Free flap transfer in reconstructive head-and-neck microsurgeries in the pediatric patient is overall a rare and underreported phenomenon in the literature. Moreover, the research that can be found usually references studies that include a limited number of subjects, making their conclusions less strong than one would like. However, abundant information about free flap procedures among adult patients does exist and while there are obviously several issues with attempting to interchange adult and pediatric parameters, there are many key pieces of information that can be gleaned from that research and be applied to children. Microsurgeons can gain considerable information about the effectiveness of various flaps in restoring functionality to specific regional structures of the head and neck, including the maxilla, hemimandible, TMJ, tongue, oral cavity, orbit of the eye, skull base, and more. Moreover, the information provided on donor-site morbidity can help surgeons rule out or rule in specific flaps for application in the pediatric patient when considering long-term morbidities that may be caused as a result of the reconstructive surgery. Doctors can also better understand the likelihood of flap loss, thrombotic complications, wound dehiscence, osseointegration, nerve sensation, and bone resorption at the recipient site. Also, key information about surgical techniques, such as feasibility of a two-team approach, locating perforating vessels and nerves, and patient recovery, can be useful in the pediatric patient as well.
Pediatric patients are not the same as adult patients in the case of free flap transfers. They possess fewer comorbidities, a smaller anatomy, they are expected to continue to grow, and the ailments that afflict them are different than those that afflict adult patients. However, using the vast information that has been generated and documented in adult patients as well as the limited research on pediatric patients can be extremely useful in guiding new procedures that will hopefully add to the current volume of literature on free flap reconstruction of the head and neck in the pediatric patient.
58 Free Flap Transfers in Head-and-Neck Reconstructions of Pediatric Patients
Free flap tissue transfers are an important part of headand-neck reconstructions, and they are often carried out following resections of tumors, trauma, and burn injuries. The first vascularized free-tissue transfer in a headand-neck reconstruction was performed in an adult in 1959 when a vascularized flap of jejunum was transplanted into the cervical esophagus. 1 In the early 1970s, the first free-tissue transfers were initiated in pediatric patients. 2 – 4 Since then, a significant body of research that has documented the use of free flap reconstruction of the head and neck has emerged. However, the available research on free flap reconstruction of the head and neck in children is limited compared to the amount of information on similar procedures carried out in adults. 5 This is understandable for several reasons. In general, there is less time for a child to undergo such a complicated procedure in terms of lifespan compared to an adult. Additionally, children are typically in better health than adults and are less likely to become afflicted by some of the diseases that damage the body in a manner that necessitates free flap reconstruction. 6 Children also have fewer comorbidities that result in defects which require repair via free flap reconstruction. Historically, some surgeons have been less likely to undertake the complex free flap reconstructive surgeries in children due to concerns regarding inadequate size of recipient vessels for microvascular anastomoses, among other factors. 7
Although free flap reconstruction is generally described as an effective method for surgical reconstruction in the pediatric population, it represents a particularly challenging practice for a number of reasons. Since the anatomy of the pediatric patient is smaller and less developed, reconstructive surgery requires the manipulation of small, narrow vessels which can make performing venous anastomoses particularly challenging. It also means that the size of potential tissue and bone donor sites for the free-tissue flap may also be limited, although, by extension, this also means that the recipient sites would also be smaller. Additionally, the patient’s future growth patterns may be severely impacted either at the site of reconstruction or the donor site, which may lead to lasting functional impairment or aesthetic harm. 7 Another factor that must be weighed in any pediatric reconstruction is that any impairment or physical damage also has the potential to have a lasting psychosocial impact. 8 Lastly, there are psychosocial factors of free flap reconstructions in children, whereby the pressures of complex microvascular reconstruction surgery are invariably compounded by concerned parents and family members who are anxious for a favorable outcome for the child. 6 There are some “advantages” that microsurgeons may encounter when performing reconstructive procedures in the pediatric population: these patients often have fewer comorbidities than adults, they may undergo more uniform and predictable wound healing, and their anatomy may be more clearly defined and unaltered. 9
