Sep
17
2008

A group of researchers from Uludag University in Turkey have published a study about using a cow bone plate-screw system for spinal stabilization in dogs. Despite the positive findings, however, academics and practitioners are skeptical, with one specialist calling it “a horrible idea.”

The study, published in the Korean Society of Veterinary Science’s Journal of Veterinary Science, is titled “Contribution of the xenograft bone plate-screw system in lumbar transpedicular stabilization of dogs: an in-vitro study.”  

In essence, the group was trying to prove that a xenograft bone plate and screw system – similar to a metal plate-screw (MPS) system except made of machined cow bone – was effective for stabilizing a dog’s spine after the facets and lamina were removed.
 
The researchers used the L2-L4 lumbar vertebrae from 20 cadaver dogs and divided them into four groups of five specimens. The muscle was removed from all of the vertebrae, but the ligaments and discs were left in place. Group I was left intact; in Group II laminectomy and bilateral facetectomy (LBF) were performed on the L3 vertebrae and no stabilization was added; Group III had LBF with transpedicular stabilization (TS) via metal plate and screws, and Group IV had LBF with TS from the xenograft bone plate-screw (XBPS) system.

Stiffness was then measured with a tensile compression testing machine to determine the stability of each group. The five groups were tested under five types of load: flexion, extension, left and right bending and rotation.

According to the study, Group III (metal plate system) was 131 percent stiffer than the intact vertebrae, and group IV (bone plate system) was only 47 percent stiffer. The researchers said that since metal screw-plate systems suffer from problems such as loosening, bending, breaking or screws being pulled out, the bone system was preferable.

“As a conclusion, considering the maximum stiffness values of group III and the disadvantages of the MPS system, the XBPS system with its excellent stiffness values can be a good choice for achieving TS.”

‘Horrible idea’

In spite of the Turkish group’s conclusion, other spinal surgery and stabilization experts said the procedure was not viable.

James Toombs DVM, MS , DACVS, a professor at the Iowa State University College of Veterinary Medicine looked over the study for this article. His research areas are spinal cord injury, bone grafts and implants and external skeletal fixation.

“The idea of fixating the spine of dog with plates made of cow bone - I’m less than excited about [it],” Toombs said. “I think it s a horrible idea.”

Toombs said that xenograft bone implants are generally not used for that purpose any more, since it was too difficult for the body to absorb them.

“These things wind up being pieces of dead bone that the body can’t incorporate and deal with,” he said. 

A private practitioner said the study had “all kinds of holes.”

“All they did was prove that you can machine raw bone into a plate and screws and then attach them to vertebra and that there is some increase, although minimal, in the amount of resistance to movement with the plate and screws,” said Terry L. Dew, DVM, MS, DACVS, owner of Azzore Veterinary Specialists in Russellville, Ark. “Spinal stabilization is tough … we can get spinal fusion in many different ways and now with locking plates and screws the complications associated have been reduced.”

Another spinal expert and professor at Iowa State, Karl Kraus, concurred. Kraus is also a co-developer of the SOP pedicular spinal system for dogs. He said the xenograft bone system was not a viable option, and the stiffness issue of the bone plate is not the main problem.

“They may be stiff, but not strong (like an egg is stiff but not strong), i.e. brittle,” Kraus said. “And they get more so over time.  Other materials and composite materials allow the appropriate mechanical characteristics.”

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