Successful maxilla reimplantation after traumatic injury in a dog

Unlike in human medicine, post-traumatic facial reconstruction has received little attention in small-animal surgery.1 Reports of treating facial trauma cases are limited,2,3 and no retrospective or prospective studies could be found in the literature. Most publications focus on oncologic surgery of the face.4-6 This case report details a successful reimplantation, without microvascular anastomosis, after traumatic subtotal amputation of the maxilla and discusses potential guidelines for decision making in similar cases.

History

A 4-year-old, 21.3-lb (9.7-kg), dolichocephalic, mixed-breed, intact male dog was evaluated at the emergency service of the veterinary teaching hospital of the Universidade Estadual de Londrina, about 20 minutes after sustaining a severe facial injury. The owner saw the accident, which occurred while the dog was asleep under farm machinery. A plow coulter fell, splitting the dog's maxilla. The owner immediately wrapped a clean towel around the dog's mandible and maxilla and brought the dog to the hospital.

Examination and treatment options

On arrival, the dog was tachycardic (176 beats/min), had a capillary refill time of more than two seconds, and had apparently lost a considerable amount of blood. An 18-ga catheter was inserted into the cephalic vein, and lactated Ringer's solution was rapidly infused (90 ml/kg/hr for the first 30 minutes) while fresh blood was collected from a donor for transfusion. Cefazolin sodium (30 mg/kg) was given intravenously before the lesion was inspected.

Initial inspection revealed a complete oblique cut that severed the skin and bones of the maxilla at the level of the nasomaxillary suture junction and reached the oral mucosa at the level of the hard palate. The laceration extended from the nasomaxillary suture dorsally to the level of the left maxillary canine tooth and the interdental space of the second and third right maxillary premolars (Figure 1). The rostral maxilla was precariously attached to the rest of the face by a thin strip of tissue (about 4 mm thick) from the left lip and a full thickness, 2.5-cm-wide portion of the upper lip on the right side (Figures 1 & 2). The right lip flap was later found to include the right infraorbital artery, which was patent. The dog was breathing through the lesion. Once the blood transfusion (about 200 ml) was initiated and the patient's hypovolemia was corrected, further physical examination revealed a 1-cm full-thickness skin laceration on the craniodistal aspect of the right antebrachium. Because this patient needed immediate surgical intervention, no preoperative diagnostic tests, including radiography, were performed.

Figure 1: A lateral view of a traumatic subtotal amputation of the maxilla in a 4-year-old dog that sustained the severe facial injury from a farm equipment accident. The laceration extends from the left maxillary canine tooth (arrows) to the interdental space between the second and third maxillary premolars on the right side (arrowhead) (A-oroesophageal tube; B-endotracheal tube).

The options for this patient were to perform primary reconstruction or a bilateral rostral maxillectomy followed by delayed facial reconstruction. The owner was informed about the potential complications of a primary reconstruction, which could result in failure, requiring a late maxillectomy, as well as the likely unacceptable cosmetic results from a radical maxillectomy. The limited availability of soft tissue for primary closure of the maxillectomy defect was a big concern, as was the possibility of a disfiguring open wound that would need to be treated until delayed reconstruction could be done.

Figure 2: A dorsal view of the facial injury in the same dog shown in Figure 1. Note the aboral extension of the laceration to the right side of the face (arrows).

Morphine (0.4 mg/kg intramuscularly) was administered for perioperative pain management. General anesthesia was induced with intravenous propofol (5 mg/kg), and the dog was intubated. Anesthesia was maintained with sevoflurane (1.5%) and 100% oxygen. After the wound was protected with sterile petroleum jelly ointment and gauze, the dog's face was clipped, and the wound was lavaged with 1.5 L 0.9% sterile saline solution and wrapped in sterile laparotomy sponges.

Surgical treatment

During surgical exploration, the wound was considered clean-contaminated and was not associated with marked crushing injuries to the surrounding soft tissue. The bone edges seemed viable and were bleeding, and, although the rostral portion of the maxilla was pale and cold, suggesting severe compromise to the arterial blood supply, I decided to perform reimplantation with complete reconstruction of the face, instead of a rostral maxillectomy.

Figure 3: A dorsal intraoperative view showing the first steps of reconstruction, which consisted of placing bone sutures (0.6-mm cerclage wire) through paired holes in the severed rostral and caudal segments of the nasal bone. The arrows point to the entrance and exit of one wire. (Oral is to the left, aboral is to the right.)

