Mayo Clinic Experience with Unfavorable Results After Free Tissue Transfer to Head and Neck

Free tissue transfer to the head and neck in the modern era has a high success rate. To maximize success with reconstructive surgery in the head and neck region, it helps to understand those factors that present unique challenges. These factors include contamination by the upper aerodigestive tract, tissue mobility, and a high percentage of patients receiving radiotherapy for oncologic treatment. This article reviews the authors’ experience in the head and neck, specifically how addressing these factors can best lead to successful functional and aesthetic outcomes. The authors share surgical techniques and lessons learned from their successes and failures.

Key points

  • Successful free tissue transfer should produce optimal functional as well as aesthetic outcomes. Anticipating potential risk factors before reconstruction is key.

  • Specific factors negatively affecting head and neck reconstruction include radiation, contamination, and mobility. Of these, radiation with its attendant damage to the capillary bed provides the biggest challenge.

  • Poor wound healing due to these factors can lead to wound breakdown and fistula formation, threatening the microvascular anastomoses, the flap, and the great vessels of the neck.

  • Maxillo-mandibular reconstruction must respect the occlusal plane for functional dental rehabilitation to be optimized.

  • Reconstruction of the pharynx and esophagus following chemoradiotherapy must factor in the ongoing negative effects that can obliterate laryngo-pharyngo-esophageal function.

Introduction

The aim of this article is to share our experience with head and neck reconstructive surgery and technical approaches we have learned from untoward results. There are several factors somewhat unique to the head and neck patient population that challenge the reconstructive surgeon.

First, the upper aerodigestive tract contaminates the reconstructed area. Second, mobility of reconstructed tissue is to be expected and can impact healing. Third, radiotherapy (RT) in the upper aerodigestive tract either before or after reconstructive surgery is the norm. The negative tissue side effects created by radiation need to be factored into the technical considerations of each surgery. Most of the discussion regarding RT references patients who have already undergone radiation because a deficient vascular bed presents unique challenges to healing. Current use of concurrent chemoradiotherapy (CXRT) produces even greater tissue damage than conventional RT.

The last and perhaps one of the most important aspects of head and neck reconstruction relates to how patients meet their world. Appearance that includes functional and aesthetic outcomes is equally or more important following head and neck reconstruction than anywhere else in the body. As we set expectations for our patients, we outline tiers of priority: oncologic success, function, and appearance. Although these goals must be prioritized in this order, the importance of function, namely, speech and swallowing, and appearance are essential to successful head and neck reconstruction and cannot be overemphasized.

Introduction

The aim of this article is to share our experience with head and neck reconstructive surgery and technical approaches we have learned from untoward results. There are several factors somewhat unique to the head and neck patient population that challenge the reconstructive surgeon.

First, the upper aerodigestive tract contaminates the reconstructed area. Second, mobility of reconstructed tissue is to be expected and can impact healing. Third, radiotherapy (RT) in the upper aerodigestive tract either before or after reconstructive surgery is the norm. The negative tissue side effects created by radiation need to be factored into the technical considerations of each surgery. Most of the discussion regarding RT references patients who have already undergone radiation because a deficient vascular bed presents unique challenges to healing. Current use of concurrent chemoradiotherapy (CXRT) produces even greater tissue damage than conventional RT.

The last and perhaps one of the most important aspects of head and neck reconstruction relates to how patients meet their world. Appearance that includes functional and aesthetic outcomes is equally or more important following head and neck reconstruction than anywhere else in the body. As we set expectations for our patients, we outline tiers of priority: oncologic success, function, and appearance. Although these goals must be prioritized in this order, the importance of function, namely, speech and swallowing, and appearance are essential to successful head and neck reconstruction and cannot be overemphasized.

Salvaging free flaps

Modern reconstructive surgeons can expect a better than 98% success rate with free tissue transfer. Improvements in microsurgical training, surgical instruments, and technique; the expansion of potential free tissue donor sites; and a better understanding of free tissue physiology have certainly contributed to the current high rates of success.

As we reviewed our experience of more than 2500 flaps, exclusively in the head and neck, we have seen our failure rates in the last 2 decades plateau at less than 1%. There remain 2% to 3% of cases that have early vascular compromise and require salvage. Most cases of vascular compromise are venous pedicle obstructions, and most of these occur within 72 hours after surgery. A very small number of arterial pedicle problems are discussed later. Our practice is not unique in that careful postoperative monitoring is used for early identification of flap compromise with urgent return to the operating room (OR) when necessary and leech therapy for temporary venous decongestion of the flap while preparing for the OR.

