22 Reconstruction of Alveolar Ridge
Summary
Defects of the alveolar ridge can lead to significant loss of function and poor aesthetic outcomes for head and neck cancer patients. The ideal reconstruction of the alveolar ridge improves both the form and function of the head and neck cancer patient, specifically restoring articulation of speech, potential for dental implants, and adequate cosmesis. Restoration of the alveolar ridge may be achieved with free grafts, locoregional flaps, or may require microvascular techniques for free tissue transfer. In considering restorative options, the advancements in new dental and oral surgery techniques should be employed to provide optimal results to patients.
22.1 Introduction
The approach to reconstruction of the alveolar ridge is multidisciplinary, involving head and neck reconstructive surgeons, oral surgeons, prosthodontists, and speech-language pathologists. As described by Chen and Zhang in 1992, the goal of reconstruction of the alveolar ridge is twofold: to restore contour and to restore continuity. 1 Adequate reconstruction requires bony structural support and viable soft tissue coverage of the substructure. The ideal reconstruction of the alveolar ridge improves both the form and function for the head and neck cancer patient, specifically by restoring articulation of speech, potential for dentition, and adequate cosmesis. 2
The concepts pertaining to the reconstruction of the alveolar process overlap with those for segmental and marginal mandibular defects. As such, this chapter will focus principally on soft tissue reconstructive options, allogenic materials, and tissue-engineered constructs.
22.2 Anatomic Considerations/Relevant Anatomy
The alveolar ridge presents unique reconstructive challenges due to its specific anatomic features (▶ Fig. 21.5). Defined by the thickened ridge of bone that contains dental alveoli (tooth sockets), the alveolar process is located at the superior surface of the mandible and the inferior surface of the maxilla. Important components of this bone include the periodontal ligament and the compact lamina dura to which it attaches.
The blood supply to the alveolar process and teeth originates from the internal maxillary artery, which gives rise to the inferior alveolar artery, supplying the mandibular alveolus, and the posterior and anterior branches of the superior alveolar artery, supplying the maxillary alveolus. The innervations of the superior and inferior alveoli and teeth are the maxillary and mandibular divisions of the trigeminal nerve, respectively. In the edentulous patient, the alveolar portion of the mandible gradually resorbs, putting the inferior alveolar nerve at increased risk of injury during any surgical intervention.
The alveolar process of the maxilla contains the opposing maxillary dentition. The bony projections are bordered by corresponding soft tissue sulci laterally, the gingivobuccal and gingivolabial sulci. Medially, the tongue articulates against the dentition and alveolar ridge, contributing to speech clarity. The alveolar ridges provide horizontal projection to the overlying lip soft tissue, creating normal facial contour. The tissue of the buccal and upper gingival mucosa is tightly bound to the alveolar ridges and this covering overlies bone of variable thickness and structural integrity.
Overall, any defect of the alveolar ridge can lead to significant loss of function and poor aesthetic outcomes for head and neck cancer patients. Loss of dentition or of occlusal surface area for restorative dental prosthetics may lead to weight loss and decreased quality of life. 3 , 4 Loss of support for facial soft tissue has ramifications for speech, articulation, and oral competence. Finally, the aesthetic value of both dentition and bony support for facial soft tissue leading to alterations in social smile, facial profile, and projection should not be overlooked.
22.3 Diagnosis and Evaluation
22.3.1 Patient Selection
In preparing for reconstruction of the alveolar ridge, it is crucial to consider the patient’s specific presentation, including comorbidities, body mass index (BMI), mental status, desire for dentition, size and location of the tumor, previous surgery, prior radiation, and need for postoperative radiation therapy. The surgeon must evaluate the status of current dentition and the preoperative mandibular bone height.
22.3.2 Evaluation of Defect and Determining Reconstructive Options
As with any preoperative evaluation, the status of the tumor, including anatomic location, size, extent of invasion, and amount of bony involvement or destruction, must be carefully assessed. Specifically, when considering the alveolar ridge, reconstructive requirements will be radically different depending upon location and extent of disease. A small defect restricted to the ridge will be repaired much differently, utilizing local tissue rearrangement or free grafts, when compared to an extended defect that requires restoration of adjacent soft tissue structures, which might require a free tissue transfer for reconstruction.
