Tibial Plateau Leveling Osteotomy
Your dog has been diagnosed with a tear of the cranial cruciate ligament (CrCL) – this is similar to the anterior cruciate ligament (ACL) in people, but has a different anatomical name because dogs have 4 legs instead of 2.
Normal Dog Stifle (Knee) Joint – Above
The “stifle” or knee is a very complex joint, but I like to simplify things by using the analogy of a car parked on a hill. The bottom of the femur (thigh bone) ends in a rounded condyle, like the tires of a car (green semi-circle on X-ray image above). The top of the tibia(shin bone) is called the tibial plateau – this surface is flat, but at an angle, like a hill (blue line on the X-ray image above). So if you look at just the bones, we have the “car” of the femoral condyle sitting on the “hill” of the tibial plateau. The CrCL is basically the “parking brake” that keeps the car parked on the hill. This ligament has more work to do in the dog because the slope of their hill is around 28 degrees, compared to people where the hill is only about 4 degrees.
After CrCL Rupture
Now that the CrCL is torn, whenever your dog tries to stand, walk, or run, the femoral condyle slides down the back of the tibial plateau, which also causes the tibia to jut forward. This feels strange to your dog, which leads to them “losing confidence” in the stifle because it seems to give out on them when they put weight on it. It also stretches out the joint capsule, which is painful. When the ligament tears, it also releases inflammatory mediators into the joint. All of these things also set the stage for arthritis in the stifle.
The TPLO Surgery
The TPLO is our best option to treat dogs with a tear of the CrCL. To describe this procedure, it helps to define the terms in the name:
● Tibial plateau: again, this is the “hill” at the top of the shin bone
● Osteotomy: a medical term that means to “cut bone”
● Leveling: to make that hill flat
For this surgery, we make a circular cut in the top of the tibia so we can then rotate that piece of bone to flatten the hill. (We do not go completely to 0 degrees, but aim for about 6 degrees.) We place a bone plate and screws to hold the bone together while it heals. We do not change the length of the limb, nor the other angles in the joint. We also do not change the cartilage surface of the tibia – the normal parts of the joint that communicate with each other are still in place.
Considerations after surgery:
● We have to shave the limb from the hip down the ankle. The fur will grow back, but it can take a couple months. Sometimes the fur grows back patchy until the next big shed cycle (spring or fall).
● The incision will be by the knee. You must protect the incision for 2 weeks while it heals – your pet cannot lick at it. Using an Elizabethan (cone) collar is the best recommendation. You may try inflatable “donut” collars, a Lick Sleeve, or “pajamas”, but make sure they can’t bother the incision.
● Your pet is under house arrest for 8 weeks while the bone and soft tissues heal – this helps ensure everything will stay in place where we want it. I have seen bone plates bend and break, and I’ve seen screws brake or back out – but only in dogs that do too much activity too soon. Dogs should always be on a short (6-foot) leash when they go outside, and only allowed outside for bathroom breaks. This means short walks of about 5 minutes. If they don’t find “their spot”, they should go back inside and try again 15-20 minutes later. They should always be supervised outside. In the house, they should be confined to 1 room, not allowed to wander through the house. Avoid stairs, furniture, running, jumping, and playing.
● It is OK for your pet to use the leg and put weight on it while standing or walking slowly. But they cannot be allowed to run, jump, or play as this will put too much force on the leg.
● You will notice that your dog will hold the operated limb out to the side a bit when standing, walking, or sitting down. This is because they are off-loading that limb and putting more of their weight on the non-surgical limb. Over time (4-6 months), while they heal and recover from surgery, they should start to be more symmetric in how they stand and walk. Some dogs will still continue to sit with that limb out to the side.
We plan to schedule 2 rechecks with your family veterinarian after surgery. The first recheck is about 2 weeks after surgery to confirm healing of the incision and remove any external stitches. The next recheck is about 6-8 weeks after surgery for X-rays will to confirm bone healing. Provided everything looks and feels good, then your pet may gradually return to normal activity over the following 6-8 weeks.