Unsp fx fourth MC bone, left hand, subs for fx w nonunion

This code signifies a fracture of the fourth metacarpal bone in the left hand that has not healed properly after an initial treatment. "Nonunion" indicates that the bone ends have failed to unite and consolidate, despite adequate time and treatment. This condition often leads to persistent pain, instability, and functional impairment of the hand.

This code is appropriate for encounters where a patient is being treated for a previously diagnosed, unspecified fracture of the left fourth metacarpal that has progressed to nonunion. This includes follow-up visits for ongoing management, evaluation of nonunion, or planning for further surgical intervention to address the nonunion.

• Ensure documentation clearly specifies "nonunion" of the fourth metacarpal and laterality (left hand).
• Always sequence this code after the appropriate external cause code, if applicable, to describe the mechanism of injury.
• Verify that this is not an initial encounter for the fracture, as "subsequent encounter" is a key component of this code.