Utilization of Modified Rhomboid Flap to Reconstruct Limb Defect after Wide Resection of Large Soft-tissue Sarcoma: Novel Application of an Old Technique

Background: Reconstruction of limb defects following wide resection of large soft-tissue sarcomas (STS) is challenging. Effectiveness of rhomboid flaps in remains to be addressed. Methods: From March 2018 through February 2019, we utilized modified rhomboid flaps to reconstruct limb defects following wide resection of the large STS (≥5 cm in diameter) in 6 patients. There were 3 males and 3 females. The average age was 65 years (47-77 years). Diagnoses included leiomyosarcoma in 3 patients, synovial sarcoma, undifferentiated pleomorphic sarcoma, and myxoid liposarcoma in 1 respectively. The anatomic locations included the anterior knee in 3 cases, upper arm in 2, and thigh in 1. The mean diameter of the tumor measured 10 cm (5-17 cm). The mean defect size was 113 cm2(38-270 cm2). Results: The mean follow-up duration was 10 months (range, 6-12 months), no patients were lost to follow-up. Skin grafts were utilized in 2 cases. The mean time to heal was 7 weeks (range, 3-13 weeks). At final follow-up, there were no recurrence and metastasis. One case had cerebral hemorrhage and 1 had wound dehiscence, whereas no reoperation was performed. The range of motion of the joints adjacent to the flap reconstructions were comparable to preoperative status. The mean Musculoskeletal Tumor Society score was 27 (range, 24-30). Conclusions: The modified rhomboid flap affords great versatility and is easy to design. This technique yields satisfactory effectiveness in reconstructing limb defects after resection of large STS. Long-term studies of large sample size are warranted.

Various flaps have been advocated to cover the limb defect after wide resection of STS. Free vascularized flaps are frequently utilized, including the latissimus dorsi flap, anterolateral thigh flap, rectus abdominis flap, etc [6,7]. The limb-salvage rate was as high as 90% [6,7]. However, microvascular procedures usually require a plastic surgeon, and can be hardly performed by orthopedic oncologists. Although local flaps and pedicled musculocutaneous flaps are technically easier, these procedures are still restricted for coverage of large limb defects due to significant local tension [8]. Some flap designs are difficult to learn [8]. Because limb STS dictates multidisciplinary management and are primarily treated by orthopedic oncologists, flap reconstructive procedures that yield favorable efficiency and moderate difficulty are warranted to simplify the surgical procedures.
The traditional RF is a local flap designed in compliance with the parallelogram principle ( Fig. 1). It proved to be an effective procedure for wound closure in the torso [11]. Although the RF and its variations are popularized, its effectiveness in reconstructing the limb defect has been rarely addressed. The traditional procedure tailors a circular defect into a rhomboid wound which necessitate sacrifice of circumferential tissue, this may increase the local tension and entail higher difficulty for reconstruction of the limb wound. Thus, we designed a modified RF to facilitate this procedure and conducted preliminary evaluation of its effectiveness in reconstructing the limb defect after wide resection of large STS. The relevant technical points were also summarized.

Postoperative management
Intravenous antibiotics (cefazolin, 3 g, 1/8 h) were applied for 7 days. Drain was removed when the output was less than 20 ml/d. Active joint exercise was allowed at 6 weeks postoperatively. Follow-up was every 3 months for the first 2 years, 4 months the third year, 6 months the fourth and fifth year, and annually thereafter. All cases received physical examination, lung computerized tomography (CT) and MRI assessment of the operated locations. In this case series, no patients received postoperative radiotherapy and chemotherapy.

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The mean follow-up length was 10 months (range, 6-12 months) ( to create a rhomboid wound, which allowed the flap to fit the defect snugly [17][18][19]. However, this procedure entails higher skin tension in the extremities. Although its variations allowed for easier closure of the wound, the geometric design was difficult to learn [20,21]. We propose a modification to the classical RF. Regardless of the defect shape (circular or elliptical), we design a rhomboid-like flap sharing the curved border with the defect, hence it's unnecessary to tailor the wound further. In the classical flap, there are two points that are in strongest tension ( Fig. 1-B, points a and D), and the flap fits the defect snugly, this increases the difficulty of wound closure since the versatility of the flap is restricted [22,23]. In our flaps, one of the points under greatest tension ( Fig. 2-B, point a) can be matched to any points on a length of the defect border ( Fig. 2-B, dotted line A'), hence the flap affords more versatility. Additionally, due to preservation of the circumferential tissue, the advancing distance of the flap is reduced (Fig. 2-B, imaginray line A'B). All these factors allow easier closure of the wound. For large defects, we also slightly reduced the 60° flap angle, so as to further reduce the skin tension [24][25][26].
The design of RF is critical. We took into account of the tumor size, the perforator, limb axis, RSTL, local tension, and joint motion before flap design. The vector of stress in the flap is placed in parallel with the limb axis. At least two of the incisions are placed in the RSTL, and no incisions cross the joint line vertically. After dissection of the flap, the two points under strongest tension should be sutured firstly, so as to avoid repeated traction of the flap [27,28]. Our flaps are easier to draw compared with the classical RF and its variations. The round and oval defects slightly decrease the advancing distance of the flap and adds its versatility. The procedure is easy to learn and viable for orthopedic oncologists.
The importance of functional outcome after limb-salvage surgery for STS has been increasingly recognized [1,4]. The postoperative limb function is associated with various factors, such as the magnitude of resection, tumor location, and reconstructive procedures [18]. A systematic review analyzed the outcomes after functioning reconstructions in the treatment of limb STS, the results indicated most patients achieved favorable functional outcomes [18]. A case-control propensity score analysis suggested flap reconstruction tended to secure a wider surgical margin, whereas the MSTS score was lower than those having primary closure [3]. In this case series, the modified RF resulted in favorable functionality. However, it's noteworthy we did not perform muscle transfer and reconstruction of the tendons and the nerves, these procedures may affect the functional outcome.
Our research is subject to the limitations of the single-center retrospective study. Due to the limited sample size, a control group in comparison with our flaps was impossible. Prospective case-control studies are warranted to demonstrate the effectiveness of the modified RF in treatment of limb defects following wide resection of the large STS.

Conclusions
The modified RF is versatile, easy to design and yields satisfactory effectiveness in treatment of limb defects after resection of large STS. In the extremities, flap designing is dependent upon the limb axis, perforator, RSTL, skin tension, and joint motion. Yet to be evaluated in long-term studies of larger sample size, we believe our flap provides a valuable option for reconstruction of large limb 8 defects after resection of the STS.   Reconstruction of the defect following resection of the leiomyosarcoma in the anterior knee.