Flaps, revisited

Cracking the Code

Alexander Miller

Dr. Miller, who is in private practice in Yorba Linda, California, represents the American Academy of Dermatology on the AMA-CPT Advisory Committee.

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You broadly excise a medial cheek basal cell carcinoma, excise redundant cones of skin bordering the superior and inferior edges of the surgical defect, place the intended line of closure into the nasofacial sulcus and the nasolabial groove, widely undermine the lateral cheek, and then advance the cheek to cover the surgical defect and suture the tissue together in a layered fashion. As you advanced a large portion of cheek, do you bill a flap (adjacent tissue transfer or rearrangement) or a repair code?

The CPT, in its definition of flap codes, 14000 – 14302, specifies that adjacent tissue transfer or rearrangement (flap) codes include the excision of the lesion. Furthermore, the CPT states: “Undermining alone of adjacent tissue to achieve closure, without additional incisions, does not constitute adjacent tissue transfer.” In the above example one could argue, however, that additional excisions for the removal of redundant skin were done, and then a broad “flap” of cheek tissue was advanced. The CPT Assistant, April 2014, p. 10, tackles just such a scenario of “dog ear” removal, stating that excess tissue removal does not constitute adjacent tissue transfer. As the extent of undermining also does not justify a flap code, coding for a flap repair is not appropriate. In the example given above, one would code for the malignant excision and for a complex repair, as broad undermining was necessary and done.

The flap CPT codes are appropriate for use in defect repair when incisions are done to specifically result in adjacent tissue transfer (advancement, rotation flaps) or rearrangement (transposition, Z-plasty, W-plasty, random island flaps). Random vessel-based island flaps (often described in past dermatologic literature as “island pedicle” flaps) are really considered to be types of V-Y subcutaneous based advancement flaps, and are to be coded with an appropriate CPT flap code, 14000-14302. The CPT code 15740, for “Flap; island pedicle,” can only be used for a flap that is based upon a named axial vessel that is identified and dissected, after which the flap is transposed into a non-adjacent defect. Consequently, criteria for the use of CPT 15740 are rarely satisfied in dermatologic surgery.[pagebreak]

Appropriate coding for adjacent tissue transfer or rearrangement flaps is determined by two factors:

  1. The location of the primary, excisional surgical defect.
  2. The sum of the surface area of the primary defect plus that of the secondary defect corresponding to the area of the detached portion of the flap.

One should then measure and note the sum surface area in the medical record. For purposes of CPT flap coding this constitutes the “defect” area size. The CPT provides site-specific codes for defects measuring 10 square centimeters or less and for defects measuring 10.1 to 30.0 sq cm. CPT 14301 specifies defects 30.1 to 60.0 sq cm in any location. An add-on CPT code, 14302, is used to specify each additional 30.0 sq cm in defect area beyond 60.0 sq cm.

Most surgical defects and raised flaps surface areas can be determined with any of three simple geometric formulas:

  1. The area of a square: multiply two adjacent sides of the square (S*S)
  2. The area of a circle: Pi (3.14) times the diameter of the defect (*D)
  3. The area of a triangle: One-half of base times height (1/2 B*H)

There are some adjacent tissue transfer flaps, such as bilateral advancement or rotation flaps, that may cause some uncertainty in coding. One may want to consider each arm of a bilateral advancement or rotation flap as a separate flap. However, such flaps constitute one flap design and are billed as a single flap, with the sum of the measured areas of each of the raised arms of the flap plus the area of the surgical defect defining the billable area of the defect. One may bill for two flaps if there are two non-contiguous defects in the same anatomical area.[pagebreak]

Example 1: A large frontal scalp defect is repaired with a broad scalp advancement-rotation flap with a back-cut. Due to scalp tension a portion of the flap donor site is repaired with a full thickness skin graft harvested from the neck base. One would code for the flap with appropriate 14000 series CPT code(s) and for the skin graft with CPT 15220/15221.

Answer: Correct. The CPT considers the repair of a flap donor site with either a skin graft or with an additional flap a separate procedure. Consequently, it is appropriate to bill for the graft.

Example 2: In the process of reconstructing a nasal sidewall defect with a transposition flap the flap is further mobilized by incising a Z-plasty at the base of the transposition flap. One then bills CPT 14060 for the transposition flap and 14060-59 for the additional Z-plasty.

Answer: Incorrect. The Z-plasty is done as a continuation of the transposition flap and is therefore a component of the entire flap. One would bill for one flap, measuring the surface area of the transposition flap and adding the area of the Z-plasty plus that of the surgical defect to determine the appropriate CPT code.

Example 3: As part of a scar revision procedure an indurated, hypertrophic surgical scar is excised from the nasal sidewall and the defect is repaired with a cheek advancement flap. As the excision of the scar constitutes a separate procedure, you bill for the excision of the scar along with the flap repair of the defect.

Answer: Incorrect. The CPT defines flap codes, 14000-14302, as including an excision of a lesion, in this case the hypertrophic scar. Consequently, only the flap repair should be billed.

Example 4: A broad, irregular nasal defect is repaired with two distinct flaps, one being a transposition flap and the other an advancement flap. You then add the area of the defect to the sum of the areas of the raised flaps to determine the square centimeter area and bill for one flap only.

Answer: Correct. The CPT Assistant, July 2008, p. 5, describes that when there are two defects within one and the same anatomical area, and each of the defects is repaired with a flap, one may bill for two separate flap repairs. However, in order to bill for two flaps there must be two separate defects with no contiguous margins.

Example 5: You excise a large tumor from a patient’s forehead and repair the defect by raising two advancement-rotation flaps on either side of the defect and advancing them centrally to cover the defect. You then bill CPT 14041 for the 14 sq cm right-sided flap and 14014-59 for the 14 sq cm left-sided flap.

Answer: Incorrect. A bilateral advancement or advancement-rotation flap is considered to be one flap. One should add the area of the defect plus that of each of the raised flaps to generate one adjacent tissue rearrangement CPT code. The CPT Assistant, July 2008, p. 5, specifically illustrates that bilateral advancement flaps should be billed as one flap.