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Surgery
The field of reconstructive microsurgery has witnessed considerable advancements over the years, driven by improvements in technology, imaging, surgical instruments, increased understanding of perforator anatomy, and experience with microsurgery. However, within the subset of microvascular head and neck reconstruction, novel strategies are needed to improve and optimize both patient aesthetics and post-operative function. Given the disfiguring defects that are encountered following trauma or oncologic resections, the reconstructive microsurgeon must always aim to innovate new approaches, reject historic premises, and challenge established paradigms to further achieve improvement in both aesthetic and functional outcomes.
- innovation head and neck reconstruction
- alternate donor site
- virtual surgical planning
- immediate dental implants
1. Introduction
The field of reconstructive microsurgery was founded on principles described by Alexes Carrell, which laid the foundation for the field of vascular surgery and, eventually, transplant surgery [1,2,3]. Over time, these foundations ushered in an era of microvascular surgery, allowing the reconstruction of complex defects that previously could not be adequately corrected, resulting in disfiguring and suboptimal outcomes [4]. The use of free flaps has not only emerged as the gold standard for the reconstruction of a variety of different defects but has also proven to be superior to pedicled flaps [5,6,7,8]. While these locoregional options are important to incorporate into the algorithmic approach to head and neck reconstruction, microsurgery has revolutionized our approach from simply trying to achieve a closed wound to truly maximizing patient satisfaction and restoring both form and function.
Numerous studies have demonstrated high success rates with microvascular reconstruction of head and neck defects [9]. As such, the reconstructive microsurgeon can now focus on the nuances of refining the reconstruction and innovating new strategies to improve outcomes. In fact, aside from simply considering the closure of the defect, standards for achieving the most optimal aesthetic outcomes are becoming increasingly important as well, where patients’ quality of life and satisfaction are affected by which donor site provides the aesthetic and functional result [10]. These strategies often incorporate both new and conventional flap options, and the reconstructive microsurgeon must be well-acquainted with both soft tissue and bony reconstruction. Alternate flap donor sites such as the lateral arm or the medial sural artery perforator (MSAP) flap are also gaining more traction and may provide a superior color match and improved donor site morbidity, and should be included in the reconstructive algorithm, particularly in the setting of a prior flap loss, recurrence, or the need for multiple free flaps [11,12,13]. In combination with soft tissue reconstruction, the reconstruction of bony defects has also witnessed tremendous advances, both in terms of technological advancements as well as the incorporation of different donor sites [14]. The use of virtual surgical planning (VSP) and medical modeling has rapidly grown in popularity and is becoming the gold standard in mandible and midface reconstruction at many institutions [15,16,17,18].
2. Soft Tissue Reconstruction
In the field of head and neck reconstruction, a variety of different soft tissue defects can be encountered that range from external skin coverage to volume replacement to the restoration of speech and swallowing function. As such, the reconstructive microsurgeon needs to have a reliable algorithm to address soft tissue defects of the scalp to a parotidectomy and also be able to reconstruct an intraoral or glossectomy defect as well as an esophageal defect [22,23,24,25]. There is little debate regarding the workhorse flaps in head and neck reconstruction, namely the anterolateral thigh (ALT), radial forearm, and latissimus dorsi muscle or myocutaneous flaps have long been the most popular donor sites. Given the reliable anatomy, large caliber vessels, adequate pedicle length, ability to tailor flap size, and minimal donor site morbidity, most defects can be reconstructed with one of these flaps.In cases when workhorse flaps are unavailable, the reconstructive microsurgeon must have exposure and comfort with alternate donor sites. While used predominantly for breast reconstruction, the profunda artery perforator (PAP) flap is an extremely reliable donor site with reliable anatomy with sufficient pedicle length, although the artery tends to be smaller than the ALT. The perforator anatomy has been well-mapped and anecdotally is more reliable than the ALT perforators [27,28]. Aside from the reliable perforator anatomy, the PAP allows for simultaneous harvest concurrently with the resection and can be harvested in the supine frog-leg position. For head and neck reconstruction, the PAP is best harvested in a longitudinal fashion allowing identification and selection of the largest perforator. When a thinner flap is needed, and the radial forearm is not an option, an ulnar forearm or ulnar artery perforator (UAP) can be considered. The ulnar artery is a large caliber artery comparable to the radial artery; however, careful attention must be paid to avoiding injury to the ulnar nerve. The microsurgeon should also be aware that the pedicle to the UAP is considerably shorter than the radial forearm flap [29,30].
In contrast to the radial and ulnar forearm flap, the donor site of the lateral forearm flap needs to be closed primarily and should not be skin grafted because the lateral epicondyle is often exposed after harvesting the flap. Harvest of the lateral forearm often provides thinner tissue and provides a significantly longer pedicle length comparable to the radial forearm flap. However, the width of the flap is limited to the pinch of the skin at the donor site, which is typically approximately six centimeters [31].
Regarding the MSAP flap, the perforator location has poor reliability. While there are landmarks that serve as a guide for designing the flap, the perforator anatomy is much less reliable than many of the other flaps. Therefore, the MSAP flap is often harvested in a freestyle fashion. Aside from the location of the perforators, the perforators may not arise from the medial sural artery resulting in a much smaller caliber artery, typically less than two millimeters. Aside from the availability of a myriad of donor sites, new technologies such as the use of intraoperative perfusion imaging using indocyanine green have also become routine practice, particularly when more volume is needed to avoid risks of partial flap loss [33,34].
