title: Odontoid lateral mass asymmetry: do we over-investigate?
abstract: OBJECTIVE
  This study aimed to evaluate the necessity for further radiological investigation in patients with suspected traumatic rotatory subluxation of the atlanto-axial complex on plain radiography following acute cervical trauma and outline guidelines for assessment of patients with atlanto-axial asymmetry on plain radiography.
  
  
  METHODS
  A retrospective review of all patients who had undergone atlanto-axial CT scanning as a result of radiographic C1-C2 asymmetry following cervical spine trauma. The plain x ray and CT images were reviewed retrospectively and correlated with the clinical presentation and outcome.
  
  
  CONCLUSIONS
  Records of 29 patients (16 men, 13 women; age range 21-44 years) were reviewed. All patients were found to have atlanto-odontoid asymmetry on the initial plain x ray. CT images of none of the patients revealed rotatory subluxation. Ten patients (32%) were found to have congenital odontoid lateral mass asymmetry. All patients were treated conservatively without any further intervention. On review, in 19 patients the orientation of the x ray beam in combination with head rotation was found to be at fault. Approximately 1050 trauma cervical spine x rays were taken in the department where this study was conducted over the period 1999-2001. This study identified 10 patients out of a total of 29 as having congenital odontoid lateral mass asymmetry. This represents approximately 1% of the patients attending the emergency department. Thus congenital odontoid lateral mass asymmetry should be considered in the differential diagnosis following acute cervical trauma.
authors.affiliation: Department of Orthopaedics, St Vincent's University Hospital, Dublin, Ireland.
authors.forename: J A
authors.initials: JA
authors.lastname: Harty
authors.forename: B
authors.initials: B
authors.lastname: Lenehan
authors.forename: S K
authors.initials: SK
authors.lastname: O'Rourke
mesh_terms: D000328:Adult; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging* / Q000293:injuries*; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000293:injuries; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008297:Male; D009809:Odontoid Process / Q000002:abnormalities / Q000000981:diagnostic imaging / Q000293:injuries*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014103:Torticollis / Q000000981:diagnostic imaging / Q000209:etiology; D019564:Unnecessary Procedures