Conjoined thoracodorsal perforator‐supercharged dorsal intercostal artery perforator propeller flap for reconstruction of a complex upper back defect: Case report and review of the literature on supercharged pedicled perforator flaps

The reported complications' rate of perforator propeller flaps is variably high, but the etiology of distal flap necrosis, potentially linked to vascular insufficiency, is yet to be clarified. Vascular augmentation procedures have been previously described involving an extra anastomosis of a superficial vein, while a perforator‐to‐perforator supercharging approach has been only sporadically documented in literature. We present a case of perforator‐to‐perforator vascular supercharging of an extended dorsal intercostal artery perforator (DICAP) propeller flap to provide a salvage option for pedicled flap complicated by venous congestion. A 71‐year‐old male patient underwent Dermatofibrosarcoma Protuberans resection in the upper back, leading to a 17 × 17 cm defect with bone exposure. A 30 × 9 cm DICAP propeller flap was planned, with the distal third of the flap designed over the adjacent Thoracodorsal artery perforasome, in a conjoined fashion. Considering the small DICAP pedicle caliber and the flap lateral extension, a thoracodorsal artery perforator vein was dissected and included in the distal flap. Once the flap was raised on its main pedicle, the skin paddle turned blue, showing signs of venous insufficiency. Indocyanine green angiography (ICG) showed a viable proximal half of the flap. Hence, after rotating the skin paddle to reach the upper margin of the defect, an additional anastomosis between the perforating thoracodorsal vein and the perforating vein of the dorsal scapular pedicle was performed according to the perforator‐to‐perforator approach. Doing so, both clinical and ICG examinations showed a well perfused flap, with normal capillary refill. The postoperative course was uneventful, and the patient obtained a good oncological and reconstructive result 4 months postoperatively. The second Vasconez law (“all of the flap will survive except the part that you need”) is often encountered in propeller flaps surgery. Our case shows that it is possible to prevent or overcome this problem by planning appropriate vascular augmentation procedures according to the perforator‐to‐perforator approach, being guided by advanced vascular imaging tools like ICG.

over the adjacent Thoracodorsal artery perforasome, in a conjoined fashion.Considering the small DICAP pedicle caliber and the flap lateral extension, a thoracodorsal artery perforator vein was dissected and included in the distal flap.Once the flap was raised on its main pedicle, the skin paddle turned blue, showing signs of venous insufficiency.Indocyanine green angiography (ICG) showed a viable proximal half of the flap.Hence, after rotating the skin paddle to reach the upper margin of the defect, an additional anastomosis between the perforating thoracodorsal vein and the perforating vein of the dorsal scapular pedicle was performed according to the perforator-to-perforator approach.Doing so, both clinical and ICG examinations showed a well perfused flap, with normal capillary refill.The postoperative course was uneventful, and the patient obtained a good oncological and reconstructive result 4 months postoperatively.The second Vasconez law ("all of the flap will survive except the part that you need") is often encountered in propeller flaps surgery.
Our case shows that it is possible to prevent or overcome this problem by planning appropriate vascular augmentation procedures according to the perforator-to-perforator approach, being guided by advanced vascular imaging tools like ICG.

| INTRODUCTION
Since their introduction in clinical practice, perforator propeller flaps have completely modified the reconstructive approach for small to moderate-sized defects throughout the body.These thin and pliable flaps can be molded easily to achieve aesthetic like-with-like reconstructions.Complication rates reported in literature are variably high, ranging from 8.3% to 42% (Cajozzo et al., 2020), the most common of which being distal flap necrosis, which can be related to arterial or venous insufficiency (Sisti et al., 2016).This concept is summarized by the second Vasconez's law, which fits perfectly to all pedicled flaps and, in particular, to propeller flaps: "all the flap will survive except the part that you need" (Vasconez, 2005).Venous congestion is a fearsome complication when performing perforator propeller flaps, potentially leading to complete or partial flap loss hampering the whole reconstructive procedure.Venous-related complications occur more frequently in the lower limb and trunk regions and are due to insufficient drainage into the perforator pedicle because of inadequate perforator selection, insufficient dissection and mobilization of the pedicle vein (Lafaye et al., 2022).When venous congestion is observed intraoperatively, it can be addressed by increasing the degree of perforator dissection, if possible, or by venous supercharging the flap through an additional microvascular venous anastomosis.
