Evaluation And Planning

Evaluation of patient risk, tumor, and donor site factors are important prior to planning repair of the oral cavity defect. Patient factors include the presence of comor-bidites such as diabetes, liver disease, chronic airway limitation, peripheral vascular disease, and a second malignancy. In addition, patient psychology plays a significant role and therefore may benefit from the assistance of a psychiatrist knowledgeable of the special needs of head and neck cancer patients. The subsequent selection of reconstructive options relies on a risk-benefit analysis that should always be considerate of the patient. Preoperative optimization of any intercurrent organic or functional disorder is vital prior to embarking on a surgical plan of management that requires prolonged anesthesia, lengthy hospitalization, and an extended period of rehabilitation.

Tumor factors should include knowledge of previous treatment, type of histology, primary site, size, and presence of distant disease. Previous external beam radiotherapy affects the microvasculature of the surrounding tissues that may result in significant problems such as soft tissue breakdown, fistula formation, osseous malunion, and carotid artery exposure. Repair generally requires the use of distant and vascularized tissue to achieve a successful outcome.

Squamous cell carcinoma (SCC) is the most common malignancy of the oral cavity but minor salivary gland tumors, primary bone tumors, and tumors of dental origin also occur with generous margins of > 1 cm required to achieve disease control.

The primary site of tumor within the oral cavity clearly influences the type of repair selected. Defects of the mobile tongue are best repaired with thin, soft, pliable, and sensate tissue whereas tumors originating from the inferior alveolar margin will likely require both bone and/or soft tissue. Palatal lesions are usually treated with simple excision and a dental prosthesis while large through-and-through defects will necessitate multiple reconstructive flaps.

Donor site factors are paramount in the selection of the tissue type used and can be divided into those specific to the patient and those vital to the reconstructive surgeon. Choice of donor tissue should result in minimal morbidity to the patient in terms of both function and form and be compatible with the needs of the defect. Qualities of donor tissue that are important include pliability, size of skin paddle, tissue volume, nature of the vascular pedicle, and the potential for both sensation and color match. Donor tissue should be relatively easy to harvest and ideally should permit a two-team approach to reduce operative time. Donor site factors that are contraindications to the successful harvest of tissue include prior injury or surgery (e.g., fractures, soft tissue trauma, peripheral vascular surgery), previous irradiation, recent intravenous cannulation (e.g., radial forearm free flap), and inadequate collateral circulation (e.g., peripheral vascular disease or dominant radial artery).

A thorough physical examination with appropriate imaging and examination under anesthesia in selected cases permits a comprehensive evaluation of the extent of the primary tumor and the type of reconstruction required. Magnetic resonance imaging provides superior soft tissue delineation of tumors especially within the tongue whereas tumors arising from or adjacent to bony structures are more accurately assessed using a CT scan. In addition, occlusal views or a dentascan may be helpful where minimal cortical bone erosion of the mandible is suspected. However, a combination of physical examination coupled with appropriate imaging as described improves both the sensitivity and specificity of tumor evaluation.

RECONSTRUCTIVE OPTIONS Non-vascularized Grafts

The extensive vascularity of the upper aerodigestive tract has permitted the successful use of a number of free, non-vascularized grafts in the repair of oral cavity defects. Historically these have included skin, mucosa, and/or bone. Many authors have reported the successful use and good functional outcome of split thickness skin grafts following ablation of oral cavity tumors (1,2). Advantages include tissue availability, ease of harvest, and minimal donor site morbidity. In addition, techniques of skin harvesting have evolved from using a simple scalpel blade to a variety of commercially available powered dermatomes. However, prior history of radiation to either the donor or recipient site are contraindications to the use of split thickness skin. Despite these limitations, many authors continue to advocate their application for the repair of moderate- to large-sized defects following tumor ablation in the oral cavity (3).

Ollier (4) is credited with the first published paper in the French journal of physiology in 1860 detailing his experience with freebone graft and bone regeneration in lower animals and man. In 1892, the German surgeon Bardenheuer reported the reconstruction of both the bony and soft tissue defect of the lower jaw using a composite flap of skin, periosteum, and bone from the forehead (5). In 1949, Blocker and Stout (6) successfully transferred iliac bone for reconstruction of large mandibular defects. During the ensuing years, numerous reconstructive options were employed and these included the clavicle, sternum, radius, fibula, scapula, and metartarsal bone (7). Historically, all of these grafts had been used as either solid or particulate free bone grafts. Their successful outcome depended on the quality of the host environment and the type of soft tissue cover. In 1918, Blair (8) proposed the sterilization and reimplantion of autogenous mandible. A contemporary application of this technique was proposed in 1981 by Hamaker who reported the use of free autogenous irradiated mandible in seven cases (9). While initially this form of reconstruction was popular, the long-term poor results from a contaminated bed led surgeons to abandon this approach.

