METHODS: There is confusion in the use of anatomic terminology of the pars interarticularis and pedicle of the C2 in literature. A fracture of the unilateral pars interarticularis of the C2 was diagnosed and treated nonsurgically by a Philadelphia collar.

RESULT: The patient was free of pain and obtained a full range of motion.

CONCLUSION: The presumed mechanism of injury in the fracture described here was hyperextension and axial loading. Keywords : C2 fracture, Unilateral pars interarticularis, Axis