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Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Ke y s tone and Ped ic le Perforator Flaps in Reconstructive Surgery New Modifications and Applications Jasson T. Abraham, MD, Michel Saint-Cyr, MD, FRCS(C)* KEYWORDS Keystone flap Perforator flap Reconstruction
KEY POINTS
INTRODUCTION Initial descriptions of perforator flaps in 1989 by Koshima and Soeda,1 by using a musculocutaneous flap with an inferior epigastric artery–based skin island for reconstruction of defects involving the floor of mouth and groin, have led to significant additional advancements in the understanding of perforator flaps and vascular anatomy. Kroll and Rosenfield2 reported that perforator flaps had vascular reliability comparable with musculocutaneous flaps, but limited donor site morbidity by avoiding muscle harvest. The transfer of tissues therefore is not limited by the requirement to include muscle or underlying deep fascia for adequate tissue perfusion. Milton3 showed that the inclusion of a pedicle with a large vessel was critical for flap survival, and also dictated the viable length of harvest for islanded flaps.
Further modifications of the perforator flap led to the advent of the propeller flaps, first introduced in 1991 by Hyakusoku and colleagues,4 with later modifications by Hallock5 and Teo.6 Propeller flaps allow significant tissue reconstruction with ideal like-for-like tissue, and maintain similar complication rates to free flap reconstruction.7–12 Recent advances in the understanding of vascular anatomy have led to significant advancements and freedom in perforator-based reconstruction. Taylor and Palmer13 introduced the angiosome concept, which was further detailed in many additional studies evaluating the static vascular territories of every source vessel and their perforators.13–26 Further anatomic studies by Saint-Cyr and colleagues27–29 and other investigators30–34 introduced the perforasome concept of distinct vascular territories of individual perforators, which
The authors have nothing to disclose. Division of Plastic Surgery, Baylor Scott & White Health, Scott & White Memorial Hospital, Temple, TX, USA * Corresponding author. Division of Plastic Surgery, Baylor Scott & White Health, 2401 South 31st Street, Temple, TX 76508. E-mail address: [email protected] Clin Plastic Surg 44 (2017) 385–402 http://dx.doi.org/10.1016/j.cps.2016.12.005 0094-1298/17/Ó 2016 Elsevier Inc. All rights reserved.
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The increase in knowledge of vascular anatomy, including the concept of the perforasome theory and perforator hot-spot versus cold-spot anatomy, has led to significant advances in reconstructive options. Pedicle perforator flap (PPF)–based reconstruction benefits patients by using autologous tissue for reconstruction and decreases operative morbidity by limiting transfer of tissue on perforators. Freestyle PPF allows greater degrees of freedom in operative planning, because flaps can be based on any dominant perforator. Keystone perforator island flap is a multiperforator advancement flap based on musculocutaneous or fasciocutaneous perforators with high rates of flap survival, decreased donor site morbidity and pain, and quick patient recovery.
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Abraham & Saint-Cyr are dynamic and have significant interactions with adjacent perforating vessels or perforasomes. The keystone perforator island flap (KPIF) is a versatile flap that was originally described by Behan35 for reconstruction of defects after excision of skin cancer, and has since been used for the reconstruction of defects located on the head and neck, trunk, and extremities.35–38 Modifications in planning, design, and execution of the KPIF by relying on a sound understanding of vascular anatomy and the perforasome theory by Saint-Cyr and colleagues have allowed large defect reconstruction after tumor resection, with high rates of flap survival, low risk of significant complications, decreased pain, and quicker postoperative recovery.39
PERFORASOME PRINCIPLES The ability of a single arterial perforator to adequately vascularize large volumes of soft tissue for reconstruction can only be understood with a comprehensive understanding of the perforasome theory. A perforasome is described as the unique vascular territory of a single arterial perforator
from an underlying source vessel. Four major principles elucidate the ability of a single perforator to sustain a large volume of soft tissue, and the consistent preferential direction of vascular flow.29,40 1. Perforasomes are linked with adjacent perforasomes by direct and indirect linking vessels (Fig. 1). Direct linking vessels are larger vessels that directly connect one perforator to another in the suprafascial plexus, whereas indirect perforators connect one perforator to another through the subdermal plexus.29 In addition, there are communicating branches that connect direct linking vessels to indirect linking vessels. Interperforator flow is bidirectional, with directionality of flow dependent on perforator perfusion pressures. With adequate perfusion pressure, a single perforator can vascularize multiple perforasomes via interperforator flow. 2. Design of the flap and orientation of the skin paddle should be in the same direction as the linking vessels, which are axial in the extremities and perpendicular to the midline in the trunk. Linking vessels allow for interperforator communication between perforators from the
Fig. 1. (A, B) Linking vessels, direct and indirect. (Courtesy of Alexandra B. Hernandez, M.A. of Gory Details Illustration; with permission.)
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 2. Linking vessels parallel to long axis of limb and parallel to source artery.
same underlying source arteries and with perforators of adjacent source arteries (Fig. 2). 3. Perforators from the same source artery are preferentially filled by interperforator flow. In addition, if a source artery has minimal perforating vessels along its vascular path, there is a decrease in the axial pattern of its vascular distribution because there are fewer interperforator linking vessels (Fig. 3). 4. Directionality of a perforator can be determined based on its proximity to an articulation. Perforators found adjacent to an articulation have preferential directionality away from the articulation, whereas perforators between 2 articulations or at the midpoint of the trunk have multidirectional flow (Fig. 4). These principles explain how large volumes of soft tissue can be harvested, because hyperperfusion of a single perforator can capture multiple adjacent perforasomes, with preferential flow in the direction of the linking vessels, reflecting the path of the underlying source artery.41
PERFORATOR HOT SPOT VERSUS COLD SPOT There are nearly 400 perforators in the body, on each of which a pedicle-based flap can be raised, allowing multiple alternative reconstructive options.13,40,42,43 Perforator flaps have been
described for reconstruction of the breast, head and neck, and extremities. The perforators are not distributed evenly, because the body has areas of higher perforator density, called hot spots, and areas of lower perforator density, called cold spots (Fig. 5). Hot spots are consistently found in the same areas of the body. In the extremities, they are found typically adjacent to articulations and midway between 2 articulations, whereas in the trunk they are found parallel to the anterior and posterior midline, and midaxillary regions.44–47 Knowledge of hot-spot territories allows optimal surgical planning of the flap, and permits quicker surgical dissection in cold spots.
PERFUSION PRINCIPLES: PERFORATOR LOCATION AND ANGLE OF PERFUSION The volume of soft tissue that can safely be harvested in a pedicle perforator flap (PPF) depends on the ability of the dominant perforator to adequately perfuse the entire flap. Principles that aid in optimizing the vascularity of a flap include the relative position of the dominant perforator within the flap, and the angle of perfusion. Designing flaps with the primary perforating vessel positioned centrally allows for greater interperforator flow by preserving the linking vessels (direct and indirect) and the communicating vessels, resulting in a greater number of adjacent
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Abraham & Saint-Cyr vessels are parallel to the long axis of the designed flap, complications of flap loss can be avoided or minimized (Fig. 6). The angle of perfusion of a perforator is defined as the angle of vascular perfusion flowing away from the perforator and confined by the mechanical borders of the flap. The angle is measured at the proximal aspect of the flap. In a cadaveric study of anterolateral thigh flaps, area of perfusion and percentage of flap perfusion were evaluated based on differing angles of perfusion, by using computed tomography (CT) angiography. Decreasing the angle of perfusion resulted in a significant decrease in the volume and percentage of flap perfusion. An acute angle of perfusion (60 ) is thought to be disruptive of interperforator flow by failing to incorporate linking vessels between adjacent perforators, and thus decreasing flap perfusion.48 The flap vascularization by the dominant perforator can be optimized by positioning the perforator in the central portion of the flap and by avoiding an acute angle of perfusion at the proximal aspect of the flap. These modifications allow for increased interperforator flow by incorporating critical linking vessels, resulting in a robustly perfused flap.
BENEFITS OF PERFORATOR FLAPS Fig. 3. Preferential filling of interperforator flow within same source artery. (Courtesy of Alexandra B. Hernandez, M.A. of Gory Details Illustration; with permission.)
perforasomes that are vascularized. Eccentric positioning of a perforator decreases the volume of tissue that can safely be harvested.48 However, if great care is taken to ensure that the linking
PPF allow complex locoregional reconstruction while avoiding microsurgical free-flap reconstruction and monitoring.40 The main advantages of perforator flaps include sparing of underlying muscle, decreased donor site morbidity, decreased operative times, and improved aesthetic outcome by supplying like with like for optimal texture, thickness, and color match (Fig. 7). The KPIF is a
Fig. 4. Perforator flow bidirectional for midpoint perforators and away from articulations for eccentric perforators. (Courtesy of Alexandra B. Hernandez, M.A. of Gory Details Illustration; with permission.)
