For most cows and bulls, a cranial cruciate ligament (CCL) injury or tear could mean a trip down the road. Unlike today’s sports superstars or even the high school soccer player who can rest with a leg up after a cruciate surgery, the sheer size and weight of a bovine has made it nearly impossible to repair these injuries, heal them and then hold up under the pressure. Until now.
David Anderson, DVM, MS, Dipl. ACVS, Kansas State University, has pioneered a cranial cruciate ligament surgery that is giving valuable cows and bulls a second chance after injury. Anderson and colleagues have developed the “Wildcat Power Cord” (WPC), named after Kansas State’s mascot, which is a unique nylon monofilament that replaces the CCL in the stifle.
Anderson started working on a CCL replacement in 1992 at Kansas State with Dr. Guy St-Jean and Dr. Andre Desrochers. He continued the research at Ohio State University with Dr. Andrew Neihaus, and finally developed a clinically useful cord when he returned to Kansas State in 2006.
How CCL injuries happen
CCL injuries are most common in cows as a result of slipping and falling during riding by another cow or a bull. “Cows usually suffer acute rupture of the CCL caused by abrupt overloading from slipping and falling while being ridden during estrus,” Anderson explains. “In bulls, we see this more often as a chronic degenerative condition that is associated with overly straight hocks and stifles (conformational predisposition), but we do occasionally see it as a sudden injury associated with bulls fighting.”
It’s more common in dairy cattle because they are mounting cows during estrus and walking to and from housing areas to the milking parlor on slippery surfaces such as wet concrete. In beef cattle, this injury is seen most often in group housing of bulls and during breeding in slippery environments such as muddy, hilly terrain, etc. “In the 1999 NCBA audit reports, arthritic joints were identified as a top quality challenge point and stifle arthritis was one of the more common arthritides leading to meat trim out of the limbs of cattle at slaughter,” Anderson notes. In that study, 12% of beef cows and 18% of beef bulls had arthritis or a stifle injury. At slaughter, 11% of carcasses had at least one arthritic joint resulting in an average meat trim out of 39 lbs per arthritic joint. So — this is a common and serious problem that leads to losses of genetics and losses of consumable product.
CCL injuries are diagnosed by severe lameness, palpation of swelling in the stifle and radiographs to show displacement of the tibia relative to the femur and degenerative joint disease. Anderson says the biggest determinate of surgery success is how quickly a bull or cow can get to surgery. “If the stifle or other joints are in an advanced state of degeneration, the surgery is less likely to be of benefit. Early intervention gives the best chance for success.”
Challenges to CCL repair
The unique challenges of trying to replace a CCL in a 2,500+ lb animal are considerable. “The techniques we use are an amalgamation of techniques described for people, dogs, and the original ground work in bovine CCL replacement done by Dr. Hamilton and Dr. Crawford in the 1970s and 1980s,” Anderson says.
The main problem has always been strength and durability of the replaced ligament. The CCL of a 2,500 lb bull can sustain up to approximately 3,800 lbs of tension during mounting. “We needed a cord that could take 5,000 lbs at least,” Anderson explains. “We started with braided polyester, but could not get more than around 2,000 lbs tolerance. Then we moved to Gore-Tex®, but could not gain sustainability or durability.”
Finally, Anderson moved to monofilament nylon cords and was able to achieve elongation similar to the original CCL strength of > 5,000 lbs, and durability so the cord would not break with wear and tear.
The WPC is made from monofilament nylon cording that is 4.5 mm in diameter or around 1⁄8th of an inch, and each cord used is about 24 inches long. Anderson places two to three cords into each stifle as he operates. “We are working on getting an easier, cheaper fixation system,” Anderson says. “At the moment, we are securing the cord into the femur using an inter-weaved orthopedic plate and attaching it with very large orthopedic screws.”
The surgery takes about three hours to complete; Anderson has done it in two hours and says the longest surgery was three-and-a-half hours. There is no question that size matters during surgery.” The larger, heavier, longer, more muscled bulls are, the harder the surgery is to complete,” he says. “The younger they are the easier it is.”
His main concern post-surgery is infection. “We do the surgery in an orthopedic operating room with filtered air and absolute sterility,” he says. “We do intensive management after surgery to protect the wound and leg from contamination. The next thing we worry about is pain which we prevent by using pre-emptive analgesia. Our pain management strategies have been greatly refined by working with Drs. Hans Coetzee and Matt Miesner.”
His final worry is about the cords breaking, though to-date post-op evaluations have shown the cord to be durable, but Anderson says he still frets about it.
Time and effort needed
The surgery is expensive, so animals have to have good genetic merit to make the $2,500–$3,500 surgery and treatment worthwhile.
Post-surgery, the total recovery time is on the order of six months. Anderson recommends three to four months pen rest in isolation from other livestock, then one to two months pasture rest. “We recommend AI for cows and semen collection for bulls. Return to natural service or pasture breeding is more challenging — so you want to make sure you have genetic material saved back ahead of time.”
Anderson and his colleagues are constantly looking to make this technique bigger and better. He is looking into a different cable system made from metal alloys and carbon fibers, but says using them is a ways off. Presently he’s working to refine and simplify the surgery so it is less expensive and faster to install.
The WPC should hold up for several years, Anderson believes, but the condition of the joint and other limbs has a lot of impact on this. “My goal is that the bull or cow would not have to be culled because of lameness — that this decision would be based on genetic merit and breeding program needs.”
Standing the test of time
In his 20+ years of veterinary surgery, Anderson has done close to 50 cruciate ligament surgeries in cattle. Since the development of the Wildcat Power Cord he has done around 10 cruciate ligament replacement surgeries.
There are very few surgical centers that have experience with this type of sophisticated stifle surgery, and Anderson has consulted with a lot of other universities about the WPC, including several in foreign countries. “I think we will be seeing this tried at more centers around the world if it holds up to the test of time,” he says.
“We have to have realistic expectations,” Anderson states. “CCL injuries in cattle are career ending injuries if not treated. Fewer than 10% of cattle having CCL ruptures are able to maintain productivity because of pain and progressive deterioration. This creates an issue of animal welfare concern. With the past techniques of CCL repair in cattle, we were only able to achieve success rates of 50% for cows and 20% for bulls.”
With the WPC surgery, however, Anderson says up to 70 % of cows and up to 60% of bulls can be restored to productivity — and that is a dramatic improvement over past techniques. “But this takes a serious commitment from the owner and veterinarians to make it happen. My patients have an amazing drive to survive — we just need to give them some help from tim