A deep sense of satisfaction about his choice to become a small animal orthopedic surgeon spread through Dr. David Knazovicky as he viewed a video that recently arrived in his email inbox unexpectedly.

A border collie named The Tick and seven other dogs were competing in the fast-paced sport of flyball, taking turns in relay teams of four sprinting down a course, jumping hurdles, grabbing a tennis ball and then returning the 51 feet over hurdles to the start.

That Knazovicky had replaced The Tick’s hip at the NC State College of Veterinary Medicine less than a year ago made the dog seem like a miracle in motion.

“After the surgery, we see these dogs walk, put weight on the leg the next day, and of course they are still in pain from the procedure, but later on you can see that for these dogs, it really takes the pain away,” he says. “We don’t always get to see them this far after, so this was an amazing surprise.”

Knazovicky, who anticipated a career as a pain researcher when arrived at NC State in 2012, estimates that he’s performed nearly 200 uncemented hip replacement surgeries on medium to large dogs throughout his training and practice. Now, Biomedtrix, maker of the press-fit implant system used at NC State, is making implants available for cats and miniature dogs, too, and Knazovicky is one of the first in line for training.

Offering state-of-the-art care to its clients is a pillar of the NC State Veterinary Hospital, which also is investing in the smaller surgical instruments required.

“This next level of ability also could lead to replacing other joints in cats and dogs,” says Dr. Anthony Blikslager, associate dean and director of Veterinary Medical Services. “Dr. Knazovicky is beginning to assess other joints such as the stifle and elbow for replacement. We are so excited to be able to continue to provide and create the innovation that has gone into joint replacement in small animal patients.”

Dr. Knazovicky, a native of Slovakia, also is one of a handful of surgeons currently completing a fellowship in Joint Replacement Surgery, a program the American College of Veterinary Surgeons approved about seven years ago. Dr. Simon Roe, a retired small animal orthopedic surgeon at NC State, is a founding fellow of the program, and NC State is one of only about 10 institutions approved to provide the extensive training required to complete the fellowship.  

Legends in the Making

As is the case with many veterinary advancements, uncemented joint replacements in dogs started in the early 1990s when a surgeon working with a research group wanted to create an uncemented hip design for humans. 

Cemented hip replacements require preparing a bed for the implant in the bone, filling it with cement and then setting the implant into the cement until it hardens. The interface between the cement and bone can loosen over time. 

Dr. David DeYoung, an orthopedist at the NC State College of Veterinary Medicine, collaborated with the group to develop the Porous Coated Anatomic System, which allowed the bone to grow into the surface of the implant without needing cement, leading to longer term stability.

DeYoung coordinated a trial of the implant at NC State that was hugely successful, which led the company to want a longer term study. DeYoung suggested that the NC State Veterinary Hospital offer the implants to its clients, most suffering from osteoarthritis from hip dysplasia or serious injury, and follow the cases over several years. 

By then, Roe, who has a Ph.D. in biomechanics in addition to his DVM, had arrived to work with DeYoung and Dr. Frank Abrams, then a professor of biological and agricultural engineering at NC State University. Abrams was instrumental in combining the mechanical and biological engineering fields into biomechanics at NC State.

The resulting five-year clinical trial in medium and large dogs proved every bit as successful as the initial trial. The problem, Roe said, was that the company reduced its research division and stopped making implants for dogs.

“So we had to stop doing uncemented hips because we no longer had implants to use,” Roe said. “That went on for about five years, and during that time we did cemented total hip replacements which had been available in dogs for quite a while.”

In 2003, Biomedtrix, which was making the cemented implants for dogs, introduced the uncemented system, with significant input from the NC State pioneers. In 2022, the American College of Veterinary Surgeons Foundation recognized DeYoung for his work on joint replacements with its Legends Award.

Over the years, DeYoung mentored Roe, and now Roe has been mentoring Knazovicky as he works part-time to complete the fellowship. With the skills developed on the many standard hip replacement surgeries that he has done, Knazovicky will also soon be able to offer the procedure in smaller animals.

In addition to hip replacement, cats and small dogs with debilitating hip pain also can receive a femoral head and neck osteopathy, or an FHO procedure, that requires cutting off the ball of the femur and letting muscles and tendons grow to keep the leg in place. While small pets that aren’t athletes tolerate an FHO because they have three other legs to compensate, Roe said, their gait is not normal.

“I’m very excited that Biomedtrix has produced uncemented implants for the micro and toy breed sizes,” Roe said. “That’s a great step forward for that group of patients, and it’s great that David will be able to bring that to NC State to help out those little ones.” 

A Choice for Clients

Knazovicky said most uncemented hip replacements at NC State have been in young animals with congenital hip disorders or in animals that are athletes with plenty of years of agility left. The treatment decisions are up to clients based on how much mobility they believe their dogs need to live good lives.

“We can do medical management for hip dysplasia for months or years, keeping the weight down, control some pain, use some PT, and some dogs do well for 10 years, and they never need surgery,” he said. “It really depends on the expectation.” 

Roe’s most memorable patient was a military dog trained to detect improvised explosive devices in Iraq and Afghanistan during Operation Desert Storm. After several tours, the dog developed hip pain and lameness, but after an uncemented hip replacement at NC State, he completed two more tours.

“Putting an artificial hip in will, in most cases, get them back to being pretty athletic, if that’s what the owners want,” Roe said. “So it’s great to get videos like The Tick’s because we actually don’t hear from all that many owners. The dogs just do wonderfully for the rest of their lives, and we see very few of them after the three-month recheck.” 

The surgery requires dedication from owners during the recovery. The patient must be very limited in activity in the first month, with a gradual return over the next two, Roe said. Most are nearly ready to run after three months.

Amanda Brown, who helped start a flyball club in Raleigh in the 1990s, invested in intensive, private rehabilitation for The Tick after his surgery last July so that he could return to the sport they both love. The dog had luxated his hip playing in the yard with her other dogs, and she chose the uncemented hip replacement because the hip kept slipping out of place despite treatment.

“The surgery was obviously amazing,” Brown said. “He has full range of motion in that hip. I am really pleased. Everything at NC State was perfect.”

When The Tick returned to flyball in May, she was so excited by his recovery that she thought the surgeons should see their handiwork and sent a link to the video to the NC State orthopedic team.

“One of the neat things about the surgery is that every case is a little bit different, the feel of things, the shape of things,” Roe said. “It requires good awareness of the nuances in order to get a good result every time, and that just mostly comes with experience.”

At the end of July, Dr. Knazovicky will continue NC State’s pioneering ways when he starts getting the experience to offer life-changing uncemented hip replacements for cats and small dogs, too.