Injuries Involving the Transverse Atlantal Ligament: Classification and Treatment Guidelines Based upon Experience with 39 Injuries

To the Editor: In their otherwise excellent article on transverse atlantal ligament injuries (1), Dickman et al. were hasty in trying to dispense with ”Spence's rule.” That rule, which arose from an elegant cadaveric study by Spence et al. (2), states that in the setting of a bursting fracture of atlas, if the combined C1 lateral mass displacements over the lateral lips of the superior articular surface of C2 (as measured on the open-mouth odontoid x-ray) exceed 6.9 mm, then it is likely that the transverse ligament has been torn. Looking at the recent report from the Barrow Neurological institute, it seems that none of the patients had Jefferson fractures with breadks through both anterior and posterior arches of C1, which are necessary to allow the kind of ring and lateral mass displacement Spence found correlated with ligament disruption. Therefore, one would not expect a correlation between lateral mass displacement and transverse atlantal injuries in this study, and none was found. In Canada, it is not possible to evaluate all neck fractures with magnetic resonance imaging, so ”Spence's rule” is of value for the right patients. J. Max Findlay Alberta, Edmonton, Canada