Pet Surgery Topics

TPLO surgery is one of the many different methods of stabilizing a dog’s knee after a cranial cruciate ligament tear. The TPLO surgery involves cutting the top of the tibia and rotating the bone then putting a plate on the bone to hold it in the new position while it heals. Sounds pretty radical just to make the knee stable but it is a very effective way of stabilizing a dog’s knee. I’ll go further into exactly what is happening in a minute.

First, to understand why we cut the tibia, you need to understand the anatomy within the dog knee. In a human, the top part of the tibia where the femur comes into contact with the tibia, called the tibial plateau, is flat. Because of this, when a person has a torn cruciate ligament, they can get around pretty well without the ligament. What the cruciate ligament does is stop the knee from turning inwards, called internal rotation, and hyperextension, in a person, the knee bending backwards. A person, as long as they don’t want to twist and turn on their leg, can get around pretty well without their cruciate. The dog’s anatomy is different. Dogs have a slanted tibial plateau. On average, the slant is about 25 degrees (see diagram). The consequence of this slant is that when all the muscles around the knee joint contract, the tibia tries to move forward compared to the femur. This movement is what the cranial cruciate ligament in the dog has to stop. Consequently, the cranial cruciate ligament in a dog is stressed every time the dog takes a step on the leg. Like I discussed in the post about CCL disease in dogs, we think this is a big reason why dogs tear their cruciate ligaments with little to no trauma. Just slowly over time becoming lame on the leg because the ligament keeps tearing more and more over time.

The concept behind the TPLO surgery is to remove the slant to the tibial plateau. Essentially, what we accomplish by doing this is we put the tibial plateau at a 90 degree angle to the dog’s patellar ligament. This is an important concept that comes up again in another surgery to stabilize the dog’s knee called the TTA (tibial tuberosity advancement). With the TPLO, a semicircular cut is made completely across the tibia using a special saw.  Once the tibial plateau is free, it is rotated a certain distance (7-9mm for most dogs) until the plateau now has about a 5 degree slant to it. In studies, around 5 degrees was found to be the optimal angle where everything is stable within the knee during a full range of motion. Once the plateau is at the appropriate angle, a bone plate is attached to it to keep it in that position until the bone heals (see diagram). Effectively, what we are doing is making so that the dog does not need his cruciate ligament anymore. In actuality, we do not replace the cruciate ligament at all. We inspect the joint to assess how torn the ligament is, remove the damaged portion of ligament, and make sure other structures within the knee like the menisci are okay. But, as far as doing anything to replace the torn ligament, we don’t. The whole effect in the end is that when a dog bears weight on the leg after a TPLO procedure, and all the muscles around the knee contract, there is no shifting of the two bones, effectively removing the need for the cruciate ligament. Why the dog can run, twist, turn, and do other things that they should need a cruciate ligament for without a problem, we don’t fully understand that. Probably other ligaments surrounding the knee take up that job. We do know though, from having performed this surgery on hundreds of thousands of dogs that they recover and do very well with the TPLO procedure.

Complications with the TPLO surgery mainly involve the bone plate and screws that we use to stabilize the bone and the fact that we have essentially fractured the bone and need to get it to heal. Breakage of the bone plate or screws is a concern but is a rare problem. Infection is a problem that occurs in about 10% of dogs.  The plate, unfortunately, is right below the skin and has little tissue covering it so it is at risk of infection. Infection manifests as swelling, discharge, lameness, and fever. It can occur close to surgery (5-7 days) or can manifest as a low-grade mild infection that appears even months post-surgery. Delay in bone healing can occur and is usually either associated with infection or with breakage of screws that hold the plate on. With most TPLO surgeries, the tibia is completely healed around 8 weeks, 12 weeks at the latest. This is somewhat age dependent, with older dogs taking longer to heal, and activity dependent, with the more active dogs post-surgery taking longer. Another common problem we see are dogs licking their incision open so your vet should always send you home with an e-collar (lamp-shade) for your pet to wear for the first two weeks. There are some other more rare complications that your surgeon should mention to you also when you discuss the procedure.

TPLO recovery varies depending on the surgeon. In my hands, I have the owners restrict their pet’s activity for a full 3 months. Restricting activity is mainly the dog needs to be on-leash whenever outside and otherwise no running, jumping, playing with other dogs, and for the early recovery, no stairs. Dogs are encouraged to take leash walks once they are willing to put the surgery leg down. This is usually one week post-op. Owners can start with 5-10 minute leash walks and gradually increase the duration from there. After 3 months, if radiographs show the bone has healed, the dog has had no complications that set back the recovery, and the dog is using the leg well, they can return to their normal, off-leash activity.

So who is the TPLO procedure for? I recommend the TPLO procedure for any dog over about 40lbs. Dogs below 40lbs. can till have a TPLO surgery, but other techniques that are less expensive can lso be done in those size dogs. The more the dog weighs, though, the more a technique like the TPLO should be considered. Also, very active dogs, I usually recommend the TPLO or similar type of surgery. As far as what is the best surgery for your dog, that is something that depends on the surgeon doing the surgery, what you can afford, and many other factors. There is really no right and wrong answer to which surgery is the best for any specific case. This is still something that is hotly debated across the field of veterinary medicine. The key for owners is to take the initiative and become educated about the options for their pet.