Alternatively, the flap could be derotated to its original position delaying wound closure.Postoperatively, venous congestion can be approached with local heparinization, small punctures or leeches application (Horta et al., 2014).Venous supercharging is technically more complex to perform and adds a microsurgical procedure with increased operative time, but it represents an effective approach to enhance flap survival and substantially limit complication rate (Zheng et al., 2016), as shown by increased blood perfusion and transcutaneous oxygen pressure.Vascular augmentation has been described for both free (Deleyiannis et al., 2014;Kim & Kim, 2012) and pedicled flaps; with regard to the latter, the superficial veins (great and short saphenous veins) appear to be the most frequently used vessels to perform an extra-anastomosis (Chaput et al., 2018;Lin et al., 2016), while a perforator-to-perforator supercharging approach has been only sporadically documented in the plastic surgery literature (Ono, Chung, et al., 2012;Ono, Ogawa, et al., 2012).
We hereby present a unique case of reconstruction of an upper back defect with a conjoined Thoracodorsal perforatorsupercharged dorsal intercostal artery perforator (DICAP) propeller flap, discussing our surgical approach and possible future applications of the technique.

| Case report
We present a case of a 71-year-old male patient who came to our attention because of a bioptic histologic diagnosis of dermatofibrosarcoma protuberans located in the midline region of the upper back (Figure 1a,b).
The patient reported the occurrence of the lesion about 10 years earlier, slowly increasing in size over time.He underwent resection of the neoformation 6 months before coming to our hospital.The histological examination resulted in a dermatofibrosarcoma protuberans, which had not been completely excised and still present at the margins.Our multidisciplinary meeting decided to start neoadjuvant therapy with Imatinib and further investigate the staging of the patient with total body Computed tomography (CT) and magnetic resonance imaging (MRI) in preparation for surgery.No evidence of metastasis was found, and the patient had successfully tolerated neoadjuvant therapy.Consequently, we opted to proceed with surgery.The general surgeons performed surgical resection of the tumor according to the updated guidelines, which led to a 17 Â 17 cm size defect with absence of a portion of the Trapezius muscle bilaterally and exposure of the dorsum muscles and the spinous processes T1-T10 (Figure 2a).
We considered pedicled latissimus dorsi as a possible reconstructive option, but in our philosophy superficial soft tissue defects are better addressed with the use of perforator flaps, which allow like with like reconstruction with minimal morbidity without sacrificing functional muscle units.This was the reason why, after careful handheld doppler identification of the perforating vessels near the defect, a 30 Â 9 cm DICAP propeller flap was planned, with the distal third of the flap reaching the mid axillary line and lying over the adjacent thoracodorsal artery perforasome (Figure 2b).Flap design was performed selecting the dorsal segment with the highest skin laxity.
Considering the small caliber of the DICAP pedicle and the flap extension in an adjacent perforasome, the thorachodorsal artery perforator (TDAP) pedicle was dissected and included in the distal flap (Figure 3a,b).
Once the flap was raised on its main pedicle, the skin paddle showed clear clinical signs of venous congestion like purplish color, shortening refill time (<3 s), dark blood at pin prick, venous bleeding on the flap edges, and increased edema particularly in its distal half (Figure 4).This was confirmed by indocyanine green (ICG) angiography performed intraoperatively in native position, which showed a viable flap only in its proximal half (Figure 5) (Yoshimatsu et al., 2023).
A perforating vein of the dorsal scapular pedicle was dissected nearby the upper margin of the defect.The flap was then rotated 120 clockwise and a salvage extra-anastomosis was performed between the thoracodorsal perforator vein and a perforator vein of the dorsal scapular pedicle according to the perforator-to-perforator supercharged technique approach (0.8-mm vessels anastomosis, 10/0 Ethilon; Figure 6).
After flap supercharging, both clinical and ICG examinations showed a well-perfused flap, with normal capillary refill, pink coloration, and valid doppler signal (Figure 5b), suggesting no need for arterial extra anastomosis.
The donor site was closed by primary intention (Figure 7a).
Postoperative course was uneventful, and the patient was discharged 6 days postoperatively.
Four months postoperative examination confirmed a satisfactory result and a stable defect coverage in absence of local recurrence (Figure 7b).Regarding the angiography evaluation, it has been widely demonstrated in literature that when there is no arterial inflow the flap does not highlight at the ICG.However, in a paper written by Yoshimatsu et al. (2021), it has been demonstrated that congested flaps behave similarly than ischemic flaps at the ICG.In fact, when there is sufficient arterial inflow but no outflow, the ICG angiography will also demonstrate reduced or no highlight.In order to distinguish these two phenomena requiring different treatments, it is important to evaluate the clinical features of the flap and the scratch test: absent bleeding indicates ischemia, while brisk and dark bleeding are indicative of venous congestion.Our flap turned blue in its distal half, with brisk capillary refill and brisk dark bleeding at the scratch test, so we knew we were facing a venous congestion.
