Bone-flap procedures sound gruesome, and while they are messy, horses tolerate it well, says Kenneth E. Sullins, DVM, MS, DACVS, a professor of surgery at Midwestern University’s College of Veterinary Medicine. The wound also heals nicely because of good blood supply in the head. “Horses are pretty tough. Give them some phenylbutazone and that same evening they’ll have their head stuck in a hay bag.”
However, sinus surgery can be risky and time is of the essence because the good blood supply that promotes healing can hinder surgery. During a standing procedure, the horse must remain quiet so the veterinarian can work quickly and accurately. If the horse repeatedly shakes or jerks his head, surgery with the horse lying down under general anesthesia may be necessary.
With standing sinus surgery, there is less blood loss because the horse’s head is above his heart. When he is lying down under general anesthesia, there may be increased blood loss because the horse’s head is lower. Some horses also panic and thrash when coming out of sedation, risking injury.
If bleeding becomes profuse or blocks visibility during surgery, the sinus can be packed with gauze to stop the bleeding. The flap may then be closed and another standing surgery performed a few days later to remove any remaining pieces.
“It’s not usually the lesion itself that bleeds. What bleeds is normal mucosa and vessels when you rip them. You have to get out as quickly as you can without causing hemorrhage,” Dr. Sullins says.
Even if there is no profuse bleeding and Dr. Sullins is able to complete a surgery, he usually will re-open a flap and re-evaluate in two or three days. “A huge component of sinus disease does not go away on the first surgery and the reason is you can’t see with the bleeding. So unpack it, flush it out, put a scope in there and look at all the corners. My opinion is that’s what makes [the treatment] work.”
Dr. Sullins studied 91 cases of horses who underwent standing sinus flaps using this post-operative treatment protocol and published his findings with coauthor Samantha K. Hart in the Equine Veterinarian Journal in 2011. In a paper titled “Evaluation of a novel post-operative treatment for sinonasal disease in the horse,” they concluded this to be a “safe and effective means to thoroughly assess and treat sinonasal disease” that may help “reduce long-term complications and recurrence rates.”
For medium to large masses, the best way to access the sinuses and ensure that all abnormal tissue has been removed is to perform a frontonasal bone flap, which can be done while the horse is sedated and standing or under general anesthesia.