Oth fx first MC bone, unsp hand, subs for fx w malunion

This code signifies a fracture of the first metacarpal bone (thumb) that has previously been treated but is now healing in an unsatisfactory position, resulting in a deformity or functional impairment. This malunion indicates that the bone fragments have joined, but not in their anatomical alignment.

Apply this code when a patient presents for follow-up care of a previously diagnosed and treated first metacarpal fracture, and clinical or radiological assessment confirms that the fracture has healed with malunion. This is appropriate for subsequent encounters where the focus is on managing the consequences of the malunion, such as pain, reduced range of motion, or planning for corrective procedures.

• Ensure documentation clearly states "malunion" and specifies the first metacarpal.
• Verify that this is a subsequent encounter, not the initial treatment or routine follow-up for a healing fracture without complications.
• Always check for laterality (left, right, or unspecified) if available in the documentation, as this code specifies "unspecified hand."