Variants of Extended Latissimus Dorsi Musculocutaneous Flap for Large Wounds in Extremities

Background: Extended latissimus dorsi musculocutaneous (LDMC) ap increasing the size of the ap and most used for breast reconstruction. This report will share our experience in designing different extended LDMC ap for large wounds in extremities. Patients and methods: From January 2004 to December 2018, extended LDMC aps were performed on 72 consecutive patients aged 2 to 68 years (37 men and 35 women). All the wounds were extensive, either in upper or lower limbs, the skin defect ranged from 18 ×10 cm 2 to 37 × 21 cm 2 . Single wing and double wings extended LDMC aps were designed and harvested based on the wounds. Results: Seventy-two patients included this series, 5 pedicle and 67 free aps were successfully harvested. The mean ap harvest time was 56.2 min. The donor sites were closed primarily in all patients. The venous compromise was noticed on the rst postoperative day in 4 cases. Two aps were salvaged after emergency re-exploration, another two patient’s aps were total necrosis. One of the patients was received lower extremity amputation, another patient was repaired by extended LDMC ap on the other side. The wounds healed well, providing reliable soft tissue coverage and good contour in the reconstructed areas. Five patients lost follow-up, the follow-up period ranged from 10 to 56 months (mean, 15.7 months). Patients didn’t occur signicant donor site morbidities that inuenced their daily activities during follow-up. Conclusion: The single wing and double wings extended latissimus dorsi musculocutaneous aps are simple and reliable methods for large skin and soft-tissue defects in extremities.


Introduction
Large skin and soft-tissue defects in extremities are still challenges faced by plastic and reconstructive surgeons. With the development of reconstructive methods improved, chimeric, sequential, and combined perforator ap transplantation are ideal ways to repair large defects with its low donor site morbidities [1][2][3] . But surgical complexity, operation time, and tolerance of surgical procedures still need to be improved.
Latissimus dorsi musculocutaneous (LDMC) ap is a useful way to reconstruct large skin and soft-tissue defects [4,5] . The ap harvest is simple and has a good blood supply. Extended LDMC ap increased the volume of the ap was rst described for breast reconstruction [6][7][8][9] . However, lots of reports focus on breast reconstruction, regarding used it for reconstructions of large soft tissue defects in extremity have not widely reported.
This report shows our experience in designing different extended LDMC aps for large defects. To our knowledge, this is the largest case series reported the variants of extended LDMC ap for large soft-tissue defects in extremities.

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These procedures were conducted in the Department of Hand and Microsurgery, Xiangya Hospital at Central South University. This report followed the Xiangya Hospital Ethical Committee guidelines. The protocol was developed in accordance with the ethical standards of the Helsinki Declaration of 1975 and all subsequent revisions.
From January 2004 to December 2018, 72 consecutive patients aged 2 to 68 years (37 men and 35 women) underwent the extended LDMC aps reconstructions, including 41 adults and 31 children. Fortyone wounds were located in the calf, 18 in the foot and ankle, 6 in the shoulder and upper arm, 4 in the thigh, 3 in the knee joint. All the wounds were extensive, the skin defect ranged from 18 × 10 cm 2 to 37 × 21 cm 2 . Twenty-eight patients combined with fractures, and six patients with segmental bone defects (ranged in size from 3 cm to 6 cm) required secondary orthopedic procedures. Patient characteristics were summarized in Table 1.

Flap Design
The soft tissue defect was rst radically debrided and measured. The defect template would guide us to choose a suitable variant of extended LDMC aps. The skin paddle of the extended LDMC was used to cover the essential part, such as exposed bone with fracture, tendons, and joints. If the essential part located at the edge of the large wound, we prefered to use the single-wing extended LDMC ap. If the essential part located at the center of the large wound, we prefered to use the double-wings extended LDMC ap. For the design of single-wing extended LDMC ap, the axis of the ap was the line connecting the midpoint of the axilla and the posterior superior iliac spine. The design of double-wings LDMC ap was a little bit different from single-wing, the axis of the ap was parallel to the single wing design, which could give some space to harvest another wing. The schematic picture of the different extended LDMC ap design was shown in Fig. 1. Of note, we routinely performed the skin pinch test to con rmed that the donor site could be closed primarily after the ap harvest.

