Versatility and reliability of the Keystone flap in oncological reconstructions A versatilidade e confiabilidade do retalho Keystone em reconstruções oncológicas

Introduction: The Keystone flap is an island flap with reliable vascularization and simple dissection, first 2003. its distinct there are few scientific on this matter, and it is not a common option in the clinical practice of reconstructive surgery. This article aims to report the experience of a cancer referral center with Keystone flaps in oncological reconstructions. Methods: A retrospective study was carried out data from medical records of patients who performed oncological plastic reconstruction with keystone flaps, operated by the Surgery team of the Cancer Institute of the State of São Paulo, in addition to the analysis of pre, intra and postoperative photographic records. Results: Nine patients were identified, all with comorbidities and a mean age of 52.7. Skin defects followed after oncological resections: five in the lower extremities, three in the trunk and one in the face. The mean of the skin resected area was 52.6cm 2 . The reconstructions were performed under shortened surgical time. There were no postoperative complications or flap losses. The average hospital stay was 2.2 days. Conclusion: The Keystone flap is technically simple and a reproducible option for covering wounds of different sizes and locations. Due to its reliability, simple and quick dissection, shortened hospital stay and low morbidity in the donor area, it should be considered for reconstructing cancer wounds from different locations in patients of all ages. ABSTRACT was collected: epidemiological data; histological type; comorbidities; location and size of the resected area; hospitalization time; complications. Pre, intra and photographic records were obtained.


RESULTS
A total of nine patients were treated with the Keystone flap (six women and three men), with a mean age of 52.7 years, four hypertensives, three people with diabetes and two smokers ( Table 1). All defects followed after oncological resections, five in the lower extremities, three in the trunk and one in the face. Melanoma was the most frequent neoplasm. The mean resected area was 52.6cm 2 , with a median of 31.4cm 2 . In all cases, the donor area was closed primarily.
The anesthetic-surgical time had an average of 289 minutes. This time includes the anesthetic act, the duration of tumor resection and reconstruction by plastic surgery. The mean hospital stay was 2.2 days. The reconstructions were completed with a single surgery, except for one patient who needed to have the scar retouched due to "dog ears," which was later performed under local anesthesia. There were no postoperative complications or flap losses. No patient was excluded from the sample.

INTRODUCTION
The Keystone flap was first described in 2003 1 . It is an island flap based on fasciocutaneous perforators recruited from the periphery of the wound to be treated. Thus, it has the reliable vascularization of a perforating flap, combined with the simple dissection and reproducibility of a local flap 2 . Despite its advantages, it is still little mentioned in the specialized literature and is far from becoming an option of choice in the clinical practice of reconstructive surgery 3 .

OBJECTIVE
This article aims to present the experience of a highly complex oncology service in the use of Keystone flaps in reconstructions. This series of cases aims to reinforce this flap's versatility and safety in managing defects of different volumes and locations.

METHODS
A retrospective study was developed by collecting data from the medical records of patients operated on by the Plastic Surgery team of the Cancer Institute of the State of São Paulo (ICESP) between February 2017 and January 2020. The following information

DISCUSSION
The advantages of locoregional reconstruction have already been widely discussed in the literature 4 . Short surgical time, stable vascularization and the satisfactory aesthetic result of coverage using tissues adjacent to the defect are some of them 2 . The Keystone flap combines these benefits with its versatility, and can be used in limb reconstruction 2 , trunk and face 5 , as demonstrated in our series (Figures 1 to 3). reliable. This design also allows for the advancement of tissue with little morbidity to the donor area, so the closure in at least one of the extremities will be similar to the V-Y 6 flap. All donor areas were closed primarily, without major morbidities in this series. The vascularization of this flap is proportional to the extension of the drawn skin island, as long as the area of contact with the underlying fascia is maintained, through which the perforating vessels emerge 3,4 . This concept allows the manufacture of Keystone flaps of different sizes5. The rate of complications described in the literature is 4%, mainly dehiscence and partial necrosis7. In our series, the reconstructed area ranged from 4.35cm 2 to 163.5cm 2 , without any complications with the vascularization of the flap.
The main limitation of the Keystone flap occurs when it is used in areas of inelastic skin, which restricts its advancement and makes it impossible to close the donor area without tension. Thus, it is not recommended to reconstruct the anterior face of the leg, irradiated or extensively traumatized areas 8 . In addition, its reliability in mucosal coverage (intraoral and intranasal) has not yet been studied 3,9 . None of our patients met these restrictions.

CONCLUSION
The Keystone flap is a technically simple and reproducible option for covering wounds of different sizes and in different locations. Due to its reliability, simple and fast dissection, shortened hospital stay and low morbidity to the donor area, it should be considered in reconstructing oncological wounds of different locations in patients of all ages.