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 5. (A) Hot spot and cold spots of perforator distribution throughout the body. (B) Perforator hot spot concentrated around the umbilicus in the abdomen. (Courtesy of Alexandra B. Hernandez, M.A. of Gory Details Illustration; with permission.)
Fig. 6. (A, B) Angle of perfusion of PPF. The more eccentric the perforator is located within the flap, the wider the angle of perfusion needs to be in order to incorporate as many linking vessels as possible and maximize perfusion. (Copyright Ó Mayo Foundation for Medical Education and Research. All rights reserved.)
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Fig. 7. (A–D) PPF based on a perforator from the superficial femoral artery. Flap was used for coverage of a soft tissue defect following postsarcoma resection in the medial-proximal left leg. (E) Final result with stable coverage four weeks after surgery.
single flap based on multiple perforators that has shown excellent reconstructive outcomes for large defects while avoiding free-flap reconstruction and allowing shorter operative times, fairly painfree postoperative course, and shorter duration of hospitalization, and is ideal for patients with multiple comorbidities who are unable to undergo prolonged complex reconstructive procedures (Fig. 8).
PATIENT SELECTION AND PREOPERATIVE PLANNING Each patient presents a unique challenge to the reconstructive surgeon because each patient introduces individual-specific comorbidities, including prior trauma, reconstructive surgery, prior irradiation, and smoking, all of which affect the vascularity and mobility of the adjacent tissue. When evaluating a patient for reconstruction with a
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 8. (A–C) Keystone flap for coverage of central upper back defect following melanoma excision. Note the multiple perforators preserved within the central portion of the flap. The flap area peripheral to these perforators was undermined for additional advancement with minimal tension.
KPIF or PPF, it is critical to evaluate the defect and the quality of the adjacent tissue, particularly noting the soft tissue laxity. Preoperative imaging is not routinely indicated for identification of perforators, because sound knowledge of perforator location based on the hot-spot principle, in conjunction with Doppler evaluation of the adjacent tissue, is sufficient (Fig. 9). Radiographic studies that are preoperatively obtained by the oncologic team for evaluation of tumor invasiveness, including CT or MRI, can help identify large perforators in the vicinity of the malignancy. In circumstances requiring the evaluation of traumatic wounds involving extremities, imaging can be obtained of the vascular anatomy to assess vascular injury with angiography or CT angiography.40,42
PEDICLE PERFORATOR FLAPS PPF have introduced a paradigm shift in the planning of reconstructive surgery, particularly introducing a significant element of freedom in flap design, resulting in multiple options for wound closure.49 Using the hot-spot principle, and familiarity with the location of dominant perforators, PPF can be harvested on any substantially sized perforator with the aid of a Doppler.40,42 Depending on the location of the pedicle in the designed flap and the length of pedicle dissected, flaps can achieve
Fig. 9. Perforator density distribution in the back with a hot-spot concentration within 10 cm from the midline. (Copyright Ó Mayo Foundation for Medical Education and Research. All rights reserved.)
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Abraham & Saint-Cyr significant rotational freedom. The propeller flap can achieve complete 180 rotation with appropriate surgical planning and execution.40 PPF can be used for reconstruction of defects located on the trunk, head and neck, and extremities.40 Examples of commonly used perforators for PPF include perforators from the superficial femoral artery, deep inferior epigastric artery, profunda artery, descending branch of lateral circumflex femoral artery, and lateral superior genicular artery.
FREESTYLE PERFORATOR FLAP However, it is important to understand that PPF are not limited to known dominant perforators, and there is no need to rely on conventional flap design. This liberty has resulted in the freestyle perforator concept of designing a flap on any dominant perforator adjacent to the defect for ad hoc reconstruction (Fig. 10). The ability to raise a freestyle flap on a single dominant pedicle has been further revolutionized by Wei and Mardini,50 by raising freestyle free perforator flaps.
PEDICLE PERFORATOR FLAP DESIGN PPF are conventionally designed with an elliptical skin paddle, but can be altered to meet the reconstructive requirements (eg, triangular pedicle perforator flap for V-Y advancement; Fig. 11). Flaps are harvested larger than the anticipated defect to account for limited tissue laxity, allow
for flap inset under minimal tension, and to accommodate postoperative swelling.42 Perforators are identified in the tissue adjacent to the defect with a Doppler.40 All Doppler-able perforators are marked on the skin, and a line is drawn over the path of the dominant axial vessels connecting the perforators, with specific marking of the most dominant perforator.42 Dominant perforator identification is not necessary when the skin island is advanced as a multiperforator flap. A skin paddle is then designed incorporating the most dominant perforator, with the long axis of the flap oriented parallel to the directionality of vascular flow, which is oriented axially along the extremities and perpendicular to midline in the trunk.39 Doing so facilitates the inclusion of linking vessels and increases the likelihood of primary closure of the donor site.40 The surgeon should plan backup options for reconstruction before wholly committing to a designed PPF. An initial exploratory incision is made on one side of the planned flap, with care taken to avoid the violation of potential secondary reconstructive options.40,42 The dominant perforator is surgically isolated and evaluated with the Doppler, and confirmed visually to be of adequate caliber (>0.5 mm). The pedicle can be further dissected to gain additional length for flap advancement. If the perforator is of adequate quality, the flap is incised circumferentially along the planned skin paddle margin and advanced into the defect. Flap perfusion is reevaluated clinically and with the
Fig. 10. (A–C) Freestyle PPF for coverage of a dorsal forearm soft tissue defect. A suitable freestyle perforator with a strong arterial and venous Doppler signal was identified and selected close to the defect.
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 11. (A, B) Freestyle V-Y triangular perforator advancement flap for melanoma reconstruction in the left upper chest.
Doppler to verify minimal changes in flow after advancement. The flap is inset under minimal tension, and the donor site is routinely closed primarily, although in rare circumstances a skin graft might be required for coverage (Fig. 12).
PROPELLER FLAP The propeller flap is a single perforator flap that requires specific mention because of its significant rotational capability, attributable to the location of the dominant perforator within the skin paddle.
The elliptical flap is based on a perforator located eccentrically closer to the defect, allowing a significant angle of rotation.42 The perfusion of the flap is enhanced by the inclusion of axial linking vessels within the flap, and by the direction of flow of the perforator. Similar principles of flap elevation, pedicle evaluation, and intraoperative monitoring are followed as previously discussed for PPF. The pedicle can be dissected to the source vessel to increase flap mobility and rotational capability, and to decrease the likelihood of vessel twisting or kinking. The flap is dissected either in the
Fig. 12. (A–D) Freestyle peroneal artery PPF for Achilles tendon coverage following melanoma excision.
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Abraham & Saint-Cyr subfascial or suprafascial plane, and inset into the defect by rotating the flap in the direction of least vessel twist or kink (Fig. 13).40,42
KEYSTONE PERFORATOR ISLAND FLAP: INTRODUCTION The KPIF is a single multiperforator advancement flap based on random fasciocutaneous or musculocutaneous perforators that allows coverage of soft tissue defects by transfer of adjacent tissue with adequate soft tissue laxity.51 This flap can be the primary reconstructive option or be planned as an adjunct for supplemental soft tissue coverage. Knowledge of hot spots of perforasomes allows KPIF skin islands to be based on regularly identified musculocutaneous and fasciocutaneous perforators, which are never surgically identified, resulting in decreased operative times (Fig. 14).51,52 The inclusion of multiple perforators allows increased vascularity and resilience of the flap (Fig. 15). The KPIF is named after the keystone of an arch in Roman architecture, and is described as a curvilinear trapezoidal design flap.35,53 Behan35 described the use of the flap for large elliptical defects, with the transfer of adjacent tissue for better color and contour match. The flap is designed as 2 opposing V-Y flaps that are oriented parallel to the long axis of the defect. The defect usually has a 3:1 long axis to short axis ratio. The ablative surgeon should plan the excisional defect to be elliptical, with the long axis parallel to the line of cutaneous nerves, veins, and/or known perforators to allow for possible preservation of cutaneous sensation.35,39 The long axis of the flap should follow
maximal axiality of flow from dominant perforators, allowing for capture of multiple perforators, which are oriented axially in the extremities, and perpendicular to the midline in the trunk.39 Advancement of the KPIF into the defect along the short axis creates redundancy and subsequent laxity of the soft tissue in the long axis of the flap, which results in an increase in the length of the flap along its short axis, which is the area of greatest tension during closure.35,52,54 The V-Y advancement closure at each end of the flap in the long axis further decreases the size of the donor site defect, and as a result decreases the tension of wound closure.35 Harvesting the KPIF with significant soft tissue laxity allows for wound closure without excessive tension by distributing the laxity to the entire flap, and typically avoids the need for adjunct procedures for donor site closure.35,52,54
KEYSTONE PERFORATOR ISLAND FLAP: MODIFICATIONS Originally, the short axis of the KPIF was designed to have a 1:1 ratio with the defect short axis, and the limbs of the flap were angled at 90 to the long axis of the defect.35,42,53 However, modifications in the design and harvest of the flap grants greater liberty to the reconstructive surgeon to maximize tissue use and to decrease risk of complications. Modifications include: 1. 2. 3. 4.