Surgical Technique
The following surgical procedures were used to harvest extended LDMC aps [10] . The patient was placed on his or her side. We rst incised the skin and subcutaneous tissue based on the design, then we detached the subcutaneous tissue with the latissimus dorsi muscle around the skin ap. Afterward, we harvested single wing or double wings latissimus dorsi muscle. Once the latissimus dorsi muscle was dissected, the attention would be turned to the thoracodorsal vessels. The thoracodorsal vessels were identi ed and underwent retrograde dissected until we saw the circum ex scapular artery.
The extended LDMC ap was transferred to the recipient site and covered extensive soft-tissue defects. The skin paddle of the extended LDMC was used to cover the essential part, the remaining muscle ap could then be covered with split-thickness skin grafts. All the split-thickness skin grafts were harvested from the anterolateral thigh. The thoracodorsal artery and paired vein were anastomosed to the recipient's vessels with either end-to-side or end-to-end. The donor site was closed primarily.
Repaired extremities were warmed and elevated postoperatively. Postoperative monitoring included constituted hourly ap checks to evaluate color, capillary re ll, turgor, and surface temperature. After surgery, patients also received appropriate antibiotics according to wound microbiological cultures, physical deep vein thrombosis prophylaxis, and multi-modal pain management.
Secondary orthopedic procedures such as vascularized iliac crest bone graft and Ilizarov technique were used in segmental bone defects, all the procedures were conducted within 4 to 8 weeks after the initial reconstruction.

Results
In the 72 patients included this series, 5 pedicle and 67 free aps were successfully harvested, including 64 single wing and 8 double wings extended LDMC aps. The mean ap harvest time was 56.2 min ( Table 2). The additional subcutaneous veins were anastomosed to the recipient's vessels in 14 patients.
The donor sites were closed primarily in all patients. The venous compromise was noticed on the rst postoperative day in 4 cases. Two aps were salvaged after emergency re-exploration. Two patient's aps were total necrosis, one of the patients received lower extremity amputation, another patient was repaired by extended LDMC ap on the other side. Case Reports

Case 1
A 20-year-old woman who was involved in a road tra c accident, presented with a large soft-tissue defect with 7 cm tibial bone defect on the right lower leg ( Fig. 2A). After radical debridement, the tibial bone defect was managed by external xator application. Then, we designed a single-wing extended LMDC ap (Fig. 2B). The skin paddle of the extended LDMC ap was 28 × 7 cm 2 , the dimension of the muscle ap was 25 × 8 cm 2 . The ap was harvested and transferred to the recipient site ( Fig. 2C and D). The skin paddle of extended LDMC was used to cover a large area of exposed tendons and bones. The exposed part of the muscle ap and the residual wounds were covered with a split-thickness skin graft. The thoracodorsal artery and paired vein were anastomosed to anterior tibial vessels. The postoperative course was uneventful. The Ilizarov was used to reconstruct the bone defect at postoperative 4 weeks. During the 27 months follow-up, all the ap remained viable, and the wound healed well (Fig. 2E and F). At the last follow-up, the patient was able to ambulate freely without assistance (Video 1).

Case 2
A 4-year-old girl suffered a road tra c accident that caused an injury with the right foot and ankle. After radical debridement, leaving a large soft-tissue defect at the foot and ankle (Fig. 3A). A double-wings extended LDMC ap was designed and harvested to reconstruct the large wound in one stage ( Fig. 3B and C). The skin paddle of the double-wings extended LDMC ap was 21 × 6 cm 2 , the size of the muscle ap was 11 × 4 cm 2 and 11 × 4 cm 2 . The ap was transferred to the recipient site. The skin paddle covered the larger areas of the ankle joint. The exposed part of the latissimus dorsi muscle ap was covered with a split-thickness skin graft (Fig. 3D). The thoracodorsal artery and paired vein were anastomosed to anterior tibial vessels. The postoperative course was uneventful. The ap remained viable, and the wound healed well during the follow-up ( Fig. 3E and F). The patient was able to walk without assistance at the 12-month follow-up. (Video 2).