After further copious lavage, the left maxillary canine tooth, which had been split longitudinally during the accident, was extracted. The first step of the reconstructive procedure involved securing the edges of the nasal and maxilla bones bilaterally. After the edges were approximated, paired 1-mm holes were drilled on both sides of the nasal bone, and six cerclage wires (0.6 mm) were preplaced. The edges of the nasal and maxilla bones were approximated to reduce the fracture, and the wires were tightened (Figures 3 & 4). The dorsal subcutaneous tissues and identifiable portions of the levator nasolabialis muscle were closed with 4-0 braided polyglactin 910 in an interrupted pattern. The skin was closed with 4-0 monofilament nylon in a simple interrupted pattern, and the patient was repositioned in dorsal recumbency to explore the oral cavity.

Figure 4: A dorsal intraoperative view of the reconstructive procedure showing that after preplacement of the cerclage wires, the wires (arrows) were tightened as the bone fragments were realigned.

The patient's upper lip was retracted dorsally. An oronasal fistula caused by the maxillary canine tooth extraction was closed with a local simple advancement flap raised from the normal adjacent gingival and buccal mucosa (Figure 5). Two 2-mm Kirschner wires (K wires) were then inserted through the mucosal surface dorsal to the first right and second left incisors into the incisive bones of the premaxilla and directed caudoventrally, emerging through the hard palate caudal to the fracture site (Figures 6). The soft palate was reconstructed with simple interrupted sutures using 4-0 monofilament polyglyconate. Two figure-of-eight 0.6-mm cerclage wires were placed to increase interfragmentary compression and stability (Figure 6). On the right side, the cerclage wire was placed around the canine tooth and the contralateral tip of the K wire, which was protruding from the hard palate (Figure 6). On the left side, the cerclage wire ran between the rostral and caudal tips of the K wire, passing just rostral to the maxillary canine alveolus. Defects in the mucosa and lips were closed with 4-0 polyglyconate in an interrupted or simple continuous pattern (Figure 5). The subcutaneous tissues and the skin of the lips were closed with 5-0 polyglactin 910 and 4-0 monofilament nylon, respectively. The soft tissue (skin) laceration on the antebrachium was lavaged with sterile saline solution, débrided, and closed with 4-0 polyglyconate in the subcutaneous tissue and 4-0 nylon in the skin in a simple interrupted pattern.

Figure 5: An oral intraoperative view showing advancement flap repair of an oronasal fistula caused by the left maxillary canine tooth extraction. The arrowhead points to the flap held by a stay suture. The arrows highlight the reapposition of the oral mucosa with simple continuous sutures.

The dog's immediate postoperative appearance is shown in Figure 7. The tip of the nose slightly tilted upward from not bending the wires implanted into the premaxilla. Postoperatively, morphine (0.2 mg/kg subcutaneously every four hours) was administered for two and a half days, and cefazolin (30 mg/kg intravenously t.i.d.) and gentamicin sulfate (5 mg/kg subcutaneously once a day) were administered for six days. Because gentamicin can be nephrotoxic, a urine specific gravity and sediment and serum blood urea nitrogen and creatinine concentrations were monitored daily. No parenteral or enteral nutrition ports were required, because the dog was able to eat and drink on its own the day after surgery. The dog was fed a commercial canned dog food and was given water ad libitum. Oral hygiene was performed after each meal by applying 0.9% saline solution and an oral antiseptic (0.12% chlorhexidine gluconate) to the intraoral suture lines.

Figure 6: An oral intraoperative view after maxilla reimplantation. Note the converging K wires (arrows) entering the premaxilla and exiting the mucosal surface after crossing the hard palate caudal to the fracture site. The figure-of-eight tension band wires were anchored to the protruding tips of the K wires (arrowhead).

The dog was discharged seven days after surgery. The owner was instructed to feed the dog canned food for two weeks and to make a slow transition to dry food after 14 days. Dry food was allowed as of the third week after discharge. Oral hygiene was strongly advised, which involved flushing the oral cavity with 0.12% chlorhexidine after each meal (at least three times a day) for two weeks.

Figure 7: An immediate postoperative view. Note that the tip of the nose tilts slightly upward because of the unbent ends of the two K wires entering the premaxilla.

Follow-up

Ten days after surgery, the dog returned for suture removal. The owner reported that the dog was breathing with its mouth closed and had resumed normal activities on the farm. On physical examination, the tip of the nose appeared pale and hypopigmented, but the capillary refill time in the upper lip was nearly normal, and the gingiva and mucosal surfaces of the mouth were pink. A small oronasal fistula had formed because of wound dehiscence near the upper left canine alveolus. The skin sutures were removed, and I recommended surgical correction of the oronasal fistula. The patient was discharged with instructions regarding oral hygiene.

