Scalp Reconstruction with a Free Anterolateral Thigh Flap: Flap Inset

Procedure: This procedure demonstrates the inset of the anterolateral thigh (ALT) flap into a large composite wound after oncologic resection. Introduction: The ALT flap is one of the most commonly used flaps in scalp reconstruction. It is extremely versatile and offers several advantages when compared to other commonly used flaps in scalp reconstruction, such as the latissimus dorsi (LD) flap. Indications/Contraindications:  Microvascular scalp reconstruction is indicated when the resultant wound is not amenable to conventional reconstructive methods, such as tissue expansion or adjacent tissue transfer. In the event of a lack of suitable recipient vessels in the head and neck, free tissue-based reconstruction is contraindicated. Injury to the descending branch of the lateral femoral circumflex artery (LCFA) or perforators to the overlying skin precludes the use of the ALT flap. Materials and Methods: The ALT flap is carefully inset into the residual defect. If a section of vastus lateralis is harvested, it can be used to resurface deeper sections of the defect. It is imperative that the flap is secured edge-to-edge with healthy skin and the pedicle is free of kinks or twists. The section of flap to be monitored by Doppler should ideally not be placed over brain tissue alone, as pulsations from the brain itself can create a falsely normal result in the event of a compromised flap.  Results: The ALT flap was successfully inset into the composite scalp wound, and all critical structures were covered with healthy, vascularized tissue. Conclusions: This report depicts successful resurfacing of a composite scalp defect utilizing an ALT free flap.

Purpose of this technique: Complex scalp reconstruction presents many challenges due to the proximity of multiple critical structures, the relative baseline inelasticity of the surrounding skin, and the effects of prior surgery, trauma, infection, malignancy and radiation.1-3 Such inciting pathologies can preclude the use of locoregional flaps and tissue-expander based reconstruction, especially when the resultant defects are large and critical structures such as exposed hardware or intracranial contents mandate a non-elective approach towards resurfacing.2-4 In such cases, healthy, vascularized tissue from distant sites must be transferred in order to achieve a successful reconstruction.1-4 Added complexities of microvascular scalp reconstruction include the need to withstand adjuvant external beam radiation, postoperative cerebrospinal fluid (CSF) leaks, and the ability to be re-elevated in the event of subsequent cranioplasty.2,4-6 Proper patient/case selection (indications):  Patients with large composite defects with exposed critical structures or those who have any scalp defect not amenable to locoregional tissue transfer or tissue-expander based reconstruction are candidates for microvascular scalp reconstruction. Contraindications (absolute and relative): Absolute contraindications to microvascular scalp reconstruction include the inability to find suitable recipient vessels or the inability to tolerate prolonged general anesthesia. Advantages and disadvantages over alternative techniques: Advantages to microvascular scalp reconstruction include the delivery of healthy, vascularized tissue in a single surgery to resurface wounds that have failed conventional scalp reconstruction methods. Oftentimes, inciting pathologies compromise the regional tissue precluding locoregional flap-based reconstruction. Additionally, due to ongoing infection, or the need to urgently cover exposed critical structures, patients may not be a candidate for subsequent tissue expansion.1-6 Complications and risks:  Complications to free tissue reconstruction of scalp include those inherent to microvascular surgery. The most dire complication is loss of the flap. Additional procedure-specific risks include injury to the underlying intracranial tissues, or catastrophic hemorrhage underneath the flap which could result in a critical mass effect on the underlying brain if exposed.1-6

