Noncemented Hips Implanted More Frequently in the Future?

Dr. Roush (left) is shown here with Dr. Darrell Carder, a local veterinarian, Mrs. Carder and their dog McKinzie, a 10-year-old Border Collie mix who received the implant. Photo courtesy of Kansas State University.

Noncemented hip replacements reduce the risk of infection, cut surgery time in half and lower chances for hip luxation, said James Roush, DVM, MS, DACVS, who implanted the first noncemented, commercial product in a client dog at Kansas State University last April.

“This is going to be the gold standard,” Roush said. “More people will eventually pick it up, but I think it will stay mostly in the hands of surgery specialists or veterinarians who are doing nothing but surgery.”

The noncemented prosthesis was originally created in 1988 by David DeYoung, DVM, DACVS, DACVA, dean of Ross University Veterinary Medical School, in conjunction with a human medical implant company. The prosthesis was used as a research model for dogs undergoing total hip replacements and researchers published information from several clinical trials in the Journal of Veterinary Surgery. The prosthesis was not made available for commercial use until BioMedtrix, a manufacturer of veterinary orthopedic implants, introduced a revised version of the prosthesis in October 2003, with DeYoung. BioMedtrix is the only U.S.-based company to offer the cement-less system, DeYoung said.

“We had the opportunity to take what we didn’t like and change it, and take what we did like and improve it,” DeYoung said. In 1988, survival rate for the noncemented or biological fixators was 87 percent, he said. “Once the implant had grown into the bone there was no failure of that interface.”

Designed with a “press fit,” biological fixators allow replacements to fit almost exactly into the femur with small beads blasted onto the central stem of the prosthesis that encourages bone growth, Roush said. The tight fit of the hip replacement eliminates the need for cement, an added foreign substance that causes infection in about 5 percent of traditional hip surgeries. And while cemented prosthetics last about 10 years, at which point the cement may start to loosen, noncemented alternatives may last indefinitely, said DeYoung and Roush.

And by eliminating the drying time for cement, biological fixator surgeries take 50 minutes, said Roush, a professor and section head of surgery at Kansas State University. Roush works with Walter Renberg, DVM, one of the first veterinarians to attend an instructional course on the biological fixator at North Carolina State University.

The new prosthesis is more expensive than the cemented version, but the total cost is about the same because veterinarians save on cement and related equipment. A veterinarian’s cost for biological fixators is about $1,325 compared with about $1,400, according to Roush.

The new system requires new tools, such as broaches and reamers, but BioMedtrix offers common bearing systems (femoral head) so surgeons can use a noncemented hip replacement on a failed prosthesis. “It gives surgeons more options,” DeYoung said.

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