Increase the ratio of flap size to defect size Deepithelialization for dead-space obliteration Circumferential incision of deep fascia Distally based or proximally based keystone rotation flap35
Fig. 13. (A–F) Freestyle perforator flap based on a distal dominant perforator from the superficial femoral artery.
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 14. (A–C) Keystone flap for trochanteric wound coverage following infected hardware removal. Note the preservation of perforators (hot spot) within the central portion of the flap. Peripheral undermining was performed for maximal flap advancement.
5. Bilateral opposing keystone flap 6. Asymmetric limb angulation for avoidance of critical structures The flap size can be made larger depending on the adjacent tissue laxity, with flap to defect short axis ratios routinely 3:1 or 4:1 and in rare circumstances up to 5:1.39 The increase in flap size decreases the tension of wound closure, and allows the integration of additional perforators by which well-vascularized tissue can be advanced into
the defect (Fig. 16). The flap should be planned with the hot spot located in the central portion of the KPIF for optimal flap perfusion. Larger flaps are designed if the quality of adjacent tissue is compromised by surgical undermining, radiation therapy, adjacent surgical procedures, or an inflammatory process.39,42 For reconstruction of defects in the inguinal region, when a notably large KPIF has been harvested, excess soft tissue can be deepithelialized and used for obliteration of empty space (Fig. 17). This maneuver can be
Fig. 15. (A, B) Keystone flap for lower third leg coverage following skin cancer resection. Note long axis of the keystone flap is designed parallel to the long axis of the limb, and concentrated over a maximal number of perforators to enhance vascularity. The keystone flap should be designed to be wide enough to incorporate as many suitable perforators as possible.
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Fig. 16. (A–E) Skin cancer lesion and resection in the leg. A larger keystone flap relative to the defect size ratio (4:1) was designed because of a lack of soft tissue laxity. Circumferential skin and fascia incisions were performed, as well as peripheral flap undermining, in order to allow proper advancement and tension-free closure.
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 17. (A–C) Large anterior thigh keystone flap used for coverage of groin soft tissue defect following sarcoma resection. Note that part of the proximal edge of the keystone flap was de-epithelialized for empty space obliteration of the groin and lower abdomen.
performed in combination with local muscle transposition, especially when there is concern for vessel exposure (Fig. 18).39 Mobility of the KPIF is significantly increased by incising the deep fascia. Originally, this was limited to the fascia along the greater (also known as the outer) curvature of the flap; however, the authors routinely incise the deep fascia in the progressive manner until appropriate mobility and laxity has been obtained.39 Our experience has shown that greater flap mobility can be achieved, with almost complete circumferential incision of the deep fascia with sparing of the proximal and distal attachments or complete circumferential incision without risking flap viability.39,55 When KPIF flaps are designed over muscle bellies and undergo complete circumferential incision, significant flap mobility is gained. Furthermore, approximately 50% of the flap can be dissected proximally or distally in the subfascial plane, by which the KPIF can obtain significant rotation to allow for closure of defects across joints or for compound fractures with exposed bone.35 Occasionally, a defect is too large for a single KPIF, necessitating the use of an adjunct procedure or reconstruction with bilateral opposing keystone flaps for additional soft tissue coverage (see Fig. 18). The KPIF allows the recruitment of native tissue with similar color, texture, and thickness, and less contour deformity, compared with a
free flap, PPF, or propeller flap. A second KPIF should always be designed on the contralateral side of the defect as a backup flap, to be raised and advanced when indicated.39 Conventional KPIF designs describe the limbs to be at 90 or perpendicular to the long axis of the defect, which introduces unnecessary surgical constraints and can result in iatrogenic injury.35 KPIF can be designed with asymmetric limbs to avoid critical structures, including joint creases and lymphatic basins, reducing the risk for joint contracture and lymphedema.39 Furthermore, limbs should be designed to align with the natural aesthetic lines along the midaxial lines to minimize deformity and to create more aesthetically natural contour.
KEYSTONE PERFORATOR ISLAND FLAP: PLANNING AND PROCEDURE Reconstruction with a KPIF requires an elliptical defect, ideally located near a known hot spot. The long axis of the elliptical defect is oriented parallel to the line of cutaneous nerves, veins, and known perforators, which is longitudinal in the extremities and perpendicular to the midline on the trunk.35 The primary KPIF is planned on the side of the defect with greater soft tissue laxity, with a second KPIF planned on the contralateral side as a backup option. Perforator localization with the use of Doppler in the adjacent tissue helps with
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Fig. 18. (A–D) Bilateral keystone flaps for coverage of a myelomeningocele in a 4-day-old boy.
identification of perforator capture and ensures the optimal central positioning of the perforator in the flap. The KPIF is oriented with the long axis following the axiality of flow from perforators, which follows the path of the underlying source artery, thus ensuring the capture of linking vessels.39 The short axis of the KPIF should be the same size or larger than the defect. The short axis of the KPIF does not include any areas of tissue undermining adjacent to the defect along the lesser curvature of the flap, because this area is void of viable perforating vessels. Smaller flaps are avoided when extensive undermining has taken place.39,55 The limbs of the flap can be designed independent of each other (asymmetric) to avoid crossing joint creases, lymphatic basins, or other local critical structures. After satisfactory design of the KPIF, the flap can be advanced in multiple variations until adequate mobility and laxity are achieved,42 including: 1. Complete circumferential skin incision. 2. Complete circumferential skin incision with progressive fascial release along the greater curvature. 3. Complete circumferential skin and fascial release, which also allows for significant flap rotation.56 4. Incision of the skin and fascia limited to the limbs of the KPIF.
5. Limited exposure or minimally invasive (endoscopic) fascial release of the greater curvature, with skin and fascial release of the KPIF limbs. 6. Limited skin incision along the greater curvature, with incision of the flap limbs and complete circumferential fascial release. Greater flap mobility can also be obtained by undermining the adjacent tissue, or by subfascial undermining of the flap. However, it is of paramount significance to only perform subfascial dissection in known cold spots to avoid injury to perforating vessels and potentially risk flap survival. If additional soft tissue coverage is needed, bilateral opposing keystone flaps can be raised. Furthermore, other flaps, such as PPF, V-Y advancement flaps, or rotation flaps, can be used in conjunction with KPIF for wound closure (Fig. 19). Defects in the inguinal region can be reconstructed with a large KPIF, with portions of the flap deepithelialized for dead-space obliteration.39
KEYSTONE PERFORATOR ISLAND FLAP: CLOSURE The surgical site is closed in multiple layers, typically beginning by reapproximating the defect at the midline with the lesser curvature of the KPIF.50 The closing tension might be too great in some
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 19. (A–C) Left thigh sarcoma resection defect covered with a combination of a freestyle PPF and anterior thigh keystone flap. A keystone flap was used to supplement the pedicle perforator flap.
instances, warranting the closure of the edges with progressive tissue advancement to the midline. Advancement of the larger KPIF tissue into the smaller defect creates flap laxity along the long axis, which results in an increase of the short axis of the KPIF. The flap shortens along the long axis and widens along the short axis with progressive closure, adopting a rounder shape. The limbs of the KPIF are then closed in a V-Y fashion, and the greater curvature of the flap is finally reapproximated. Progressive tension suture and 3-point suture techniques can be used for redistribution of tension and for dead-space obliteration.39 Routine surgical drain placement is not necessary, unless indicated for the primary defect, or if extensive soft tissue undermining has taken place.39,51 Avoid drain placement adjacent to flap hot spots to prevent unintentional distortion of the underlying perforators.
