Due to the aesthetic and functional importance of the oral cavity, surgical defects caused by cancer in this region, if not repaired in time, may lead to disfigurement, masticatory disorders, voice changes, swallowing difficulties and other serious consequences, as well as the resulting psychological and social support problems. With the development of reconstructive surgery techniques, especially the widespread use of vascularized free tissue flap transplantation, not only does it ensure more extensive and complete resection of oral cancer, but also makes it possible for such patients to obtain good appearance, function and quality of life.
Therefore, whenever possible, immediate reconstruction (first-stage reconstruction) should be performed for postoperative defects in oral cancer, and the idea of postponing reconstruction (second-stage reconstruction) to facilitate monitoring of tumor recurrence has been gradually abandoned.
More than 30 years ago, the goal of postoperative defect repair after oral cancer was only to close the wound to avoid serious complications [2]. Today, good closure of the wound with the aim of obtaining a one-stage healing remains one of the main goals of reconstruction in this region. In advanced oral cancer, the widely accepted treatment option is surgery + postoperative radiotherapy [3,4], and the optimal timing of postoperative radiotherapy should be within 4-6 weeks postoperatively, as delayed timing will result in decreased control rates and/or increased radiation dose [5]. Therefore, the significance of one-stage wound healing is not only to shorten the hospital stay and relatively prolong the patient’s limited life time; more importantly, it is not to delay the subsequent radiation therapy, thus potentially increasing the local control rate and tumor-free survival rate of patients.
Maximizing the function and shape of the patient is another important goal of reconstruction in this region. According to the traditional view, the choice of reconstruction modality should follow a so-called ladder, starting with the simplest methods, such as direct suturing and free skin grafting, and then, in case of failure or as a last resort, trying higher-level methods, such as local flaps and tipped (muscle) flaps; finally resorting to vascularized free tissue flaps. It is now widely accepted that the best reconstructive approach for the patient’s form and function should be considered, for example, in young patients with mandibular defects, a vascularized free bone flap should be preferred over a reconstructive plate combined with a tipped myocutaneous flap.
Advances in microsurgical techniques have made free flaps at least as reliable as regional flaps, with success rates of over 95% for experienced plastic surgeons. Of course, the regional flap requires relatively little skill and is much easier to master. In fact, the traditional view of stepwise reconstruction was an anachronism due to the limitations of technology and experience at that time, but modern oral cancer defect repair and reconstruction should no longer be confined to this view. Of course, the selection of reconstructive surgery should also take into consideration the patient’s age, general condition, needs, economic status, disease stage and prognosis, etc.
1. Mandibular defect
As long as technically possible, most of the mandibular defects should be reconstructed. Of course, factors such as prognosis, general condition, site of bone defect, extent of soft tissue defect, and the patient’s economic status and needs should be taken into consideration.
(1) Reconstructive mandibular surgery may not be considered for patients with poor general condition, who cannot tolerate prolonged surgery, or who have advanced cancer and are not expected to survive for more than a few months.
②Unilateral posterior or ascending mandibular defects may cause deformities such as mandibular deviation and depression of the inferior part of the face, but as long as the contralateral teeth are intact, the functional defects are relatively minor.
(3) The middle portion of mandibular defect can lead to serious deformity and functional impairment, and should be repaired if possible.
1.1 Non-vascularized bone graft
Mandibular defects caused by malignant tumors of the oral cavity are usually difficult to provide a good soft tissue bed for non-vascularized bone grafts. The survival rate of such bone grafts is low due to infection; even if they do survive, long-term bone resorption can significantly affect the outcome of the repair. Therefore, the following conditions should be met for the use of this method:
(i) unilateral, short (less than 125 px) bone defects;
(ii) No significant intraoral mucosa or soft tissue defects;
(iii) No previous treatment and no need for postoperative radiotherapy.
1.2 Reconstructive titanium plate
The main problems encountered when reconstructing the mandible using reconstructive titanium plates are:
(i) functional stresses in the mandible lead to loosening of the titanium nail and fracture of the titanium plate.
Although the hollow titanium nail osseointegrated reconstruction plate system is superior to the common solid screw metal plate in preventing plate rejection and exposure, the serious long-term complications, such as plate exposure and fracture, cannot be ignored compared with vascularized free bone flaps.
