Anyone who's ever been inadvertently bumped by their horse's head knows just how heavy and solid these structures are. But horses' heads aren't invincible: They can suffer injuries ranging from harmless scratches to severe bone fractures.
At the 2013 Western Veterinary Conference, held Feb. 17-21 in Las Vegas, Nev., Jim Schumacher, DVM, MS, Dipl. AVCS, MRCVS, a professor in the Department of Large Animal Clinical Sciences at the University of Tennessee College of Veterinary Medicine, reviewed how to manage some specific head injuries in horses.
Schumacher explained that cutaneous head wounds (or those involving only the skin) generally heal rapidly. They're less likely than limb wounds to become infected (simply due to the fact they're located further away from contaminants on the ground), the head's excellent blood supply contributes to healing, and many wounds can be sutured successfully days after they occur, he said.
But unfortunately, even seemingly innocuous head wounds can be accompanied by serious damage to important internal structures, Schumacher said, including facial nerves, the nasolacrimal (or tear) duct, the nasal septum, dental structures, and ocular structures. Complications associated with head wounds range from restricted breathing and ocular damage to neurologic deficits and hypovolemia (an abnormally low circulating blood volume) due to hemorrhage.
During his presentation Schumacher reviewed how to manage different types of head injuries in horses for his veterinary audience.
Facial Bone Fractures
Veterinarians identify many facial fractures simply using visual inspection and palpation, Schumacher said. Immediately following injury, a depression at the fracture site is often noticeable, he said. This depression can become less obvious after a hematoma forms between the fracture fragments and the periosteum (the soft tissue covering bone), he noted. The depression again becomes noticeable when the hematoma resolves, he said.
Veterinarians can reduce (or bring back into place) some facial fractures—especially those overlying sinuses—using a bone hook or their finger with the horse standing, Schumacher said. If the fracture can't be reduced using this minimally invasive technique, the veterinarian will need to expose, reduce, and stabilize the fracture site via cutaneous and periosteal flaps.
The latter technique generally involves placing the horse under general anesthesia and stabilizing the fracture site with sutures or plates and screws, he said. One complication that can arise with this method is suture periostitis, which Schumacher described as inflammation of the articulation (or suture) between the frontal, nasal, and lacrimal bones, evident as a hard, linear swelling, generally between or below and between the eyes. There's no good treatment for this issue, he said, and the related defect takes a long time, if ever, to resolve.
Schumacher also noted that horses with some fractures—such as a crushed nasal or maxillary (upper jaw) bone resulting in crushed internal nasal structures that restrict breathing—require a
temporary tracheotomy (emergency surgery opening the lower part of the trachea) so they can breathe. If internal nasal structures are damaged, Schumacher said, owners should be forewarned that the horse might require additional surgery to correct nasal septum and other problems after the fracture heals.
Lip and Nostril Lacerations
Schumacher said lip lacerations can be successfully sutured long after injury occurs; however, veterinarians face a challenge when dealing with these defects. Because horses' lips move constantly, many lip lacerations dehisce, or reopen. To avoid this, Schumacher recommended veterinarians close the laceration in three layers before anchoring the lip to the jaw with heavy, nonabsorbable suture material. Another option, he said, is to suture mesh over the wound to relieve tension placed on it by motion.
Similarly, nostril lacerations can be closed for some time after injury occurs, but often dehisce due to motion, Schumacher said. He recommended using mesh over the sutured wound to relieve tension in these cases.
Tongue Lacerations Schumacher said tongue lacerations in horses are rare. If left untreated tongue lacerations typically heal well and, despite potential defects in the musculature, their function is often preserved, he said. Tongue wounds can also be sutured with absorbable material, he said, although he cautioned practitioners to expect some degree of dehiscence during healing.
"If (a wound is) irreparable, you can remove a large portion of the tongue without causing any ill effects," he added.
Ear Lacerations
Schumacher said veterinarians usually suture ear lacerations in two layers: one layer on the outside (or convex surface) of the ear and the other on the inside (or concave surface). Because both cosmetic defects and dehiscence are concerns with ear lacerations, he recommended splinting affected ears with rolled gauze and elastic adhesive tape.
More severe "degloving" ear wounds, however, require different treatment. Schumacher explained that these wounds will cause the ear to curl up if left to heal on its own due to wound contraction (when the skin edges are pulled together and the wound bed is shrinking). Thus, he recommended using a skin graft on the damaged tissue.
For these injuries, "Long periods of splinting might be required to prevent deformity," he said.
Parotid Salivary Gland and Duct Lacerations
In horses, the parotid salivary gland and duct is located below the ear and behind the jaw. Because of their location, Schumacher said, horses lacerate these glands often. He said to expect large
volumes of saliva to leak from the wound, but that some gland lacerations (which aren't as serious as duct lacerations) and even some duct lacerations can heal on their own.
If a parotid duct is completely transected, the veterinarian will need to either destroyed it or treat it by re-establishing the duct's continuity. Schumacher noted that in most cases it's easier and more practical to simply destroy the gland. This option can also be used if the gland is lacerated and doesn't heal. Veterinarians can either inject a destructive chemical (such as formalin) into the parotid gland for about 90 seconds or they can ligate (tie off) the duct and cause the organ's physiologic death, Schumacher said.
Schumacher stressed that there have been no complications reported after eliminating the use of one parotid salivary gland.
Mandible or Premaxillae Fractures
Finally, Schumacher described how to manage mandible (lower jaw) or premaxillae (the very front of the upper jaw, where the horse's upper incisors are located) fractures. He said these fractures generally occur when the horse's incisors "become entrapped in a solid object, such as a hay rack." Many fractures of this sort can be stabilized with the horse standing, he said, using simple interdental wiring.
Fractures further back on the horse's mandible or maxilla generally require more extensive surgery, and common stabilization techniques include lag-screw fixation, acrylic prosthesis, and applying a plate to the fracture, he said.
Take-Home Message
Understanding how to manage head wounds can help veterinarians provide the best possible care when faced with an injured horse.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.