As with all oral cavity defect reconstruction, areas of importance to reconstitute include the gingivolabial sulcus, gingivobuccal sulcus, and lateral tongue gutter or floor of mouth. These anatomic structures are challenging to recreate, and blunting, excess bulk, and/or scarring of these areas may lead to difficulties with speech and swallowing as well as improper fitting of dental restorative prosthetics. Often times, delayed secondary revision surgeries or vestibuloplasties are required.
22.4 Surgical Considerations and Approaches
22.4.1 Approaches to the Alveolar Ridge
Depending on the exposure necessary for both the oncologic excision of the tumor and the reconstruction of the defect, surgical approaches to the alveolar ridge include transoral, transcervical, and mandibular split, or a combination of the latter approaches. Reconstruction can include skin graft, local or regional flaps, or free tissue transfer. The location of facial, angular, and superficial temporal vessels may allow for more minimal access procedures when free flaps are employed. 5
22.4.2 Ideal Characteristics for Reconstruction of the Alveolar Ridge
An ideal reconstruction of the alveolar ridge would provide thin and pliable soft tissue to allow optimal fit into the oral cavity without persisting excess bulk, conform to underlying bony structures, and be sufficiently durable to support the functions of the ridge, including mastication. Specific to the alveolar ridge, the ideal reconstruction allows for dental rehabilitation with implants or prosthodontics for both function and cosmesis. In the case of bony deficit, an osseous component to the reconstruction may be required to restore ridge height and provide a stable platform for soft tissue reconstruction. The ideal reconstruction creates minimal donor site morbidity and is able to be harvested distal to the site of resection, allowing for a two-team surgical approach. In the oral cavity, reconstruction of the alveolar ridge provides a barrier to infection by covering surgically exposed structures with viable soft tissue to prevent saliva and oral flora from extending into the neck. In addition, soft tissue coverage improves postoperative pain. The ideal reconstruction is able to integrate with surrounding soft tissue and mucosalize over time to mimic surrounding tissues. The complexity of this region creates surgical challenges and often no single ideal approach exists to meet all the above goals simultaneously. Thus, reconstructive planning depends on patient’s wishes, patient-specific anatomy, and surgeon’s preference within a multidisciplinary team.
22.5 Reconstructive Options
22.5.1 Secondary Intention, Primary Closure, and Buccal Advancement Flap
For very small, superficial defects, healing by secondary intention may be an option in some patients. However, coverage of the defect with soft tissue improves wound healing and decreases postoperative discomfort. Unfortunately, primary closure of gingival edges recruited from both the lingual and buccal sides of the defect is often not feasible after an oncologic extirpative surgery for alveolar ridge tumors. In select cases of a small, easily accessible, and soft tissue only defect of the alveolar ridge, a buccal advancement flap may be employed to free more local tissue for coverage. Branches of the maxillary artery (buccal artery, anterior, middle, and posterior superior alveolar arteries) richly supply the buccal mucosa, and leaving a broad base to the elevated mucopericondrial flap allows for a sufficient vascularity to the flap. Lengthening incisions can be made through the periosteum at the flap base when needed. 6 The primary drawback to this flap is blunting of the vestibule, which can require revision vestibuloplasty. However, in most cases, this improves with time as the buccal mucosa accommodates to the shape of the underlying bone.
22.5.2 Free Grafts: Full and Split Thickness Skin Grafts, Dermal Matrix Substitutes, and Bone Grafts
Skin Grafts
Full and split thickness skin grafts can be used to cover small defects of the alveolar ridge that are unable to be covered by local advancement of surrounding tissue. These options are possible over a well-vascularized wound bed, such as the periosteum or the bone marrow. Free skin grafts have minimal chance to grow over bare cortical bone surfaces, as the graft initially survives by diffusion of nutrients from fluids and blood in the wound bed into the graft until neo-vascularization and integration occurs. Convenient sites for full thickness skin graft harvest include the pre and postauricular skin (for small defects), supraclavicular skin, and the skin of abdomen or groin (for larger defects). Drawbacks of the use of skin grafts primarily include the potential for wound retraction and the relatively thin and delicate nature of the skin grafts that puts the graft’s healing at risk on occlusive surfaces. Nonetheless, a temporary barrier serves as an advantage during healing, and some surgeons may opt for skin grafts, even while assuming they may eventually fail to incorporate.
