Scalp Reconstruction with a Free Anterolateral Thigh Flap: Microvascular Anastomosis

Procedure: This procedure depicts the microvascular anastomosis between the free anterolateral thigh (ALT) flap and the superficial temporal artery (STA) and superficial temporal vein (STV). Introduction: Patients requiring scalp reconstruction often have a suitable STA and STV. Given the anatomy of these vessels and the proximity to the scalp, they serve as excellent recipient vessels for free tissue-based reconstruction of complex scalp defects. Indications/Contraindications: The STA/STV can be utilized in patients who do have patent vessels identified by physical examination, Doppler examination, or computed tomography (CT). Patients who have had prior vessel harvest or STA biopsy are generally not candidates for utilization. Patients with radiation, trauma, or infection in the area are often not suitable candidates. Materials and Methods: Using anatomical landmarks and handheld Doppler examination, the STA and STV are identified coursing along the preauricular area. The vessels are dissected free, side-branches are ligated, and the vessels are traced back to a point that allows for a suitable size match with the flap vessels. The flap vein is then anastomosed to the STV using a venous coupling device, and the flap artery is anastomosed to the STA using hand-sewn technique. Conclusion: This report demonstrates the critical steps involved in flap anastomosis to the superficial temporal vessel system.

Purpose of this technique: Trauma and cancer extirpation of the head and neck can result in significant functional and aesthetic issues.1 In the recent past, reconstruction of such composite defects has moved away from pedicled flaps toward free microvascular tissue-based reconstruction. Common options for free flap reconstruction of head and neck defects include the radial forearm flap (RFF), anterolateral thigh flap (ALT), and the rectus abdominis (RA) flap.1             Given the rich vascularity of the head and neck and the regional effects of trauma and malignancy resection, recipient vessel selection is extremely important. Arterial branches from the external carotid artery system, such as the superficial temporal artery (STA), lingual artery, and superior thyroid artery, are often utilized, while the jugular venous system is a common site for venous anastomosis.1-3 Proper patient/case selection (indications): Patients with composite defects of the head and neck are candidates for microvascular free tissue-based reconstruction. Patients ideally have a stable wound base with negative oncologic margins that has been adequately debrided. Additionally, an absence of radiation to the planned recipient site is preferred.2-5 Contraindications (absolute and relative): Absolute contraindications include an absence of planned recipient vessels identified by preoperative computed tomography, involvement of the planned recipient site by trauma, radiation, infection, or malignancy, or an inability to tolerate prolonged general anesthesia. Relative contraindications include active tobacco use, advanced age, and uncontrolled diabetes.2-5  Advantages and disadvantages over alternative techniques: Advantages of microvascular reconstruction of the head and neck include the ability to reconstruct multiple defects of varying contours and compositions. The head and neck region has a high proportion of specialized tissues that are often composed of multiple different types of tissue. This makes free tissue transplantation attractive given the ability to harvest multiple types of tissue off a single vascular pedicle. Additionally, distant tissue precludes involvement by trauma, infection, malignancy, or radiation. Given the close proximity of specialized tissues in the head and neck, any of these inciting factors tend to involve regional tissues, precluding local tissue rearrangement. The vascular anatomy of the head and neck increases the potential to identify a suitable pair of recipient vessels, as well. Complications and risks: Complications include those inherent to free-tissue transfer, most notably flap loss. Additional risks include injury to major vascular structures during recipient vessel dissection. The head and neck also contain multiple motor and sensory nerves which are at risk during complex dissections in an injured field.

