Successful maxilla reimplantation after traumatic injury in a dog - Veterinary Medicine
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Successful maxilla reimplantation after traumatic injury in a dog
This clinician suggests that maxillectomy is not the only possible treatment choice in cases of severe facial injury and suggests criteria that may help you assess similar candidates for reconstruction.


VETERINARY MEDICINE


Discussion


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.
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 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.
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.


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

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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