title: A prospective, double-blind, randomized controlled trial of treatment of atlantoaxial instability with C1 posterior arches >4 mm by comparing C1 pedicle with lateral mass screws fixation.
abstract: BACKGROUND
  C1 posterior arch screw placement is one of the most effective treatments for atlantoaxial instability (AAI), which can be performed by either pedicle or lateral mass screw fixation. This study attempted to compare the feasibility and clinical outcomes of C1 pedicle with lateral mass screw fixations for treatment of AAI with C1 posterior arches >4 mm.
  
  
  METHODS
  A total of 140 patients with AAI (C1 posterior arches measuring >4 mm) was enrolled in this single-center, randomized, double-blind trial. The subjects were randomly assigned into two treatments: C1 pedicle (group A) or lateral mass (group B) screw fixation. The patients, independent evaluating physicians and radiologists were blinded throughout the entire study. Patients were assessed before operation and in a series of follow-ups at 6 weeks, 6 months, 1 year, and 3 years post-surgery. The operation time, volume of blood loss, intraoperative complications, bone fusion rates, Japanese Orthopaedic Association (JOA) and visual analog scale (VAS) scores were monitored.
  
  
  RESULTS
  All 140 patients showed overall improvements in clinical symptoms after surgery. The mean follow-up time was 24.5 ± 13.0 months. In both groups, the mean JOA scores improved significantly at the time of final follow-up as compared to prior surgery (group A: 7.1 ± 1.4 vs 13.7 ± 1.9; group B:7.3 ± 1.8 vs 13.1 ± 1.4; improvement rates: 87.2% (group A) and 86.5% (group B)). The VAS scores also decreased significantly in both groups at the time of final follow-up as compared to prior surgery (group A: 6.0 ± 1.3 vs 1.7 ± 0.8, and group B: 5.7 ± 1.1 vs 2.1 ± 1.2). Bone fusion was achieved within 12 months postoperatively in the patients from both groups. The operation time was significantly shorter and volume of blood loss was significantly less in the patients from group A as compared to group B (p < 0.01). Furthermore, thirteen patients had burst bleeding from the C1-2 venous plexus and nine patients had immediate pain and numbness in the occipitocervical region due to C2 nerve roots irritation during lateral mass screw replacement, which were not observed in the patients with C1 pedicle screw insertion. No complications such as screw loosening, shifting, breakage, or AAI were observed in both groups.
  
  
  CONCLUSIONS
  C1 pedicle screw fixation is less invasive and simpler, and has fewer complications. It renders better clinical outcomes than lateral mass screw fixation for treatment of AAI.
  
  
  BACKGROUND
  Current Controlled Trials ChiCTR-IOR-15006748 .
authors.affiliation: Department of Spinal Surgery, Hong Hui Hospital, Xi'an Jiaotong University College of Medicine, 555 Friendship East Road, Shaanxi, 710054, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Yan
authors.affiliation: Department of Spinal Surgery, Hong Hui Hospital, Xi'an Jiaotong University College of Medicine, 555 Friendship East Road, Shaanxi, 710054, China.
authors.forename: Baorong
authors.initials: B
authors.lastname: He
authors.affiliation: Department of Spinal Surgery, Hong Hui Hospital, Xi'an Jiaotong University College of Medicine, 555 Friendship East Road, Shaanxi, 710054, China.
authors.forename: Tuanjiang
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Orthopaedics, First Affiliated Hospital, Shaanxi University of Chinese Medicine, 2 Weiyang West Road, Shaanxi, 712000, China.
authors.forename: Lixue
authors.initials: L
authors.lastname: Yang
authors.affiliation: Department of Spinal Surgery, Hong Hui Hospital, Xi'an Jiaotong University College of Medicine, 555 Friendship East Road, Shaanxi, 710054, China. haodingjunspine@sina.com.
authors.forename: Dingjun
authors.initials: D
authors.lastname: Hao
mesh_terms: D000293:Adolescent; D000328:Adult; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D004311:Double-Blind Method; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016268:Internal Fixators; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D065289:Pedicle Screws; D011446:Prospective Studies; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D055815:Young Adult
keywords: Atlantoaxial instability; C1; Complications; Lateral mass; Pedicle