Converse and Campbell in 1954 were one of the first to use free particulate bone marrow and block grafts for the reconstruction of the mandible with varying results (10). Boyne (11) in 1969 employed vitalium metallic crib to support particulate iliac bone graft for the reconstruction of the non-irradiated mandible in patients with predominantly benign osseous neoplasms. He reported a successful outcome in excess of 80%. However in 1979, Adamo and Szal demonstrated an unsatisfactory outcome in 50% of cases and an 80% complication rate when employed in irradiated patients (12).

Local Tissue Rearrangement

Local flaps with either a random blood supply or a distinct axial vascular pedicle have been commonly used for the reconstruction of the oral cavity. A wide variety of options exist that date back to 600 b.c. when Indian surgeons first described this technique in the repair of nasal defects. Since then many different flaps have been used with varying success (13).

Malgaigne was the first to describe the successful use of the nasolabial flap in 1834 for repairing nasal defects. However, Rosenthal (1916), Esser (1918), and Thiersch (1968) expanded its usefulness for the repair of anterior or lateral oral cavity defects and remains a viable alternate option in select cases to date (13).

The palatal rotation flap as described by Gullane and Arena has been used to resurface defects involving the ipsilateral tonsil, retromolar trigone, and buccal mucosa (14). It is a simple local option, however, limited by pedicle length and contraindicated in the irradiated patient.

Klopp and Schurter (15) in 1956 proposed the tongue flap for the reconstruction of posterior oral cavity defects. It can be either based on an anterior or posterior pedicle. In 1969, Chambers and Jacques (16) popularized the use of this flap and DeSanto and Yarington (17) in 1983 reiterated the need for the contemporary head and neck surgeon to be aware of this option when treating oral cavity tumors.

A further contemporary option includes the buccinator musculomucosal flap as described by Bozola et al. (18) in 1989 and modified by Carstens et al. (19) in 1991. Its application and successful outcome makes this a reasonable local alternative in select patients with anterior or lateral oral cavity defects.

Over the past many years, lip reconstruction has significantly challenged many reconstructive surgeons. In general, defects less then one-third of the lip can be closed primarily. However, larger defects require local tissue transfer to provide an acceptable functional and cosmetic result. In 1837, Sabattini first proposed the concept of borrowing composite lip from the opposite side. Abbe in 1898 described this flap in detail, and therefore his name became associated with this technique. Similarly Stein's technique of lip reconstruction, as first described in 1848 became known as the Estlander flap in 1865 (13). In 1920, Gillies (20) described the rotation of adjacent residual lip around the commissure to repair moderate defects of the lower lip. Karapandzic (21) in 1974 recognized the need to maintain innervation when he proposed his modification of Gillies technique. Many local flaps have since been proposed to deal with total lip loss and these include the Bernard bilateral cheek advancement flap and Webster modification, which helped to improve both function and cosmesis (22,23).

Regional Flap Transfer

The use of adjuvant radiotherapy in the management of advanced oral cavity neoplasms has necessitated the need for distant, well-vascularised tissue for the reliable repair of the post-surgical defect. The evolution of pedicled regional flaps has fulfilled this reconstructive goal, the successful outcome of which has been further enhanced with modern advances in anesthesia, peri-operative care, and surgical techniques.

In 1791, Chopart is credited with the first description of using pedicled neck skin to repair a lip defect. Gersuny in 1887 expanded the usefulness of this approach in the reconstruction of oral cavity defects. Further developments of these techniques include the anterior and lateral apron flap and the Mutter flap (13). In 1968, Bakamjian (24) described the deltopectoral fasciocutaneous pedicled flap, which remained the ''work horse'' in head and neck reconstruction until the mid 1970s with the advent of free tissue transfer and pedicled musculocutaneous flaps. During that same era, the forehead flap as described by McGregor in 1969 was a popular alternative for primary reconstruction of the oral cavity (25). It provided primary repair for a number of subsites within the oral cavity with reliable blood supply but its cosmetic deformation was a significant contraindication. A more contemporary reconstructive option is the pedicled temporoparietal fascial flap, which can be employed in a small subset of patients with oral cavity neoplasms (26).

In 1896, Tansini (27) was the first to describe the use of a pedicled myocuta-neous flap to repair a surgical defect. He employed the latissimus dorsi muscle with overlying skin for the reconstruction of a mastectomy defect. Owens (28) in 1955 first described this approach using the sternocleidomastoid myocutaneous flap for reconstruction in the head and neck region. This technique gained wide popularity in 1979 when Ariyan first described the pectoralis major myocutaneous flap in the reconstruction of the oral cavity (29). It subsequently became the work horse in head and neck reconstruction replacing the deltopectoral flap, and continues to be a viable alternative to date. Other pedicled musculocutaneous options include the sternoclei-domastoid, the trapezius, the latissimus dorsi, and the temporalis muscle (30). Further variations of immediate mandibular reconstruction with regional osteomus-culocutaneous flaps comprising the pectoralis major muscle, overlying skin, and a segment of the underlying 5th rib provided acceptable short-term results but few reports of reliable long-term outcome exist (31). Similar techniques using the sternocleidomastoid with the attached clavicle, the trapezius with the scapular wing and the temporalis with the outer cortical table have been described with successful outcomes varying from 30% to 80% in primarily non-irradiated beds (32). The unreliability and the many unacceptable donor site defects have made this method unattractive in primary reconstruction of the mandible after tumor ablation.

