Retrospective study of freestyle perforator-based peninsular flaps

This study aimed to present a simple, fast, and safe technique, called freestyle perforator-based peninsular flap (FPBPF), for pressure sore reconstruction. Among the 21 patients who underwent pressure sore reconstruction between May 2013 and October 2016, 12 patients (Group A) and 9 patients (Group B) were subjected to perforator-based island flap (PBIF) and FPBPF, respectively. We retrospectively reviewed and statistically analyzed the data of both groups. All flaps completely survived in both groups. No significant differences were found in patient demographics, complications, hospital stay, and follow-up period. The mean arc of rotation (102.50 ± 17.645° vs 83.33 ± 14.142°; P = .01), mean flap harvest time (35.83 ± 2.552 minutes vs 20.88 ± 1.763 minutes; P < .001), and mean operative time (145.41 ± 6.788 minutes vs 131.66 ± 10.770 minutes; P = .002) were significantly decreased in Group B compared with Group A. The FPBPF is a simpler and faster technique than the PBIF. FPBPF is a good modality with a few complications for sore reconstruction.

Related papers:

title: Gluteal perforator flaps for coverage of pressure sores at various locations.
abstract: Management of pressure sores is one of the most formidable challenges confronting the reconstructive plastic surgeon. Traditionally, muscle and musculocutaneous flaps were used for the treatment of pressure sores. However, this clinical approach of using the “pressure dispersing” effects of muscle appears to conflict with certain experimental observations. In the 1960s, Kosiak1 and Keane2 demonstrated that muscle is more susceptible to the effects of pressure than either skin or subcutaneous tissue. Keane2 demonstrated that body weight is borne on superficial bony prominences covered only by skin and subcutaneous tissue, thus protecting muscle from the effects of ischemia. In normal weight-bearing positions over bony prominences, muscle is rarely interposed between bone and skin. When muscle and musculocutaneous flaps are used, the use of adjacent flaps is often obviated because of violation of vascular territories. Furthermore, muscle, and its function are sacrificed, which is especially important in ambulatory patients. In the late 1980s, Kroll and Rosenfield3 introduced the concept of perforator flaps. Perforator flaps, supplied by musculocutaneous perforators, obviate the need for muscle or musculocutaneous flaps, thus minimizing donor-site morbidity. These flaps have gained popularity during the past decade with their current application to pressure sore management by the authors. The rationale for the use of fasciocutaneous perforator flaps can be found in some of the earlier literature on flap physiology.1,2 Fasciocutaneous perforator flaps are durable, safe, and reliable; can be elevated in various locations; permit freedom in flap design; and are associated with low donor-site morbidity. The donor site can often be closed directly. Coşkunfırat and Özgentaş are to be congratulated for their impressive experience with 35 gluteal perforator flaps for coverage of 22 sacral, seven ischial, and six trochanteric pressure sores in 32 patients including 18 who were plegic and five who were bedridden. The authors report an excellent survival rate, with only one flap loss, two wound dehiscences treated by secondary closure, and only one recurrence during the 13.6-month follow-up period. These results are quite remarkable because the factors contributing to recurrence following surgery are often beyond the surgeon’s control. Soft-tissue integrity ultimately depends on the patient’s ability to restore blood flow following ischemia and the avoidance of prolonged pressure. Malnutrition, anemia, concomitant medical problems, shear forces, spasm, infection, and patient compliance are the major variables in the equation. Perhaps the most frustrating aspect of pressure sore management is the high incidence of recurrence, which tremendously increases medical costs and patient morbidity. The authors’ results are outstanding, especially when one considers their exceptionally low incidence of recurrence. Although the follow-up period is short, the recurrence rate is nevertheless the lowest of which I am aware for a similar series. In 1956, Conway and Griffith4 reported on 1000 ischial pressure sore patients, consisting predominantly of plegic and bed-dependent patients. Regardless of the type of treatment (surgical or nonsurgical), recurrence rates were 75 to 77 percent. In 1992, Disa et al.5 reported a 61 percent recurrence rate after