Figure 8: The patient one month after maxilla reconstruction. Note the depigmentation of the nose and upper left lip and the presence of a small skin ulcer on the upper left muzzle.

Three weeks later, the patient returned for oronasal fistula correction and radiographic evaluation of maxillary bone healing. The radiographic examination showed adequate healing and no implant problems. The tip of the nose and the left upper lip were still hypopigmented, but the paleness had subsided. A small orocutaneous fistula had developed, which was communicating with the oronasal fistula (Figures 8-10). The oronasal fistula was surgically corrected by using a simple pediculate advancement flap with tension release, and all orthopedic implants were removed. The orocutaneous fistula was lavaged and allowed to heal by second intention. Twice-daily flushing with saline solution was recommended.

Figure 9: An oral view one month after maxilla reimplantation showing the exit points of the two K wires, the loss of the left tension band wire, and the presence of an oronasal fistula where the left upper canine tooth was extracted. Note the extensive depigmentation of the upper left lip.

On reexamination two months later, repigmentation of the lip and nose had occurred. The cutaneous fistula was closing by second intention (Figure 11). Overall, healing was considered good. The final cosmetic result, four months after surgery, is shown in Figure 12. A mild left upper lip elevation was present, resulting from scar contraction of the orocutaneous fistula.

Figure 10: This view of the patient one month after facial reconstruction shows adequate dental occlusion. The arrow points to the contaminated oronasal fistula, a post­operative complication observed in this case.

Discussion

The usefulness and limitations of mandibulectomies and maxillectomies have been reported.7 The most common indication for these procedures is to excise invasive oral tumors.4-7 Occasionally, a maxillectomy may be indicated in trauma patients when primary reconstruction is not possible. Oronasal fistula formation is the most common complication after maxillectomy.8 Other complications include ulceration of the labial flap mucosa or the skin on the lateral surface of the lip, damage to adjacent teeth, and, rarely, dehiscence at suture lines.8 If a surgeon develops a clear understanding of the prevention and treatment of potential complications of maxillectomies,9 the learning curve becomes relatively smooth and the complications are reduced to an acceptable level.

Figure 11: An oral view three months after the maxillary reimplantation. The oronasal fistula has resolved after surgical correction, and the oral mucosa and skin of the upper lip are repigmented.

With well-described techniques published in most general small-animal surgery textbooks,8,10,11 these en bloc resection procedures have become more popular. Although oncology patients pose a marked challenge to alternative reconstruction techniques, mandibulectomies and maxillectomies in these patients have been shown to improve both the span and quality of life.5,12,13 The quality of a pet's life, as perceived by its owners, is considered most improved after rostral mandibulectomy and least improved after partial maxillectomy.14 So in circumstances in which reconstruction can be attempted, maxillectomy should not be considered the treatment of choice, especially in potentially salvageable trauma cases.

Figure 12: The appearance of the dog four months after surgery. Note the repigmentation of the nose. There is slight retraction of the left upper lip resulting from scarring contracture formed by the healing of the facial ulcer shown in Figure 8.

Because of this dog's extensive facial injury, many practitioners may have considered a maxillectomy as the treatment of choice. Most practitioners are familiar with maxillectomies, and the outcome of attempted reimplantation is uncertain. The experience of managing this case shows that reimplantation is possible, even without vascular anastomosis. However, objective criteria must be carefully considered before deciding whether to try reconstruction in cases of traumatic maxillectomy. The criteria I suggest are presented in Table 1. These criteria are in accord with basic principles of wound care and follow well-established standards of good practice. I also use these criteria as a scoring scale to predict outcome and discuss prognosis and treatment choices with owners. I find that the higher the score in each category, the better the prognosis. Findings that assign the lesion lower scores result in a progressively poorer prognosis.

Table 1: Suggested Criteria to Assist Decision Making in Cases of Traumatic Maxillary Injury in Dogs*

The rate, type, and severity of complications may also be more easily predicted according to the scores within each category featured in Table 1. For example, soft tissue infection and suture dehiscence may be expected when the scores are low for contamination levels and the interval between wounding and treatment. Similarly, the possibilities of osteomyelitis, delayed union, and nonunion can be discussed with owners when patients score lower on contamination, crushing injury, ischemia, and fracture pattern categories. Soft tissue necrosis and sloughing with secondary bacterial infection or delayed soft tissue healing might be expected in patients that score poorly on blood supply, such as when a crushing injury is associated with major artery loss.

