Solitary bone cyst, unspecified ulna and radius

This code represents a benign, fluid-filled lesion within the bone of the forearm, specifically when the exact bone (ulna or radius) is not specified. These cysts are typically asymptomatic and discovered incidentally, but can cause pain or pathologic fractures.

Use this code when documentation confirms a solitary bone cyst located in the forearm, but the specific bone (ulna or radius) is not identified. This code is appropriate for initial encounters, follow-up, and treatment of such a cyst. Supporting documentation would include imaging reports (X-ray, MRI) and physician notes describing the lesion.

• Do not use this code if the specific bone (ulna or radius) is documented; instead, select a more specific code from the M85.43 series.
• Ensure the documentation specifies "solitary bone cyst" and not another type of bone lesion.
• Consider an additional code for any associated pathologic fracture if present.