3. Virtual Surgical Planning and CAD-CAM
The use of medical modeling and virtual surgical planning (VSP) has become mainstream and is generally now considered the new gold standard in bony head and neck reconstruction at many centers. The earliest descriptions using high-resolution CT scans to plan the resection and reconstruction using a free fibula flap demonstrated proof of concept and paved the way for further advancements and developments using this technology [35,36,37]. The reconstructive surgeon is now able to couple CT angiograms of the donor site with the three-dimensional bony models allowing for detailed planning of both the skin paddle and bony components and ultimately resulting in a more reliable reconstruction [38,39].
With improvements in technology and imaging, VSP and computer-assisted design and computer-assisted modeling (CAD-CAM) have expanded beyond simply providing cutting guides and templates. Patient-specific customized titanium plates can now be milled or printed to intricate and precise configurations without compromising the strength and durability of the construct [40]. Printed reconstruction plates offer the advantage of lower profile design while minimizing the hardware burden. While early experience using VSP may have been prohibitively expensive, some institutions have developed in-house systems rather than outsourcing the design and modeling to commercial vendors [41]. Regardless of the actual costs associated with CAD-CAM, numerous studies have demonstrated the benefits of cost-utility with shorter operative times and potentially improved outcomes [42,43].
4. Dental Rehabilitation
CAD-CAM technology has also ushered in an era of immediate dental rehabilitation where pre-determined screw holes can be designed to avoid interference with dental implants that are placed at the time of the fibula flap reconstruction. For the majority of patients who undergo a free fibula flap, radiation is often critical for the control of microscopic disease, which increases the risks and complications, often precluding patients from dental implants altogether. While some reports have demonstrated successful implant engraftment into a radiated fibula, other studies have demonstrated increased rates of implant failure in radiated flaps [47,48].
Another noted benefit of CAD-CAM mandible reconstruction was fortuitously noted in the setting of a posterior mandibulectomy where the condyle has been sacrificed. Historically, reconstruction was commonly performed using a soft tissue flap simply to restore the volume; however, patients, unfortunately, suffered from a greater degree of malocclusion as well as a suboptimal cosmetic result [53,54].
5. Nerve Reconstruction and Reinnervation
Aside from the advancements made in bony reconstruction, strategies have been investigated to address other deficits resulting from a composite mandibulectomy. The inferior alveolar nerve and its distal continuation, the mental nerve, are routinely sacrificed with the resection, which results in sensory deficits in the chin and lower lip. Sensory restoration of the mental nerve may now be achieved through nerve coaptation with the use of an intervening nerve allo- or autograft. While studies have demonstrated spontaneous recovery of lower lip sensation following a mandible resection [58], advancements in nerve repair and restoring sensation have proven effective in other aspects of head and neck reconstruction, such as in the reconstruction of glossectomy defects where the creation of a sensate flap has proven superiority in optimizing patients’ speech and swallowing function. A sensory nerve can routinely be harvested with the flap, such as the lateral antebrachial cutaneous nerve with the radial forearm flap or the lateral femoral cutaneous nerve with the ALT flap. Despite the deleterious effects of post-operative radiation therapy, subtle improvements in sensory restoration may provide potential benefits in improving patients’ quality of life.
6. Alternate Bone Flaps
The use of VSP has also revolutionized the reconstruction of the midface. Custom-3D printed titanium plates are also used for multi-segment stabilization of bone flap reconstruction of the maxilla and reconstruction of the orbit. Just as restoration of proper alignment and occlusion is critical in optimizing functional outcomes for the mandible, the establishment of precise positioning of the globe is vital to restoring proper binocular vision for patients who undergo an orbitomaxillectomy. The advent of customized 3D-printed titanium plates based on patients’ preoperative imaging maximizes the chances of achieving normal vision [60]. However, hardware burdens in the midface and peri-orbita are at increased risk for delayed hardware infection given the exposure to and involvement of the nasal and maxillary cavities. The oncologic patient is often at elevated risk for hardware complications, including infection, extrusion, and non-union, given the need for post-operative radiotherapy.
Therefore, vascularized tissue remains the gold standard to minimize issues with hardware infection, exposure, and the need for removal. While the use of non-vascularized bone grafts, such as the rib and iliac crest, is also a reasonable option, the preference is to use vascularized bone flaps in the midface when possible. The fibula and scapula continue to be widely used in osseous flaps in the midface region. A recent addition to the armamentarium is the medial femoral condyle (MFC) flap [61]. The MFC is most commonly used in the reconstruction of extremity defects, in particular, scaphoid non-unions or avascular necrosis of the carpal bones, but its relatively reliable anatomy can also be harnessed for the reconstruction of bony midface defects.
7. Facial Reanimation
The sequelae of facial paralysis from skull base or parotid tumors create significant morbidity, and for patients who undergo a radical parotidectomy, the aesthetic deformity and functional impairments are dramatic. Historically, free flaps were used to correct the volume deficit following a radical resection, while reconstruction of facial nerve defects was achieved using static approaches and nerve grafting [63,64]. Given the relatively older age of most patients as well as the requisite need for adjuvant radiation, serious doubts pervaded the benefit and functionality of a functional muscle transfer in this patient population. Consequently, the primary modality for reconstruction in this setting focused on more conservative approaches. Previous studies have demonstrated restoration of resting tone for some patients with nerve grafts, even in the setting of adjuvant radiation [64].
8. Conclusions
A number of novel advancements have been achieved in microvascular head and neck reconstruction with the goal of optimizing and maximizing both form and function. Ultimately, it is the responsibility of all surgeons and physicians to continue to innovate and develop novel strategies in order to improve and enhance the quality of life of patients, minimize complications, and optimize outcomes.
This entry is adapted from the peer-reviewed paper 10.3390/medicina59071194
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