Another element that differentiates free flap reconstruction in adults and children is the pathology that typically precipitates the ablative defect that creates the need for a reconstructive procedure. In adults, the predominant cause of surgical resections of the head and neck that require free flaps is squamous cell carcinoma. In children, the most frequent cause of malignant tumors that require reconstruction is a sarcoma, particularly rhabdomyosarcoma, osteosarcoma, and Ewing’s sarcoma. 5 This difference also has implications on the reconstruction that is performed following the tumor resection since sarcomas are present in the bone, cartilage, blood vessels, and other connective tissues and thus may require more aggressive and invasive surgical procedures for a complete cure. In turn, these more aggressive procedures require more robust reconstructions. Moreover, pediatric patients with these malignancies often receive preoperative neoadjuvant therapy, which is intended to facilitate a complete surgical resection of the tumor by shrinking it and targeting micrometastases that may already have occurred. 10 However, this form of therapy often complicates the microreconstructive procedure and makes manipulation of the vessels more challenging. Finally, while the adult head-and-neck tumors may develop from comorbidities, such as smoking, alcohol consumption, or HPV, tumor development in children is more likely to be sporadic or genetic. 6 , 11
There are many options to choose from when it comes to donor sites for free flap reconstruction in both adults and children. Selection should primarily be based on the functional requirement of the area that is being reconstructed. The main emphasis should be placed on designing a surgical plan that will ensure the integrity of the anatomical structures in question at both the donor and recipient sites. For example, in the case of a skull base reconstruction, maintaining a separation between intracranial contents and the paranasal sinuses is a primary functional concern. 8 , 12 Once the integrity of anatomical regions has been addressed, attention should be paid to maintaining functions, such as facial expression, swallowing, and speech. Lastly, if integrity and function of the relevant structures can be maintained, the form or aesthetics of the region being reconstructed should be addressed to ensure optimal cosmetic appearance. For instance, it is possible to use various flaps for reconstruction of the mandible or the maxilla. However, the use of a segmented free fibular flap might be preferred over a scapula free flap (SFF) since the fibula may provide more structural support and allow for the use of dental implants. 13 It is also important to address the potential morbidity at the site of tissue elevation, since each free flap carries with it its own set of potential long-term morbidities. For example, if a free flap procedure does not explicitly require muscle at the recipient site, it may be best to use a fasciocutaneous flap in order to lessen the likelihood of future muscular dysfunction at the donor site in children. Selection of the proper free flap for each procedure is crucial. Great care should be taken to ensure that total reconstruction can be accomplished using a single free flap. Procedures involving multiple free flaps are rare and should be avoided whenever possible.
Free flaps can be classified in a number of different ways, including their donor or recipient site, primary blood supply, type of tissue, and proximity to the site of reconstruction. In pediatric patients, free flaps can be divided into two main categories, soft tissue free flaps and osseous free flaps. Specifically, the former contains soft tissue, such as skin, fat, muscle, cartilage, and other connective tissue, and the latter includes all of these along with a section of bone from the donor site. Soft tissue free flaps that are used in the pediatric population include the radial forearm flap, the abdominis rectus flap, the anterolateral thigh flap, the parascapular flap, and the latissimus dorsi. free flaps that include bone include the fibula flap, the SFF, and the iliac flap.
58.2 Soft Tissue Free Flaps
58.2.1 Anterolateral Thigh Flap
The anterolateral thigh (ALT) flap has emerged as a workhorse flap for reconstructions that require ample soft tissue without a component of bone. The ALT was first described by Song et al in 1984 and originates from the descending branch of the lateral circumflex femoral artery. 14 It is considered as being a versatile flap, and one that is easy to raise with low donor-site morbidity. 15 The ALT offers many advantages. First, it is very reliable and has low reported levels of total and partial failure. 16 Second, it appears to be favored by many patients due to the fact that the scar left behind by its elevation can be easily concealed due to its location compared to other free flaps, such as those from the radial forearm and fibula. 17 Additionally, the ALT offers surgeons the option of creating a “chimeric” flap that can incorporate surrounding tissue. 12
In order to raise an ALT flap, an incision is made above the rectus femoris along a line that runs from the anterior superior iliac spine to the lateral angle of the patella. The rectus femoris and tensor fascia lata are separated from one another in the proximal third by retracting the rectus femoris medially, which should expose the vascular pedicle to the tensor fascia lata. The space between the rectus femoris and vastus lateralis is then identified and opened at the middle third to reveal the vascular pedicle to the vastus lateralis. Once the perforators are located, the skin flap is circumcised and the rectus femoris can be released from its insertion at the quadriceps tendon to the patella 18 , 19 (▶ Fig. 58.1).
In the pediatric population, one particularly relevant area of head-and-neck reconstruction in which the ALT is effective is among burn patients. Yu et al reported a 100% success rate in 11 procedures involving fasciocutaneous ALT flaps that were transplanted onto the scalps of pediatric burn patients. Those authors advocated the ALT for these cases because it can be used to reconstruct large-scale defects with a single-stage procedure that can be conducted using a “two team” approach. 20 According to Yu et al one difference between adult and pediatric patients is that the vessels used in anastomoses in the ALT flap in children must be selected carefully since only selected ones, such as the temporal artery, possess the necessary caliber for anastomosis with the flap’s vascular pedicle.
