title: Atlantoaxial fusion with screw-rod constructs: meta-analysis and review of literature.
abstract: OBJECTIVE
  To review published series describing C1-2 posterior instrumented fusions and summarize clinical and radiographic outcomes of patients treated with screw-rod constructs (SRC).
  
  
  METHODS
  Online databases were searched for English-language articles published between 1991 and April 2011 describing posterior atlantoaxial instrumentation with C1-2 SRC. There were 24 studies including 1073 patients treated with SRC that fulfilled inclusion criteria. Meta-analysis techniques were used to compare outcomes.
  
  
  RESULTS
  All studies provided class III evidence. The 30-day perioperative mortality rate was 0.6%, and neurologic injury occurred in two patients with vertebral artery injury (VAI) from screw malpositions (0.2%). The incidence of clinically significant screw malpositions was 2.4% (confidence interval [CI], 1.1%-4.1%), the incidence of VAI was 2.0% (CI, 1.1%-3.4%), and the rate of fusion with the SRC technique was 97.5% (CI, 95.9%-98.5%).
  
  
  CONCLUSIONS
  SRC is a safe and effective treatment option for C1-2 instability. The low but nonzero incidence of screw malposition and VAI emphasizes the necessity of having a thorough knowledge of atlantoaxial anatomy for successful insertion of screws.
authors.affiliation: Neurosurgical Care, LLC, Royersford, Pennsylvania. Electronic address: robertelliottmd@gmail.com.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Elliott
authors.affiliation: Department of Neurosurgery, New York University Langone Medical Center, New York, New York, USA.
authors.forename: Omar
authors.initials: O
authors.lastname: Tanweer
authors.affiliation: Department of Neurosurgery, New York University Langone Medical Center, New York, New York, USA.
authors.forename: Akwasi
authors.initials: A
authors.lastname: Boah
authors.affiliation: Department of Neurosurgery, New York University Langone Medical Center, New York, New York, USA.
authors.forename: Amr
authors.initials: A
authors.lastname: Morsi
authors.affiliation: Department of Neurosurgery, New York University Langone Medical Center, New York, New York, USA.
authors.forename: Tracy
authors.initials: T
authors.lastname: Ma
authors.affiliation: Department of Neurosurgery, New York University Langone Medical Center, New York, New York, USA.
authors.forename: Michael L
authors.initials: ML
authors.lastname: Smith
authors.affiliation: Department of Neurosurgery, New York University Langone Medical Center, New York, New York, USA.
authors.forename: Anthony
authors.initials: A
authors.lastname: Frempong-Boadu
mesh_terms: D001268:Atlanto-Axial Joint / Q000033:anatomy & histology / Q000601:surgery*; D001863:Bone Screws; D006801:Humans; D007593:Joint Instability / Q000473:pathology / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods*; D016896:Treatment Outcome