Triple Tibial Osteotomy
The function of a dogs’ cranial cruciate ligament is essentially like a cars’ handbrake. If you have a steep driveway, then you would always have to pull the handbrake on – tight! With time, your handbrake would stretch, and if something wasn’t done about it, eventually the handbrake would fail. The same thing can happen to your dogs’ cranial cruciate ligament. The top of the tibia (shin bone) is essentially like the steep driveway (tibial plateau), and the bottom of the femur (thigh bone) is rounded, much like car tyres are round. If the cranial cruciate ligament becomes “stretched” or partially torn, then pain, inflammation and lameness can occur. Sometimes this can settle down with rest and medications, but often it keeps re-occurring, and eventually the “handbrake” (cranial cruciate ligament) can completely break, which can be really painful and cause other problems.
After a car’s handbrake has snapped completely, the car can roll down the driveway and damage other things that are in its path (like the neighbour’s house). In the case of a completely torn cranial cruciate ligament in a dogs knee, this can often lead to damage of the medial meniscus. The medial meniscus is an important structure that sits between the femur and tibia and acts like a “shock absorber” in your cars’ suspension system. Much like broken suspension components, a damaged medial meniscus doesn’t do a very good job of shielding the body from the impact of daily activities. Not only that, but it can also be quite painful, as it is attached to the sensitive structures surrounding knee joint (the joint capsule).
Ideally, stretching of the cranial cruciate ligament should be treated early on in the disease process to try to minimise any further damage to other important knee joint structures (like the medial meniscus) because unfortunately, nothing protects the medial meniscus quite like the cranial cruciate ligament. So if we can intervene early by “flattening the driveway” (i.e. tibial plateau), then we can take the strain off the handbrake (cruciate ligament) which can allow it to heal and protect the medial meniscus.
To flatten the tibial plateau (the driveway), the steepness (angle) of the tibial plateau (the driveway) is measured off the radiographs (xrays). To correct the steep angle, three cuts are made in the tibia (triple tibial osteotomy) and a wedge of bone is removed that corresponds to the steepness of the tibial plateau (steepness of the driveway). Then the pieces of bone are held together using a stainless steel plate and several screws.
Post-operative appearance of a triple tibial osteotomy in a large breed dog.
(This patient had been hit by a car and also had a medial collateral ligament rupture that needed repair with a spiked washer and screw in the distal femur and eyelet screw in the proximal tibia and prosthetic ligament running between them).