Instrumentation: A standard plastic surgical tray is required for flap inset. Both monopolar and bipolar cautery should be available. A surgical burr and a Rongeur as well as hemostatic agents are required, along with a hand-held Doppler probe and either a Penrose or a closed suction drain. Setup: The patient is often supine during microvascular reconstruction. The entire scalp should be included in the surgical field to allow for intraoperative repositioning during flap inset. Utilization of headrest extensions such as the Mayfield Standard Cranial Stabilization System (Integra LifeSciences, Princeton, NJ) assists in access to all parts of the scalp. There should be a separate set of instruments available for the team working at the head to facilitate simultaneous flap elevation and recipient site preparation to decrease operative time. Preoperative Workup: Preoperative workup should consist of a thorough history and physical with special attention to the quality of the wound bed. All missing and exposed structures should be noted, and the area should be free of active infection. A computed tomography scan is often helpful to delineate the complete calvarial and intracranial involvement. Anatomy and Landmarks: The edges of the defect should be clearly delineated, and all critical structures to be covered should be identified. Detailed Steps to Procedure: Perhaps the most important component of flap inset is a thorough wound debridement. This is most efficiently conducted in conjunction with a neurosurgical team. All non-viable soft tissue should be excised and discarded. Non-viable cranium should be resected back to healthy bleeding bone using a high-speed burr and/or a Rongeur. Non-viable intracranial contents are dealt with at the discretion of the neurosurgical team, and every effort should be made to obtain a water-tight dural reconstruction to avoid postoperative CSF leakage. If simultaneously cranioplasty or open reduction and internal fixation is to be performed, it should be done prior to microvascular anastomosis to avoid any unnecessary movement of the flap. Prior to flap inset, the surrounding native scalp tissue was elevated in the plane just superficial to the periosteal to allow for smooth contouring of the flap. Any excess tissue on the flap should be trimmed at this time. The flap should be carefully inset into the recipient site, and a water-tight edge-to-edge closure should be completed with sutures selected by the surgeon. In this case, the dermis was closed with 3-0 vicryl, and the skin was closed with 3-0 and 5-0 nylon. Oftentimes a Penrose or a closed suction drain is placed beneath the flap to prevent fluid accumulation which could compromise the intracranial contents and the flap itself. The pedicle is examined to ensure an absence of tension, kinks, or twists. There should be zero tension on the pedicle during incision closure. In the event that skin closure over the pedicle compromises flap perfusion, the pedicle can be skin grafted. A point on the flap should be selected to monitor with handheld Doppler and should be marked by a stitch or staple. This point should ideally be over solid bone to avoid capturing brain vascular signals during Doppler examination. Postoperatively, the patient should be placed in a monitored unit with appropriate flap vascularity examinations per institutional protocol. Any preoperative suppressive antibiotics should be continued postoperatively.   Donor Site Closure A deep drain should be placed between the rectus femoris and vastus lateralis muscles. These muscles are then imbricated together. The proximal and distal portions of the donor site were able to be closed primarily in this case; however, the widest portions of the donor site required skin grafting for closure. The dermis of the tissue surrounding the donor site can be advanced and sutured down to the muscle to ultimately reduce the total size of skin graft required for closure. Once harvested, the skin graft can be secured to the surrounding tissue using staples peripherally, and the any portions of the graft that need to be joined together can be sewn with chromic sutures. Closure is completed with application of a wound vacuum to the flap donor site and dressing to the skin graft donor site. In this case, the skin graft donor site was dressed with negative pressure Silverlon.

At the completion of the procedure the ALT flap harvested should completely cover the scalp defect. The flap should be inset edge-to-edge with healthy skin and should contour well to the remaining cranial vault. The flap pedicle should reach its recipient vessels with ease and should be free of tension, twists, or kinks. Soft tissue closure over the vascular pedicle should be tension-free.

The importance of microvascular flap inset is often underappreciated as it is generally the last step in a long, physically and mentally demanding surgical procedure. Nevertheless, it is equally as important as the rest of the procedure as a poor inset can compromise the entire operation. The importance of a healthy wound bed cannot be overstated. Residual uncontrolled soft tissue infection, necrosis, or osteomyelitis can compromise even the best free flap. Additionally, every attempt should be made to obtain a water-tight dural seal to prevent the development of a CSF leak which can also result in flap compromise.1-6 Composite microvascular reconstruction of the scalp is most commonly achieved with a free latissimus dorsi (LD) flap or an ALT flap.1,6,8 Multiple other flaps have been used, including but not limited to the scapular/parascapular flap, rectus abdominis flap, and the radial forearm flap; however, the LD and ALT flaps are reliably able to resurface large defects.1 While the LD flap is an invaluable tool in composite scalp reconstruction, it does possess certain disadvantages when compared to the ALT flap. The LD flap is primarily a muscle flap, and the size of the skin paddle is often limited.1,6 In the setting of large scalp defects this may result in the need for additional skin grafting over bare muscle which can result in a less robust reconstruction, especially in the setting of underlying hardware.1,6 Additionally, the degree of muscle atrophy can be unpredictable, resulting in significant contour irregularities. Muscle-to-skin inset is not as reliable as skin-to-skin and can increase the risk of wound breakdown.1,6 Adjuvant radiation can result in muscle fibrosis that complicates subsequent cranioplasty.6 The pedicle anatomy of the LD is reliable; however, LD sacrifice can result in substantial donor site morbidity, especially if a patient is wheelchair-bound and reliant on their upper extremity strength for mobility.9 From a technical standpoint, microvascular scalp resurfacing is often completed in a supine position. Utilization of a free LD flap often complicates a dual-team approach and often results in intraoperative patient repositioning, which can prolong operative times.8,10,11             The ALT flap offers several advantages during complex scalp reconstruction. It has a reliable pedicle which is often up to 14cm and can be lengthened by proximal pedicle dissection and/or complete intramuscular perforator dissection.1,6 The versatility of the ALT allows for harvesting as an adipocutaneous, fasciocutaneous, or musculocutaneous flap. It can be harvested as a sensate flap and can also be chimerized with a separate pedicled segment of vastus lateralis and/or tensor fascia lata.1,6,11,12 The skin and subcutaneous tissue of the ALT flap is robust and can provide reliable coverage for underlying hardware and can withstand adjuvant external beam radiation.2,6,13 Skin paddles as large as 3-400 cm2 can be reliably harvested. It allows for skin-to-skin inset and can be contoured to any segment of the bony calvarium.6,14 The fascial layer allows for dural sealing and relative ease of re-elevation in the case of subsequent cranioplasty.6,12 Harvest from the thigh allows a two-team approach which can decrease operative time. Additionally, there is minimal donor site morbidity, even in the event of concomitant harvest of the vastus lateralis muscle.2,6,8,10             Secondary contouring operations including liposuction debulking, flap excision and advancement, and dermabrasion can be performed at least 3 months post-operatively.             Future applications of the ALT flap in scalp reconstruction will likely involve increasing the complexity of the chimeric components in order to achieve a more natural appearing result. Advances in hair transplantation may also allow for transplantation into the flap for complete, hair-bearing scalp restoration.