Studies have shown that up to 30% of these patients still require salvage surgery with a vascularized free flap. To prevent titanium plate exposure, a combination of reconstructed plates and soft tissue flaps can be used. Soft tissue flaps include tipped flaps, such as the pectoralis major flap, and free flaps, such as the forearm flap and rectus abdominis flap. In our opinion, reconstructive plate combined with free flap has many disadvantages such as long and complicated operation time and the use of heterologous materials, so vascularized free bone flap should be preferred as long as the patient can tolerate microsurgery.
1.3 Vascularized free bone flap
The vascularized free bone flap has become the mainstay of mandibular reconstruction and is a reliable treatment with satisfactory long-term results; the best aesthetic and functional results can be obtained with the use of condylar autograft and osseointegrated dental implants. The four most commonly used bone flaps are the free radial forearm flap, the iliac crest myocutaneous flap, the scapular flap, and the fibular flap, each of which has its own advantages and disadvantages.
The fibular flap has become the preferred and universal method for mandibular reconstruction because of its long bone supply, excellent bone quality for implant placement, multiple osteotomies for precise three-dimensional contouring, distance of the donor area from the head and neck for “double surgery”, and minimal postoperative complications.
Our experience with the use of the fibular flap includes:
If the clinical examination shows normal pulsation of the dorsalis pedis and posterior tibial artery, then angiography is not necessary; angiography is only indicated in cases of abnormal clinical examination of the lower extremity vessels, in cases of severe trauma to the lower extremity, and in cases of peripheral vascular disease. In addition, magnetic resonance is a good non-invasive detection method.
(2) Preoperative ultrasound Doppler flowmetry is routinely used to detect peroneal artery penetration, which can improve the accuracy and reliability of skin island design.
(3) The blood supply of the skin island is safe and reliable, and it has great flexibility in the repair of maxillofacial defects, which can be used not only for the repair of intra/extraoral soft tissue defects, but also as a postoperative observation window for the monitoring of the blood supply of the free fibular flap. Therefore, whenever possible, free fibula flap grafts should carry a skin island.
④The use of a modified preparation method can shorten the operative time, reduce the probability of vascular tip injury, and reduce donor complications.
⑤ For patients with surviving dentition, intraoperative temporary arch splinting and preformation of the defective bone segment with an arch bar can help ensure a good postoperative occlusal relationship; for patients without dentition and tumor breaking through the cortical bone, an external fixation device can be used to maintain the position of the broken bone.
(6) In patients with large intra- and extra-oral soft tissue complex defects, a fibular flap combined with a forearm flap or rectus abdominis flap, or a lateral femoral flap often achieves the best repair results.
(7) In order to solve the defect of insufficient height of fibula bone and poor implant placement, folded fibula bone can be used to reconstruct the mandible or to perform vertical distraction osteogenesis in the second stage.
2.Tongue defect
The tongue is a complex muscular organ, which plays an important role in mastication, swallowing, articulation, airway protection and oral hygiene maintenance. Reconstruction of tongue defects is the most critical factor to obtain good oral function, but the high specificity of tongue tissue and the resulting flexibility of tongue movement and complexity of sensory feedback make its reconstruction much more difficult than restoring static continuity of the jaws only.
Small defects of the tongue or tongue root are easy to repair and have little impact on tongue function; however, large tongue defects that result in dysfunction often require more complex repair. To achieve the goal of functional reconstruction, the movement, volume, and sensation of the tongue should be restored as much as possible [2]; for compound defects involving the floor of the mouth and/or mandible, eliminating dead space and reconstructing the tonic floor to maintain the normal position of the residual tongue in the oral cavity are important to restore function.
2.1 Lingual defects
For small defects that do not exceed 1/3 of the width of the tongue, direct suturing has little effect on tongue function. However, when the defect involves the mucous membrane of the floor of the mouth, a cutaneous skin graft can be used to avoid the restriction of tongue movement caused by direct suturing. To prevent the adverse effects of skin contracture, the tongue should be stretched and the flap prepared to the maximum diameter of the defect; care should be taken to secure the flap to ensure its viability. Tongue flaps are a good source of tissue for repairing small defects of the tongue, but as the defect grows larger, the use of tongue flaps may impair the function and shape of the tongue, so the indications should be strictly controlled and are generally not recommended.