title: The Pacman Perforator-Based V-Y Advancement Flap for Reconstruction of Pressure Sores at Different Locations
abstract: BackgroundMany procedures have been proposed for the treatment of pressure sores, and V-Y advancement flaps are widely used to repair a defect. Unfortunately, the degree of mobility of a V-Y advancement flap is dependent on the laxity of the underlying subcutaneous tissue. This is an important disadvantage of traditional V-Y advancement flap and limits its use.We used V-Y advancement flaps as perforator-based to overcome mobility restriction problem, with a further modification (Pacman-like shape) to improve the covering surface area of the flap. MethodsBetween January 2012 and December 2014, the authors used 37 V-Y Pacman perforator-based flaps in 33 consecutive patients for coverage of defects located at sacral (n = 21), ischial (n = 13), trochanter (n = 1) regions. There were 27 male and 6 female patients with a mean age of 49.9 years (range, 15–74 years). ResultsAll flaps survived completely (92.3%) except 3 in which one of them had undergone total necrosis due to hematoma and the other 2 had partial necrosis. No venous congestion was observed. The mean follow-up period was 14.9 months (range, 2–38 months). No flap surgery-related mortality or recurrence of pressure sores was noted. ConclusionsThe V-Y Pacman perforator-based advancement flaps are safe and very effective for reconstruction of pressure sores at various regions. The advantage of our modification procedure include shorter operative time, lesser pedicle dissection, low donor site morbidity, good preservation of muscle, and offers remarkable excursion to the V-Y flap, which make the V-Y Pacman perforator-based flaps an excellent choice for large pressure sore coverage.

title: The gluteal perforator-based flap for repair of sacral pressure sores.
abstract: A gluteal perforator-based flap employing the gluteus maximus muscle perforators located around the sacrum is described. A cadaveric study disclosed the existence of several significant perforators all around the gluteal region. Among these, the parasacral perforators originating from the internal pudendal artery and lateral sacral artery have proven useful for the repair of sacral pressure sores. A total of eight decubitus in seven patients were treated with gluteal perforator-based flaps. There were no postoperative complications, such as flap necrosis and wound infection, with the exception of fistula formation in one case. This flap requires no transection or sacrifice of the gluteus maximus muscle, and elevation time for the flap is short. However, the perforators are located at various sites and thus require some careful dissection.

title: Modified lumbar artery perforator flaps for gluteal pressure sore reconstruction
abstract: Gluteal perforator flaps (GPFs) are the most useful for gluteal region pressure sore reconstruction. However, application is difficult if the surrounding area has scar tissue from previous operations or trauma, especially with recurrent sores. We describe the use of modified lumbar artery perforator flaps when GPFs cannot be used.

title: Perineal Perforator–Based Island Flaps: The Next Frontier in Perineal Reconstruction
abstract: Perineal reconstruction is a challenging prospect. Conventional flap reconstruction often involves the sacrifice of a source artery and muscle, resulting in significant donor morbidity. Perforator flaps sought to overcome this but required tedious dissection. In this article, the authors introduce a new concept in perineal reconstruction using perforator-based island flaps.  The perineal perforator-based island flap is raised based on perforators that most commonly arise from the perineal artery. The flap is designed in the inguinal and gluteal folds in order to achieve aesthetic, tension-free primary closure of the donor site. Eleven patients underwent perineal reconstruction using this approach. Patients ranged in age from 8 to 75 years, with a female-to-male ratio of 10:1.  All 11 operations were performed by a single surgeon (S.Y.M.H.). There were no cases of flap loss or donor-site complications, as defined by wound infection, dehiscence, or keloid formation. All 11 patients reported excellent satisfaction with regard to donor-site aesthetics.  Perineal perforator-based island flaps represent one of the most successful outcomes of the perforator concept. There is no sacrifice of donor vessels or muscle and minimal donor morbidity. The flap is also easily harvested and allows for challenging free-form flap design because it is based on reliable perforators.

title: Perineal reconstruction using a bilobed pudendal artery perforator flap.
abstract: To reconstruct the perineal region, including the urogenital and anal triangle that differ from each other in tissue characteristics and function, we applied pudendal artery perforator flaps with a bilobed flap design. This bilobed flap design could improve the arc of flap rotation and the mobility of the flap so it could cover wide and deep defects. Moreover, it could preserve the characteristics of each triangle.



This study enrolled a total of 15 female patients who had undergone perineal reconstruction with pudendal artery perforator flaps. Seven of them had vulva cancer, seven others had extramammary Paget's disease and the remaining one patient had rectovaginal fistula. We examined the location and shape of the defects, flap designs and their clinical courses.



