centerline of Cory’s exercising larynx. With each breath, the paralyzed cartilage and sagging vocal cord were dragged into his windpipe. His airway was occluded by 70 percent at work.
The dynamic endoscopy confirmed what the veterinarians had suspected all along: Cory was a prime candidate for prosthetic laryngoplasty, the installation of permanent sutures to hold the paralyzed portion of the larynx open. Specifically, the arytenoid cartilage that opens and closes the larynx is stitched to the cricoid cartilage, creating a fixed opening on the left side. The arytenoid cartilage on the right side continues to function normally, opening and closing with each breath.
First attempted in 1893, prosthetic laryngoplasty has undergone refinements for the last 125 years. Success rates for the procedure vary from 5 percent to 95 percent, depending on many factors: breed, use, definitions of success, prosthetic material, variations in technique, owner compliance, recovery procedures and rehabilitation methods. But the factor of greatest importance is surgical experience with prosthetic laryngoplasty, and Hackett has that in spades. She does six of the procedures a month.
Still, Cory’s surgery was daunting to me. The worst part was seeing him unconscious on a gurney. He was lying immobile on his side, thick ropes binding his feet together at the pasterns, legs wrapped in heavy plastic, tongue dangling a half-foot out the side of his mouth, eyes glazed and wide open, seeing nothing.
I watched as the surgeon, residents, technicians and upper-level veterinary students prepared his body, their hands approaching and retreating in quick movements like bees to a hive. A plastic tube the size of a drainpipe pumped oxygen and anesthetic into his airway, and the endoscope was threaded up to the larynx. Hackett could see her maneuvers magnified onto a computer screen as well as through the four-inch incision she carved into Cory’s throat.
The delicacy of the larynx’s location cannot be overstated. Within two square inches lies the machinery for breathing, eating, drinking and circulating blood between heart and brain. The arytenoid cartilage is buried in soft tissue, and the cricoid cartilage takes different shapes among individual horses, so surgeons never know exactly what they will find.
The prosthesis must manipulate every breath the horse takes for the rest of his life, sleeping or racing, tranquil or hysterical. That’s about 20 years, given that most larynxes are corrected before maturity. Prosthetic sutures undergo forces of 10 pounds per swallow---and a horse swallows more than 1,000 times daily. With each cough, the prosthesis is pressured even more. If it’s a little too tight or a little too loose, it will fail.
Hackett retracted tissue layer by layer until she reached the larynx, then she sewed fat blue sutures from the arytenoid cartilage to the cricoid cartilage, tying the larynx open. She