The ALT is currently used to repair many defects that were formally repaired using a radial forearm free flap (RFFF). 15 The thigh flap is preferred over the radial forearm flap since harvesting of the RF flap requires destruction of a major blood vessel in the arm and the closure of the donor site necessitates a skin graft, both of which may compromise the function of the arm. 21 However, it should be noted that RFFF flaps are considered easier to raise since the ALT has a more complex anatomy owing mostly to a thin perforator that originates from the descending branch of the lateral circumflex femoral artery. 21 As mentioned above, for pediatric patients, the ALT appears to be a much more suitable option than the RFFF flap for head-and-neck reconstructions that require soft tissue, given the risk of donor-site morbidity with which the radial flap is associated.
The ALT flap can be used in a number of head-and-neck reconstruction procedures. Bianchi et al reported that the ALT is particularly well suited to partial or total glossectomies. 22 The flap is able to provide the muscular “bulk” that is necessary to allow for the lingual-palatal contact that is an important part of the oral phase of deglutition, as well as necessary obliteration of any submandibular dead spaces, ensuring a complete separation between the oral cavity and the neck. Moreover, the option to harvest chimeric ALT flaps makes the ALT flap especially flexible in terms of where it can be used in head-and-neck reconstructions. The ALT flap has been described as being effective in the reconstruction of radical parotidectomy defects due to its ample skin and neural tissue and ability to avoid the need for a second donor site. 23 – 25 Haynes et al reported that the ALT flap is useful for severe deformities of the pediatric anophthalmic orbit, adding that it also aids in the retention of an ocular prosthesis. 26 Lastly, Garfein et al indicated that the ALT flap is recommended for use in midface reconstruction of the pediatric patient, noting that the procedure should be conducted in children the same way it is in adults since the goals of the procedure are the same in both populations: to maintain facial dimensions, provide a framework for soft tissues of the cheek, and isolate the oral cavity from the neck. 27
Donor-site morbidity of the ALT flap has been consistently reported as low, although this may depend on several factors, including the surgical technique used, the specific outline of the ALT that is selected and the flap size. 28 , 29 In a systematic review that analyzed 42 articles which included 2324 patients, Collins et al determined that the most common donor-site morbidity reported by patients who underwent ALT free flap surgery was lateral thigh paresthesia, most likely due to damage to lateral femoral cutaneous nerve of the thigh. 30 Additionally, some damage has been reported to occur to the vastus lateralis muscle as a result of the dissection of perforator vessels of the ALT flap, which can lead to problems with knee extension. 31 Flap losses were reported at a rate of 7% in a study by Horn et al that examined 41 ALT transfers conducted over a 9-year period. 32 Overall, however, the ALT is associated with limited donor-site morbidity, thus making it a good candidate for pediatric head-and-neck reconstruction procedures.
58.2.2 Radial Forearm Free Flap
The RFFF was traditionally one of the most commonly used fasciocutaneous free flaps. First described in 1981 by Yang et al, the RFFF has many advantages for use in head-and-neck reconstructions, including long pedicle length, sparsity of hair, high vessel caliber and appropriate thickness. 33 – 35 The RFFF is often preferred for small- to medium-sized defects in buccal, floor of mouth, lower lip and soft palate reconstructions. 36 The radial flap also provides two venous drainage systems: one is a superficial system of veins that drain to the cephalic and basilic veins and the other is a deep system that drains via venae comitantes that travel alongside the radial artery. This duality confers an advantage during flap harvest since it offers surgeons a choice of vessels from which to select for micro anastomoses. 37 However, the RFFF is associated with many significant donor-site morbidities, which have made it less preferable in many reconstruction cases in children, with some sources indicating a specific preference of the ALT flap over the RFFF. 36 , 38 – 40
The RFFF is raised with an incision along the ulnar border to expose the flexor carpi ulnaris tendon. The subfascia is dissected until the flexor carpi radialis tendon is reached and identification of the radial vessels is possible. The vascular pedicle is then dissected superiorly along the brachioradialis muscle and the appropriate length of flap is elevated. 18
One of the main considerations for donor-site morbidity associated with the RFFF is the aesthetic appearance of the residual scar. In a review of 56 patients who had undergone RFFF procedures with a mean post-procedure follow-up of 7.9 years, Li et al found that patients felt that the donor-site scar significantly impacted their appearance and most of them did not feel comfortable wearing short-sleeved shirts. 33 Smith et al reported that 90% of patients who underwent an RFFF procedure viewed their arm as “disfigured.” 41 This factor should be considered when weighing free flap reconstruction options, especially in younger patients.
