The combination of a custom prosthetic hoof, bold surgical techniques, and seven months of round-the-clock care at New Bolton Center made it possible for a unique patient to regrow an entire hoof.
Zippy, an 18-year-old zebra, is back home at Skirmish Hill Farm in West Chester, delighting his owner, local equestrian Mrs. Roberta Odell. Watching him gallop to greet her is remarkable, considering that a year earlier Zippy’s entire hoof fell off.
An abscess in his foot made it impossible for Zippy to bear weight on his right hind leg. Despite medical treatment, the infection was so serious that the structure of the hoof was completely compromised, and it separated from the bone.
“We knew there was a chance that, if we could just keep him comfortable and alive and thriving, he could simply regrow his hoof,” said Dr. Dean Richardson, Chief of Large Animal Surgery at New Bolton Center. “So that’s what we set out to do.”
The chance of success? About 20 to 25 percent, Richardson thought at the time.
“I absolutely thought he had a legitimate chance. He was small and he was tough,” Richardson said. “He had lost only one foot, which makes it a whole lot easier than if he had lost more. I wouldn’t have encouraged treatment if I didn’t think he had a chance.”
Slim odds, yes, but Odell was committed to saving Zippy’s life, if at all possible.
Why? “Because we like him,” she said, smiling.
Zippy, a Zebra with Personality
It may seem peculiar to like a zebra, since Zippy will bite a finger off if given the chance. In fact, he has done so. Zebras are known for being aggressive, wild animals that are difficult to domesticate.
But Zippy also has an outsized personality that has entertained Odell ever since she got him as a foal, only a week old, from the New Bolton Center Neonatal Intensive Care Unit. Zippy is one of many animals owned by Odell, including several horses on which she rides dressage, and a team of four white mules that she drives in events.
Zippy is well-known by the New Bolton Center community, and despite his dangerous behavior, he is also well-liked. Born a maladjusted, or “dummy” foal, he started his life in the NICU at New Bolton Center, and over the years has returned several times. During his recent months-long treatment, he became a bit of a celebrity, braying loudly and opening his mouth to have little treats tossed in by visitors.
“We have a good, long-standing relationship with Zippy,” said Patrick Reilly, Chief of Farrier Services. “I genuinely like him. He is one of my favorite patients, ever. But you don’t treat him like a horse. You have to respect that he is a wild animal.”
Zippy has to be anesthetized every time the medical teams touch him, which made treating his condition a complicated challenge.
“Zippy represents a very good collaboration between anesthesia, surgery, and farrier,” said Reilly, an integral member of Zippy’s medical team. “All were very important to his care and success.”
Zippy arrived at New Bolton Center on September 3, 2013, referred by New Bolton Center’s Field Service for lameness. After a series of radiographs, the abscess was drained. A poultice was applied, and Zippy was treated with several medications.
Reilly made a special shoe for the affected hoof to make it more comfortable for Zippy to support weight on the leg. When Zippy tried to stand for the first time in weeks, the severity of the problem became apparent when the entire hoof capsule came off, in one piece.
“In Zippy’s case, the abscess undermined the whole foot,” Reilly said, explaining that the infection expanded between the hard hoof on the outside and the soft foot on the inside, destroying the sensitive lamina that connects them.
Dr. Richardson performed several surgeries on Zippy over the next several months. First, he put a transfixation pin across the cannon bone and surrounded the pin with a cast.
“What that does is allow him to bear weight on that leg without putting weight on his foot,” Richardson explained. “The pin transmits his weight. The foot was completely protected from weight-bearing forces.”
Reilly fabricated a hydrophilic sock, which easily absorbs moisture, made out of urethane foam to help make the cast more comfortable. The material is not one usually used on horses; it was developed as a wrap for human burn victims. A traditional wrap has fibers that can cause infection.
Keeping Zippy healthy and comfortable was critical to making it possible for the transfixation pin to stay in long enough to allow the hoof to start to grow, Richardson said. Regular cleaning and several cast changes allowed the pin to remain and function well for two full months. The hoof started to regenerate, growing down from the upper limit of the hoof capsule, known as the coronary band.
“It was a matter of intermittent intensive work,” Richardson said. “We regularly had to put him under anesthesia to inspect and clean the foot, but in between, there really was not much we could do other than feed him and monitor his comfort.”
In October, an evaluation showed that the infection had severely damaged the coffin bone – the bone within the hoof. Richardson surgically removed nearly a third of that bone.