A brief literature review with different supercharging techniques for pedicled perforator flaps and propeller flaps is presented in Table 1.Ono, Chung, et al. (2012)    When dealing with large defects, the deep inferior epigastric perforator (DIEP) flap, free or pedicled, is always among the reconstructive options.Specifically, Malkoc et al. (2023) propose a reconstruction of a large postoncological defect of the supero-lateral portion of the thigh by means of a supercharged bilateral pedicled DIEP flap.This case highlights how the supercharging technique allows large flaps to be set up even in patients with comorbidities and poor wound healing capabilities.
More similarly to our flap, Ono, Ogawa, et al. (2012) also described a superficial cervical artery perforator propeller flap (SCAP) supercharged with a DICAP which can be anastomosed either to facial or thoracoacromial vessels for postburn scar contractures respectively in the neck and axilla regions.
Although the concept of vascular augmentation is very useful in pedicled flaps, there are many published cases in the literature in which this technique is also exploited in the context of free flap reconstructions, particularly for breast and complex limb reconstructions.Vascular augmentation techniques, which enhance both blood supply and tissue perfusion as well as drainage, provide distinct benefits, particularly in the context of harvesting larger flaps in patients with comorbidities and reduced wound healing capacity, ultimately leading to a reduction in complication rates (Blondeel et al., 2000;Deleyiannis et al., 2014;Kim & Kim, 2012;Mahajan et al., 2016).
Most cases of venous supercharged flaps reported in the literature are represented by upper and lower extremity flaps.A perforatorto-perforator supercharging approach has been only sporadically documented in the plastic surgery literature, whereas in the majority of cases a superficial vein was anastomosed in an extra flap fashion.However, this is not always possible in the trunk region, where superficial veins are more rarely encountered, and the flaps are mainly dependent on the deep perforators vasculature.
For this reason, we proceeded with an innovative, first time described, supercharging procedure involving a perforator-to-perforator approach for an upper back postsarcoma excision defect reconstruction.This procedure requires microsurgical expertise since it involves a venous microsurgical anastomosis of vessels of very small diameter, extending the average operative time of a pedicled flap.Nevertheless, it allows to harvest a flap of bigger dimensions with an extended reach, making possible to overcome the limits of locoregional flaps in posterior trunk reconstruction.Supercharged flaps are associated with lower venous congestion rates, but this remains a possible complication: in fact, it is not always possible to clinically detect venous congestion intraoperatively in a precise manner.In our experience, in presence of intraoperative signs of venous congestion (nonhomogeneous/blue discoloration of the skin flap, brisk capillary refill) it is advisable, when possible, to scan the vascular status of the flap with ICG and perform a venous supercharge procedure to reduce the chance of venous congestion, especially when harvesting large flaps which are particularly prone to this complication.Some might argue that in presence of such a large defect a microsurgical reconstruction would have been advisable.We agree on the fact that large defects with exposure of noble structures are better reconstructed with microsurgical flaps.However, it is important to consider the patient in his/her whole and accurately select the reconstructive procedure thinking about position change, age of the patient, comorbidities, defect position, presence of adequate recipient vessels and how one procedure or the other might affect operatory time, which should be as short as possible in order to limit flap related complications.
With this approach, we have both prevented flap venous congestion and reduced the length of hospital stay, improving the efficacy of the procedure.However, our operative time was significantly increased, as was the difficulty with the surgical technique because of the microsurgical procedure.
Based on literature, there are more than 400 cutaneous perforators in the whole body (Morris & Miller, 2006).
This freestyle fashion allows us to harvest various combinations of perforator-supercharged conjoined propeller flaps, making it a viable option for many new operative indications.
This case report provides a salvage option of a propeller flap complicated by venous congestion.It shows that it is possible to overcome the second Vasconez's law also in the back region by planning appropriate vascular supercharging procedures according to the perforator-to-perforator approach and being guided by advanced vascular imaging tools like ICG.

