Preparedness for dog bites takes bite out of injury

March 1, 2011

Dog bite injuries frequently affect the periocular area, and clinicians should be familiar with the clinical examination, as well as the surgical and medical management paths to take in such cases.

Baltimore-Dog bite injuries frequently affect the periocular area, and clinicians should be familiar with the clinical examination, as well as the surgical and medical management paths to take in such cases, said Nicholas Mahoney, MD, here at the 23rd annual Current Concepts in Ophthalmology meeting, held in association with Ophthalmology Times.

Each year, about 5 million dog bite injuries occur in the United States, and about 25% of these occur in children,1 began Dr. Mahoney, assistant faculty in ophthalmology, Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore.

Dog bite injuries accounted for the majority of bites (75%) treated in university-based urban hospitals from 1996 to 1998.2 The most common breeds that inflict bites are the pit-bull types, Rottweilers, and German Shepherds, Dr. Mahoney said.

In 1996, dog bites accounted for 330,000 emergency room visits with associated significant costs. Subsequent hospitalization was needed in a small number of this population.3 Between 2004 and 2009, there were about 23 to 34 deaths per year from dog bites in the United States.4

Types of injury

Injuries that result from dog bites include lacerations, puncture wounds, and avulsion injuries.

"Because of the canine mouth structure and strength of the masseter-pterygoid complex, avulsions are frequent," Dr. Mahoney said. "These consist of a puncture hole and related skin tear and underlying soft tissue crush from the bite force."

Bite location in children is commonly on the face, he continued. In addition, bites that occur in children are very likely to be from dogs known by the children.

"It's unfortunate that dog bites that occur in children are associated with the facial area," he said. "Perhaps because children are smaller, or closer in proximity to the dog's mouth, or because they don't have a good inhibition with their interactions with dogs."

Clinical exam, surgical repair

Dr. Mahoney offered clinicians a few caveats about examining these patients. First, he noted, there are usually two wounds, one from the top jaw of the dog, and one from the bottom jaw. Fractures are rare, but if they do occur, they are usually of the orbit or nasal bones (70%). Rarely, if the second jaw injury occurs to the scalp, the scalp itself can actually be displaced at the time of injury and an underlying full-thickness skull puncture can be overlooked, he noted.

"Always look for the second wound," he stressed.

Repair of these injuries may include margin repair, canalicular repair, medial canthal tendon reconstruction, levator tendon repair, devitalized fat removal, and debridement.

Canalicular repair should include intubation, Dr. Mahoney continued. Options for canalicular repair include:

To find the severed canaliculus, Dr. Mahoney noted that inspection with loupe or surgical microscope magnification is necessary. Techniques to aid in identification include irrigation to white tissue, retrograde air/milk/fluorescein injection, and use of a pigtail probe.

"Use extreme caution when attempting to use a pigtail probe [because] the probe can damage the otherwise uninjured structures," he said. "Certainly never use a pigtail probe with a hook. Rather use an eyelet probe."

Canalicular repair can be delayed, he noted, but 5 or 6 days is the maximum time to wait. The sooner these injuries are repaired, the better, Dr. Mahoney said. If there is a delay in repair, patch the wound with ointment and Xeroform gauze.

"Regarding canalicular repair techniques, consider the extent of the lacrimal system injury, the complexity of other eyelid injuries, and the safety of the patient," he said. "In an adult with a simple canalicular injury, sedation may be avoided. In a more complex injury, you can use a bicanalicular approach to support a medial canthal disruption, but this requires sedation."

Simple marginal lacerations can be repaired directly after debridement, Dr. Mahoney continued.

"As with any other eyelid laceration, you should never discard any skin," he said. "Remember to use interrupted sutures when you are closing these. In cases of infection, you can just pop out one or two sutures, especially in children."