Large soft-tissue defects caused by high-energy trauma and war are challenges to micro-surgeon[11–13]. Those kinds of defects are usually combined with exposed bones, tendons, and joints, flap coverage is essential to these defects. The local flap is limited in this situation, for there is little expendable donor tissue for large defect coverage. A large single flap has been previously reported to cover the extensive wound[14, 15]. The literature reported some large flaps, such as anterolateral thigh (ALT) flap 40 × 20 cm2, deep inferior epigastric perforators (DIEP) flap 50 × 17 cm2. But the donor site morbidities may limit using these large flaps. Even if no other complication occurs, the cosmetic appearance of donor sites will be poor because of closing them with skin grafts.
To reduce the donor site morbidities, sequential chimeric flaps were used to repair large soft-tissue defects[16–18]. Qing et al reported using the bilateral chain-linked ALT perforator flaps for large defects. All the patients have got a good result with limited donor site morbidities. However, this method requires using more than one flap involves multiple donor sites as well as extra surgical risks associated with each flap. Moreover, the flap harvest needs too much intra-muscle dissection process, which increased the complexity of the surgery.
The LDMC flap, since its first description by Tanzini in 1906, has been used for breast reconstruction and other parts of bodies[20, 21]. With the introduction of the thoracodorsal artery perforator flap (TDAP), the LDMC flap is gradually disregarded because of donor site morbidities [22, 23]. But it still plays an important role in large skin and soft-tissue defects[24, 25]. Ma et al used the pedicle LDMC flap for large defects in the upper extremity. All the patients had good functional results, the wound was primary healing with minor complications. Yu also reported used bilateral LDMC flaps to cover large soft tissue defects in the lower limbs of children. With bilateral LDMC flaps combined transplantation, it can repair even larger wounds without significant functional impairments at the donor site. However, the cross-bridge flaps from the contralateral leg were used in four of their cases because no vessels were available for anastomosis at the recipient site. Thus, various modifications to increase the volume of the flap have been reported to simplify the operation and avoid additional vascular anastomosis. The extended LDMC flap was first reported in the breast reconstruction to get enough volume of tissue. Moreover, the extended LDMC flap in breast reconstruction usually was transverse design, which was a benefit for the contour of the breast and left a hidden scar. But in our report, we used an oblique design to get enough length of the skin flap. With latissimus dorsi muscle designed as a single wing or double wings, the donor site can close primary without much tension. Currently, there are no reports regarding those two variants for large soft tissue defects in extremities. This is also the largest case series as we know to share the experience in using extended LDMC flap for large wounds.
In our report, most of the patients have achieved good results. The mean flap harvest time was 56.2 min. All the patients' donor sites closed directly without a skin graft. Although the donor site scar is hard to hide, the donor site function was not significantly reduced. All the patients didn’t show late wound complications or breakdown during the follow-up. The extended LDMC flap has the following advantages. First, flap harvest time is short, which doesn’t need much intra-muscle dissection. The surgery technique is not complex compare with combined transplantation of perforator flaps. Second, there is no need for an extra flap donor site for covering large defects. Split-skin grafted muscle flaps have been claimed to as stable as fasciocutaneous flaps. In our series, no cases are requiring combined or fabricated chimeric perforator flaps based on thoracodorsal vessels. Third, the donor site has sufficient area, which allows us customized design based on the defect template. Besides, the donor site can be closed directly without skin graft, most of the patients are satisfied with the cosmic appearance of the donor site.
The extended fleur-de-lis LDMC flap is one of the other variants and was first introduced by McGraw and Papp in 1991 for breast reconstruction, but later it was applied in other reconstructions as well. Pedro Ciudad et al also used modified extended fleur-de-lis LDMC flap for large defects. This design is similar to the double-wings extended LDMC flap. But it is useful for multi-directional defects with a single flap by positioning vertical and horizontal parts in different combinations. The donor site is closed as Y shaped scar. All donor sites in our report were closed with a linear scar. This kind of flap is also useful to repair large defects in extremity, but we don’t have much experience in this design.
One of the biggest concerns about the use of the extended LDMC flap is the donor site functional loss because of harvesting lots of latissimus dorsi muscle. In our patients, the donor site function has not significantly reduced during the follow-up, all the patients can regain normal daily activities at postoperative 3 months. The muscle-sparing descending branch latissimus dorsi flap may be a useful way to reduce donor site complications, we recommended to use it if the defect was not extensive. Some of the patients showed signs of venous congestion in the early stage. In our report, no one observed venous comprised when anatomized extra subcutaneous vein. According to our experience, we highly recommended harvesting additional subcutaneous vein anatomized to the recipient's vessels. Although some authors reported that donor site hypertrophic scar, we also observed in 3 patients. We think the pinch test is a simple and effective way to evaluate donor site tension to reduce the incidence of the donor site scar. In addition, five patients complained about the anterolateral thigh hypertrophic scar. The “graft back” method and hydrocolloid dressings for donor sites may be helpful to improve the cosmetic outcomes.[33, 34].