KEYSTONE PERFORATOR ISLAND FLAP AND PEDICLE PERFORATOR FLAP: COMPLICATIONS The most common complications are typically minor, involving wound separation and delayed
wound healing, which are treated conservatively with local wound care.37,39,51,57 Risk of wound complications is increased by an active smoking history and preoperative irradiation.51 Major complications with flap compromise resulting in partial or total flap loss are rare (less than 10%).35,51 Modifications to the KPIF are safe, with no events of partial or total flap loss noted in a recent retrospective study of 42 consecutive KPIF-based reconstructions.39
KEYSTONE PERFORATOR ISLAND FLAP: ADVANTAGES KPIF have many advantages compared with microsurgical free flap–based reconstruction, including: 1. Shorter operative times than free flap or single perforator flaps, with quick flap elevation and inset (2–3 hours).51,58,59 2. Avoid technical demands of perforator dissection.39 3. High reproducibility, technically easy flap harvest, and reliable vascularity.39,51
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Fig. 20. (A–D) Plantar surface melanoma defect covered with an adjacent keystone flap in a diabetic patient. Recruiting local similar tissue characteristics has an advantage over the plantar surface.
4. Single-region donor site, allowing superior aesthetic match by advancing adjacent tissue with similar color and mechanical qualities such as texture, thickness, color match (Fig. 20).39,51 5. Transfer of sensate tissue for reconstruction.35,39 6. Ideal for patients with significant medical comorbidities who are unable to undergo prolonged operative procedures. 7. Avoid need for postoperative flap monitoring.39 8. Decreased postoperative pain, postoperative edema, earlier patient ambulation, and shorter duration of hospitalization.35
KEYSTONE PERFORATOR ISLAND FLAP: DISADVANTAGES AND CONTRAINDICATIONS Limitations of the KPIF primarily depend on the availability of perforators and the laxity of the adjacent soft tissue. Reconstruction of scalp defects with a KPIF is contraindicated because of the lack of perforators.51 Relative contraindications include wounds that have been irradiated, undergone significant undermining, or are currently in an inflammatory state, because these conditions compromise the vascularity and laxity of the flap.51 Contour deformities usually improve through a combination of tissue creep and stress relaxation, and are typically less severe compared with reconstruction with perforator or propeller flaps.37,39,44
Larger flaps have longer incisions, which can result in more noticeable scarring, so it is essential to plan flaps along aesthetic lines.39,42
SUMMARY The increase in wealth of vascular anatomy knowledge, including the perforasome theory and identification of perforator hot spots, has led to major advances and freedom in reconstructive surgery. Tissue selection for locoregional reconstruction should be based on known hot spots and dominant perforators, and flaps should be designed to maximize interperforator flow through linking vessels. The PPF and KPIF have allowed the transfer large volumes of soft tissue for reconstruction and have minimized donor site morbidity, avoiding technically challenging microsurgical free-flap reconstruction and achieving superior aesthetic outcomes, and has resulted in minimal postoperative monitoring, decreased patient reported pain, and shorter periods of hospitalization. These advantages allow patients with significant medical comorbidities to undergo essential, complex surgical reconstruction and avoid the risks inherent with long periods of general anesthesia. Future understanding of vascular anatomy will allow additional modifications, leading to increasing surgical liberty in the planning and execution of reconstructive flaps, with the eventual
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery goal of optimizing patient care and surgical outcomes. 17.
REFERENCES 1. Koshima I, Soeda S. Inferior epigastric artery skin flaps without rectus abdominis muscle. Br J Plast Surg 1989;42:645–8. 2. Kroll SS, Rosenfield L. Perforator-based flaps for low posterior midline defects. Plast Reconstr Surg 1988; 81:561–6. 3. Milton SH. Experimental studies on island flaps: 1. The surviving length. Plast Reconstr Surg 1971;48: 574–8. 4. Hyakusoku H, Yamamoto T, Fumiiri M. The propeller flap method. Br J Plast Surg 1991;44:53–4. 5. Hallock GG. The propeller flap version of the adductor muscle perforator flap for coverage of ischial or trochanteric pressure sores. Ann Plast Surg 2006;56:540–2. 6. Teo TC. The propeller flap concept. Clin Plast Surg 2010;37:615–26. 7. Schaverien MV, Hamilton SA, Fairburn N, et al. Lower limb reconstruction using the islanded posterior tibial artery perforator flap. Plast Reconstr Surg 2010;125:1735–43. 8. Lu TC, Lin CH, Lin CH, et al. Versatility of the pedicled peroneal artery perforator flaps for soft-tissue coverage of the lower leg and foot defects. J Plast Reconstr Aesthet Surg 2011;64:386–93. 9. Hallock GG. A paradigm shift in flap selection protocols for zones of the lower extremity using perforator flaps. J Reconstr Microsurg 2013;29:233–40. 10. Gir P, Cheng A, Oni G, et al. Pedicled perforator (propeller) flaps in lower extremity defects: a systematic review. J Reconstr Microsurg 2012;28: 595–601. 11. Nelson JA, Fischer JP, Brazio PS, et al. A review of propeller flaps for distal lower extremity soft tissue reconstruction: is flap loss too high? Microsurgery 2013;33:578–86. 12. Lazzeri D, Huemer GM, Nicoli F, et al. Indications, outcomes, and complications of pedicled propeller perforator flaps for upper body defects: a systematic review. Arch Plast Surg 2013;40: 44–50. 13. Taylor GI, Palmer JH. The vascular territories (angiosomes) of the body: experimental study and clinical applications. Br J Plast Surg 1987;40:113–41. 14. Atik B, Tan O, Mutaf M, et al. Skin perforators of back region: anatomical study and clinical applications. Ann Plast Surg 2008;60:70–5. 15. Hallock GG. Anatomic basis of the gastrocnemius perforator based flap. Ann Plast Surg 2001;47: 517–22. 16. Hamdi M, Spano A, Van Landuyt K, et al. The lateral intercostal artery perforators: anatomical study and
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clinical application in breast surgery. Plast Reconstr Surg 2008;121:389–96. Hamdi M, Van Landuyt K, de Frene B, et al. The versatility of the inter-costal artery perforator (ICAP) flaps. J Plast Reconstr Aesthet Surg 2006;59:644–52. Heitmann C, Guerra A, Metzinger SW, et al. The thoracodorsal artery perforator flap: anatomic basis and clinical application. Ann Plast Surg 2003;51:23–9. Koshima I, Moriguchi T, Soeda S, et al. The gluteal perforator-based flap for repair of sacral pressure sores. Plast Reconstr Surg 1993;91:678–83. Kato H, Hasegawa M, Takada T, et al. The lumbar artery perforator based island flap: anatomical study and case reports. Br J Plast Surg 1999;52:541–6. Minabe T, Harii K. Dorsal intercostal artery perforator flap: anatomical study and clinical applications. Plast Reconstr Surg 2007;120:681–9. Moscatiello F, Masia J, Carrera A, et al. The “propeller” distal anteromedial thigh perforator flap: anatomic study and clinical applications. J Plast Reconstr Aesthet Surg 2007;60:1323–30. Mun GH, Lee SJ, Jeon BJ. Perforator topography of the thoracodorsal artery perforator flap. Plast Reconstr Surg 2008;121:497–504. Ogawa R, Hyakusoku H, Murakami M, et al. An anatomical and clinical study of the dorsal intercostal cutaneous perforators, and application to free microvascular augmented subdermal vascular network (ma-SVN) flaps. Br J Plast Surg 2002;55: 396–401. Rad AN, Singh NK, Rosson GD. Peroneal artery perforator-based propeller flap reconstruction of the lateral distal lower extremity after tumor extirpation: case report and literature review. Microsurgery 2008;28:663–70. Thione A, Valdatta L, Buoro M, et al. The medial sural artery perforators: anatomic basis for a surgical plan. Ann Plast Surg 2004;53:250–5. Saint-Cyr M, Schaverien M, Arbique G, et al. Threeand four-dimensional computed tomographic angiography and venography for the investigation of the vascular anatomy and perfusion of perforator flaps. Plast Reconstr Surg 2008;121:772–80. Saint-Cyr M, Schaverien M, Rohrich RJ. Preexpanded second intercostal space internal mammary artery pedicle perforator flap: case report and anatomical study. Plast Reconstr Surg 2009;123: 1659–64. Saint-Cyr M, Wong C, Schaverien M, et al. Perforasome theory vascular anatomy and clinical implications. Plast Reconstr Surg 2009;124:1529. Schaverien M, Saint-Cyr M, Arbique G, et al. Arterial and venous anatomies of the deep inferior epigastric perforator and superficial inferior epigastric artery flaps. Plast Reconstr Surg 2008;121:1909–19. Schaverien M, Saint-Cyr M, Arbique G, et al. Threeand four-dimensional arterial and venous anatomies
