Stress fracture, right ulna, subs for fx w malunion

This code signifies a stress fracture affecting the right ulna that has previously been treated, but has healed in an unsatisfactory position, resulting in malunion. A stress fracture is a hairline crack in the bone caused by repetitive stress or overuse, rather than a single traumatic event. The malunion indicates that the bone fragments have united in a deformed or misaligned way.

Apply this code when documentation clearly states a stress fracture of the right ulna and explicitly mentions a "subsequent encounter" for treatment or management of a "malunion." This typically applies to follow-up visits where the malunion is being assessed, monitored, or treated (e.g., for corrective surgery planning or conservative management).

• Ensure the documentation specifies "right ulna" and not another forearm bone or side.
• Verify that the encounter is for a "malunion" and not a nonunion (M84.331N) or routine healing (M84.331D, M84.331G, M84.331K, M84.331P).
• Confirm the fracture type is a "stress fracture" and not a pathological or other type of fracture.