Distant Tissue Transfer

The advent of microvascular surgical techniques, knowledge of vascular territories, and improved systems of magnification have permitted the successful distant transfer and restoration of extensive defects in both irradiated and non-irradiated beds using vascularized skin, muscle and/or bone.

Harii et al. in 1976 and Panje et al. in 1976 were the first to employ free vascu-larized tissue transfer in the reconstruction of head and neck defects (33,34). However, it was not until the description of the radial forearm flap by Yang et al. (35) in 1981, that this technique gained widespread popularity and acceptance in soft tissue repair of the oral cavity. Factors such as ease of harvest, a long vascular pedicle, large skin paddle, pliability, potential for sensitivity, and low failure rates have supported the widespread use of this flap. Other soft tissue donor sites include the dor-salis pedis, the lateral arm, the scapular, rectus abdominus, latissimus dorsi, and groin flaps (36). More recently the recognition and description of perforator flaps such as the DIEP flap (i.e., deep inferior epigastric perforator) have helped to reduce tissue bulk and minimized donor site complications (37). A contemporary alternative is the anterolateral thigh flap, which is reliable, easy to harvest, has minimal donor site morbidity and allows for a two-team approach (38).

The pioneering experimental work by Ostrup and Frederickson (39) in 1975, in which they successfully demonstrated the ability to transfer free, vascularized rib graft into mandibular defects in an animal model, provided the background for the development of a number of bony reconstructive options for the management of oral cavity malignancies. Subsequently, a variety of vascularized free osseous flaps have included metatarsus, rib, radius, iliac crest, scapula, and fibula (40-45). The most popular contemporary options include both the fibula and the scapular osseo-cutaneous free flaps, which provide timely and efficient reconstruction of the entire spectrum of mandibular defects. One of the major advantages of osteocu-taneous tissue is that the grafted site provides a bed in which the final stage of oral rehabilitation can be successfully completed using osseointegrated dental implant pegs.

Implants and Biomaterials

A number of synthetic biomaterials are available that help in the reconstruction of head and neck defects. These include mandibular reconstruction plates, maxillary prostheses, and dental implants. The ideal biomaterial should be inert, malleable, resilient, provide stablility over time, be cost effective, and easy to use.

Historically, a wide variety of materials have been used to reconstruct and alter the shape and function of the upper aerodigestive tract. These include a variety of metals, ivory, wax, and paraffin. Some of these were injected subcutaneously and moulded before solidification took place. The resultant significant foreign body reaction caused grotesque disfigurement. The early experience of most surgeons with alloplastic implants including steel, aluminum, brass, and magnesium were disappointing. They irritated the body tissues, produced necrosis and had to be discarded. The search for an ideal inert biomaterial resulted in numerous scientific evaluations of various combinations of metals. The earliest application of metals for mandibular reconstruction included the use of stainless steel wires by Scudder in 1912 (46). However, these resulted in loosening, migration, exposure, and malunion of the bony segments. Subsequently significant advances were made in 1936 when Venable and Stuck discovered vitallium (i.e., an alloy of cobalt, chromium, and molybdenum) (47). This was the most ideal alloplast available to date and was successfully used in reconstruction of the mandible by Winter et al. in 1945, Freeman in 1948, and Conley in 1951 (48-50). A major disadvantage of vitallium was its low malleability and significant failure rates in irradiated patients. In attempts to overcome the technical problems associated with this alloy, surgeons turned their attention to stainless steel devices using mesh trays and, subsequently, in the mid 1970s to a three-dimensional reconstruction plate (3-DBRP). In the early part of 1980, titanium began to replace stainless steel because of its superior malleability and inertness. Modifications of the titanium reconstruction system have resulted in a thinner and more pliable plate with improved screw design and reduced failure rates. Finally, the compatibility of stainless steel and titanium with either pre- or post-operative radiotherapy was confirmed in 1991 with the recognition of limited dose uptake, minimal effect on adjacent bone, and soft tissue with the use of parallel apposed fields (7).

The first use of prosthetics as cited by Conley (50) dates back to 1565 when Petronius devised a gold plate for the repair of a cleft palate defect. Since then the emergence of synthetic polymers has permitted the development of a wide range of oral prosthetics, which attempt to recreate normal oral anatomy, separate the sinonasal and oral cavity, and provide both form and function. This has resulted in prompt rehabilitation with an improvement in the overall quality of life in patients with oral cavity malignancies.

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