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of the thoracodorsal artery perforator flap. Plast Reconstr Surg 2008;121:1578–87. Schaverien M, Saint-Cyr M, Arbique G, et al. Threeand four-dimensional computed tomographic angiography and venography of the anterolateral thigh perforator flap. Plast Reconstr Surg 2008;121: 1685–96. Wong C, Saint-Cyr M, Arbique G, et al. Three- and four-dimensional computed tomography angiographic studies of commonly used abdominal flaps in breast reconstruction. Plast Reconstr Surg 2009; 124:18–27. Wong C, Saint-Cyr M, Rasko Y, et al. Three- and fourdimensional arterial and venous perforasomes of the internal mammary artery perforator flap. Plast Reconstr Surg 2009;124:1759–69. Behan FC. The keystone design perforator island flap in reconstructive surgery. ANZ J Surg 2003;73: 112–20. Behan FC, Sizeland A, Porcedu S, et al. Keystone island flap: an alternative reconstructive option to free flaps in irradiated tissue. ANZ J Surg 2006;76: 407–13. Moncrieff MD, Bowen F, Thompson JF, et al. Keystone flap reconstruction of primary melanoma excision defects of the leg: the end of the skin graft? Ann Surg Oncol 2008;15:2867–73. Peters LJ. Keystone island flaps: a radiation oncologist’s perspective. ANZ J Surg 2006;76:1127. Mohan AT, Rammos CK, Akhavan AA, et al. Evolving concepts of keystone perforator island flaps (KPIF): principles of perforator anatomy, design modifications, and extended clinical applications. Plast Reconstr Surg 2016;137:1909–20. Lecours C, Saint-Cyr M, Wong C, et al. Freestyle pedicle perforator flaps: clinical results and vascular anatomy. Plast Reconstr Surg 2010;126:1589–603. Rubino C, Coscia V, Cavazzuti AM, et al. Haemodynamic enhancement in perforator flaps: the inversion phenomenon and its clinical significance: a study of the relation of blood velocity and flow between pedicle and perforator vessels in perforator flaps. J Plast Reconstr Aesthet Surg 2006;59:636–43. Mohan AT, Sur YJ, Zhu L, et al. The concept of propeller, perforator, keystone, and other local flaps and their role in the evolution of reconstruction. Plast Reconstr Surg 2016;138:710e–29e. Saint-Cyr M, Schaverien MV, Rohrich RJ. Perforator flaps: history, controversies, physiology, anatomy, and use in reconstruction. Plast Reconstr Surg 2009; 4:132e–45e. Saint-Cyr M, Schaverien M, Wong C, et al. The extended anterolateral thigh flap: anatomical basis and clinical experience. Plast Reconstr Surg 2009; 123:1245–55.
45. Wong C, Saint-Cyr M, Mojallal A, et al. Perforasomes of the DIEP flap: vascular anatomy of the lateral versus medial row perforators and clinical implications. Plast Reconstr Surg 2010;125:772–82. 46. Aho JM, Laungani AT, Herbig KS, et al. Lumbar and thoracic perforators: vascular anatomy and clinical implications. Plast Reconstr Surg 2014; 134:635e–45e. 47. Bailey SH, Saint-Cyr M, Wong C, et al. The single dominant medial row perforator DIEP flap in breast reconstruction: three-dimensional perforasome and clinical results. Plast Reconstr Surg 2010;126:739–51. 48. Laungani AT, Christner J, Primus JA, et al. Study of the impact of the location of a perforator in the perfusion of a perforator flap: the concept of “Angle of Perfusion”. J Reconstr Microsurg 2017;33:49–58. 49. Mardini S, Al-Mufarrej FM, Jeng SF, et al. Free-style free flaps. In: Blondeel PN, Morris SF, Hallock GG, et al, editors. Perforator flaps: anatomy, technique, & clinical applications, vol. 2, 2nd edition. St Louis (MO): Quality Medical; 2013. p. 1245–60. 50. Wei FC, Mardini S. Free-style free flaps. Plast Reconstr Surg 2004;114:910–6. 51. Khouri JS, Egeland BM, Daily SD, et al. The keystone island flap: use in large defects of the trunk and extremities in soft-tissue reconstruction. Plast Reconstr Surg 2011;127:1212–21. 52. Pelissier P, Santoul M, Pinsolle V, et al. The keystone design perforator island flap: part I. Anatomic study. J Plast Reconstr Aesthet Surg 2007;60:883–7. 53. Behan F, Findlay M, Lo CH. The keystone perforator island flap concept. Sydney (Australia): Churchill Livingstone; 2012. 54. Shayan R, Behan FC. Re: the “keystone concept”: time for some science. ANZ J Surg 2013;83: 499–500. 55. Behan FC, Paddle A, Rozen WM, et al. Quadriceps keystone island flap for radical inguinal lymphadenectomy: a reliable locoregional island flap for large groin defects. ANZ J Surg 2013;83:942–7. 56. Monarca C, Rizzo MI, Sanese G. Keystone flap: freestyle technique to enhance the mobility of the flap [corrected]. ANZ J Surg 2012;82:950–1. 57. Rao AL, Janna RK. Keystone flap: versatile flap for reconstruction of limb defects. J Clin Diagn Res 2015;9:PC05–7. 58. Rubino C, Figus A, Mazzocchi M, et al. The propeller flap for chronic osteomyelitis of the lower extremities: a case report. J Plast Reconstr Aesthet Surg 2009;62:e401–4. 59. Pignatti M, Pasqualini M, Governa M, et al. Propeller flaps for leg reconstruction. J Plast Reconstr Aesthet Surg 2008;61:777–83.
KEY POINTS
INTRODUCTION Initial descriptions of perforator flaps in 1989 by Koshima and Soeda,1 by using a musculocutaneous flap with an inferior epigastric artery–based skin island for reconstruction of defects involving the floor of mouth and groin, have led to significant additional advancements in the understanding of perforator flaps and vascular anatomy. Kroll and Rosenfield2 reported that perforator flaps had vascular reliability comparable with musculocutaneous flaps, but limited donor site morbidity by avoiding muscle harvest. The transfer of tissues therefore is not limited by the requirement to include muscle or underlying deep fascia for adequate tissue perfusion. Milton3 showed that the inclusion of a pedicle with a large vessel was critical for flap survival, and also dictated the viable length of harvest for islanded flaps.
Further modifications of the perforator flap led to the advent of the propeller flaps, first introduced in 1991 by Hyakusoku and colleagues,4 with later modifications by Hallock5 and Teo.6 Propeller flaps allow significant tissue reconstruction with ideal like-for-like tissue, and maintain similar complication rates to free flap reconstruction.7–12 Recent advances in the understanding of vascular anatomy have led to significant advancements and freedom in perforator-based reconstruction. Taylor and Palmer13 introduced the angiosome concept, which was further detailed in many additional studies evaluating the static vascular territories of every source vessel and their perforators.13–26 Further anatomic studies by Saint-Cyr and colleagues27–29 and other investigators30–34 introduced the perforasome concept of distinct vascular territories of individual perforators, which
The authors have nothing to disclose. Division of Plastic Surgery, Baylor Scott & White Health, Scott & White Memorial Hospital, Temple, TX, USA * Corresponding author. Division of Plastic Surgery, Baylor Scott & White Health, 2401 South 31st Street, Temple, TX 76508. E-mail address: [email protected] Clin Plastic Surg 44 (2017) 385–402 http://dx.doi.org/10.1016/j.cps.2016.12.005 0094-1298/17/Ó 2016 Elsevier Inc. All rights reserved.
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The increase in knowledge of vascular anatomy, including the concept of the perforasome theory and perforator hot-spot versus cold-spot anatomy, has led to significant advances in reconstructive options. Pedicle perforator flap (PPF)–based reconstruction benefits patients by using autologous tissue for reconstruction and decreases operative morbidity by limiting transfer of tissue on perforators. Freestyle PPF allows greater degrees of freedom in operative planning, because flaps can be based on any dominant perforator. Keystone perforator island flap is a multiperforator advancement flap based on musculocutaneous or fasciocutaneous perforators with high rates of flap survival, decreased donor site morbidity and pain, and quick patient recovery.
