Experimental study of atlas injuries. II. Relevance to clinical diagnosis and treatment.

Atlas injuries were produced in vitro and evaluated by radiographic examinations and anatomic studies from a clinical viewpoint. Ten cadaveric human upper cervical spine specimens were subjected to a high-speed axial impact. Injuries to the atlas consisted of six bursting fractures, two ruptures of the transverse ligament, one four-part fracture without a prominent bursting, and one posterior arch fracture. The major soft tissue injury involved the transverse ligament. There were five bony avulsions and three midsubstance tears. In this study, computed tomographic examinations clearly demonstrated the sites of fracture and bony avulsions of the transverse ligament. The best diagnostic tool for function of the transverse ligament was determined to be the atlantodental interval on flexion radiographs. Axial traction force reduced a bursting fracture of the atlas ring. The in vitro atlas injury model gives useful information for clinical diagnosis and treatment.