Discussion
Large soft-tissue defects caused by high-energy trauma and war are challenges to micro-surgeon [11][12][13] . Those kinds of defects are usually combined with exposed bones, tendons, and joints, ap coverage is essential to these defects. The local ap is limited in this situation, for there is little expendable donor tissue for large defect coverage. A large single ap has been previously reported to cover the extensive wound [14,15] . The literature reported some large aps, such as anterolateral thigh (ALT) ap 40 × 20 cm 2 , deep inferior epigastric perforators (DIEP) ap 50 × 17 cm 2 . But the donor site morbidities may limit using these large aps. 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 aps were used to repair large soft-tissue defects [16][17][18] . Qing et al reported using the bilateral chain-linked ALT perforator aps for large defects [19] . All the patients have got a good result with limited donor site morbidities. However, this method requires using more than one ap involves multiple donor sites as well as extra surgical risks associated with each ap. Moreover, the ap harvest needs too much intra-muscle dissection process, which increased the complexity of the surgery.
The LDMC ap, since its rst 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 ap (TDAP), the LDMC ap 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 ap for large defects in the upper extremity [26] . All the patients had good functional results, the wound was primary healing with minor complications. Yu also reported used bilateral LDMC aps to cover large soft tissue defects in the lower limbs of children [27] . With bilateral LDMC aps combined transplantation, it can repair even larger wounds without signi cant functional impairments at the donor site. However, the cross-bridge aps from the contralateral leg were used in four of their cases because no vessels were available for anastomosis at the recipient site. Thus, various modi cations to increase the volume of the ap have been reported to simplify the operation and avoid additional vascular anastomosis. The extended LDMC ap was rst reported in the breast reconstruction to get enough volume of tissue. Moreover, the extended LDMC ap in breast reconstruction usually was transverse design, which was a bene t 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 ap. 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 ap for large wounds.
In our report, most of the patients have achieved good results. The mean ap 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 signi cantly reduced. All the patients didn't show late wound complications or breakdown during the follow-up. The extended LDMC ap has the following advantages. First, ap harvest time is short, which doesn't need much intra-muscle dissection. The surgery technique is not complex compare with combined transplantation of perforator aps. Second, there is no need for an extra ap donor site for covering large defects. Split-skin grafted muscle aps have been claimed to as stable as fasciocutaneous aps [28] . In our series, no cases are requiring combined or fabricated chimeric perforator aps based on thoracodorsal vessels. Third, the donor site has su cient 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 satis ed with the cosmic appearance of the donor site.
The extended eur-de-lis LDMC ap is one of the other variants and was rst introduced by McGraw and Papp in 1991 for breast reconstruction, but later it was applied in other reconstructions as well [29] . Pedro Ciudad et al also used modi ed extended eur-de-lis LDMC ap for large defects [30] . This design is similar to the double-wings extended LDMC ap. But it is useful for multi-directional defects with a single ap 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 ap 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 ap is the donor site functional loss because of harvesting lots of latissimus dorsi muscle. In our patients, the donor site function has not signi cantly reduced during the follow-up, all the patients can regain normal daily activities at postoperative 3 months. The muscle-sparing descending branch latissimus dorsi ap may be a useful way to reduce donor site complications, we recommended to use it if the defect was not extensive [31] . 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 [32] , 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, ve 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] .

Conclusions
In summary, our report represents the largest series of extended LDMC ap repairs of large skin and soft tissue defects in extremities. The single wing and double wings extended LDMC ap is a simple and reliable method for large wounds.
Primary limitations of this report were the lack of a comparative group and lack of a standardized measure for long-term outcomes after large wound reconstruction. Comparing outcomes against chimeric, sequential, or combined perforator ap transplantation between extended LDMC ap with other pre-expanded ap repairs may represent is an area for further study and improvement.

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