Ever wonder how a horse can lift such a large head? Well, a horse’s head is pretty large—after all, it has to have pretty large cheek muscles to chew all that hay—but nature designed the equine skull to be fairly light in spite of its large dimensions. Horses have extensive sinuses: their frontal, maxillary, and basisphenoid bones have large, air-filled spaces instead of being solid bone. Just like humans, horses can get sinusitis (infection of the sinuses that manifests as large amounts of pus and fluid), which makes them cranky because of the inflammation and internal pressure.
The best way to treat sinusitis in horses is to flush out the infection as best you can so that the intravenous antibiotics can work on a smaller population of bacteria. To access the sinuses, we cut a small hole through the thin bone using a hand-powered trephine, a circular saw that cuts as you twist it. In the sedated horse, we bore one hole into the frontal sinus and take a fluid sample to see what type of bacteria grows, so that we’re confident the type of antibiotic we chose will be effective. After boring a second hole into the maxillary sinus, we flush saline into the frontal sinus until the fluid coming out the maxillary sinus is perfectly clear.
I was excited to practice the trephining technique during a recent clinical anatomy lab. Using donated cadavers, we practiced locating the sinuses; making a skin incision, and then boring holes using the trephine. It was harder than I expected, but I think part of that was due to the fact that the trephines were very dull!
Roberta
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