INTRODUCTION In tumor cases requiring extensive resection of the pelvis and proximal lower extremity, fillet flaps allow for reconstruction of massive defects without the addition of donor site morbidity. Flaps of this size simply are not available without harvesting spare parts, highlighting the importance of reliable reconstructive techniques and avoiding the additional morbidity associated with other flap donor sites. This method of reconstruction is currently done in only selected centers, and this article provides a more detailed description of this technique to elucidate the steps of this surgical procedure so that surgeons proficient in microsurgical techniques can assist orthopedic oncologists in the care of these sarcoma patients. SURGICAL VIDEOS The narrated supplemental digital content videos can help surgeons simplify operative planning and avoid complications. These videos highlight the utility of the upfront above the knee amputation (AKA) strategy of flap harvest, operative steps, and potential complications. SURGICAL TAKEAWAYS This article aims at reconstructive surgeons familiar with microsurgical techniques to help them perform this procedure in selected patients who otherwise would have the additional morbidity of a large donor site when undergoing resection of large sarcomas in the hip region. The AKA at the start of an external hemipelvectomy procedure is an excellent first step in fillet flap harvest. (See Video 1 [online], which shows a demonstration of proximal thigh sarcoma anatomy necessitating external hemipelvectomy.) Unlike in situ harvest techniques,1,2 the amputation step allows for the reconstructive and ablative teams to work in parallel, saves operative time, and permits aggressive oncologic resection when tumors encase neurovascular structures. The upfront AKA approach also avoids the possibility of flap injury during resection. {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 1.","caption":"This video displays demonstration of proximal thigh sarcoma anatomy necessitating external hemipelvectomy. Above knee amputation is demonstrated prior to hemipelvectomy.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_mqd4rfxh"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} The main pitfall of performing an AKA at the beginning of the hemipelvectomy is the possibility of long ischemia times.1–3 Careful coordination between surgical teams and contact cooling can be used to minimize these risks. (See Video 2 [online], which shows how contact cooling can be used in a separate operating space to allow for flap dissection in parallel with the oncology procedure.) (See Video 3 [online], which shows tibia and fibula osteotomies to complete soft tissue fillet dissection.) Shaw et al’s retrospective review of contact cooling in 189 consecutive free flaps concluded that surface cooling does not affect flap outcomes if not done for more than 4 hours.4 Still, mindfulness toward the duration of ischemia is necessary, as the longest reported ischemia time before successful fillet transfer is 7 hours.1 Our group has performed at least three reconstructions with upfront AKA for flap harvest with no adverse ischemic outcomes. {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 2.","caption":"This video contact cooling can be used in a separate operating space to allow for flap dissection in parallel with the oncology procedure. Pretibial and thigh incisions start fillet dissection. The femur is removed.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_4enas18l"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 3.","caption":"Tibia and fibula osteotomies complete soft tissue fillet dissection.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_sx54teuh"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} Another highlight of this video is the inevitability of aggressive vascular resection by the ablative surgeon, a phenomenon acknowledged by multiple authors.2,3 In this context, reconstructive surgeons should be proficient in end-to-side anastomosis of flap vessels and have large vascular clamps to obtain proximal and distal control of recipient vessels or stumps off of the aorta (See Video 4 [online], which shows dissection of recipient vessels in the pelvis and set up for vascular anastomosis). Reconstructive surgeons should also anticipate marginal wound healing difficulties with these resections by planning additional wound debridement and larger flap harvests before flap inset. Future investigations into hemipelvectomy reconstruction and refinement in techniques may improve the high wound-complication rates present in this patient population.3 {"href":"Single Video Player","role":"media-player-id","content-type":"play-in-place","position":"float","orientation":"portrait","label":"Video 4.","caption":"This video displays dissection of recipient vessels in pelvis and set up for vascular anastomosis are demonstrated.","object-id":[{"pub-id-type":"doi","id":""},{"pub-id-type":"other","content-type":"media-stream-id","id":"1_s7icc5d1"},{"pub-id-type":"other","content-type":"media-source","id":"Kaltura"}]} DISCLOSURE The authors have no financial interest to declare in relation to the content of the article. ACKNOWLEDGMENTS The authors acknowledge the assistance of Patrick Getty, MD (Musculoskeletal Surgical Oncology, Seidman Cancer Center, University Hospitals of Cleveland) and and Julian Kim, MD (University of South Carolina; Columbia, S.C.). An IRB exemption was obtained from the University Hospitals of Cleveland Institutional Review Board Office. The project was designated as nonhuman research. This article complies with the Declaration of Helsinki.