Path fx in oth disease, unsp foot, subs for fx w nonunion

This code signifies a fracture of an unspecified foot bone that occurred due to an underlying disease process, not from trauma. The fracture is currently in a state of nonunion, meaning it has failed to heal, and the patient is presenting for follow-up care related to this ongoing issue.

Apply this code for patients presenting for subsequent treatment of a pathological foot fracture that has not healed. Documentation should clearly state "nonunion" and link the fracture to an underlying systemic disease (e.g., osteoporosis, metabolic bone disease, neoplasm) rather than an acute injury.

• Ensure documentation specifies "nonunion" and the encounter is for subsequent care.
• Always code the underlying disease causing the pathological fracture first.
• Distinguish from malunion (M84.4-) and stress fractures (M84.3-).