Although not done in this case, I could have used a Doppler ultrasound flowmeter to assess the peripheral pulse and patency of arterial perfusion to the wounded tissue. Alternatively, I could have used tissue oximetry with a standard monitor, such as that used during general anesthesia, to help indirectly assess arterial perfusion in different areas of the oral mucosa. (To assess perfusion, I simply place the sensor probe on different locations and interpret the oxygen reading as a percentage of the reading from normal tissue.) Finally, I could have injected fluorescein intra-arterially to identify the limits of unperfused areas. However, this invasive technique has produced unreliable results, so it has fallen out of favor for assessing blood perfusion.

Applying the proposed scoring scale, the patient in this case would have scored 5 (time since trauma) + 4 (wound contamination) + 5 (soft tissue crushing injury) + 5 (fracture pattern) + 4 (arterial supply). The dog healed without serious complications. An oronasal fistula occurred, which is a common complication after maxillary canine tooth extraction.15 The fistula likely occurred because of low arterial perfusion of the rostral edge of the wound and excessive tension on the suture line. It is reasonable to think that if an advancement flap with tension release, similar to the one later used to treat this complication, was originally performed, the oronasal fistula could have been prevented.

The copious lavage with sterile saline solution helped decrease the superficial contamination of the wound, improving the prognosis relative to wound infection. Bacterial culture and sensitivity testing could have been performed to identify potential pathogens and direct specific antibiotic therapy; this testing is recommended whenever an open wound is associated with devitalized tissue. This patient's wound was open, and the rostral portion of the maxilla had compromised arterial perfusion, especially on the left side of the face where the palatine and infraorbital arteries were lost. A culture and sensitivity test, however, was not performed and, instead, empirical antibiotic therapy was initiated considering the likelihood of pathogen types found on the skin and in the oral cavity. Staphylococcus intermedius and Streptococcus and Pseudomonas species are frequently associated with skin wound contamination, and the oral cavity may add Pasteurella species to the wound. Cefazolin, a first-generation cephalosporin, has good activity against gram-positive bacteria such as Staphylococcus and Streptococcus species, while gentamicin is usually efficient against gram-negative bacteria such as Pasteurella and Pseudomonas species.

The upward tilt of the tip of the nose illustrated in Figure 7 could have been easily prevented by a simple 90-degree bending of the protruding ends of the K-wires inserted into the premaxilla, which is recommended when using this technique.

To my knowledge, no information is available on the importance of main arterial blood perfusion or revascularization capabilities of such an extensive facial injury. This patient's outcome shows that revascularization can occur. The extensive collateral circulation and the rapid revascularization ability of dogs, which is different in people, may have contributed to this dog's favorable outcome, even though major vessels were disrupted and not surgically anastomosed.

This case also demonstrates that depigmentation (i.e. loss of melanin expression) may occur, but it can be completely reversible. This transitory depigmentation is likely associated with ischemia and inefficient perfusion of melanocyte-populated skin and mucosal tissues. It is possible that once reperfusion is established, melanin is again normally produced in the area. Experimental studies could further address this hypothesis and clarify whether the depigmentation is due to either loss of pigment granules (later newly synthesized) or to loss and subsequent repopulation of melanocytes themselves.

Conclusion

Maxillary reimplantation without vascular anastomosis was successful in the dog in this report and may be feasible in similar cases, even when only one infraorbital artery is preserved and the contralateral infraorbital and the two main palatine arteries are lost. The successful outcome described in this case was credited in part to the application of the salvage criteria I suggest herein to assist decision making in cases of traumatic maxillary injury in dogs. Careful consideration of these or similar criteria may decrease the probability of an unsatisfactory outcome and help owners make educated decisions on treatment choices. Owners who are fully informed and actively participate in the decision making usually show increased compliance with postoperative care and greater satisfaction with the final outcome.

ACKNOWLEDGMENTS

I wish to thank the staff of the Veterinary Teaching Hospital of Universidade Estadual de Londrina, Paraná, Brazil, for the many years of good nursing care provided to my patients. Special thanks go to small-animal anesthesiologist Dr. Angelita Zanata Reia for volunteering to work after hours, providing invaluable anesthetic support, not only in this case, but in several other trauma patients seen by me while associated with that institution. Finally, thanks to Dr. Dale Bjorling for kindly reviewing this manuscript.

Maria L.E. Faria, DVM, MS, PhD*

Hospital Veterinário

Universidade Estadual de Londrina

Londrina, Paraná, Brazil 86051-990

*Current address:

Comparative Orthopaedic Research Laboratory

Department of Medical Sciences

School of Veterinary Medicine

University of Wisconsin

Madison, WI 53706-11102

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