All flaps survived during the entire follow-up period. The flap sizes ranged from 3x4 to 13x12 cm, and the follow-up period was 4.6 months on average. Bilobed flaps were used in nine patients, and unilobed flaps were used in six patients. The reconstructed areas were in good functional and aesthetic conditions.



We used a bilobed pudendal artery perforator flap according to the location and shape of defect areas in the perineal region. As a result, we could preserve the functional, morphological and cosmetic characteristics of the defect areas.

title: Perineal reconstruction with multiple perforator flaps based on anatomical divisions
abstract: Reconstruction of perineal defects remains a challenge because such defects can be extensive, complex, and three‐dimensional. This report presents a retrospective review of our past 5 years of experience in perineal reconstruction, and suggests a simple algorithmic approach according to anatomical divisions with multiple pedicled perforator flaps for extensive perineal defects.

title: Perfecting the Design of the Gluteus Maximus Perforator–Based Island Flap for Coverage of Buttock Defects
abstract: The new design of the gluteus maximus perforator–based island flap for coverage of gluteal defects has the distinct advantage of being able to use customizable tissue components for coverage and at the same time sparing the source vessel. This adds a further option for use in reconstruction.  After excisional débridement of the lesion, a perforator adjacent to the defect is selected. The tissue of the donor region is pinched to simulate closure. The change in shape of the recipient defect is noted and the dimensions of this new shape are measured. This will serve as the new dimensions of the donor tissue. The tissue components required to fill the defect are then analyzed and the flap is raised. It can be either muscle-sparing, muscle-splitting, or muscle-inclusive. A 1- to 2-cm diameter of soft tissue around the perforator is preserved. The flap is islanded and transposed, and the donor site is closed primarily, acting as a “locking barrier” to the flap. Tension-free closure of the recipient flap is then carried out. Seventy-five patients underwent closure of varying defects of the gluteal region using this technique.  The authors had a total of three minor complications. The rest of the patients healed well, with no recurrence at a mean follow-up of 15 months.  The flap design for coverage of gluteal defects has a great impact on recurrence and complications. This design is novel and the flap is simple to elevate. This is an ideal flap in any high-risk patient in whom the risk of recurrence is high.

title: An Improved Perforator–Based Island Flap: The Heart Balloon Flap
abstract: Reconstructive surgery has entered a “perforator flap era” with more surgeons performing successful perforator flap procedures. The perforator-based island flap is an extension of this perforator concept and one of the most successful. In perforator-rich or -reliable areas, this allows for primary closure of the donor site and the construction of highly customized flaps with little tissue waste.  The authors present a design modification of the perforator-based island flap used in 73 patients who underwent heart balloon perforator-based island flap reconstruction between 2008 and 2012.  There were no reported cases of total flap necrosis. Marginal necrosis of the flap was noted in three cases, which resolved with simple dressings. The donor sites were closed primarily in all cases.  The heart balloon perforator-based island flap enables tension-free closure of the donor site, reduces donor-site complications, and minimizes tissue waste. The resulting shape resembles a heart and gives rise to the flap’s name. Key principles for success are perforators close to the defect, a flap axis that allows for primary donor-site closure, flap border adjacent to the defect that is smaller than the postresection defect, flap harvest until an adequate arc of rotation is obtained, primary closure of the donor site before flap inset, and preservation of a triangular area between the proximal apex of the flap and the defect.

title: Freestyle Pedicle Perforator Flaps: Clinical Results and Vascular Anatomy
abstract: Perforator flaps have increased in use, with advantages such as sparing of the underlying muscle with resultant decreased donor-site morbidity and the possibility of improving aesthetic outcome. Theoretically, a flap can be based on any perforator, whether free or pedicled, based on the perforasome theory. In this study, the principle of free-style perforator flaps was used to harvest pedicled flaps.  The authors report the cumulative experience with freestyle perforator flaps of two medical centers (Hôpital Maisonneuve-Rosemont and University of Texas Southwestern Medical Center). Fifty-three pedicled perforator flaps were performed on 49 patients for local reconstruction of a range of defects at various anatomical locations: head and neck (n = 3), anterior trunk (n = 13), posterior trunk (n = 9), perineal/gluteal (n = 4), lower limb (n = 20), and upper limb (n = 4).  Complete flap survival was obtained in 48 of 53 flaps. Complications included three cases of partial flap necrosis and two total flap failures, the latter in high-risk patients. Complete primary closure of the donor site was possible in 37 cases, especially in the trunk. Twelve patients had partial primary closure complemented by skin grafting, three cases required complete skin grafting, and one donor site required another local flap for closure. Five clinical examples are given—anterior trunk, posterior trunk, cervical region, lower limb, and upper limb.  This is a large series on clinical applications of the freestyle pedicled perforator flap. Because of its many advantages and its versatility, the authors believe it will find its place as a valued reconstructive option and, when indicated, a simpler alternative to free flaps.