A flap repair should be considered when the defect exceeds 1/3 of the tongue volume. As long as the residual tongue has intact motor innervation, the primary goal of reconstruction should be to ensure maximum mobility of the residual tongue, restore the volume and shape of the tongue and restore sensation as much as possible. When the size of the defect does not exceed 2/3, thin and soft tissue flaps such as frontal flap and forearm flap should be used. To isolate the tongue from the floor of the mouth to better preserve tongue movement, Urken et al. used a bilobed free forearm flap with sensory nerve anastomosis to reconstruct a hemiglossal defect with good results [26].
For large defects with more than 2/3 of the defect volume or even total tongue defects, vascularized free tissue flaps are the preferred method. Although thick and bulky tipped muscle flaps, such as the pectoralis major flap, are sufficient to repair the defect, the pulling of the tip and the relaxation of the tip over time can impede tongue movement. A thin, soft, sensory flap may reduce the restriction of residual tongue movement.
Koshima et al. emphasized the importance of eliminating dead space, providing good support for the residual tongue, and preserving tongue movement as much as possible when reconstructing large lingual defects with floor of mouth defects, and used a multileaf folding flap to achieve these goals. These goals were achieved by using a multi-lobed folded flap.
2.2 Tongue Root Defects
In the case of lingual root defects, in addition to consideration of the motion of the residual tongue root, the restoration of volume and sensation are also key factors to consider. Restoring tissue volume so that the new tongue can contact the soft palate and pharyngeal wall and reestablishing sensation as much as possible to prevent aspiration are important goals of tongue root reconstruction. For small lingual root defects, either direct suturing or posterior lingual body thrusting can be used.
If the tongue body is significantly displaced by pushing back, or if the tongue root defect is accompanied by a lateral pharyngeal wall defect, tissue flap repair should be considered, either a thin tipped flap or a sensitized forearm flap. In large defects of the tongue root, a forearm flap with additional subcutaneous tissue is prepared and embedded in the flap to obtain a volume that ensures contact of the new tongue with the soft palate and pharyngeal wall and that does not shrink over time.
Salibian et al. used an ulnar forearm flap to reconstruct a large lingual root defect with good results and concluded that a fleshy stem-like flap shape is important to maintain the motility of the residual tongue root, emphasizing that the method of repair is more important than the volume of the defect in influencing the outcome of functional tongue root reconstruction.
2.3 Total tongue defects
Total tongue defects or loss of innervation of the residual tongue tissue is the most challenging topic in tongue reconstruction. Tongue function is the result of the interaction between tongue movement and tongue volume. In cases of limited or even lost motion, restoration of tongue volume is particularly important.
Therefore, the main goals of total tongue reconstruction are to restore the volume and vertical height of the new tongue with a thick muscle flap or large flap, to maintain the position of the new tongue with a suspension method, to support the new tongue with a tensioned floor in the absence of the floor muscles, and to reestablish sensory and muscle contraction movements of the new tongue by anastomosis or grafting of sensory and motor nerves whenever possible. Sensory restoration of the new tongue is essential to induce a protective laryngeal reflex and prevent aspiration; while anastomosis of the motor nerve helps to reduce the degree of atrophy of the grafted muscles, but does not yet allow meaningful functional movement of the new tongue.
For repair of total tongue defects with preserved mandible, a subcutaneous fat-rich tissue flap is preferred over a denervated myocutaneous flap to restore volume to the new tongue in order to achieve good long-term tongue-palate contact. Over time, tipped myocutaneous flaps, such as pectoralis major and rhomboid flaps, may become gravity-dependent and may cause the tissues to sag, thereby pulling the new tongue downward; severe muscle atrophy due to loss of innervation may also reduce laryngeal protection and even affect articulation and swallowing.
Free tissue flaps, such as the rectus abdominis flap, may provide good long-term results [30]. The rectus abdominis flap can be adjusted in volume by removing some of the subcutaneous fat and can be sutured directly to the mandible or masticatory muscle stump using strong tendon sutures or perforated sutures, thus creating a soft tissue platform at the floor of the mouth to support the surface fat and skin and maintain the height and position of the new tongue. To achieve both goals of good sensation and sustained volume repair, free lateral upper arm flaps and anterolateral femoral flaps are used. The problem is that it is difficult to suspend and maintain the position of the new tongue, but this can be improved by removing some of the epidermis and burying the subcutaneous fat into the flap.
