Osteonecrosis due to drugs of right ulna

This code signifies the death of bone tissue in the right ulna, specifically caused by the adverse effects of medication. This condition, also known as avascular necrosis, results from an interruption of blood supply to the bone, leading to its collapse.

Apply this code when documentation clearly states osteonecrosis of the right ulna and explicitly links its etiology to drug use. This typically occurs in patients with a history of corticosteroid use, bisphosphonate therapy, or other medications known to cause avascular necrosis.

• Ensure the documentation specifies the right ulna; laterality is critical.
• Always code the drug causing the osteonecrosis as an adverse effect (T36-T50 with a 5th or 6th character of 5).
• Distinguish from osteonecrosis due to other causes (e.g., trauma, alcoholism) which have different codes.