title: Modification of the superior gluteal artery perforator flap for reconstruction of sacral sores.
abstract: Despite advances in reconstruction techniques, the treatment of sacral sores remains challenging to plastic surgeons. The superior gluteal artery perforator (SGAP) flap is reliable and preserves the entire contralateral side as a future donor site. The ipsilateral gluteal muscle is preserved, and the inferior gluteal artery flaps are viable. However, dissection of the perforator is tedious and may compromise the perforator vessels.



Between April 2003 and March 2013, we performed two modified flap-harvesting techniques: a rotational and a tunnel method, with only a short pedicle dissection to cover 30 sacral defects. Patient characteristics including sex, age, cause of sacral defect, flap size, perforator number, use and postoperative complications were recorded.



All flaps survived except two, which developed partial flap necrosis and were finally treated by contralateral V-Y advancement flap coverage. The mean follow-up period was 14.8 months (range, 3-24 months). No flap surgery-related mortality or recurrence of sacral pressure sores or infected pilonidal cysts were noted.



Perforator-based flaps have become popular in modern reconstructive surgery because of low donor-site morbidity and good preservation of muscle. The advantages of our modification procedure include shorter operative time, lesser bleeding and lesser pedicle trauma, which make the SGAP flaps an excellent choice for sacral sore coverage.

title: Free-Style Free Flaps
abstract: Free-tissue transfer has become the accepted standard for reconstruction of complex defects. With the growth of this field, anatomic studies and clinical work have added many flaps to the armamentarium of the microvascular surgeon. Further advancements and experience with techniques of perforator flap surgery have allowed for the harvest of flaps in a free-style manner, where a flap is harvested based only on the preoperative knowledge of Doppler signals present in a specific region. Between June of 2002 and September of 2003, 13 free-style free flaps were harvested from the region of the thigh. All patients presented with an oral or pharyngeal cancer and underwent resection and immediate reconstruction of these flaps. All flaps were cutaneous and were harvested in a suprafascial plane. The average size of the flaps was 108 cm2 (range, 36 to 187 cm2), and the average length of the vascular pedicle was 10 cm (range, 9 to 12 cm). All flaps were successful in achieving wound coverage and functional outcomes without any vascular compromise necessitating re-exploration. Free-style free flaps have become a clinical reality. The concepts and techniques used to harvest a free-style free flap will aid in dealing with anatomic variations that are encountered during conventional flap harvest. Future trends in flap selection will focus mainly on choosing tissue with appropriate texture, thickness, and pliability to match requirements at the recipient site while minimizing donor-site morbidity.

title: Reverse Sural Artery Island Flap With Skin Extension Along the Pedicle.
abstract: The distally based sural flap is an efficient flap for reconstruction of soft tissues defects of lower limb. The unstable vascular pedicle, however, is prone to compression by the subcutaneous tunnel, especially when a long pedicle covers the distal area of the foot. The aim of the present study was to introduce a modified surgical technique that leaves the skin extension over the pedicle and to report the clinical results of this modification. A total of 25 consecutive patients with a mean age of 51.7 ± 14.7 years underwent surgery. We modified the conventional sural flap technique by leaving a skin extension over the entire length of the pedicle, creating a fasciocutaneous vascular pedicle. The postoperative flap survival rates, complications, and the characteristics of the flaps such as flap size, pedicle length, and the most distal area that could be covered with this modification, were reviewed. At the last clinical follow-up examination, all the flaps survived, although partial necrosis was observed in 2 (8%) cases. Four cases of venous congestion developed but healed without additional complications. The mean flap size was 5.9 ± 1.8 × 9.2 ± 2.7 cm. With this modification, the sural flap could cover the defect located in extreme distal areas, such as the medial forefoot and dorsum of the first metatarsophalangeal joint, with a longer pedicle (≤27 cm) in 7 patients (28%). A skin extension along the pedicle achieved the favorable survival rate of the sural flap and successfully extended the surgical indications to more distal areas.