Our protocol for dealing with venous thrombosis is based on lessons learned from untoward results. Failure to trim microstay sutures following anastomosis can result in inadvertent traction on the microvascular anastomoses during even the most gentle clot removal in those patients with hematomas in the neck surrounding the anastomoses. Our technique has not fundamentally changed for 30 years. When all blood clots have been completely removed in the neck and an engorged venous pedicle is identified together with a patent arterial pedicle, the venous pedicle is sectioned at the anastomosis. A mechanical thrombectomy of the venous pedicle is performed, which by itself rarely, if ever, restores flow. The recipient artery is clamped proximal to the arterial anastomosis, and intra-arterial injection of a thrombolytic is administered. This practice has changed over 30 years from streptokinase to urokinase to the tissue plasminogen activator (TPA) currently used. The concentration of thrombolytic can be much greater than a systemic dose as the agent will not enter the systemic circulation because the venous pedicle has been severed. The arterial clamp is removed, and the agent can work its way into the flap. Retrograde irrigation with the same high concentration of thrombolytic is performed. Sometimes with engorged thrombosed veins within the venous system of the flap, intravenous injections of these veins are also performed with the concentrated thrombolytic. Venous outflow slowly returns, during which time all venous outflow is extracorporeal. While awaiting the return of adequate venous outflow, an alternative recipient vein is prepared. Depending on the patient, this may be the original shortened vein, a new vein, or even a vein graft in exceptional cases. Once full venous outflow has been reestablished and all injected thrombolytic has been flushed from the flap, the venous anastomosis is performed ( Fig. 1 ). We do not routinely anticoagulate our free flap patients with anything more than aspirin or ketorolac tromethamine (Toradol). However, in salvage patients, we heparinize the patients for a few days. In the 1980s, we salvaged a dozen or more flaps using this technique and always heparinized the patients following salvage. When we decided to not heparinize one salvaged patient, rethrombosis occurred. Regardless of whether a lesson was learned from untoward results or we responded to an anecdotal experience, we now heparinize our patients after salvaging their flaps.

Fig. 1
Salvage of gastro-omental free flap. ( A ) Intraoperative view left neck, demonstrating complete thrombosis of the gastroepiploic vein anastomosed to the external jugular vein. ( B ) Intraoperative view after mechanical thrombectomy and TPA thrombolysis, demonstrating return of good venous outflow from the gastroepiploic vein. ( C ) Intraoperative view following successful salvage with reanastomosis of the gastroepiploic vein with shortened external jugular vein.

Radiotherapy considerations

The negative impact of RT and CXRT presents the greatest challenge to successful head and neck reconstructive surgery. Radiation produces subintimal fibrosis in the microvasculature of the radiated field and can dramatically decrease or even obliterate the capillary bed. This loss of the capillary bed dramatically decreases the affected tissues’ nutrient and oxygen delivery system resulting in predictably compromised healing. Reconstruction in an irradiated bed will have higher rates of orocutaneous or pharyngocutaneous fistulae even when well-vascularized flaps are used. The nonradiated free flap will not heal as well to heavily radiated, poorly vascularized, contaminated, and mobile tissues. Several strategies are used to minimize the risk fistula poses to a free flap. When possible we try to locate the microvascular anastomosis to the contralateral neck, which is far less likely to become contaminated by a fistula. If a fistula seems imminent or does develop, the drainage must be redirected not only away from the carotid artery but also away from the microvascular anastomosis.

If the microvascular anastomosis must be in the ipsilateral neck, it is beneficial to devise ways to ensure that if a patient were to fistulize, the vascular anastomosis would be protected from the drainage. One technique is to imbricate a strip of the intraoral skin paddle under intraoral suture lines. This de-epithelized imbricated skin paddle serves to shield the microanastomosis if a fistula were to develop and provides a second line of healing if intraoral suture lines were to dehisce, often avoiding a fistula. The de-epithelialized lateral aspect of the skin paddle can also be draped over the microanastomoses in the upper neck such that, if a fistula were to occur the drainage would be superficial to the paddle and thereby not affect the anastomosis.

Nonpliable radiated soft tissues also pose a problem. In cases of severe soft tissue radiation damage and a woody neck resecting more of this tissue may actually be preferred and result in fewer healing complications ( Fig. 2 ). This point is particularly important if poor wound healing might result in carotid or vascular pedicle exposure. Here again, it is wise to imbricate in these cases. By harvesting a larger flap or skin paddle than is needed, a de-epithelialized rind of the skin paddle can be imbricated beyond the suture lines with the neck skin. Then if suture lines were to separate there is still a good chance of wound healing by secondary intention without the patient suffering a full wound dehiscence.

Fig. 2
Reconstruction of defect following salvage laryngopharyngectomy and removal of poorly vascularized neck skin after failed chemoradiotherapy. ( A ) Intraoperative view demonstrating a 2-paddle anterolateral thigh flap. The larger paddle will be used to reconstruct the laryngopharyngectomy defect. The smaller paddle on the right will reconstruct the missing anterior neck skin and protect the great vessels of the neck. ( B ) Early postoperative view of the anterior neck skin replacement. ( C ) Postoperative view, 3 years later.