3. Buccal defects
The defect caused by buccal tumor resection is often extensive, sometimes even involving the whole layer, resulting in a cavernous defect. Care should be taken to maintain normal mouth opening and fullness of the cheek as much as possible. For particularly early lesions, where the mucosal resection is small and superficial (not through the muscle layer), free skin grafts can be used, and if adjacent to the posterior cheek, buccal fat pad or palatal flap can be used. If the defect is extensive and deep to the muscle layer, free flap repair should be preferred, such as forearm flap, anterolateral thigh flap, etc.; posterior cheek defect can also be repaired with frontal flap and pectoralis major flap. For cavernous buccal defects, a folded forearm flap is preferred. Two tissue flaps can be used, such as frontal flap + pectoralis major flap, etc.
4. Oral mandibular composite defect
Most postoperative oral cancer defects can be repaired by a single tissue flap, but for some large oral mandibular composite defects, a single tissue flap is often unable to meet the need for simultaneous restoration of shape and function. For such defects, a better repair method is the double free flap grafting technique. The most common combinations of flaps are: iliac flap + forearm flap, fibula flap + forearm flap, fibula flap + rectus abdominis flap, and fibula flap + anterolateral thigh flap. For large oral mandibular complex defects that cannot or do not cooperate with double free tissue flap grafting, free tissue flap combined with tipped pectoralis major flap grafting can achieve more satisfactory results.
5.Maxillary defect
For the composite tissue defect left after maxillectomy, the traditional pseudoprosthetic repair has the disadvantages of poor retention, inability to overcome the oral-nasal cavity or oral maxillary sinus communication, difficulty in cleaning, and unsatisfactory restoration of mastication and speech function of patients. In the early stage of repair, various tipped tissue flaps were used to fill the dead space of the defect, but due to the limitation of rotation arc and tissue volume, it was difficult to obtain the expected results. The application of microsurgical techniques has brought the repair of maxillary defects into a new historical period. The use of various free tissue flaps, especially free bone flaps combined with dental implants, has allowed the repair of maxillary defects to move from the elimination of dead space to a functional repair.
The use of free fibula composite flap for maxillary bone reconstruction can complete the repair of soft and hard tissue defects in one phase, and completely close the oral and nasal cavity, thus obtaining good shape and articulation function. When repairing maxillary defects with free fibula flaps, the maxillary sinus cavity can be filled with muscle, the alveolar process can be reconstructed with fibula segments, and the oral mucosal defects can be repaired with skin islands.
In order to overcome the disadvantages of a bulky skin island that affects the retention of the flap and the need for second-stage thinning to facilitate denture insertion, we propose the use of a free fibula-thumb flexor fascial flap without a skin island to repair maxillary defects. For the unilateral Class III (Brown classification) maxillary defect involving the infraorbital wall, the free fibula block abandoned during maxillary reconstruction was used to reconstruct the infraorbital wall, which not only restored the infraorbital wall but also partially restored the anterior maxillary sinus wall and effectively prevented the postoperative depression of the infraorbital area due to the atrophy of the thumb flexor muscle.
The bilateral maxillary defects were not suitable for pseudoprosthetic repair because there was no solid abutment for pseudoprosthesis. The use of free fibula flaps for the repair of class I and II bilateral maxillary defects can achieve satisfactory results. In addition to the free fibula flap, a double-skin island folded rectus abdominis flap or anterolateral thigh flap can also be used for the repair of bilateral maxillary defects of category III. For the elderly patients with class I and II maxillary defects, a relatively less invasive forearm flap or lateral upper arm flap can be used to cover the wound.
6.Summary
After more than 30 years of development and evolution, free tissue flap grafting has become the most widely used and most effective conventional technique for postoperative reconstruction of oral cancer defects. The double free tissue flap grafting technique provides an ideal option for the repair of large oral mandibular composite defects. The application of sensory flaps to repair intraoral defects provides a good basis for the restoration of oral function. The combination of vascularized free bone flap and dental implant technique can restore the patient’s shape and masticatory function, and achieve the real sense of functional jaw reconstruction.