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Abraham & Saint-Cyr are dynamic and have significant interactions with adjacent perforating vessels or perforasomes. The keystone perforator island flap (KPIF) is a versatile flap that was originally described by Behan35 for reconstruction of defects after excision of skin cancer, and has since been used for the reconstruction of defects located on the head and neck, trunk, and extremities.35–38 Modifications in planning, design, and execution of the KPIF by relying on a sound understanding of vascular anatomy and the perforasome theory by Saint-Cyr and colleagues have allowed large defect reconstruction after tumor resection, with high rates of flap survival, low risk of significant complications, decreased pain, and quicker postoperative recovery.39
PERFORASOME PRINCIPLES The ability of a single arterial perforator to adequately vascularize large volumes of soft tissue for reconstruction can only be understood with a comprehensive understanding of the perforasome theory. A perforasome is described as the unique vascular territory of a single arterial perforator
from an underlying source vessel. Four major principles elucidate the ability of a single perforator to sustain a large volume of soft tissue, and the consistent preferential direction of vascular flow.29,40 1. Perforasomes are linked with adjacent perforasomes by direct and indirect linking vessels (Fig. 1). Direct linking vessels are larger vessels that directly connect one perforator to another in the suprafascial plexus, whereas indirect perforators connect one perforator to another through the subdermal plexus.29 In addition, there are communicating branches that connect direct linking vessels to indirect linking vessels. Interperforator flow is bidirectional, with directionality of flow dependent on perforator perfusion pressures. With adequate perfusion pressure, a single perforator can vascularize multiple perforasomes via interperforator flow. 2. Design of the flap and orientation of the skin paddle should be in the same direction as the linking vessels, which are axial in the extremities and perpendicular to the midline in the trunk. Linking vessels allow for interperforator communication between perforators from the
Fig. 1. (A, B) Linking vessels, direct and indirect. (Courtesy of Alexandra B. Hernandez, M.A. of Gory Details Illustration; with permission.)
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Fig. 2. Linking vessels parallel to long axis of limb and parallel to source artery.
same underlying source arteries and with perforators of adjacent source arteries (Fig. 2). 3. Perforators from the same source artery are preferentially filled by interperforator flow. In addition, if a source artery has minimal perforating vessels along its vascular path, there is a decrease in the axial pattern of its vascular distribution because there are fewer interperforator linking vessels (Fig. 3). 4. Directionality of a perforator can be determined based on its proximity to an articulation. Perforators found adjacent to an articulation have preferential directionality away from the articulation, whereas perforators between 2 articulations or at the midpoint of the trunk have multidirectional flow (Fig. 4). These principles explain how large volumes of soft tissue can be harvested, because hyperperfusion of a single perforator can capture multiple adjacent perforasomes, with preferential flow in the direction of the linking vessels, reflecting the path of the underlying source artery.41
PERFORATOR HOT SPOT VERSUS COLD SPOT There are nearly 400 perforators in the body, on each of which a pedicle-based flap can be raised, allowing multiple alternative reconstructive options.13,40,42,43 Perforator flaps have been
described for reconstruction of the breast, head and neck, and extremities. The perforators are not distributed evenly, because the body has areas of higher perforator density, called hot spots, and areas of lower perforator density, called cold spots (Fig. 5). Hot spots are consistently found in the same areas of the body. In the extremities, they are found typically adjacent to articulations and midway between 2 articulations, whereas in the trunk they are found parallel to the anterior and posterior midline, and midaxillary regions.44–47 Knowledge of hot-spot territories allows optimal surgical planning of the flap, and permits quicker surgical dissection in cold spots.
PERFUSION PRINCIPLES: PERFORATOR LOCATION AND ANGLE OF PERFUSION The volume of soft tissue that can safely be harvested in a pedicle perforator flap (PPF) depends on the ability of the dominant perforator to adequately perfuse the entire flap. Principles that aid in optimizing the vascularity of a flap include the relative position of the dominant perforator within the flap, and the angle of perfusion. Designing flaps with the primary perforating vessel positioned centrally allows for greater interperforator flow by preserving the linking vessels (direct and indirect) and the communicating vessels, resulting in a greater number of adjacent
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Abraham & Saint-Cyr vessels are parallel to the long axis of the designed flap, complications of flap loss can be avoided or minimized (Fig. 6). The angle of perfusion of a perforator is defined as the angle of vascular perfusion flowing away from the perforator and confined by the mechanical borders of the flap. The angle is measured at the proximal aspect of the flap. In a cadaveric study of anterolateral thigh flaps, area of perfusion and percentage of flap perfusion were evaluated based on differing angles of perfusion, by using computed tomography (CT) angiography. Decreasing the angle of perfusion resulted in a significant decrease in the volume and percentage of flap perfusion. An acute angle of perfusion (60 ) is thought to be disruptive of interperforator flow by failing to incorporate linking vessels between adjacent perforators, and thus decreasing flap perfusion.48 The flap vascularization by the dominant perforator can be optimized by positioning the perforator in the central portion of the flap and by avoiding an acute angle of perfusion at the proximal aspect of the flap. These modifications allow for increased interperforator flow by incorporating critical linking vessels, resulting in a robustly perfused flap.
BENEFITS OF PERFORATOR FLAPS Fig. 3. Preferential filling of interperforator flow within same source artery. (Courtesy of Alexandra B. Hernandez, M.A. of Gory Details Illustration; with permission.)
perforasomes that are vascularized. Eccentric positioning of a perforator decreases the volume of tissue that can safely be harvested.48 However, if great care is taken to ensure that the linking
PPF allow complex locoregional reconstruction while avoiding microsurgical free-flap reconstruction and monitoring.40 The main advantages of perforator flaps include sparing of underlying muscle, decreased donor site morbidity, decreased operative times, and improved aesthetic outcome by supplying like with like for optimal texture, thickness, and color match (Fig. 7). The KPIF is a
Fig. 4. Perforator flow bidirectional for midpoint perforators and away from articulations for eccentric perforators. (Courtesy of Alexandra B. Hernandez, M.A. of Gory Details Illustration; with permission.)
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 5. (A) Hot spot and cold spots of perforator distribution throughout the body. (B) Perforator hot spot concentrated around the umbilicus in the abdomen. (Courtesy of Alexandra B. Hernandez, M.A. of Gory Details Illustration; with permission.)
Fig. 6. (A, B) Angle of perfusion of PPF. The more eccentric the perforator is located within the flap, the wider the angle of perfusion needs to be in order to incorporate as many linking vessels as possible and maximize perfusion. (Copyright Ó Mayo Foundation for Medical Education and Research. All rights reserved.)
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Fig. 7. (A–D) PPF based on a perforator from the superficial femoral artery. Flap was used for coverage of a soft tissue defect following postsarcoma resection in the medial-proximal left leg. (E) Final result with stable coverage four weeks after surgery.
single flap based on multiple perforators that has shown excellent reconstructive outcomes for large defects while avoiding free-flap reconstruction and allowing shorter operative times, fairly painfree postoperative course, and shorter duration of hospitalization, and is ideal for patients with multiple comorbidities who are unable to undergo prolonged complex reconstructive procedures (Fig. 8).
PATIENT SELECTION AND PREOPERATIVE PLANNING Each patient presents a unique challenge to the reconstructive surgeon because each patient introduces individual-specific comorbidities, including prior trauma, reconstructive surgery, prior irradiation, and smoking, all of which affect the vascularity and mobility of the adjacent tissue. When evaluating a patient for reconstruction with a
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 8. (A–C) Keystone flap for coverage of central upper back defect following melanoma excision. Note the multiple perforators preserved within the central portion of the flap. The flap area peripheral to these perforators was undermined for additional advancement with minimal tension.
KPIF or PPF, it is critical to evaluate the defect and the quality of the adjacent tissue, particularly noting the soft tissue laxity. Preoperative imaging is not routinely indicated for identification of perforators, because sound knowledge of perforator location based on the hot-spot principle, in conjunction with Doppler evaluation of the adjacent tissue, is sufficient (Fig. 9). Radiographic studies that are preoperatively obtained by the oncologic team for evaluation of tumor invasiveness, including CT or MRI, can help identify large perforators in the vicinity of the malignancy. In circumstances requiring the evaluation of traumatic wounds involving extremities, imaging can be obtained of the vascular anatomy to assess vascular injury with angiography or CT angiography.40,42
PEDICLE PERFORATOR FLAPS PPF have introduced a paradigm shift in the planning of reconstructive surgery, particularly introducing a significant element of freedom in flap design, resulting in multiple options for wound closure.49 Using the hot-spot principle, and familiarity with the location of dominant perforators, PPF can be harvested on any substantially sized perforator with the aid of a Doppler.40,42 Depending on the location of the pedicle in the designed flap and the length of pedicle dissected, flaps can achieve
Fig. 9. Perforator density distribution in the back with a hot-spot concentration within 10 cm from the midline. (Copyright Ó Mayo Foundation for Medical Education and Research. All rights reserved.)