Another byproduct of head and neck RT is osteoradionecrosis (ORN) of the mandible. During mandibulectomy for ORN it is important to ensure that the mandible resection is extended into well-vascularized, bleeding bone. Otherwise a valuable flap can be expended only to have the adjacent bone develop radionecrosis and require replacement.

In heavily radiated cases

  • When possible, perform the microvascular anastomosis in the neck contralateral to a potential fistula.

  • Remove and replace anterior neck skin that, if compromised, would expose the microanastomosis, great vessels, or the flap reconstruction.

  • Imbricate excess de-epithelialized flap skin under recipient tissue to minimize the consequences of suture line dehiscence.

  • Resect the osteoradionecrotic bone back to a healthy bleeding bone.

Microvascular arterial pedicle rupture

Radiation damage associated with ORN is not always limited to bone. We have observed that ORN serves as an indicator of the severity of the radiation damage to surrounding tissue. Radiation damages the vasa vasorum and vasa vasorae of all vessels in the radiated field, with resultant decreased flow and frequent occlusion. Obliteration of the nutrient vessels to the arterial wall over time increases the risk of rupture.

We have had a small number of recipient artery ruptures in our ORN population undergoing fibula free flap reconstruction. Interestingly, these ruptures always occurred in the recipient artery well proximal to the anastomotic suture line where the adjacent vessel wall had been subjected to adventitial trimming and clamping. None of these cases had had fistulae or contamination around these ruptures. We postulate that mechanical and inflammatory stress from dissecting and isolating these radiated arteries from their radiated and scarred surroundings combined with relative devascularization of their vessel walls secondary to radiation led to pseudoaneurysm and eventual rupture. Pathologic analysis of the ruptured arterial segments supports this hypothesis, demonstrating acute arteritis and pseudoaneurysm.

The time to arterial rupture ranged from 7 to 17 days. In these cases, after the anastomosis was reestablished, repeat rupture usually occurred within a week and should be anticipated. Ultimately all of these anastomoses required ligation. Despite this, we were able to salvage all of these flaps without any partial or total flap loss because flap vascularization was sustained for more than 15 days. Although delayed when compared with nonradiated native tissues, the radiated recipient surgical bed can obviously still ultimately provide neovascularization that supports the free flap restoring tissue perfusion independent of the vascular pedicle.

A real exception to this expectation is found when using jejunal or gastro-omental flaps in radiated recipient beds. Expect poor neovascularization across the serosa of these transplants.

  • ORN may be an indicator of the severity of radiation injury to surrounding soft tissue.

  • Mechanical and inflammatory stress accompanying harvest and preparation of recipient vessels with compromised vasa vasorum(ae) may predispose these arteries to rupture, so vessel isolation and prep should be minimized.

  • If arterial rupture occurs, we think it is beneficial to revise the anastomoses with proximal artery or a new recipient artery to extend the time of flap tissue vascularization. Although one should be prepared for the high likelihood of rerupture, this may afford enough time for neovascularization from the surgical bed to support the free flap without loss even for composite flaps.

The vessel-depleted neck

Previously operated and radiated (especially chemoradiated) necks may simply have no veins available for anastomosis of a free tissue transfer. This deficit is not unique to radiated necks but is far more common in tertiary/quaternary care patients who usually have already had repeat multimodality therapies on arrival. To overcome a vessel-depleted neck, one must either bring recipient vessels to the neck or use flaps with long pedicles that can reach unconventional recipient vessels below the clavicle.

Vein grafts can extend deficient vascular pedicles but bring added risks with dual anastomoses required, and we use them only as a last resort. Because of the proximity of the cephalic vein to the neck, it is a very useful option for venous outflow from the head and neck. The distal cephalic vein is sectioned in the arm and through retrograde dissection delivered to the neck with all of its branches having been secured in the arm. When anastomosed to the flap donor vein in the head and neck, the venous outflow travels anterograde through the cephalic vein to the subclavian vein ( Fig. 3 ).

Fig. 3
Salvage of compromised scapular free flap in vessel-depleted neck. ( A ) Intraoperative view of left neck, demonstrating completely thrombosed subscapular vein ( solid arrow ) and external jugular vein ( double arrow ). Note the internal jugular vein was resected during the cancer surgery. Incision in deltoid groove to left arm to procure cephalic vein. ( B ) Intraoperative view of the left neck following successful flap salvage. The cephalic vein ( solid arrow ) has been harvested from the left upper arm and anastomosed to the subscapular vein. The thrombosed external jugular vein ( double arrow ) is seen posterior to the new venous pedicle.
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Nov 21, 2017 | Posted by in Dental Materials | Comments Off on Mayo Clinic Experience with Unfavorable Results After Free Tissue Transfer to Head and Neck
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