Atlas ( C1) Fractures - "Jefferson fracture"
Classification
Classically the "Jefferson" fracture is a burst fracture of the ring of C1. Bursting the ring in 4 places. Normally sustained by axial loading.
There are three general types of Jefferson fracture:
- I - Bilateral single arch (anterior or Posterior)
- II - Concurrent anterior and posterior arch fractures (classical 4 points)
- III - Lateral mass fracture
Levine (1991) described 5 variants of C1 fractures
| Classification | Mechanism of injury | Stability |
| I -Isolated bony apophysis fracture (extraarticular fracture of transverse process) | Stable may involve vertebral foramen/ artery | |
| II - Isolated posterior arch fracture | Hyperextension | Stable |
| III - Isolated anterior arch fracture | Hyperextension, the Dens is forced anteriorly through the arch | Unstable if displaced |
| IV - Comminuted lateral mass fracture | lateral axial compression | Unstable |
| V - Burst fracture, three or more fragments | Axial compression | Depends on displacement/ integrity of transverse atlantal ligament |
Stability
In assessing the stability of a C1 injury you need to look at:
- Configuration of the bony fracture
- Integrity of the transverse atlantal ligament.
Transverse atlantal ligament rupture
Classification of transverse atlantal ligament injuries:
- I - Ligament rupture. midportion(IA), periosteal insertion(IB)
- II - Avulsion of insertion of the transverse ligament into lateral mass. involving a comminuted C1 lateral mass (IIA) or avulsing the tubercle from an intact lateral mass (IIB)
Diagnostic imaging of transverse ligament.
Plain radiographs are not sensitive enough to exclude injury to the transverse atlantal ligament. Normal relationships of the C1 lateral masses on open-mouth radiographs or a normal atlantodental interval on lateral cervical radiographs does not exclude injury to the transverse ligament. Up to half the cases of atlas fractures just using >7 mm would miss an injury to the transverse atlantal ligament, and if you use a ADI cut off of 3mm roughly 1/3 of transverse atlantal ligament injuries would be missed. Therefore if radiographs are within these normal limits and you suspect injury, suggest CT and/ or MRI
Featuressuggesting loss of integrity of transverse atlantal
ligament:
- Spence's rule - >7mm combined overlap of lateral masses on open mouth.
- Bony avulsion fragments on CT also suggest loss of ligamentous integrity.
- An increased ADI on the lateral >3 mm in adults > 5mm children implies rupture transverse atlantal ligament.
- MRI may demonstrate ligmentous rupture.
Treatment
Depends on stability
If stable, transverse ligament intact
Orthosis/ rigid collar
If Unstable
Halo jacket
Fusion C1 to C2 (if midsubstance rupture of transverse atlantal ligament - ligaments will not heal sufficiently strong) (or bony fragment fails to unite only 3/4ths of bony injuries to transverse atlantal ligament will unite, consider fusing if not united by 12-16 weeks))
For patients who sustain a concurrent subaxial cervical fracture, the treatment is generally for the subaxial fracture, unless the Jefferson fracture itself is unstable.
References
Lee, Thomas T. MD. Green, Barth A. MD, FACS. Petrin, David R. RN. Treatment of Stable Burst Fracture of the Atlas (Jefferson Fracture) With Rigid Cervical Collar. Spine. 23(18):1963-1967, September 15, 1998.
Dickman, Curtis A. M.D.. Greene, Karl A. M.D., Ph.D.. Sonntag, Volker K.H. M.D.. Injuries Involving the Transverse Atlantal Ligament: Classification and Treatment Guidelines Based upon Experience with 39 Injuries. Neurosurgery. 38(1):44-50, January 1996