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Abraham & Saint-Cyr significant rotational freedom. The propeller flap can achieve complete 180 rotation with appropriate surgical planning and execution.40 PPF can be used for reconstruction of defects located on the trunk, head and neck, and extremities.40 Examples of commonly used perforators for PPF include perforators from the superficial femoral artery, deep inferior epigastric artery, profunda artery, descending branch of lateral circumflex femoral artery, and lateral superior genicular artery.
FREESTYLE PERFORATOR FLAP However, it is important to understand that PPF are not limited to known dominant perforators, and there is no need to rely on conventional flap design. This liberty has resulted in the freestyle perforator concept of designing a flap on any dominant perforator adjacent to the defect for ad hoc reconstruction (Fig. 10). The ability to raise a freestyle flap on a single dominant pedicle has been further revolutionized by Wei and Mardini,50 by raising freestyle free perforator flaps.
PEDICLE PERFORATOR FLAP DESIGN PPF are conventionally designed with an elliptical skin paddle, but can be altered to meet the reconstructive requirements (eg, triangular pedicle perforator flap for V-Y advancement; Fig. 11). Flaps are harvested larger than the anticipated defect to account for limited tissue laxity, allow
for flap inset under minimal tension, and to accommodate postoperative swelling.42 Perforators are identified in the tissue adjacent to the defect with a Doppler.40 All Doppler-able perforators are marked on the skin, and a line is drawn over the path of the dominant axial vessels connecting the perforators, with specific marking of the most dominant perforator.42 Dominant perforator identification is not necessary when the skin island is advanced as a multiperforator flap. A skin paddle is then designed incorporating the most dominant perforator, with the long axis of the flap oriented parallel to the directionality of vascular flow, which is oriented axially along the extremities and perpendicular to midline in the trunk.39 Doing so facilitates the inclusion of linking vessels and increases the likelihood of primary closure of the donor site.40 The surgeon should plan backup options for reconstruction before wholly committing to a designed PPF. An initial exploratory incision is made on one side of the planned flap, with care taken to avoid the violation of potential secondary reconstructive options.40,42 The dominant perforator is surgically isolated and evaluated with the Doppler, and confirmed visually to be of adequate caliber (>0.5 mm). The pedicle can be further dissected to gain additional length for flap advancement. If the perforator is of adequate quality, the flap is incised circumferentially along the planned skin paddle margin and advanced into the defect. Flap perfusion is reevaluated clinically and with the
Fig. 10. (A–C) Freestyle PPF for coverage of a dorsal forearm soft tissue defect. A suitable freestyle perforator with a strong arterial and venous Doppler signal was identified and selected close to the defect.
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Fig. 11. (A, B) Freestyle V-Y triangular perforator advancement flap for melanoma reconstruction in the left upper chest.
Doppler to verify minimal changes in flow after advancement. The flap is inset under minimal tension, and the donor site is routinely closed primarily, although in rare circumstances a skin graft might be required for coverage (Fig. 12).
PROPELLER FLAP The propeller flap is a single perforator flap that requires specific mention because of its significant rotational capability, attributable to the location of the dominant perforator within the skin paddle.
The elliptical flap is based on a perforator located eccentrically closer to the defect, allowing a significant angle of rotation.42 The perfusion of the flap is enhanced by the inclusion of axial linking vessels within the flap, and by the direction of flow of the perforator. Similar principles of flap elevation, pedicle evaluation, and intraoperative monitoring are followed as previously discussed for PPF. The pedicle can be dissected to the source vessel to increase flap mobility and rotational capability, and to decrease the likelihood of vessel twisting or kinking. The flap is dissected either in the
Fig. 12. (A–D) Freestyle peroneal artery PPF for Achilles tendon coverage following melanoma excision.
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Abraham & Saint-Cyr subfascial or suprafascial plane, and inset into the defect by rotating the flap in the direction of least vessel twist or kink (Fig. 13).40,42
KEYSTONE PERFORATOR ISLAND FLAP: INTRODUCTION The KPIF is a single multiperforator advancement flap based on random fasciocutaneous or musculocutaneous perforators that allows coverage of soft tissue defects by transfer of adjacent tissue with adequate soft tissue laxity.51 This flap can be the primary reconstructive option or be planned as an adjunct for supplemental soft tissue coverage. Knowledge of hot spots of perforasomes allows KPIF skin islands to be based on regularly identified musculocutaneous and fasciocutaneous perforators, which are never surgically identified, resulting in decreased operative times (Fig. 14).51,52 The inclusion of multiple perforators allows increased vascularity and resilience of the flap (Fig. 15). The KPIF is named after the keystone of an arch in Roman architecture, and is described as a curvilinear trapezoidal design flap.35,53 Behan35 described the use of the flap for large elliptical defects, with the transfer of adjacent tissue for better color and contour match. The flap is designed as 2 opposing V-Y flaps that are oriented parallel to the long axis of the defect. The defect usually has a 3:1 long axis to short axis ratio. The ablative surgeon should plan the excisional defect to be elliptical, with the long axis parallel to the line of cutaneous nerves, veins, and/or known perforators to allow for possible preservation of cutaneous sensation.35,39 The long axis of the flap should follow
maximal axiality of flow from dominant perforators, allowing for capture of multiple perforators, which are oriented axially in the extremities, and perpendicular to the midline in the trunk.39 Advancement of the KPIF into the defect along the short axis creates redundancy and subsequent laxity of the soft tissue in the long axis of the flap, which results in an increase in the length of the flap along its short axis, which is the area of greatest tension during closure.35,52,54 The V-Y advancement closure at each end of the flap in the long axis further decreases the size of the donor site defect, and as a result decreases the tension of wound closure.35 Harvesting the KPIF with significant soft tissue laxity allows for wound closure without excessive tension by distributing the laxity to the entire flap, and typically avoids the need for adjunct procedures for donor site closure.35,52,54
KEYSTONE PERFORATOR ISLAND FLAP: MODIFICATIONS Originally, the short axis of the KPIF was designed to have a 1:1 ratio with the defect short axis, and the limbs of the flap were angled at 90 to the long axis of the defect.35,42,53 However, modifications in the design and harvest of the flap grants greater liberty to the reconstructive surgeon to maximize tissue use and to decrease risk of complications. Modifications include: 1. 2. 3. 4.
Increase the ratio of flap size to defect size Deepithelialization for dead-space obliteration Circumferential incision of deep fascia Distally based or proximally based keystone rotation flap35
Fig. 13. (A–F) Freestyle perforator flap based on a distal dominant perforator from the superficial femoral artery.
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 14. (A–C) Keystone flap for trochanteric wound coverage following infected hardware removal. Note the preservation of perforators (hot spot) within the central portion of the flap. Peripheral undermining was performed for maximal flap advancement.
5. Bilateral opposing keystone flap 6. Asymmetric limb angulation for avoidance of critical structures The flap size can be made larger depending on the adjacent tissue laxity, with flap to defect short axis ratios routinely 3:1 or 4:1 and in rare circumstances up to 5:1.39 The increase in flap size decreases the tension of wound closure, and allows the integration of additional perforators by which well-vascularized tissue can be advanced into
the defect (Fig. 16). The flap should be planned with the hot spot located in the central portion of the KPIF for optimal flap perfusion. Larger flaps are designed if the quality of adjacent tissue is compromised by surgical undermining, radiation therapy, adjacent surgical procedures, or an inflammatory process.39,42 For reconstruction of defects in the inguinal region, when a notably large KPIF has been harvested, excess soft tissue can be deepithelialized and used for obliteration of empty space (Fig. 17). This maneuver can be
Fig. 15. (A, B) Keystone flap for lower third leg coverage following skin cancer resection. Note long axis of the keystone flap is designed parallel to the long axis of the limb, and concentrated over a maximal number of perforators to enhance vascularity. The keystone flap should be designed to be wide enough to incorporate as many suitable perforators as possible.
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Fig. 16. (A–E) Skin cancer lesion and resection in the leg. A larger keystone flap relative to the defect size ratio (4:1) was designed because of a lack of soft tissue laxity. Circumferential skin and fascia incisions were performed, as well as peripheral flap undermining, in order to allow proper advancement and tension-free closure.
