Idiopathic aseptic necrosis of left tibia

This code describes the spontaneous death of bone tissue in the left tibia due to a lack of blood supply, without an identifiable cause such as trauma, infection, or medication. It represents avascular necrosis (AVN) affecting the shin bone, specifically the left side, where the etiology is unknown.

Use this code when documentation clearly states idiopathic avascular necrosis or osteonecrosis of the left tibia. This diagnosis is typically supported by imaging studies (e.g., MRI, X-ray) showing bone infarction and clinical findings consistent with AVN, in the absence of secondary causes.

• Ensure laterality is explicitly documented as "left tibia" to support this specific code.
• Distinguish from secondary AVN (e.g., due to steroid use, trauma), which would require different codes.
• Confirm that the "idiopathic" nature is either stated or implied by the absence of other causative factors in the medical record.