title: Posterior occipito-axial fixation applied C2 laminar screws for pediatric atlantoaxial instability caused by Down syndrome: Report of 2 cases.
abstract: BACKGROUND
  Upper cervical spine instability is one of the most critical orthopedic problems in patients with Down syndrome. However, arthrodesis of the upper cervical spine in these patients can be very difficult to achieve and has a high complication rate because of mental retardation and accompanying various medical conditions of the vital organs. Even now, surgeries in such patients, especially pediatric cases, are challenging and the optimal operative procedure remains unsettled. The purpose of this study was to report 2 cases of pediatric atlantoaxial instability due to Down syndrome in which posterior occipito-axial fixation with C2 laminar screws was performed.
  
  
  METHODS
  Case 1 was a girl aged 6 years 10 months who had atlantoaxial rotatory fixation with os odontoideum. Atlantoaxial rotatory fixation was incompletely reduced by halo traction, and it was not maintained without halo-ring and -vest fixation. Posterior occipito-axial fixation with bilateral C2 laminar screws was then performed. Case 2 was a boy aged 10 years 7 months who had atlantoaxial subluxation with os odontoideum. He also had incomplete quadriplegia, so he could neither walk nor have a meal by himself. Posterior occipito-axial fixation with right C2 pedicle and left C2 laminar screws was then carried out.
  
  
  RESULTS
  In case 1 bone union was obtained at 3 months after surgery and the patient's symptoms were resolved. In case 2 bone union was obtained at 3 months after surgery and the paralysis was improved.
  
  
  CONCLUSIONS
  In cases of atlantoaxial instability due to Down syndrome, symptomatic patients often present between ages 5 and 15 years and mental retardation interferes with postoperative cervical immobilization. C2 laminar screws can be safely applied for the pediatric axis and biomechanically accomplished rigid fixation. The C2 laminar screw is one of the most useful options to achieve stability of the pediatric atlantoaxial complex without the risk of vertebral artery injuries (level IV case series).
authors.affiliation: Department of Orthopaedic Surgery, University of Miyazaki Faculty of Medicine, Miyazaki, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kuroki
authors.affiliation: Department of Orthopaedic Surgery, University of Miyazaki Faculty of Medicine, Miyazaki, Japan.
authors.forename: Shinichiro
authors.initials: S
authors.lastname: Kubo
authors.affiliation: Department of Orthopaedic Surgery, University of Miyazaki Faculty of Medicine, Miyazaki, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Hamanaka
authors.affiliation: Department of Orthopaedic Surgery, University of Miyazaki Faculty of Medicine, Miyazaki, Japan.
authors.forename: Etsuo
authors.initials: E
authors.lastname: Chosa
keywords: Atlanto-axial instability; Down syndrome; Laminar screw; Posterior occipito-axial fixation; pediatric patients