title: Safe dissection of the distally based anterolateral thigh flap.
abstract: The distally based anterolateral thigh (ALT) flap is an interesting reconstructive solution for complex soft tissue defects of the knee. In spite of a low donor site morbidity and wide covering surface as well as arch of rotation, it has never gained popularity among reconstructive surgeons. Venous congestion and difficult flap dissection in the presence of a variable anatomy of the vascular pedicle are the possible reasons.



An anatomical study of 15 cadaver legs was performed to further clarify the blood supply of the distally based ALT. Our early experience with the use of preoperative angiography and a safe flap design modification that avoids distal intramuscular skeletonization of the vascular pedicle and includes a subcutaneous strip ranging from the distal end of the flap to the pivot point is presented.



The distally based ALT presents a constant and reliable retrograde vascular contribution from the superior genicular artery. Preoperative angiography reliably identified and avoided critical Shieh Type II pedicled flaps. The preservation of a subcutaneous strip ranging from the distal flap end to the upper knee was associated with the absence of venous congestion in a short case series.



Preoperative angiography and a flap design modification are proposed to allow the safe transfer of the distally based ALT to reconstruct soft tissue defects of the knee.

title: Increasing versatility of the distally based sural flap.
abstract: Repairing distal lower limb soft tissue defects remains challenging for reconstructive surgeons. Relatively few procedures have real efficiency and low morbidity. Since its initial description, the distally based sural flap has been used increasingly for this indication. However, controversy exists about the upper limit of the skin paddle of the sural flap. In the present series, 11 patients underwent surgery with distally based sural flaps. In 6 patients, the flap skin paddle was partially or totally placed beyond this controversial limit on the proximal calf region. To increase the skin irrigation of this region, whole mesenteric tissue under the deep fascia of the leg was included in the flap. Venous congestion and distal tip necrosis can impair the success of flap surgery. To overcome these problems, the flap pedicle was not passed through the subcutaneous tunnel. All flaps survived completely, and no cases of venous congestion developed. Thus, extending the donor area to the upper part of the leg is a reliable maneuver to repair more distal defects of the leg and foot, and abstaining from passing the pedicle through a subcutaneous tunnel could contribute to a decreased risk of venous congestion.

title: Free-style local perforator flaps: concept and classification system.
abstract: Defect reconstruction according to the free-style concept applied to perforator flaps allows flap harvesting in any anatomical region where an audible Doppler signal of a perforator is detected. We report the results of a study in which local perforator flaps were selected for reconstruction in different anatomical areas and were harvested using the free-style concept.



During a 2-year period, defect coverage was carried out in 21 patients (n=21) in the following anatomical areas: cervical (n=3), sternal/parasternal (n=4), axillary (n=2), tibial (n=5), trochanteric (n=2) and sacral/gluteal (n=5). The mean age of patients (15 male and six female) was 57.8 years. Flap selection was based solely on preoperative Doppler mapping in areas adjacent to soft-tissue defects. The mean follow-up period was 1 year.



All flaps survived, demonstrating postoperatively acceptable aesthetic results with good patient satisfaction. The donor sites were closed primarily in 17 patients; four patients required skin grafting. Two patients required surgical revision due to flap-margin dehiscence. There was no loss of function at donor sites. Increased flap mobility could be achieved through extended perforator dissection. One perforator-based flaps offered the widest arc of rotation serving as propeller flaps. If more than one perforator vessel was preserved, flap mobility was limited, but still allowed sufficient flap movement either as a rotation or advancement flap or as a combination of both. A classification is proposed according to the number of perforator vessels preserved and to the type of flap movement.



