TPLO – Tibial Plateau Leveling Osteotomy for the Treatment of Dog Cruciate Ligament Injury

April 1, 2010

in Cat Health

Tibial plateau leveling osteotomy (TPLO) is a very commonly performed surgery to treat dog cruciate ligament injury. Cruciate ligament tears in dogs are by far the most common orthopedic injury that veterinarians see. There are many different ways of treating cruciate ligament injury in the dog and there is, unfortunately, no “right” way of treating it. Below I am describing the TPLO, what it is, how it works, complications, and recovery.

The underlying idea behind the tibial plateau leveling osteotomy is that the top part of the tibia is cut and then rotated to remove the slant that is present on the weight-bearing surface of the tibia. Once the slant is removed, a special bone plate is applied to the bone to hold it still while it heals in this abnormal position. By removing the slant in the tibia, the knee during weight-bearing, is in a neutral position and there is no shifting of the femur compared to the tibia. This effectively eliminates the need for the dog to have a cruciate ligament. Understanding why this works requires an understanding of the anatomy within the dog’s knee or stifle.

The part of the tibia that the TPLO is altering is the tibial plateau. The tibial plateau is the top part of the tibia where the condyles of the femur come into contact. Both cruciate ligaments originate from and menisci sit on the tibial plateau. We term the tibial plateau the “weight-bearing surface” of the tibia. In humans, the tibial plateau is a flat surface. Dogs have a slant to their tibial plateau, usually around 25 degrees, because unlike people, they do not walk upright. What we have discovered in dogs is that when they bear weight on the leg and all the muscles around the knee contract, because of this slant in their tibial plateau, the femur and tibia try and shift on each other with the femur trying to slide off the back of the tibial plateau. This desire to shift has been termed cranial tibial translation. The dog’s cranial cruciate ligament is the ligament that counteracts this force and keeps the femur and tibia from shifting. Unfortunately for the dog, every time they take a step, the cruciate ligament gets stressed trying to stop this force. We suspect this is the reason that dogs develop degeneration of their cruciate ligaments over time and why they can often tear their cruciate ligaments slowly over time without having traumatic injuries like people require.

The TPLO procedure involves cutting straight across the top part of the tibia with a semi-circular or biradial saw blade to free up the tibial plateau then turning the plateau so that the slant goes from around 25 degrees on average to 5 degrees. The plateau is then stabilized in this new position with a specially designed bone plate and bone screws while it heals back together in this abnormal position. By doing this, when the muscles around the knee contract against the now almost flat tibial plateau, the two bones are neutral and there is no desire for the femur to shift on the tibia. Effectively, this eliminates the need for the dog to have its cruciate ligament. This does sound like a very radical approach to fixing a torn ligament, but it has been shown over many years and hundreds of thousands of dogs to be very effective.

Complications with the TPLO can occur and range from 10-20% depending on what you read. The most common complications involve the bone plate and screws that are placed to hold the bone still while it heals. Breakage of the bone screws holding the plate in place occurs more frequently than breakage of the plate. Fortunately, both of these are rare. Breakage of screws holding the plate can result in delayed bone healing or the bone not healing at all. Plate infection can occur and if it does, can be very difficult to completely eliminate. This will require long term antibiotic treatment and may ultimately require that the plate and screws be removed once the bone has healed, usually around 3 months. Fracture of the tibia or fibula can occur but is also rare. Subsequent meniscal damage after the surgery can occur which would require a second surgery to remove the damaged meniscus. This is a complication of every procedure that is done to repair cruciate ligament tears and occurs in about 10% of dogs. Inflammation of the patellar tendon can occur during the recovery leading to pain. This is usually a temporary problem that resolves over a few weeks on its own. Finally, the most common complication is infection or opening of the skin incision, both of which can be treated relatively easily.

Recovery from TPLO surgeries varies depending on the veterinarian performing the surgery. In general, dogs are limited for 3 months to on-leash activity only. This is to prevent running, jumping, twisting and turning motions that could damage the repair or the other hind leg. Dogs are encouraged to use the leg when they are willing so once they are putting it down with each step and no longer holding it up, they can start leash walks. These leash walks should be gradually increased over the full three months. After 3 months, if the bone has healed radiographically and the dog has not had any set-backs, they can return to normal, off-leash activity. Other things during the recovery like physical therapy are also sometimes advocated to speed up the recovery.

The prognosis with the TPLO procedure in a majority of cases (90%+) is good to excellent function on the leg. The dog is expected to return to normal or near normal performance on the leg. Determining which dogs are good candidates for TPLO surgeries is not an easy thing because there are no hard and fast rules when it comes to cruciate ligament repairs in dog. It really is more dependent on surgeons preference than on one technique that is correct for all situations. TPLO surgeries tend to be used most often in medium, large, and giant-breed dogs and the more active, younger dogs. The procedure can be performed, however, on almost any size dog except for your toy breeds like Teacup Poodles or Chihuahuas. Determining which surgery is best for your dog is best done in collaberation with your veterinarian who will give you their recommendations.

Robert Vonau is a boarded veterinary surgeon in Denver, CO. Most days a spent performing TPLO surgeries to repair dog cruciate ligament injuries. Learn more about tibial plateau leveling osteotomy at my site www.petsurgerytopics.com

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