A 39-year-old man diagnosed with schwannoma of the sacrum underwent total excision of the tumor with L5 total laminectomy and S1–3 sacrectomy, thus resulting in a 2 × 3 × 3 cm defect in the middle posterior trunk with the overlying skin intact (Fig. 3A). Based on preoperative tracing of the perforator and after identifying the perforator, an elliptical propeller flap with a dimension of 10 × 5 × 1 cm was designed at the superolateral end of the skin incision. Flap was elevated suprafascially, totally deepithelialized, rotated 130 degrees clockwise, folded inward, and inset into the defect (Fig. 3B). The skin over the resection and the donor site were closed primarily. There were no acute complications related to the recipient and donor site. At 12 months, the patient showed a well-healed posterior trunk with good contour (Fig. 3C).
Wounds that undergo debridement due to wound complications frequently result in large dead spaces and exposure of hardware. Also, primary lesions such as cancer that need wide resection may end up with volume depletion after removal. In these wounds with large dead spaces, insufficient obliteration of the dead space permits congestion of blood or serum and may result in complications such as wound dehiscence, infection, and eventually operation failure.1,7,9,13 In defects that result in formation of large dead spaces, the reconstructive goal would be to obliterate the dead space with a well-vascularized tissue along with resurfacing over the defect. There can be many strategies involved with obliteration of dead spaces. One can close the wound with multiple quilting sutures and compression, or in smaller defects, one can advance the surrounding tissue to obliterate the dead space. However, providing optimal closure for posterior trunk defects with dead space can be challenging when the dead spaces are large, infected, or located in the middle of the posterior trunk.
Muscle flaps with or without skin paddles are the first line to reconstruct defects on the posterior trunk. But they have limits to obliterate defects that are large or located in the midtrunk requiring extended reach. The trapezius muscle flap is commonly used for the upper posterior trunk defects but with the drawbacks of short pedicle, lack of soft-tissue bulk, and possible functional morbidity.1,2,8,13,14 For mid posterior trunk defects, latissimus dorsi and parasipinous (erector spinae) muscle flaps can be used. The latissimus dorsi muscle flap, especially in reserve pattern, has multiple advantages, where a segment can be harvested sparing muscle function and can be innervated by sensory nerves.15–17 However, the latissimus dorsi muscle flap may have risk of insufficient volume and reduced blood supply in the distal part of the flap, and the paraspinous muscle is only suitable in spine patients with fusion in whom the muscle is no longer required for spinal stabilization or extension.1,2,8,13,14,18 The gluteal muscle flap is useful to cover lower posterior trunk defects, and in larger defects, multiple muscle flaps may be used together to achieve satisfactory coverage but may result in significantly increased donor side morbidity.1,2,5,10,13,14 Thus, to overcome these limits, we searched for a flap that provides larger bulk, better reach, and reliable vascular supply.
The concepts of perforator flaps, propeller flaps, and free-style approach have become popular in the microsurgical field. The basics for the perforator flaps formulated after Taylor and Palmer8 showed that the branches of the cutaneous vessels radiate after piercing the deep fascia in all directions and interconnect to form a continuous vascular network. The use of various perforator flaps was then introduced.9,12 But the use of perforator flaps as a versatile local flap came with Hyakusoku et al.4 describing an adipocutaneous flap based on a adipofascial pedicle or a subcutaneous fat pedicle, designed like a propeller with 2 unequal blades that allow the long side to fill the defect. Subsequently, a skeletonized perforator pedicle-based fasciocutaneous flap with a 180-degree arch of rotation was presented by Hallock,19 which allows to close donor side more easily. With further advancements and experience with perforator flaps, in 2004, Wei and Mardini7 introduced the “free-style approach” that allows harvest of a flap in a free-style manner based only on the preoperative tracing of a perforator acquired by Doppler signals on a specific region. Using these concepts for reconstruction allows avoiding microsurgery for free flaps while achieving reasonable closure. The posterior trunk is no exception and reports have shown the efficacy of perforator-based local flaps to close complex and large posterior trunk defects.10,20 We further explored the possibility of using this approach to not only resurface the wound but also obliterate the dead space.