Instrumentation:  In addition to a standard plastic surgical tray, a set of specialized instruments and a microscope are required for microvascular reconstruction. The microscope should have a stable full floor column with an adjustable elbow that attaches to the head. Ideally, the head should have a second set of eyepieces for an assistant. Microscopes often have a magnification range of 4-20 x which is generally sufficient for microvascular anastomosis. Microvascular fine jeweler’s forceps, micro vessel dilators, and Castroviejo scissors and needle drivers are also required. Additional required instruments include microvascular vessel clamps and vessel clips such as the GEM Superfine MicroClips (Synovis, Birmingham, AL). For venous anastomoses, an automatic coupling system is often utilized, such as the GEM Microvascular Anastomotic Coupler (Synovis, Birmingham, AL). Arterial anastomoses are often completed with hand-sewn technique using 8-0, 9-0 or 10-0 Nylon or Prolene suture. Setup: The patient should be prone. Extended headrests such as the Mayfield Standard Cranial Stabilization System (Integra LifeSciences, Princeton, NJ) facilitate access to the neck and allow for easier cranial manipulation and access to the surgical site by multiple assistants. A handheld Doppler probe can generally be used to identify the course of the STA, and the incision is planned to overlie its course in a cosmetically appropriate area, which is generally in the preauricular region extending towards the hairline. Preoperative Workup: Preoperative workup should include a thorough history and elicit prior trauma, infection, radiation, or surgery on the planned recipient site. When reconstructing a wound for oncologic purposes, clear margins should be confirmed with the pathologist and extirpative surgeon. Physical examination should assess the entire head and neck for the presence of scars and radiation changes. The STA and facial artery can at times be palpated and can usually be identified by handheld Doppler. Computed tomography with arterial angiography is invaluable in identifying recipient vessels, especially in the case of reoperation. Anatomy and Landmarks: The STA is the terminal branch of the external carotid artery. It begins within the substance of the parotid gland, becomes more superficial as it crosses the zygomatic arch, and branches into frontal and parietal branches within the superficial temporal fascia.6-10 A palpable and/or Dopplerable pulse can often be identified anterior to the tragus and cranially along the hairline. Occasionally, this vessel can be visualized. The two branches of the superficial temporal vein are the frontal and parietal branch. Both converge and run into the main trunk, which joins the parotid and pterygoid plexuses and the posterior auricular vein, becoming the retromandibular vein. The STV is most often found alongside the STA.6-10 Detailed Steps to Procedure: After proper positioning and preoperative markings, a pre-tragal incision is made along the course of the STA/STV. The incision is carefully deepened using sharp dissection, as these vessels are often quite superficial. The temporoparietal fascia is divided, below which the STA and STV can be visualized. The vessels are then traced proximally and distally as far as possible to free up any fascial attachments that may kink the vessel. Vascular sites that are suitable for anastomosis are identified, and these should be measured from the defect to ensure that the flap pedicle is of adequate length to allow defect coverage without any tension on the pedicle. Once these points are identified, proximal and distal control of each vessel should be obtained with atraumatic microvascular clamps. The artery should be divided and irrigated with heparin infused solution, and the adventitia should be cleared. Vascular patency should be checked by temporarily releasing the proximal clamp in a controlled fashion, confirming a strong pulsatile arterial flow. The vein should be transected, and adventitia should be cleared. Vascular patency should be checked by temporarily releasing the proximal clamp in a controlled fashion and observing slow backbleeding. The proposed anastomotic site should be free of valvular tissue. The venous anastomosis is often completed first. The venous pedicle of the flap and the recipient STV are measured, and an appropriate venous coupling device is selected. In this case, a 3mm GEM coupler was used. The pedicle vein and STV are each inserted into one end of the venous coupler and the venous walls are gently draped over the coupler tines, ensuring that the vein does not twist during the process. The coupler is then closed and contact between each end of the coupler is confirmed by gently squeezing them together with a hemostat. The arterial lumens are then approximated and sutured using interrupted, hand-sewn techniques. A variety of techniques can be employed, and care must be taken to ensure that the vessel is not back-walled and that the lumen is patent after completion with no leaking between the sutures. This anastomosis was completed using the 6 o’clock, 12 o’clock, front wall, then back wall technique. Both the artery and the vein should be continuously irrigated with heparinized saline solution to ensure that all clots are flushed out. The flap should then be assessed for good dermal bleeding at its distal portion. Re-perfusion of the flap should be confirmed by Doppler.

A properly completed arterial anastomosis should be visibly pulsatile with no pulsatile bleeding in between sutures. A small amount of oozing is commonly observed and can often be controlled by covering the anastomosis temporarily with a piece of adipose tissue. A strong arterial doppler should be present proximal and distal to the anastomotic site. A properly completed venous anastomosis should not demonstrate venous dilation on the flap side and venous filling should be clearly evident on the recipient vessel side. There should be no leaking from the coupler. A continuous venous hum should be evident by Doppler probe.

Recipient vessel selection in the setting of free tissue-based reconstruction of the head and neck can be complex. Perhaps the most essential part of vessel selection is a thorough history and physical examination alongside a computed tomography scan with angiography, especially in the setting of reoperation. With proper planning, success rates of microvascular head and neck reconstruction can reach 93-99%.1,13 While reconstruction of the head and neck is complicated by the proximity of critical structures, there is also a robust vascular supply to assist in recipient vessel selection. Oftentimes the vessels in closest proximity to the defect are affected by the inciting lesion. This emphasizes the importance of preoperative planning, and backup recipient vessels should always be selected in the event that the initial recipient vessels are not suitable for microvascular anastomosis. Modifications such as vein grafting and arterio-venous loop creation can prove invaluable in this setting. These techniques allow the surgeon to access regional vessels that are unaffected by the inciting pathology.             The decision regarding vessel selection should be patient- and surgeon-dependent. Commonly used arteries include the STA, facial, lingual, and superior thyroid. Additional regional arteries that are often used as backup selections include the transverse cervical artery and the external carotid artery. Care should be taken when selecting the left transverse cervical artery given its proximity to the thoracic duct.1 Commonly utilized veins include the STV, the facial vein, and the external jugular vein. The transverse cervical vein can be selected in the event that the former vessels are not suitable.1             As microvascular head and neck reconstruction becomes more commonplace and success rates remain above 90%, future directions will likely be aimed at more complex composite reconstruction. The complexity of free tissue transferred will likely increase with regards to tissue composition and chimericity. Additional areas of exploration include partial and full facial/scalp transplantation. While these techniques are currently reserved for very specific indications, as experience grows, indications will likely expand.