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 17. (A–C) Large anterior thigh keystone flap used for coverage of groin soft tissue defect following sarcoma resection. Note that part of the proximal edge of the keystone flap was de-epithelialized for empty space obliteration of the groin and lower abdomen.
performed in combination with local muscle transposition, especially when there is concern for vessel exposure (Fig. 18).39 Mobility of the KPIF is significantly increased by incising the deep fascia. Originally, this was limited to the fascia along the greater (also known as the outer) curvature of the flap; however, the authors routinely incise the deep fascia in the progressive manner until appropriate mobility and laxity has been obtained.39 Our experience has shown that greater flap mobility can be achieved, with almost complete circumferential incision of the deep fascia with sparing of the proximal and distal attachments or complete circumferential incision without risking flap viability.39,55 When KPIF flaps are designed over muscle bellies and undergo complete circumferential incision, significant flap mobility is gained. Furthermore, approximately 50% of the flap can be dissected proximally or distally in the subfascial plane, by which the KPIF can obtain significant rotation to allow for closure of defects across joints or for compound fractures with exposed bone.35 Occasionally, a defect is too large for a single KPIF, necessitating the use of an adjunct procedure or reconstruction with bilateral opposing keystone flaps for additional soft tissue coverage (see Fig. 18). The KPIF allows the recruitment of native tissue with similar color, texture, and thickness, and less contour deformity, compared with a
free flap, PPF, or propeller flap. A second KPIF should always be designed on the contralateral side of the defect as a backup flap, to be raised and advanced when indicated.39 Conventional KPIF designs describe the limbs to be at 90 or perpendicular to the long axis of the defect, which introduces unnecessary surgical constraints and can result in iatrogenic injury.35 KPIF can be designed with asymmetric limbs to avoid critical structures, including joint creases and lymphatic basins, reducing the risk for joint contracture and lymphedema.39 Furthermore, limbs should be designed to align with the natural aesthetic lines along the midaxial lines to minimize deformity and to create more aesthetically natural contour.
KEYSTONE PERFORATOR ISLAND FLAP: PLANNING AND PROCEDURE Reconstruction with a KPIF requires an elliptical defect, ideally located near a known hot spot. The long axis of the elliptical defect is oriented parallel to the line of cutaneous nerves, veins, and known perforators, which is longitudinal in the extremities and perpendicular to the midline on the trunk.35 The primary KPIF is planned on the side of the defect with greater soft tissue laxity, with a second KPIF planned on the contralateral side as a backup option. Perforator localization with the use of Doppler in the adjacent tissue helps with
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Fig. 18. (A–D) Bilateral keystone flaps for coverage of a myelomeningocele in a 4-day-old boy.
identification of perforator capture and ensures the optimal central positioning of the perforator in the flap. The KPIF is oriented with the long axis following the axiality of flow from perforators, which follows the path of the underlying source artery, thus ensuring the capture of linking vessels.39 The short axis of the KPIF should be the same size or larger than the defect. The short axis of the KPIF does not include any areas of tissue undermining adjacent to the defect along the lesser curvature of the flap, because this area is void of viable perforating vessels. Smaller flaps are avoided when extensive undermining has taken place.39,55 The limbs of the flap can be designed independent of each other (asymmetric) to avoid crossing joint creases, lymphatic basins, or other local critical structures. After satisfactory design of the KPIF, the flap can be advanced in multiple variations until adequate mobility and laxity are achieved,42 including: 1. Complete circumferential skin incision. 2. Complete circumferential skin incision with progressive fascial release along the greater curvature. 3. Complete circumferential skin and fascial release, which also allows for significant flap rotation.56 4. Incision of the skin and fascia limited to the limbs of the KPIF.
5. Limited exposure or minimally invasive (endoscopic) fascial release of the greater curvature, with skin and fascial release of the KPIF limbs. 6. Limited skin incision along the greater curvature, with incision of the flap limbs and complete circumferential fascial release. Greater flap mobility can also be obtained by undermining the adjacent tissue, or by subfascial undermining of the flap. However, it is of paramount significance to only perform subfascial dissection in known cold spots to avoid injury to perforating vessels and potentially risk flap survival. If additional soft tissue coverage is needed, bilateral opposing keystone flaps can be raised. Furthermore, other flaps, such as PPF, V-Y advancement flaps, or rotation flaps, can be used in conjunction with KPIF for wound closure (Fig. 19). Defects in the inguinal region can be reconstructed with a large KPIF, with portions of the flap deepithelialized for dead-space obliteration.39
KEYSTONE PERFORATOR ISLAND FLAP: CLOSURE The surgical site is closed in multiple layers, typically beginning by reapproximating the defect at the midline with the lesser curvature of the KPIF.50 The closing tension might be too great in some
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery
Fig. 19. (A–C) Left thigh sarcoma resection defect covered with a combination of a freestyle PPF and anterior thigh keystone flap. A keystone flap was used to supplement the pedicle perforator flap.
instances, warranting the closure of the edges with progressive tissue advancement to the midline. Advancement of the larger KPIF tissue into the smaller defect creates flap laxity along the long axis, which results in an increase of the short axis of the KPIF. The flap shortens along the long axis and widens along the short axis with progressive closure, adopting a rounder shape. The limbs of the KPIF are then closed in a V-Y fashion, and the greater curvature of the flap is finally reapproximated. Progressive tension suture and 3-point suture techniques can be used for redistribution of tension and for dead-space obliteration.39 Routine surgical drain placement is not necessary, unless indicated for the primary defect, or if extensive soft tissue undermining has taken place.39,51 Avoid drain placement adjacent to flap hot spots to prevent unintentional distortion of the underlying perforators.
KEYSTONE PERFORATOR ISLAND FLAP AND PEDICLE PERFORATOR FLAP: COMPLICATIONS The most common complications are typically minor, involving wound separation and delayed
wound healing, which are treated conservatively with local wound care.37,39,51,57 Risk of wound complications is increased by an active smoking history and preoperative irradiation.51 Major complications with flap compromise resulting in partial or total flap loss are rare (less than 10%).35,51 Modifications to the KPIF are safe, with no events of partial or total flap loss noted in a recent retrospective study of 42 consecutive KPIF-based reconstructions.39
KEYSTONE PERFORATOR ISLAND FLAP: ADVANTAGES KPIF have many advantages compared with microsurgical free flap–based reconstruction, including: 1. Shorter operative times than free flap or single perforator flaps, with quick flap elevation and inset (2–3 hours).51,58,59 2. Avoid technical demands of perforator dissection.39 3. High reproducibility, technically easy flap harvest, and reliable vascularity.39,51
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Fig. 20. (A–D) Plantar surface melanoma defect covered with an adjacent keystone flap in a diabetic patient. Recruiting local similar tissue characteristics has an advantage over the plantar surface.
4. Single-region donor site, allowing superior aesthetic match by advancing adjacent tissue with similar color and mechanical qualities such as texture, thickness, color match (Fig. 20).39,51 5. Transfer of sensate tissue for reconstruction.35,39 6. Ideal for patients with significant medical comorbidities who are unable to undergo prolonged operative procedures. 7. Avoid need for postoperative flap monitoring.39 8. Decreased postoperative pain, postoperative edema, earlier patient ambulation, and shorter duration of hospitalization.35
KEYSTONE PERFORATOR ISLAND FLAP: DISADVANTAGES AND CONTRAINDICATIONS Limitations of the KPIF primarily depend on the availability of perforators and the laxity of the adjacent soft tissue. Reconstruction of scalp defects with a KPIF is contraindicated because of the lack of perforators.51 Relative contraindications include wounds that have been irradiated, undergone significant undermining, or are currently in an inflammatory state, because these conditions compromise the vascularity and laxity of the flap.51 Contour deformities usually improve through a combination of tissue creep and stress relaxation, and are typically less severe compared with reconstruction with perforator or propeller flaps.37,39,44
Larger flaps have longer incisions, which can result in more noticeable scarring, so it is essential to plan flaps along aesthetic lines.39,42
SUMMARY The increase in wealth of vascular anatomy knowledge, including the perforasome theory and identification of perforator hot spots, has led to major advances and freedom in reconstructive surgery. Tissue selection for locoregional reconstruction should be based on known hot spots and dominant perforators, and flaps should be designed to maximize interperforator flow through linking vessels. The PPF and KPIF have allowed the transfer large volumes of soft tissue for reconstruction and have minimized donor site morbidity, avoiding technically challenging microsurgical free-flap reconstruction and achieving superior aesthetic outcomes, and has resulted in minimal postoperative monitoring, decreased patient reported pain, and shorter periods of hospitalization. These advantages allow patients with significant medical comorbidities to undergo essential, complex surgical reconstruction and avoid the risks inherent with long periods of general anesthesia. Future understanding of vascular anatomy will allow additional modifications, leading to increasing surgical liberty in the planning and execution of reconstructive flaps, with the eventual
Keystone and Pedicle Perforator Flaps in Reconstructive Surgery goal of optimizing patient care and surgical outcomes. 17.
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