An open-mouth anteroposterior radiograph of a 20-year-old diver shows displacement of the lateral masses of C1 relative to the odontoid process, with a combined overhang exceeding 7 mm. What complication must be suspected?

• A Rupture of the transverse ligament of the atlas ✓
• B Fracture of the body of the axis
• C Disruption of the alar ligaments alone
• D Occipitocervical dissociation

Explanation

This is a Jefferson burst fracture of the atlas from axial loading. Rule of Spence states that when the combined lateral displacement of both C1 lateral masses exceeds about 7 mm on the open-mouth view, the transverse atlantal ligament is presumed ruptured, making the injury unstable and mandating immobilisation rather than simple collar treatment. Alar ligament injury alone does not produce lateral mass overhang of this magnitude.

Reference: Campbell's Operative Orthopaedics, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.