By the end of November, enough hoof wall had grown to form a surface for Reilly to attach a prosthetic hoof he created just for Zippy.
“This was a first,” Reilly said, explaining the process. He cut a piece of hard plastic the size of Zippy’s foot. “I put it in a toaster oven during surgery to get it soft, and molded it right around Zippy’s foot,” he said.
Reilly filled holes he made in the plastic with special polymers, and also glued the cuff of the plastic shoe onto the new hoof. Reilly is familiar with these polymers, since he regularly puts “glue-on” shoes, pioneered at Penn Vet, on his patients.
Zippy wore the prosthetic hoof for four months, living at New Bolton Center, allowing the hoof to grow underneath.
“And that just continued to grow until finally his foot had become completely encased in hoof wall,” Richardson said. “It really was that simple.”
Zippy grew an entirely new hoof. “It’s a perfectly normal-looking foot now,” Reilly said.
Zippy suffered from a type of laminitis, when the hard, outer part of the hoof separates from the soft inner core, an excruciatingly painful condition. Richardson said he has treated horses that have sloughed off part of a hoof, but he has not had a case like Zippy’s, in which the whole hoof fell off and was regrown.
However, Zippy is not the first case at New Bolton Center involving the loss and regrowth of a hoof. Mystic Park, a famous Standardbred racehorse, came to New Bolton Center in the summer of 1983, suffering from Potomac Fever. Laminitis set in, and he eventually lost all four of his hooves.
New Bolton Center’s unique recovery pool made it possible for this champion to survive while his hooves grew back, giving him relief for several hours a day. In addition, he received round-the-clock care, nurses literally fluffing and adjusting pillows to help alleviate the consequences of lying down for long periods. Mystic Park survived and went on to become a successful breeding stallion.
The fact that Zippy lost only one hoof, and that he is small and tough, helped his prognosis, Richardson said. Zippy, about half the size of a full-sized horse, was happy to lie down for long periods of time and didn’t develop the sores that often occur in horses that cannot stand normally.
In many laminitis cases, pain is a limiting factor in the decision to go forward with treatment. But pain was not a major issue for Zippy, Richardson said, adding that the transfixation cast was key to alleviating much of the pain as his foot grew down.
Zippy’s success, Richardson said, is further evidence that transfixation casts are a useful option, even in full-sized horses, especially combined with the much-improved slings that make it possible to keep a horse off the ground for longer periods of time. Transfixation casts have frequently been used at New Bolton Center for treatment of certain types of severe fractures.
“This case gives more support to the idea that total regrowth of a hoof is something that is possible if you can manage the nursing challenges,” Richardson said.
An enormous nursing challenge with Zippy was that he could not be treated without going under anesthesia. New Bolton Center nurses have worked with patients like Zippy, including large animals from zoos and circuses.
“The first time we anesthetized him was the easiest because he didn’t know what was coming,” said Dr. Kim Olson, staff veterinarian at New Bolton Center, specializing in anesthesia.
“He struck me as incredibly smart,” Olson continued. “I think with a lot of creatures it gets easier after doing something new again and again, but with Zippy it got harder. We had to get more innovative on how to approach him.”
When he saw a group of people wearing blue scrubs, he would back away. Olson said she would need extra staff each time they approached him. “He certainly was challenging,” she said, explaining that they used a “pole syringe” to inject him from afar. “We just had to persevere.”
Zippy loved treats, however, and became excited when people approached his stall to toss bits of carrots or peppermints into his open mouth from afar. He seemed to recognize his favorites, like Amber Slonaker, a devoted nurse, who earned his trust.
Each day she scratched his ears through the stall bars. Over the weeks she slowly worked her way into the stall, grooming tools in hand. She continued the favorite scratches, and gave him peppermints. Slonaker eventually was able to groom him, and he was not aggressive with her.
“I made it a point to try and show him love and compassion during his stay, and I think he enjoyed it,” Slonaker said. “It was a joy to see him light up when he saw me with the brushes, knowing I made at least part of his day enjoyable. Seeing him walk out of here to go home was one happy day!”
Reilly removed Zippy’s prosthetic hoof on March 27, and he was discharged to go home on April 9. Odell visits daily, Zippy racing to meet her at the fence, knowing she will give him chunks of carrots from the end of a very long knitting needle she uses to protect her hands from his bite.
Odell said she is very pleased New Bolton Center veterinarians were able to save Zippy. “It wasn’t easy, because he’s so hard to deal with,” she said. “He seems like he’s 100 percent.”