F
I G U R E (a, b) Preoperative back view and three-quarter back view of the tumor with the designed margin of the planned surgical resection.F I G U R E (a) Postoperative back view, 17 Â 17 size defect with muscle and bone exposure; (b) flap planning after doppler identification of the main DICAP (blue X) and TDAP pedicle (red X).DICAP, dorsal intercostal artery perforator; TDAP, thorachodorsal artery perforator.F I G U R E (a, b) TDAP pedicle dissected and included in the distal part of the flap.TDAP, thorachodorsal artery perforator.
2 | DISCUSSION Sarcoma surgery involves invasive procedures with resection of whole compartments implying challenging reconstructions, especially in the posterior trunk region, where reconstructive options are limited.The ideal reconstruction should fill the dead space, provide tension free closure of the wound with minimal donor site morbidity and allow secondary procedures to be performed in case of failure or tumor recurrence.Considering age and patient comorbidities, a loco-regional flap was preferred to microsurgical reconstruction, ensuring a F I G U R E 4 Clinical signs of venous congestion, particularly evident in the distal part of the flap (D).F I G U R E 5 (a) ICG angiography showing a viable flap only in its proximal half; (b) ICG angiography showing a well perfused flap in its whole after performing the supercharging extra-anastomosis.ICG, indocyanine green angiography.F I G U R E 6 Microsurgical perforator-to-perforator anastomosis (circled in blue).like-with-like reconstruction, allowing us to perform the reconstructive stage without changing position intraoperatively, hence reducing operative time and allowing a low donor site morbidity with primary closure.In our experience, DICAP flap showed to be a reliable technique to address posterior trunk reconstruction, with minimal donor site morbidity, no muscle unit sacrificed, achieving "like-with-like" reconstruction (Brunetti et al., 2016).There is not much in the literature about reconstructive options for extensive defects of the dorsum by means of pedicled flaps.In the past, Prasad and Morris (2012) published a case report of a large posterior trunk reconstruction through a propeller DICAP flap, which was based on a single perforator.Schmidt et al. (2020) described bipedicled dorsal intercostal artery propeller flaps for reconstruction of extensive cervicothoracic midline defects.Further modifications in surgical technique were published, thus allowing the flap to reach to the posterior neck region in selected cases of defects located in a more cranial location(Brunetti et al., 2021).To date it is not clear if the distal necrosis which frequently occurs in pedicled perforator flaps is produced by insufficiency in the arterial or venous architecture of the flap.The possible solutions to overcome this problem involve the use of venous supercharging techniques, or the complete recruitment of adjacent perforasomes converting the flap into a bipedicled conjoined flap, thus reconnecting arterial input and venous output in the distal skin island with extra flap anastomosis to secondary recipient vessels.The literature often confuses the terms "supercharge" and "turbocharge."Civelek et al. (1998) have shed light on the correct nomenclature by stating how the term "Supercharge" defines a vascular augmentation based on distant source vessels, while the term "Turbocharge" defines a vascular augmentation using vascular sources within the flap territory.In our case, a step-by-step approach based on clinical observation and ICG evaluation was adopted, starting with an extra perforator vein anastomosis (supercharged technique) which eventually turned out to be sufficient to solve the vascular complication without adding an extra arterial anastomosis.
described the occipito-cervico-pectoral flap for lower face and neck reconstruction in which the internal mammary artery perforator was included in the distal portion of the flap and anastomosed with recipient facial artery and vein in a supercharging fashion in order to enlarge the original flap length.Horta et al. (2014) published a case report about lower limb reconstruction in which a venous branch of the great saphenous vein was found at the same rotational plane of the posterior tibial artery perforator propeller flap and included in it to augment venous drainage and the flap survival.Lin et al. (2016) described the distally based venous supercharged anterolateral thigh (ALT) flap for proximal leg and knee coverage.The comitans vein of the pedicle which was found to be dominant was anastomosed to the great saphenous vein to obtain an antegrade F I G U R E 7 (a) Immediate postoperative, donor site closed by primary intention, the flap appears pink and well perfused; (b) 4 months postoperative, back view.T A B L E 1 Literature review with possible supercharging techniques for pedicled perforarator flaps and propeller flaps.
venous drainage, reducing venous congestion rate in a statistically significant way compared to not supercharged flaps.More recently,Chaput et al. (2018) shared their findings about lower limb reconstruction.The group developed a standardized procedure of venous supercharging in the lower limb reconstruction with propeller perforator flaps (posterior tibial artery perforator [PTAP]; fibular artery perforator [FAP]) using saphenous veins anastomosis, reaching a significant reduction of flap complications rate and hospital stay length.