Code the flap based on location, bone, muscle, subcutaneous and skin or buccal mucosa. The artery and vein that are harvested are used for the anastomosis.
If root operations such as Excision, Extraction, Repair or Inspection are performed on overlapping layers of the musculoskeletal system, the body part specifying the deepest layer is coded. Ref, PCS Guidelines, B.3.5
Example: Excisional debridement that includes skin and subcutaneous tissue and muscle is coded to the muscle body part.
B3.9: Excision for Graft – Code the harvesting of free flaps separately.