Other secondary osteonecrosis, unspecified ankle

This code signifies the death of bone tissue in an unspecified ankle joint due to an underlying condition, rather than a primary cause. This osteonecrosis is a secondary complication, often resulting from systemic diseases, long-term corticosteroid use, or trauma. It leads to bone collapse and joint destruction.

Use this code when documentation clearly indicates secondary osteonecrosis affecting an unspecified ankle. This diagnosis requires a confirmed underlying cause, such as lupus, sickle cell disease, or prolonged steroid therapy, leading to the bone death. The physician's notes should specify "secondary osteonecrosis" and identify the affected ankle as unspecified.

• Ensure the documentation explicitly states "secondary osteonecrosis" to differentiate from primary or idiopathic forms.
• Always code the underlying cause of the secondary osteonecrosis first, if known and applicable, following ICD-10-CM sequencing guidelines.
• Avoid using this code if a more specific ankle (e.g., right or left) is documented; instead, use M87.371 or M87.372.