Dermal Matrix Substitutes
Cadaveric-derived acellular, nonimmunogenic dermal substitutes, originally used for skin grafting, have gained popularity in bony defect coverage within the oral cavity. 7 , 8 Girod et al demonstrated that acellular dermal matrix (ADM) had advantages over split thickness skin graft (STSG) in limited oral cavity mucosal defects, including decreased surgical time and donor-site morbidity with improved quality of life. 9 The bipolar organization of ADM allows for epithelial cell migration along the basal lamina and fibroblast/angiogenic cell migration along the dermal matrix. 10 Studies examining their use in bone coverage along the alveolar ridge have demonstrated good incorporation, increased gingival thickness, and keratinization of tissue with an acceptable cosmetic result. 7 , 11 – 13 Certain skin substitutes provide temporary wound coverage, barrier protection, and may secrete cytokines and growth factors that promote epithelialization (e.g., Dermagraft ®), while others restore the epidermal barrier to become integrated within the wound (e.g., Alloderm ®).
It is important to note that, as with native skin grafts, skin substitute grafts will only be able to promote cell growth and heal wounds in a well-vascularized recipient site. For example, these products may be placed over periosteum, peritenon (fascial layer around tendon providing vascular supply to overlying skin graft), fascia, and muscle. However, cortical bone would need to be drilled down to expose marrow in order to support grafted material and allow for epithelialization.
Bone Block Grafting
Bone grafts, either autogenic or allogenic, are employed for the restoration of the alveolar ridge when severe resorption has occurred or a large marginal bone defect has been created. A variety of free bone grafts have been used to successfully add contour and bulk to the alveolar ridge. Deproteinized bovine bone graft material as well as deproteinized cadaveric human bone graft material have been used for alveolar ridge augmentation. 14 However, autogenic bone graft remains the gold standard, when available. Autogenic block bone grafts can be taken intraorally from the chin or mandibular ramus, or can be harvested distantly from the anterior iliac crest or rib. Autogenous bone can be harvested as block graft from the anterior iliac crest 1 and can be implanted en bloc or as particulate to restore alveolar ridge height and depth when deficient after oncologic resection. Free bone grafts may also be used as second stage reconstruction after fibular free flap mandibular reconstruction when the bony contour remains insufficient for dental restoration.
Jacotti et al described the use of allogenic block grafts wrapped in allogenic pericardial membrane for the atrophic mandible needing dental implantation. 15 After grafting, there was histologic evidence of healthy lamellar bone which was reliably used for dental rehabilitation. Krasny et al have similarly described the use of allogenic, frozen, radiation-sterilized block grafts for the restoration of atrophic alveolar ridge prior to dental rehabilitation with implants. 16
Current research has focused on synthetic substitutes for allogenic bone graft material. Calcium phosphate ceramics (alone or in combination with calcium sulfate), calcium sulfate hemihydrate, and hydroxyapatite have been demonstrated to be viable options for reconstruction of the alveolar ridge in the case of bone loss after dental extractions and may be useful for smaller bony alveolar ridge defects. 17 – 19 It should be noted that for patients who have been radiated, or for whom radiation is planned, bone graft and synthetic graft material should be wrapped with vascularized tissue in the form of a free flap, for example, a free fascia lata flap wrapped around a block bone graft. Without a reliable blood supply, graft material will be unlikely to integrate in these patients.
