ATLAS Type IV

These may collapse, causing deformity or result in posttraumatic arthritis. Therefore, primary fixation should be considered. This requires an occipital cervical fusion.

For the ATLAS fractures the Gehweiler classification is used together with the Dickman classification. 

Displaced intra articular fractures that are left unreduced will result in posttraumatic arthritis.

If unreducible, consider fusion.

While all techniques are possible for this fracture, if a C1 lateral mass screw can be placed lateral to the fracture line, it can aid in the anatomic reduction of the displaced fracture, which minimizes the risk of posttraumatic arthritis. After placement of bilateral C1and C2 screws and rods, one can place a cross link and compress the rods together, thereby reducing the fracture.

If one cannot place a screw into the broken lateral mass, an occipital cervical fusion may be necessary. An alternative in patients who have an anatomic reduction of the lateral mass fracture, but in whom C1 lateral mass fixation is not possible, one can instrument up to the skull but only fuse the C1-C2 joint. Once the fractures have healed, the instrumentation can be removed.