Redefining the Anatomic Boundaries for Safe Dissection of the Skin Paddle in a Gracilis Myofasciocutaneous Free Flap: An Indocyanine Green Cadaveric Injection Study.

The gracilis flap remains a versatile option in reconstructive plastic surgery. Originally described as a pedicled flap by Orticochea et al1 in 1972 for lower extremity reconstruction1 and later McCraw2 for pedicled rotational flap coverage of vaginal defects, it’s role has continued to evolve.3–11 Tamai et al.12 first described functional restoration using a transferred muscle in a canine model in 1970.13 The first reported use of the gracilis as a free muscle flap was described by Harii and Ohmori14 in 1976 for coverage of head and neck and lower extremity defects. In 1978, Manktelow and McKee15 described the free gracilis muscle to replace the long flexor musculature of the finger, and later went on to describe its use in replacing forearm musculature, facial reanimation, and anterior lower leg to treat foot drop.16–18 The gracilis flap can be harvested with or without a skin paddle. The traditional gracilis myocutaneous flap was known for partial skin flap necrosis, especially in the distal one-third to one-half of the skin island.2 Based on the unreliable distal skin paddle, McCraw2 described the musculocutaneous gracilis pedicled flap in 1976, stating “If the gracilis muscle is divided into thirds, the distal limit of the cutaneous flap lies at the junction of the middle and distal thirds of the muscle.” Our understanding of the gracilis myofasciocutaneous flap perfusion, however, was expanded in Whetzel and Lechtman’s 1997 article.19 They described harvesting a gracilis pedicled flap with adjacent fascia to improve vascularity of the skin paddle in vaginal wall reconstruction and used a cadaveric ink injection study to demonstrate separate vascular territories distally over the gracilis muscle. Despite this, there is still a wide spread belief that the gracilis myocutaneous free flap does not have a reliable distal skin paddle, and that surgeons should be extremely cautious—even avoid harvesting the distal skin altogether. Giordano et al.20 in 1990 described in their anatomic study that the distal 40% of the skin overlying the gracilis muscle belonged to the sartorius muscle system and should be delayed to improve safety of harvest. Wei and Mardini21 state in their book of microsurgical flaps that the gracilis free flap “skin island over the distal half of the thigh is not reliable.” Juricic et al.22 performed a meta-analysis and found that 13 of 192 (6.8%) gracilis musculocutaneous flaps had total skin necrosis. Our positive clinical experience with the free gracilis myofasciocutaneous flap in both free muscle coverage and free functional muscle transfer has led us to seek to redefine the safe boundaries for harvesting a reliable and robust skin paddle.23,24 Until now, cadaveric injection techniques were not able to definitively confirm our hypothesis that extended harvest of deep adjacent fascia could reliably perfuse a large skin paddle based off the single dominant pedicle. We are now able to corroborate our original hypothesis using a cadaveric dissection model. By enlisting a novel cadaveric injection technique for free flap perfusion via the dominant single pedicle using cadaveric blood containing indocyanine green (ICG), we are able to assess skin paddle perfusion with near-infrared imaging technology (SPY-PHI, Stryker, Kalamazoo, MI). We demonstrate our findings in 9 cadaveric gracilis free flaps containing large cutaneous paddles (average 770 cm2: range 507–912 cm2 or 39 × 19 cm: range 36–41 × 13 – 24 cm) and accompanying harvested deep fascia. With this same perfusion technique, we also confirm the lack of extended skin paddle perfusion when harvesting the myocutaneous gracilis free flap without deep fascia harvest, consistent with previous findings by prior authors and injection studies.