22.5.3 Local Pedicled Flaps: Palatal Island Rotational, Buccal Fat Pad, and Facial Artery Musculomucosal (FAMM) Flaps
Palatal Island Rotational Flap
The palatal island rotational flap was introduced for cleft palate repair by Millard in 1962, and its indications for use were expanded by Gullane for reconstruction of other oral cavity defects in 1977. 20 This flap is pedicled off the paired greater palatine arteries, branches of the descending palatine artery. Notably, one artery is sufficient to supply a palatal mucoperichondrial flap that spans the midline of the palate. The flap is raised sharply from the bone of the hard palate, and incisions are designed based on the anatomy of the extirpative defect. The procedure has limited donor site morbidity, as the hard palate granulates in and heals secondarily. 21 This rotational flap is best used to reconstruct posterior maxillary alveolar ridge defects while anterior maxillary alveolar ridge defects are unable to be reached due to geometry of rotation and limited pedicle length.
Buccal Fat Pad Pedicled Flap
The buccal fat pad pedicled flap offers a vascularized source of soft tissue that is easily accessible through the oral cavity and can be mobilized to provide soft tissue coverage for alveolar ridge defects. 22 While initially utilized primarily for closure of oroantral fistulas, the buccal fat pad has been demonstrated to be useful in the closure of defects after oncologic resection of oral cancer, including those involving the alveolar ridge. 23 , 24 The buccal fat pad has several advantages over other sources of tissue adjacent to the alveolar ridge that make it an excellent reconstructive tool. 25 Anatomically, the buccal fat pad is lobulated and easily mobilized while maintaining excellent vascularity. This robust blood supply makes it advantageous when compared to free graft in cases of compromised wound bed vascularity or wound healing concerns, such as radiated fields or in diabetic patients. In addition, the buccal fat pad can supply enough tissue to cover approximately 10 cm2 and does not seem to significantly atrophy with age, thus remaining a viable option in the elderly. 26 A limitation of this flap is that, although it easily reaches more posterior alveolar ridge defects of the maxilla and mandible, even with maximal mobilization of the vascular pedicle, it will not adequately reach more anterior defects.
Surgical technique begins with identification of Stenson’s duct to ensure the duct is not harmed during the procedure. Next, a mucosal flap is elevated and the buccinator muscle is divided to identify the fat pad. Gentle delivery of the fat pad allows the fat pad to herniate through the muscles and rotate into position without injuring the vascular supply. This may be allowed to epithelialize or used in combination with other local flaps or graft materials for a superficial layer, such as a skin graft or even dermal matrix substitutes. 6
Facial Artery Musculomucosal (FAMM) Flap
The facial artery musculomucosal (FAMM) flap is perhaps the best suited of the smaller rotational flaps to reconstruct soft tissue alveolar ridge deficits. The FAMM flap was initially designed as a combination of the concepts of the nasolabial and buccal mucosal flaps as described by Pribaz et al in 1992. 27 It is based off of the facial artery and can be designed on either antegrade or retrograde flow through the artery, making it geometrically versatile for oral cavity reconstruction. It provides a thin, pliable soft tissue covering for alveolar ridge reconstruction that has a robust vascular pedicle. 28 One limitation of this flap is that the width of the flap is usually limited to less than 2 cm due to the need to close the donor site primarily while leaving enough laxity to prevent scarring and trismus. 29
Briefly, surgical technique begins with first identifying the course of the facial artery, typically using doppler ultrasound. The position of the posterior cut is limited by the need to remain anterior to Stenson’s duct, and the anterior cut should be at least 1 cm posterior to the oral commissure. The width of the flap should be planned based on the size of the defect. However, it is limited to less than or equal to 2 cm to avoid tension during primary closure of the donor site. The facial artery is isolated by making an incision through mucosa, submucosa, and buccinator, usually at the most distal aspect of the flap. The vascular pedicle is then traced and the flap elevated to include buccinator, submucosa, and mucosa, taking care to keep the facial artery closely adhered to the elevated flap. The flap can then be rotated into place to use for the reconstruction of the alveolar ridge (▶ Fig. 22.1). 30 A modification of this flap includes the use of the angular artery branch of the facial artery as the vascular pedicle to create a superiorly based flap. 31
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