We first started by partially deepithelializing the propeller flap that can accommodate the dead space and to resurface the defect. Deepithelializing part of the flap to obliterate dead space is not new. Using a random pedicled flap, Hill and Riaz6 first described the deepithelialized gluteus maximus island flap to obliterate a cerebrospinal fluid (CSF) leak and Moon et al.5 published a series of 13 cases of partially deepithelialized superior gluteal artery perforator flaps for small lumbosacral defects. We also use similar approaches when the defect is small and close to the recipient pedicle allowing the arc of rotation and advancement to reach the defect. However, when the defect is far from the recipient pedicle and requires large volume to obliterate dead space, this approach lacks the reach and the volume.
The approach using a perforator-based propeller flap allows a large skin flap to be harvested with adequate vascular supply and can supply a flap dimension up to 15 × 8 × 2.5 cm as shown in this series. The muscles are spared, minimizing donor site morbidity. There are few factors to consider when designing the flap. After identifying a pulsatile perforator, one should design the flap that allows the donor site to close primarily to achieve superior aesthetic outcome. The existence of multiple perforators around the defect allows having increased options for design. The flap design on the posterior trunk is usually made in a horizontal fashion to accommodate the axiality of the perforasome.11 However, our experience shows that obliquely designed flaps have no circulation problems as shown in case 2. Now, we base the design not only on the axiality of the perforasome of the posterior trunk but also on the amount of rotation the flap will make. Thus, designs allowing less rotation are more favored. Another factor to consider is to design the flap volume larger than the defect to maximize obliteration. There are some technical considerations during elevation as well. During the elevation, it is important not to deepithelize too much of the skin paddle as the preservation of the dermis and subdermal plane will play an important role in linking the perforasomes.11
The midline defect often involves exposure of spine and hardware. After neurosurgical procedures, the rates of postoperative infection of the wound still vary from 1% to 16%.21,22 Risk factors for wound infection after neurosurgery are CSF leak, foreign body, repeated surgery, or operations lasting more than 4 hours. Hence, if a dead space is expected or if there is a risk for CSF leak or instrumentation exposure, a tight and bulky flap must be used to obliterate the dead space. Although there have been debates over the superiority of vascularity of muscles over skin flaps to fight infection, recent trend has been focused on adequate debridement and coverage with perforator flaps.23–26 Using perforator flaps has shown to be feasible with good outcome as using muscle flaps. The debate on how much a single perforator can supply the skin flap still remains to be solved. Multiple factors are considered to have a viable flap, but ideally, if the skin flap has more than 2 or 3 angiosome territories, it would be wise to consider using more than 1 flap to achieve the goal. The deepithelialized flaps can be stacked into double layers if a single layer of adipocutaneous flap is not enough. If the defect requires more coverage, more than 1 perforator flap can also be used to accommodate the large defect.20 Nevertheless, a single perforator-based flap can cover defects of up to 700 cm3 as shown in this series while still obtaining primary closure. The postoperative monitoring can be done using a Duplex scan to measure the velocity of the artery and vein of the pedicle. Another advantage in using ultrasound technology is to see if there is any unwanted fluid collection underneath the skin. Another option for monitoring would be to leave a small island of skin that can be removed at a later date. We start compressing the reconstructed site on day 7 with bandages or garments to further obliterate dead space or to minimize any fluid collection. This approach has shown to be effective to minimize shearing to obtain stable closure and to ambulate early.
The indication for this procedure is large 3-dimensional wounds with or without skin defect, where conventional flaps are difficult to reach or cannot provide adequate volume. This series focused on large extensive wounds that required full deepithelialized propeller flaps on the midline posterior trunk and demonstrates the efficacy of this approach. With accurate design and free-style approach, these flaps can be used for dead space management.
In large-volume defects on the posterior trunk, where conventional flaps may lack volume and reach, the use of deepithelialized propeller flap can provide adequate bulk and vascularity to successfully reconstruct the defects with minimal donor site morbidity.
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