Another concern highly relevant to the pediatric patient is that RFFF volumes have been reported to become significantly reduced in the long term. Joo et al observed that RFFF volumes were reduced by 42.7% on average during post-procedure follow-ups from 3 months to 5 years, leading those researchers to conclude that RFFF procedures should be undertaken with flaps that are 40% larger than the recipient site for which they are intended. 42 Finally, harvesting the RFFF results in complete interruption of the radial artery, an important vessel of the arm, causing perfusion of the limb to occur via the ulnar artery, which does not always allow for equal perfusion of all parts of the hand. 18 Additional donor-site complications, such as edema formation, reduced strength and extension of the hand, and cold intolerance have also been reported. 43
58.2.3 Rectus Abdominis Flap
Originating from the deep inferior epigastric vessels, the rectus abdominis flap (RAF) can be harvested with the rectus abdominis muscle as an RMFF or without muscle (or limited muscle) as a musculo-adipose rectus free flap (MARF). The muscle is often included in the flap in order to provide increased volume and pliability for decreasing the likelihood of infection when used in the oral cavity or the orbit, or for decreasing the likelihood of cerebrospinal fluid leakage when used in the skull base. RMFFs are useful for repairing a defect within a contained space that requires ample subcutaneous fat tissue. Some examples of a possible defect that would be suitable for a rectus free flap transplant include the orbit of the eye, glossectomy defects, maxillary reconstruction, and other soft tissue defects of the oral cavity. 44 , 45
The RAF is elevated with a vertical incision from the distal ribs to the pubic ramus. The muscle is then progressively liberated from the rectus sheath that surrounds it anteriorly. The muscle is then posteriorly separated to reveal the inferior epigastric vessels distally, which serve as the vascular pedicle, and excised. Finally, the muscle is released from its origin at the pubic crest and symphysis pubis. 19
The MARF has many advantages, including an ample supply of subcutaneous fat, which can be helpful in a reconstructive procedure of an obese patient that requires ample subcutaneous fat at the recipient site. Conversely, some surgeons avoid the rectus flap in obese patients for the same reason, since it may require thinning of the flap once it is removed. 46 This may be less applicable in the case of pediatric patients who tend to have lower body mass indices than adult patients. The RMFF offers an ample pedicle length, which has been described as being as long as 18 cm, and it is useful for patients with defects distant from recipient vessels or damaged vessels at the recipient site. 45 This is typically less of an issue in the pediatric patient due to the smaller anatomy and fewer comorbidities, such as atherosclerosis or previous tissue transplants. Use of the MARF may be preferred over the RMFF in the pediatric patient undergoing maxillary defect repair given that many sources have shown that vascularized fat has a much lower rate of atrophy than muscle. 47 – 49 Thus, for a pediatric patient, it may be more prudent to opt for the MARF, which contains less muscle than the RMFF, with the hope of preventing future atrophy and preserving function and aesthetics in the long-term.
The RMFF has been described as a suitable flap for use in complex midfacial defects, including maxillectomy defects that require medium-to-large surface area volume flaps with muscle to provide bulk. One of the advantages of the rectus flap in those cases is the ease with which surgeons can create multiple skin islands that can be used to repair defects in the nasal and palatal tissues concurrently as, for example, in the case of a maxilla defect repair. 13 The RMFF has also been described as useful in the repair of a skull base defect in the pediatric patient. Iida et al described a case in which an RMFF was used to repair an anterior skull base defect in a one-year-old child. The surgeons opted to include 3 cm of the rectus abdominis muscle in the flap while leaving 1 cm of the muscle in place in that case. 50 By doing so, they used a thicker, more substantive barrier while attempting to limit the potential for long-term complications at the donor site. In contrast, Duek et al described the MARF as being particularly suitable for reconstruction of pediatric anterior skull base defects, specifically because the vascularized adipose tissue in the flap is less likely to atrophy over time, as mentioned above. 8
Donor-site morbidity for the rectus free flap has been reported as being low by many sources in the literature, but patients who have undergone abdominal surgery in the past need special consideration since the blood supply to their rectus flap may be compromised. 51 – 54 The risk of an abdominal hernia may also be increased if donor-site repair is not adequately accomplished, which is something that should be borne in mind in the pediatric patient whose body is still developing. 44