I work for a wound clinic. The billing department is having a disagreement as to which of these two ICD-10-CM codes would be the first diagnosis - T86.821 for a skin graft failure or S81.802D for an unspecified open wound. The reason the patient was referred to the wound clinic is an open wound and failed skin graft due to radiation necrosis. Also let us know if you just disagree with the code selections, please.