How to perform a partial mandibulectomy in dogs

Partial mandibulectomies are well-tolerated in dogs and often provide good to excellent cosmesis and function. They can provide a cure for patients with epulides and are a crucial component of therapy for many other oral neoplasms.

A partial mandibulectomy is a relatively easy procedure if you have the right tools and a sound knowledge of regional anatomy. Helpful tools include an oral speculum, a Freer periosteal elevator and an oscillating saw. Important structures are the inferior alveolar nerve and the mandibular alveolar artery and vein, both of which run within the mandibular canal.

Presurgical considerations

Obtain a histologic diagnosis, dental radiographs or computed tomographic scans to reveal the biologic behavior or gross extent of a lesion before determining the borders of excision. In general, one to two teeth that are rostral and caudal to the gross margins of a neoplasm should be removed to allow for a margin of normal tissue.

Once you've determined the amount of mandible to be removed, clip the surrounding skin and rinse the mouth with an antiseptic solution. Place the patient in the appropriate recumbent position, depending on the portion of mandible to be removed (Figure 1). Place an oral speculum between the contralateral mandibular and maxillary canines. Place one or two gauze sponges in the oropharynx to prevent blood from pooling around the endotracheal tube.

Figure 1: An 11-year-old Belgian Tervuren with an undifferentiated sarcoma on the mandible.

Perform a mandibular nerve block by placing the index finger of one hand into the patient's mouth and locating the most caudal aspect of the mandibular body. Insert a needle percutaneously, aiming toward the intraoral index finger, which denotes the entrance of the inferior alveolar branch of the mandibular nerve into the mandibular canal. Inject a local anesthetic agent just under the oral mucosa and continue it through the local tissues as you withdraw the needle out through the skin.

If access to the caudal mandible is necessary, perform a commissurotomy with a full-thickness incision beginning at the lip commissure and extending caudally. Judicious use of electrocautery is extremely helpful in maintaining hemostasis during commissurotomy since the maxillofacial region is particularly vascular.

Surgical procedure

To begin the mandibulectomy, make four initial cuts. The first two are in the gingiva—one on the rostral aspect of the most rostral tooth to be excised and one on the caudal aspect of the most caudal tooth to be excised. Next, make one incision in the buccal mucosa to connect these rostral and caudal cuts and one in the lingual mucosa to do the same.

Use a Freer periosteal elevator to boost the gingiva from the mandible along these incised areas and delineate the margins of excision.

Next, use an oscillating saw or osteotome and mallet to cut the bone. You may also use a Gigli wire saw, although it's more difficult to handle because of the traction needed and because it can easily lift the patient's head off the surgical table. It's helpful to have bone wax on hand to plug the mandibular canal, as bleeding from the mandibular alveolar artery and vein can be profuse.

Try to cut both ends of bone as quickly as possible so the entire piece of mandible can be removed, providing the best exposure for hemostasis. Smooth or taper the cut edges of the mandible using a pair of rongeurs to reduce tension during closure. Submit the removed portion of mandible for histopathologic examination, with the cut edges marked as rostral or caudal to allow for margin evaluation.

To close a hemimandibulectomy, undermine the cut buccal mucosal edge to create a mucosal flap, which is then sutured to the lingual mucosa and gingival edges. Although closure may be possible without creating a flap, a tension-free closure is paramount in oral surgery. Additionally, undermining this tissue will prevent or minimize the unsightly "dimple" that can occur when the skin is pulled medially with the mucosa and submucosa during closure.

First, close the submucosa with 3-0 or 4-0 absorbable sutures. You can achieve mucosal-to-mucosal apposition by using a simple continuous pattern with 4-0 to 5-0 absorbable sutures. Whether monofilament or multifilament suture is used, intraoral absorbable sutures do not need to be removed, as they will break down and be swallowed by the patient. If a rostral mandibulectomy has been performed, a V-shaped wedge of full-thickness tissue will often need to be removed from the chin to prevent the dog from having a "pouty" lip, which could cause excessive drooling and dropping of water.

Closure is in three or four layers, from the inside out: mucosa, submucosa, connective tissue and muscle (the submucosa and connective tissue and muscle may be closed as one layer where appropriate) and skin (Figure 2). If a commissurotomy has been performed, close it in the same manner.

Figure 2: Closure to recreate the chin.

After surgery

Postoperatively, continue injectable opioid pain medications for 12 to 24 hours, followed by oral pain medications including a nonsteroidal anti-inflammatory, if not contraindicated. Offer patients water and a small meal of canned food in meatball form the day after surgery (Figure 3). Soft food should be fed for two weeks postoperatively to minimize trauma to the mucosal suture line. An Elizabethan collar should be sent home with patients having a skin incision (e.g., commissurotomy) to prevent scratching at the site and grooming by housemates.

Figure 3: Postoperatively, the patient was able to fully retract the tongue into the mouth and learned how to prehend food within the first 48 hours.

Recheck patients at 10 to 14 days to evaluate the surgical site, particularly the intraoral component.

Dr. Nicki Green is a board-certified veterinary surgeon currently performing relief work for various universities and privately owned practices. In her spare time, she enjoys running, drawing and spending time with her husband, dog and two cats.