, median and hard groups respectively. One hundred and seven transarticular screws were placed in 56 patients, and 71.03% of which were ideal screws, and 28.97% were acceptable screws. Five patients had unilateral screws placed. There was no significant difference in screw positioning among the three groups (χ2=0.46, 0.54, 1.18; P=0.50, 0.46,0.28). The mean follow-up period was 44.7 months (range, 6-120 months). At the latest follow-up, according to Nurick score, there are 30 patients scoring 0, 25 patients scoring 1, and 1 patient scoring 2. According to Odom’s criteria, outcomes were as follows: excellent, 66.1%; good, 26.8%; fair, 7.1%; and poor, 0%. All patients with preoperative neck pain had symptom relief or improvement, with more than 89.33% improvement in visual analogue scale scores. No dural laceration, injury to the vertebral artery, spinal cord, or hypoglossal nerve were noted. Conclusion ITFN is a safe, accurate, and effective tool for transarticular screw placement in patients with atlantoaxial instability. Key words: Cervical atlas; Axis; Joint instability; Surgery, computer-assisted