The authors have no funding for this project, relevant disclosures or conflicts of interest.

None

1. Lin PY, Miguel R, Chew KY, Kuo YR, Yang JC. The role of the anterolateral thigh flap in complex defects of the scalp and cranium. Microsurgery. 2014 Jan;34(1):14-9. doi: 10.1002/micr.22103. Epub 2013 May 2. PMID: 23640870. 2. O'Connell DA, Teng MS, Mendez E, Futran ND. Microvascular free tissue transfer in the reconstruction of scalp and lateral temporal bone defects. Craniomaxillofac Trauma Reconstr. 2011 Dec;4(4):179-88. doi: 10.1055/s-0031-1286119. PMID: 23205168; PMCID: PMC3314257. 3. Wei FC, Tsao SB, Chang CN, Noordhoff MS. Scalp, skull, and dura reconstruction on an emergency basis. Ann Plast Surg. 1987 Mar;18(3):252-6. doi: 10.1097/00000637-198703000-00014. PMID: 3592514. 4. Beasley NJ, Gilbert RW, Gullane PJ, Brown DH, Irish JC, Neligan PC. Scalp and forehead reconstruction using free revascularized tissue transfer. Arch Facial Plast Surg. 2004 Jan-Feb;6(1):16-20. doi: 10.1001/archfaci.6.1.16. PMID: 14732639. 5. Hussussian CJ, Reece GP. Microsurgical scalp reconstruction in the patient with cancer. Plast Reconstr Surg. 2002 May;109(6):1828-34. doi: 10.1097/00006534-200205000-00008. PMID: 11994580. 6. Lamaris GA, Knackstedt R, Couto RA, Abedi N, Durand P, Gastman B. The Anterolateral Thigh Flap as the Flap of Choice for Scalp Reconstruction. J Craniofac Surg. 2017 Mar;28(2):472-476. doi: 10.1097/SCS.0000000000003404. PMID: 28114212. 7. Robson MC, Zachary LS, Schmidt DR, Faibisoff B, Hekmatpanah J. Reconstruction of large cranial defects in the presence of heavy radiation damage and infection utilizing tissue transferred by microvascular anastomoses. Plast Reconstr Surg. 1989 Mar;83(3):438-42. doi: 10.1097/00006534-198903000-00004. PMID: 2645596. 8. Horn D, Jonas R, Engel M, Freier K, Hoffmann J, Freudlsperger C. A comparison of free anterolateral thigh and latissimus dorsi flaps in soft tissue reconstruction of extensive defects in the head and neck region. J Craniomaxillofac Surg. 2014 Dec;42(8):1551-6. doi: 10.1016/j.jcms.2013.11.017. Epub 2013 Nov 20. PMID: 24530070. 9. Lee KT, Mun GH. A systematic review of functional donor-site morbidity after latissimus dorsi muscle transfer. Plast Reconstr Surg. 2014 Aug;134(2):303-314. doi: 10.1097/PRS.0000000000000365. PMID: 24732650. 10. Fischer JP, Sieber B, Nelson JA, Kovach SJ, Taylor JA, Serletti JM, Wu LC, Kanchwala S, Bartlett SP, Low DW. A 15-year experience of complex scalp reconstruction using free tissue transfer-analysis of risk factors for complications. J Reconstr Microsurg. 2013 Feb;29(2):89-97. doi: 10.1055/s-0032-1329918. Epub 2012 Dec 19. PMID: 23254537. 11. Chana JS, Wei FC. A review of the advantages of the anterolateral thigh flap in head and neck reconstruction. Br J Plast Surg. 2004 Oct;57(7):603-9. doi: 10.1016/j.bjps.2004.05.032. PMID: 15380693. 12. Shimizu F, Oatari M, Matsuda K, Uehara M, Sato S, Kato A. Algorithm for reconstruction of composite cranial defects using the fascial component of free anterolateral thigh flaps. J Craniofac Surg. 2013 Sep;24(5):1631-5. doi: 10.1097/SCS.0b013e3182999a33. PMID: 24036741. 13. Lutz BS. Aesthetic and functional advantages of the anterolateral thigh flap in reconstruction of tumor-related scalp defects. Microsurgery. 2002;22(6):258-64. doi: 10.1002/micr.10047. PMID: 12375293. 14. Ozkan O, Coskunfirat OK, Ozgentas HE, Derin A. Rationale for reconstruction of large scalp defects using the anterolateral thigh flap: structural and aesthetic outcomes. J Reconstr Microsurg. 2005 Nov;21(8):539-45. doi: 10.1055/s-2005-922433. PMID: 16292730.