TPLO explained with XRAYS

Why is my dog lame? Why does he need surgery? So what exactly is TPLO surgery? Tibial Plateau Leveling Osteotomy? I will attempt to explain my understanding—in simple language—of how this procedure helps our beloved dogs return to full function on their bad knees.

In Koda's case, the ligament (CCL) inside his left knee joint had a 20% tear (as the surgeon found out during the surgery). It wasn't completely ruptured, but it was being stressed while trying to keep the knee stable as the femur (thigh bone) slid down the steeply angled slope (30 degrees) created by the head of the tibia bone (shin bone) with every bend of the knee.

This stress and pulling of this CCL is what causes the pain when walking and running. Eventually the pull on this ligament increases the tearing, to the point of a complete tear. Or worse, a traumatic incident could just rupture it immediately. Koda was lucky that his was only a partial tear. Other dogs we saw, were so bad they could barely stand to put any weight on the bad leg.

However, Koda's right knee was fine. Though genetically, he still has a very steep 30 degree slope on this leg, there was no evidence of any CCL tearing or arthritis in the joint. A healthy knee! This is great news!

But Dr. Munjar did caution me that there was a 25-30% chance that Koda's CCL in his right knee could eventually tear because of that steep 30 degree angle. The best preventative measure we could take was to keep Koda's fitness level up, keep him at a healthy weight and discourage jumping up and down (which stresses the knees).

So the TPLO surgery is essentially the "leveling" of the contact area between the femur (top bone) and the tibia (bottom bone) - the knee joint. The goal is to reduce the angle to between 2 and 4 degrees.

What the surgeon does is pretty extreme - so make sure you have the procedure done by someone who is board certified and has a lot of experience doing this surgery. What happens is he cuts the entire top portion (tibia head) of the tibia bone, then rotates it to change the angle of slope. Then he uses 6 very long screws to secure a metal plate, fastening the rotated head back onto the tibia bone.

Koda's post-operation Xray: you can see how the tibial head has been "reseated" and secured by the metal plate. The angle has been drastically reduced, so that there is no longer any stress on the CCL.

The "claw-like" hook of residual bone on the left side will naturally dissolve into more of a nub, and filling in towards the tibial head. On the right side, the area of the tibial head that seems to be hanging over will start to fill in toward the rest of the bone, so that eventually it will be well-fused together. This process takes about 8 weeks. Which is why the 8 weeks of inactivity is so crucial - so that the bone can set properly and heal.

Here is another view of Koda's post-operated leg with the metal plate and screws. You can see how long the screw are - running all the way through the leg bone. You may feel that the length of the screws are excessive, but the length is necessary because bones are hollow, so in order for the screws to be secure, they need to be in contact with both sides of the bone - otherwise they will wobble.

For a professional explanation of TPLO surgery, read this.