The jigsaw sign. A reliable indicator of congenital aetiology in os odontoideum

European Spine Journal

Andrew B. Fagan²  Geoffrey N. Askin³  John W. S. Earwaker¹ 

[1] Queensland Diagnostic Imaging, Brisbane Private Hospital and Department of Radiology, University of Queensland, Brisbane, 4000 Queensland Australia;Spinal Unit Department of Orthopaedics and Trauma, Royal Adelaide Hospital and the University of Adelaide, North Tce, 5000 Adelaide, Australia;Mater Private Clinic, 550 Stanley St, South Brisbane, 4100 Queensland Australia

关键词: Os odontoideum;    Aetiology;    Computerized tomography;    Diagnosis;   

DOI  :  10.1007/s00586-004-0732-2

学科分类：骨科学

来源: Springer

【 摘 要 】

There is evidence in the literature for both a congenital and a post-traumatic aetiology for os odontoideum. In no series published to date has CT been used to aid in the diagnosis. This is a prospective study of the history of trauma and presence of diagnostic features on CT of 18 consecutive cases with os odontoideum. Our objective was to derive clinically useful radiological features enabling accurate differentiation between congenital and post-traumatic aetiologies. A mid-sagittal CT reconstruction of the atlanto-dens joint was obtained. Hypertrophy of the anterior arch of the atlas was quantified by measurement of the arch-peg-area ratio. The presence of dysplastic features (a positive “jigsaw” sign) of the atlanto-axial joint were noted. These included narrowing of the cartilage space and interdigitation of the two joint surfaces. A history of a potential traumatic aetiology was only obtained in one of the 18 (6%) in our series. A significant elevation of the arch–peg ratio was found when comparing this series to 85 controls. And a positive jigsaw sign was observed in 75% of cases. These features were not seen in paediatric cases of atlanto-axial instability, including odontoid non-union. In conclusion, an elevated arch–peg ratio and the presence of a jigsaw sign are sensitive and specific diagnostic criteria for os odontoideum. This series supports a congenital aetiology for this condition.

【 授权许可】

Unknown