Displ post arch fx 1st cervcal vert, subs for fx w nonunion

This code signifies a fracture of the posterior arch of the C1 vertebra that has shifted from its normal anatomical position. It specifically indicates that the fracture has failed to heal properly and the patient is in a subsequent phase of care for this nonunion.

Use this code when a patient presents for ongoing treatment of a previously diagnosed displaced posterior arch fracture of the atlas, and documentation confirms the fracture has not united. This applies to follow-up visits, cast changes, or surgical interventions addressing the nonunion. Documentation must clearly state "nonunion" and specify the "subsequent encounter" for the fracture.

• Ensure documentation explicitly states "nonunion" for the fracture.
• Verify that the encounter is for ongoing care of the fracture, not the initial treatment.
• Distinguish from codes for initial encounters or encounters for routine healing.