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

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1. Chung JH, Kim KJ, Jung KY, Baek SK, Park SH, Yoon ES. Recipient vessel selection for head and neck reconstruction: A 30-year experience in a single institution. Arch Craniofac Surg. 2020 Oct;21(5):269-275. doi: 10.7181/acfs.2020.00339. Epub 2020 Oct 20. PMID: 33143393; PMCID: PMC7644354. 2. Serletti JM, Higgins JP, Moran S, Orlando GS. Factors affecting outcome in free-tissue transfer in the elderly. Plast Reconstr Surg. 2000 Jul;106(1):66-70. doi: 10.1097/00006534-200007000-00012. PMID: 10883613. 3. Moon KC, Lee JM, Baek SO, Jang SY, Yoon ES, Lee BI, Park SH. Choice of recipient vessels in muscle-sparing transverse rectus abdominis myocutaneous flap breast reconstruction: A comparative study. Arch Plast Surg. 2019 Mar;46(2):140-146. doi: 10.5999/aps.2018.00913. Epub 2019 Mar 31. PMID: 30934178; PMCID: PMC6446025. 4. Colen LB, Stevenson A, Sidorov V, Potparic Z, Pacelli E, Searles J, Lee S, Li L. Microvascular anastomotic thrombosis in experimental diabetes mellitus. Plast Reconstr Surg. 1997 Jan;99(1):156-62. doi: 10.1097/00006534-199701000-00024. PMID: 8982199. 5. Bengtson BP, Schusterman MA, Baldwin BJ, Miller MJ, Reece GP, Kroll SS, Robb GL, Goepfert H. Influence of prior radiotherapy on the development of postoperative complications and success of free tissue transfers in head and neck cancer reconstruction. Am J Surg. 1993 Oct;166(4):326-30. doi: 10.1016/s0002-9610(05)80325-3. PMID: 8214285. 6. Pinar YA, Govsa F. Anatomy of the superficial temporal artery and its branches: its importance for surgery. Surg Radiol Anat. 2006 Jun;28(3):248-53. doi: 10.1007/s00276-006-0094-z. Epub 2006 Mar 28. PMID: 16568216. 7. Halvorson EG, Cordeiro PG, Disa JJ, Wallin EF, Mehrara BJ. Superficial temporal recipient vessels in microvascular orbit and scalp reconstruction of oncologic defects. J Reconstr Microsurg. 2009 Jul;25(6):383-7. doi: 10.1055/s-0029-1220859. Epub 2009 Apr 23. PMID: 19391089. 8. Hansen SL, Foster RD, Dosanjh AS, Mathes SJ, Hoffman WY, Leon P. Superficial temporal artery and vein as recipient vessels for facial and scalp microsurgical reconstruction. Plast Reconstr Surg. 2007 Dec;120(7):1879-1884. doi: 10.1097/01.prs.0000287273.48145.bd. PMID: 18090750. 9. Shimizu F, Lin MP, Ellabban M, Evans GR, Cheng MH. Superficial temporal vessels as a reserve recipient site for microvascular head and neck reconstruction in vessel-depleted neck. Ann Plast Surg. 2009 Feb;62(2):134-8. doi: 10.1097/SAP.0b013e318172b91d. PMID: 19158521. 10. Doscher M, Charafeddine AH, Schiff BA, Miller T, Smith RV, Tepper O, Garfein ES. Superficial temporal artery and vein as recipient vessels for scalp and facial reconstruction: radiographic support for underused vessels. J Reconstr Microsurg. 2015 May;31(4):249-53. doi: 10.1055/s-0034-1394160. Epub 2015 Jan 28. PMID: 25629208. 11. Nahabedian MY, Singh N, Deune EG, Silverman R, Tufaro AP. Recipient vessel analysis for microvascular reconstruction of the head and neck. Ann Plast Surg. 2004 Feb;52(2):148-55; discussion 156-7. doi: 10.1097/01.sap.0000095409.32437.d4. PMID: 14745264.