Fracture of atlas (C1) - Gehweiler classification

The Gehweiler classification divides fractures of the first cervical vertebra into five types. Type III is also refered to as Jefferson fracture. The classical Jefferson fracture is a four part fracture, where both the anterior and the posterior arch is fractured twice, but fractures with two or three fracture parts may also occur.

Type Description
Type I fracture of the anterior arch
Type II fracture of the posterior arch
Type III combined fracture of both the anterior and the posterior arch = Jefferson fracture
Type IV fracture of massa lateralis
Type V fracture of the transverse process

References:

1. Gehweiler JA, Osborne RL, Becker RF. The radiology of vertebral trauma. Saunders; 1980.
2. Gehweiler JA, Duff DE, Martinez S, Miller MD, Clark WM. Fractures of the atlas vertebra. Skeletal Radiol. 1976 Dec 1;1(2):97–102
3. Suchomel P, Choutka O. Reconstruction of Upper Cervical Spine and Craniovertebral Junction. Springer; 2010.