The concept of free-style local perforator flaps represents a safe, versatile and reliable surgical procedure. It not only offers a greater freedom in flap selection but also provides good aesthetic results. The classification proposed might aid in the decision-making process involved in order to achieve adequate results with this procedure.

title: The Effect of Twisting on Perforator Flap Viability: An Experimental Study in Rats
abstract: Perforator flaps increasingly find acceptance and use in the field of reconstructive surgery due to their decreased donor-site morbidity and increased like-tissue coverage. Nevertheless, they are more prone to vascular compromise, especially when the meticulous technique they require is not employed. Pedicle twisting is a condition occasionally encountered in flap procedures, sometimes inadvertently, sometimes inevitably. In this study, circulatory comprise induced by twisting of the pedicle on a true perforator flap in a rat model is investigated. Thirty-eight Wistar-Albino rats were randomized into 4 groups, and cranial epigastric artery true perforator flaps were elevated on a single perforator. The flaps were returned as they were in the control group (n = 9), and with 90°, 180°, and 270° of torsion in groups 2 (n = 9), 3 (n = 10), and 4 (n = 10), respectively. The flaps were evaluated by their flap survival area, weight, and histopathological appearance by the end of the first week. The mean flap survival ratios for groups 1, 2, 3, and 4 were 97.78 ± 4.41%, 72.22 ± 44.10%, 73.50 ± 30.46%, and 30 ± 30.18% (mean ± SD), respectively. The degree of degenerative changes in group 4 was found to be statistically significant (P < 0.016). Our histopathological examinations indicate that vascular compromise was moderate in group 3 and severe in group 4. Our findings suggest that under normal conditions, the pedicle of a true perforator flap must not be twisted more than 180°.

title: Risk Factor Analysis of Freestyle Propeller Flaps
abstract: Freestyle propeller flaps have been widely used as a reconstructive option for both trunk and extremities. It offers the advantage of “like‐with‐like” reconstruction with an adjacent tissue with no dissection to the source vessels. However, there is the risk of vascular complications. In the present study, the authors investigated the incidence of vascular complications and their risk factors following freestyle propeller flap in the trunk and extremities.  The authors conducted a retrospective review of 50 patients who underwent soft tissue reconstruction of the trunk and the extremities with 55 freestyle propeller flaps from 2004 to 2015. Data regarding patient demographics, surgical details, including the arc of rotation, and flap complications were collected from a prospectively maintained database and analyzed.  There were 10 flap complications (18.2%), including 7 superficial partial necrosis, 2 full‐thickness partial necrosis, and 1 total necrosis from the 55 freestyle propeller flaps harvested. Previous irradiation was a significant risk factor for flap complications and the propeller flap harvested from the extremities showed a significantly higher rate of complications compared with those harvested from the trunk. Complication rates were higher in flaps with the arc of rotation between 150 and 180 degrees with marginal significance compared with flaps with the arc of rotation less than 150 degrees.  Freestyle propeller flaps proved to be a valid and reliable option for reconstruction of defects in the trunk, while complication rate was quite high in the extremities. A prudent preoperative evaluation and preparation may be necessary before performing this surgical technique in the extremities.

title: Nonlinear Finite Element Simulations to Elucidate the Determinants of Perforator Patency in Propeller Flaps
abstract: The propeller-type flap design is increasingly used in reconstructive surgery for various regions of the body. To date, determinants of perforator patency when subjected to twisting have not been elucidated. We propose a simulation model to study parameters affecting perforator patency under such conditions. Nonlinear finite element procedure was used to simulate a perforator consisting of an artery and a vein with both ends fixed. A rigid body was attached to the top of the perforator for applying prescribed angular displacement. The effect of the following parameters on the pedicle patency was determined: (1) increasing angle of twist, (2) vessel stiffness, (3) vessel length, (4) diameter, (5) intraluminal pressure, and (6) the presence or absence of blood flow during twisting. Simulation results were reported in effective stress and strain on the twisted pedicle. In the context of perforator patency, effective strain, which is a measure of vessel deformation or collapse, is the more relevant outcome. The vein was more prone to occlusion because of its weaker wall and lower intraluminal pressure. Four factors that affected perforator patency were identified: angle of twist, intraluminal blood pressure, and perforator diameter and length. There was no significant difference whether twisting was performed prior to or after restoration of blood flow (P > 0.05). Therefore, to optimize condition for maintaining perforator patency, the angle of twist should be kept <180 degrees, perioperative blood pressure should be kept stable (avoiding periods of hypotension), and the selected perforator should be approximately 1 mm in diameter and >30 mm in length. We found that the propeller flap is a feasible design. This study defined the determinants of perforator patency and will serve as a useful guide when performing such flaps.