Axial pattern flaps (APF) are a type of pedicle flap that include a large direct cutaneous artery and vein.
Axial pattern flaps (APF) are a type of pedicle flap that include a large direct cutaneous artery and vein. The inclusion of a direct cutaneous artery allows movement of a large skin segment that is predictably robust with a large percentage of the flap surviving.
APF's were first described in the dog by Pavletic in the 1980's. Subsequently, many APF's have been described in the canine and feline by various authors. In general, the direct cutaneous vessels of the dog and cat are similar thus landmarks for construction of the flaps are similar but do have minor variation in regards to lengths of the specific flaps. Some APF's in cats are capable of covering larger defects when compared to the dog especially on the extremities.
General guidelines for construction of any axial pattern flap includes the following:
• Carefully consider the appropriate anatomic landmarks for development of each flap. Consult a surgery text for description of anatomic landmarks
• Position the animal and use the "pinch test" to assess the size of the donor flap that may be constructed and allow closure of the donor site without excessive tension.
• Use of a sterile marking pen is recommended to "map" out the flap to ensure Inclusion of the intended artery. Flaps are usually constructed in a "peninsular" design and rotated into adjacent or more distant defects.
• A "bridge incision" is made to join the donor and recipient sites allowing the flap to be positioned in the created defect. Alternatively, if the flap is to be used more distally, the flap can be "tubed" rather than making a long bridge incision. A disadvantage of the latter technique Is a second surgery is necessary to take down the tube once the flap has helaed adequately.
The most versatile and commonly used APF's, in cats are the caudal superficial epigastric and throracodrosal flaps. Other useful APF's especially for cranial and facial reconstruction are flaps based on the caudal auricular and superficial temporal arteries
The caudal superficial epigastric APF is an extremely versatile flap that is used for closure of defects of the flank, inguinal area, perineum, thigh, and importantly, the rear limbs. This flap when used for reconstruction of the rear limb can extend as far as the tarsus/metatartsus in the cat. In comparison, the flap reaches only to the level of the stifle in most breeds of dogs.
The caudal superficial epigastric artery leaves the inguinal ring to supply the caudal 3 mammary glands in the cat.
Mammary teats, ventral midline
Medial incision caudal ventral midline to include the skin and teats #2, 3, 4.
Lateral incision 2x the distance from nipples to midline ("pinch test")
The flap is dissected from the abdominal wall in the same fashion as performing a mastectomy and rotated into the defect using a "bridge incision" in most cases. The flap is sutured with 3/0 or 4/0 nylon and a padded bandage applied to the recipient site.
The thoracodorsal flap is utilized to cover defects of the axilla,thorax, and forelimb. This flap can reach as far as the carpus in the cat but is limited to the olecranon in the dog.
Spine of the scapula
Caudal edge of the scapula (shoulder depression)
Vessel originates in caudal shoulder depression
Cranial incision based on acromion and runs parallel and over the spine of the scapula to the midline if necessary.
Caudal incision 2x the distance from the acromion to the shoulder depression and the same distance caudal to the depression and the incsion parallel to the original incision. Either a bridge incision or "tubing" is utilized to place the flap on the forelimb or other locations.
Ventral limit from acromion through axilla.
This flap is based on the caudal auricular artery which originates in the depression just caudal to the ear and supplies the lateral cervical skin. The flap is useful for reconstruction of the lateral and dorsal (temporal) facial areas.
Caudal auricular depression
Rostral edge of scapula caudally
The flap is based rostrally at the caudal edge of the ear. Take care to do the "pinch test" to assure closure of the donor site. Sometimes the donor site is closed as a "Y" on each end and linearly in the middle.
This flap is useful for facial reconstruction especially defects involving the orbit and rostral facial area.
Rostral pinnal area
The flap is based on the zygomatic arch ipsilaterally and may extend across the temporal area to the contralateral arch. Use the "pinch test" to determine the width of the flap that may be constructed.
This flap consists of the skin from the tail that is preserved after "deboning" the tail by amputation. The skin of the tail is supplied by two arteries that course in the lateral skin. The flap may be used for defects in the perineal area, tail head area, or caudal rear limb.
Base of the tail
A linear incision is made on EITHER the dorsal or ventral midline over the length of the tail. The inscision is made dorsally for dorsal defects and ventrally for ventral defects. The skin flap is then dissected free of the caudal vertebrae and the tail amputated at the base preserving the skin flap. The flap is moved into the recipient defect and sutured with 3/0 or 4/0 nylon.