Orthopaedic Surgery for Dogs & Cats
Cranial Cruciate Ligament Rupture
This is a common disease in dogs and is mostly due to degenerative changes in the cruciate ligament. Sometimes the ligament is so degraded and slack it is effectively functionless. The ligament sometimes is torn from pure trauma. In both instances the knee becomes very unstable whenever the dog attempts weight bearing, with the shin bone popping forward with shearing of the knee joint, sometimes including partial or complete tears of a half moon shaped cartilage lying between the femur and tibia called the medial meniscus. Arthritis acceleration follows, and stress transference to the opposite leg can precipitate failure of the knee joint on the opposite limb.
The cruciate ligament never repairs. Once it is degraded or torn it is torn forever. There are several types of joint recovery methods. In very small dogs rehabilitation procedures like dry sand or water walking are often sufficient. For most dogs up to the upper end of medium size a procedure referred to as extra-articular lateral strapping is generally sufficient. For smaller dogs we normally just use dual 50 lb breaking strain nylon placed between two drill holes at the front of the tibial crest (top and front of the shin bone) and to a tight small bone attached to the back of the end of the thigh bone called a fabella.
This partially replicates the action of the cruciate ligament inside the knee and eventually creates a band of scar tissue to do the job when the nylon eventually tears free. For dogs that are heavier and or more explosively active, we use a method called Liga Fibre Toggle. This is a 250 or 500 lb breaking strain woven fibre that is attached to both the tibia and the femur in a closer location to the attachments of the original cruciate ligament using two plastic toggles via 45 degree tilted drill holes in the shaft of both bones. There is a slight risk with what is called polyfibre in any surgical procedure in that bacteria can invade the fibre and antibiotics won't move them out. Apart from that small risk the results appear better than nylon lateral strapping, especially in bigger dogs.
For big dogs above 35 kg there are bone modification surgeries that are probably better than lateral strapping techniques, but at this stage there are no real studies that compare lateral strapping and methods changing joint angles of the knee by remodeling the shin bone to compensate for cruciate failure in large dogs. The earliest procedures (TWO and TPLO) change the angle of the tibial plateau closer to a human style knee without the 25 or more degree backward slope of dogs, so the shear forces are reduced.
The more recent techniques (TTA and TTO) rely on creating a near 90 degree angle between the patellar ligament (kneecap to shin bone) and the tibial plateau, which seems to create a more stable knee though the whole arc of movement. TTO also uses a small horizontal wedge out to reduce the tibial plateau angle and so does a bit of both classes of procedure. TTA just takes a long axis wedge of the front of the tibia with the patellar ligament attached and moves it forward with a titanium cage. Not cheap. None of them are, and are best done in surgery specialty centres if you are insured or can afford it. If you aren’t and you can’t, we do the TTO type procedure. I won’t try and explain them in detail, but Google will provide you with plenty of views, and may help you deal with insomnia.