Reconstruction of Oral Defects
Using Mucogingival Pedicle Flaps
©2001 Dr. Ira R. Luskin Diplomate AVDC
|There is a wide diversity of pathology, which can affect the oral cavity. Disease that evolves from congenital, traumatic, infectious and neoplastic etiologies affect the tissues of the mouth. Depending on the tissue types that are affected and where the lesion is located, clinical signs and history can aid in determining the diagnosis. Face pawing, trismus, dental malocclusion, salivation, nasal discharge, respiratory distress, dropping food, halitosis, interest in food but inappetence, and weight loss, can all be manifestations of oral disease. The symptomology might point either to a primary local involvement or a secondary oral cavity involvement by systemic disease. These symptoms necessitate urgency in therapy since the underlying problem can lead to a rapid decline in the animal’s health.
The lesion’s origin might be either congenital or an acquired defect. In the case of the former, clefts involving the hard and soft palate and hypoplasia of the soft palate require surgical management. Acquired defects involve a loss or damage to the teeth, bone and or soft tissue. These defects can be caused by chronic infection i.e. periodontal disease, traumatic injuries like bite wounds, falls, electric cord injuries or neoplasia.
The surgical approach to correction often requires the use of an oral flap to reconstruct the oral anatomy. By definition, a flap that remains attached at its base with an adequate blood supply is called a pedicle flap. Depending on the mode of tissue movement, these flaps are classified as “advancement flaps” if there are no deviation along its axis on route to the recipient site or “rotational” whereby the flap is pivoted at it’s base and rotated. Pedicle flaps maintain their own blood supply and therefore their survival is less dependent on the recipient tissues ability to diffuse nutrients or neovascularize the flap. Due to the more then adequate donor tissue, very large oral defects can be closed with this single layer flap technique. The tissues’ inherent strength and elasticity and proximity to the recipient site make it ideally suited to grafting. The donor site can incorporate buccal, gingival and alveolar mucosa as well the muco-periosteum of the hard palate.
The closure of the created defects necessitates planning. The age of the animal as in congenital defects like the cleft palate should be delayed until 2-4 months of age 2. Traumatic defects should be delayed for 24 to 72 hours to allow for the demarcation of necrotic or dying tissue. Immediate closure might lead to dehiscence due to inadequate blood supply to the tissues. In the case of neoplasia, dependent on the type and extent of tissue involvement, the surgical margins are predicated on whether the attempt is at palliation of symptoms or curative excision. Physical or anatomical barriers to flap creation or advancement must be dealt with prior to closure. Planned extraction of teeth that are in “the way” of the flap or crown reduction of teeth that would traumatize the flap, must be considered.
The consideration of using extraoral alimentation i.e. esophagostomy or gastrostomy tube feeding versus intraoral force feeding postoperatively is dependent on the client’s ability to follow through with home care. The affect on oral healing of the flap in either method is not known. It is this author’s experience that rarely the type of surgery or closure’s success is dependent on how the food is administered. The movement of the oral tissue in tongue thrusting or swallowing occurs in both extra and intra oral feeding techniques. The rationale to place a tube is dependent on if postoperative inappetence is a sequellae of inadequate pain control or rather a consequence of concurrent systemic illness that has reduced the pet’s drive to eat. This article reviews first the principles of utilizing flaps and then describes four clinical cases in which muco-gingival pedicle flaps are used to close the surgical defects after the underlying pathology is corrected.
Principles of Flap Reconstruction
All flaps should have adequate underlying connective tissue. In the mandible and maxilla where the flaps originate at either the attached gingiva or the palatal mucosa, they will also contain deep lying periosteal cells. The flap margins and as well the recipient site should be freshly excised to bleeding tissue. Using a scalpel blade rather then scissors will prevent any potential for crushing. Electrosurgery or cauterization to control bleeding should be avoided. The tissue must always be kept from desiccation by using sponges soaked in sodium chloride or frequent lavage. The size and shape of the flap must allow for adequate tensionless tissue appositition. Harvesting of excess tissue for the flap that will give at least a 5-8 mm overlap on all margins of the defect is important. Long narrow flaps should be prevented due to the inadequate blood supply to the tip and subsequent tissue necrosis. In the creation of palatal flaps, always use a full-thickness mucoperiosteum, which incorporates the palatal artery.
Buccal mucosal flaps should be dissected away from the underlying muscle layer but leaving adequate connective tissue. The vertical releasing incisions of the buccal mucosa, should extend apically (towards the tooth root) in a divergent line therefore giving the flap a much larger base of tissue. It can either be of an envelope design in which there is only one releasing vertical incision or containing two vertical releases, which allow greater mobilization of the tissue. The flap at the base is released whereby the periosteum and connective tissue only is severed parallel to the base with a scalpel. Be careful not to cut through to the overly mucosa which is highly elastic. Holding the flap in tension with a thumb forcep allows the surgeon to feel the “point of release or stretch” of the flap.
Removal of all obstacles in the path of the intended flap is imperative. Non-essential teeth should be extracted and the crestal alveolar bone lowered with a water-cooled bone bur or a cylindrical cutting bur.
Like with all tissue healing, a closure without tension is very important. Factors, which aid in this tensionless closure, are adequate amounts of donor tissue, release of the connective tissue and periosteum, and using a walking tissue technique. This technique delivers the tension uniformly along the flap’s margin. This is accomplished by starting the suture pattern at the vertical margins of the flap’s base and apposing it with diagonal sutures to the ventral border of attached gingiva on the cranial and caudal borders of the recipient site. This relieves the tension along the horizontal margin of the sutured flap.
Increasing the surface area of the recipient site by either creating a beveled incision or a “shelf” allows greater contact and healing. All recipient epithelium should be scarified. A fast and accurate way of achieving this scarification is by using a coarse diamond in a water-cooled high speed drill to superficially abraid this layer. The endpoint is a fine bleeding of the site with the appropriate contour (which is more difficult when creating the recipient site in the palatal rugae folds)
The sutured incision line should not be located over a void, which could, in the case of a cleft palate, lead to drying out of the flap and increased movement with subsequent dehiscence. Sutures should be in a simple interrupted pattern and be of an absorbable material. The author finds that, although more time consuming, this pattern adds to the success of closure due to the exact tissue apposition which eliminates the epithelium of the flap from rolling in on the cut edge and causing suture line breakdown with the recipient site. The sutures are placed 3-5 mm apart. The author uses 4-0 gut with a swaged-on reverse cutting needle to close all oral lesions. The use of a synthetic monofilament absorbable suture like polydioxanone has a tendency to persist to long in the oral cavity and be very elastic and difficult to work with especially in non-rigid tissue like mucosa.
A seldom discussed, but a key factor in allowing the flap to heal, is the prevention of trauma by teeth from the opposing arch. This is of special importance when working with pedicle flaps to close anterior maxillary defects. The constant trauma of the lower canines can greatly influence the flaps healing. It is this author’s opinion that performing a crown reduction and vital pulpectomy of the mandibular canine teeth of the affected side will greatly enhance the flaps vitality. Although beyond the scope of this paper, the procedure is covered in depth in most small animal dental texts.