Fractures: Beyond the Limbs, Part 1

A broken bone in a large quadruped is serious stuff. Unlike a kid with a broken arm, you can’t just slap a cast on a horse and send him on his way. Thankfully, fractures aren’t frequent occurrences in horses. When they do happen the most common site is in the distal limb, particularly the cannon bone. But bones can break in a variety of places, and understanding the causes and associated complications will help you become more familiar with these less-common but no-less-important potential fracture sites.

Skull Fractures

The equine skull is a formidable 40-pound (on average) structure that by all appearances is sturdy, but its 14 major bones are susceptible to external traumatic injury. Horses most commonly injure the frontal, nasal, and maxillary (upper jaw) bones that form the front of their face by running into solid objects. Horses can also fracture these thin bones if they toss their head into a hard object or get it stuck in a small space. If the eye is involved, the zygomatic arch (cheek bone) and the orbit bones can fracture as well.

If your horse receives a blow to the head, have your veterinarian evaluate him carefully to detect fractures that might not be immediately obvious. Horses with displaced frontal and maxillary bone fractures might sport a recognizable depression or divot in the skull, even though the overlying skin is often intact.

Your veterinarian should palpate the injured area gently for any evidence of instability or crepitus (grating bone on bone). Because several of these bones overlie the sinuses, their fracture often causes bloody nasal discharge. Your veterinarian can take skull radiographs (X rays) or, for complex fractures, a computed tomography (CT) scan to definitively diagnose the injury.

If a fractured bone’s edges are not displaced, you can treat the injury using conservative management—stall rest and careful handling for several weeks to months. Depressed fractures require surgical intervention for proper healing and cosmetic outcome. In these cases a surgeon elevates the indented bone and fixes it to the more stable areas, using bone plates or pins. They might need to remove small and badly damaged fragments completely.

“Surgery not only provides good cosmesis (physical appearance) but will also help to prevent secondary problems like chronic sinus inflammation,” notes Travis Tull, DVM, Dipl. ACVS, of Rood & Riddle Equine Hospital in Saratoga, located in Saratoga Springs, New York.

Because the frontal, nasal, and maxillary bones come in contact with the normal bacteria flora of the sinuses and nasal passage, all horses with facial fractures should be on antimicrobial medications to prevent infection. Additionally, these horses benefit from anti-inflammatory medications to reduce pain and swelling.

Other common skull fracture sites include the incisors and one or both sides of the mandible (lower jaw), usually resulting from trauma. Mandibular fractures are less common but easy to recognize because the horse’s lower lip droops dramatically and his lower incisors appear displaced. The tongue might also protrude from the mouth, and some incisors might be broken or missing. In more stoic animals the first signs of trouble might only be excessive salivation (see page 30), malodorous breath, and a reluctance or inability to eat.

Horses with bilateral (both sides), displaced, or unstable jaw fractures require surgical repair. “Uncomplicated fractures of the incisors or mandible can usually be stabilized with intraoral wiring techniques that result in good cosmetic outcomes and immediate return to function,” Tull says. Again, veterinarians administer anti-inflammatories and prophylactic antimicrobials in these cases.

Horses that rear and flip over backward, striking their poll on the ground, can fracture structures deeper within the skull: the basisphenoid and petrosal bones located at the skull base and the occipital bones around the eyes. Because these bones help form the chamber encasing the brain, fractures in this region can cause neurologic damage and carry a guarded prognosis. The specific signs depend on the location and severity of the damage, but horses might display an altered attitude, circle or head press, and become incoordinated. These horses might also appear blind and could show signs associated with cranial nerve damage, such as a head tilt, ear droop, or inability to swallow.

Veterinarians use radiographs to identify these fractures, though it’s important to note that brain trauma can occur even without concurrent fracture. Because deep skull fractures are extremely difficult to access surgically, veterinarians typically focus their efforts around treating and managing any neurologic damage. They might administer anti-inflammatories to reduce brain swelling, as well as anticonvulsive medications if the horse develops seizures.

Rib Fractures

Rib fractures most commonly occur in neonatal foals—typically due to the incredible pressure exerted on the thorax (chest) during birth. Five percent of foals are born with fractured ribs. The majority of these cases involve the most forward ribs, and multiple ribs are typically affected, usually only on one side of the chest. The breaks occur approximately 2-3 cm above the sternum (breastbone), which overlies the heart and lungs.

“The fracture itself doesn’t pose a risk to the foal, but the complications associated with lacerations of the lungs, diaphragm, and heart do,” explains Samantha Morello, DVM, Dipl. ACVS, clinical assistant professor of Large Animal Surgery at the University of Wisconsin. Clinical signs of damaged lungs or heart include increased respiration and heart rate, evidence of blood in the thorax, or damage to the diaphragm apparent on ultrasound.

To check for fractures, veterinarians carefully palpate a foal’s chest after birth by gently running their fingers along the length of each rib. Clinical signs include swelling, discomfort, or instability. If the foal has many consecutive fractured and displaced ribs, he will develop a “flail chest,” where the injured section of the chest moves out of synch with the the stable segment, impairing his ability to inflate his lungs. Fractured ribs are one of the few types of fractures for which radiography is not the diagnostic tool of choice. Ultrasound is much more sensitive for detecting these breaks.

If rib fractures are displaced and only one or two ribs are involved, veterinarians typically recommend conservative treatment: quiet stall rest. Treatment for fractures associated with lung and/or heart lacerations is far more intensive.

“Fractures that are causing or at risk of causing complications require immediate attention,” says Morello. Veterinarians repair more extensive displaced fractures surgically using bone plates, stainless steel sutures, monofilament, or even sterilized plastic cable ties to prevent further damage. Since the advent of these techniques, the survival rate of foals with displaced rib fractures has improved significantly.

Rib fractures in adult horses are rare and usually happen when a horse sustains traumatic injury such as a kick from another horse or a fall. Clinical signs can be subtle and include swelling at the bone lesion, forelimb lameness, an altered respiratory pattern, or discomfort when being saddled. Veterinarians use ultrasonography to diagnose these breaks as well.

Stay tuned for part 2!

Happy Riding!

Source: http://www.thehorse.com/articles/34635/fractures-beyond-the-limbs