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Surgery Library


Ruptured Cranial Cruciate Ligament in the Dog
Matt G. Oakes, DVM, ACVS
Kimberly R. Cox, DVM, ACVS

Anatomy:
The stifle joint (knee) of the dog is comprised of two bones, the femur (thighbone) and the tibia (shinbone). The patella (kneecap) sits on top of these bones in the middle of the joint. There are four ligaments supporting the stifle: the medial collateral ligament (on the inside of the joint), the lateral collateral ligament (on the outside of the joint), and the cranial and caudal cruciate ligaments (within the joint). Cranial cruciate ligament (CCL) tears represent over 90% of the stifle injuries in the dog. There are two kidney shaped cartilages (menisci) in each stifle joint which act as shock absorbers. The meniscus on the inside of the joint is often also damaged in many dogs with a CCL tear.

When the dog is standing, walking, or running, the CCL is always under tension. The CCL may tear when it is overloaded by hyperextension or twisting of the stifle joint. The ligament is made up of many small fibers, which may break all at once or individually. Dogs with a partial tear of the CCL will sometimes improve with rest. These dogs usually begin limping again as more of the ligament tears. A partially torn CCL is never as strong as the original ligament, and the torn fibers cannot heal themselves. Surgery is recommended for dogs with complete CCL ruptures and for dogs with partial CCL ruptures and persistent lameness.

Clinical Signs:
Most dogs that rupture the CCL do so while running, jumping, or playing. There may initially be significant pain, and the dog may yelp and hold the affected leg off the ground. With a partial CCL tear, they may begin using the leg after a few days of strict rest. A complete tear will usually cause persistent lameness. Larger dogs and those with chronic CCL ruptures are more likely to have concurrent damage to the medial meniscus. Meniscal injuries increase the pain and disability associated with a torn CCL.

Diagnosis:
Palpation of the stifle, radiographs, exploratory surgery, or a combination of these may be used make a positive diagnosis of a ruptured CCL. Your pet may need to be sedated in order to palpate (feel) the stifle joint for instability. If the injury has been present for an extended period of time (greater than 4 weeks), arthritis may be evident radiographically.

Surgery:
At least a dozen techniques for repairing the ruptured CCL have been proven to be successful over the last 50 years. Each surgeon usually has several techniques that he/she is comfortable with, and may use different techniques for different sizes or types of dogs (small vs. large, athletic vs. couch potato). The surgeon will assess your dog's condition, body type, and life style and make a recommendation that he/she feels will most likely result in a complete return to function for your pet.

First, the stifle joint is opened and the remnants of the torn CCL are removed. The CCL is like a small shoestring. It is a short, thick band of fibers that is attached to the femur and tibia. The fibers retract when torn and there is no way to reattach the ends. The meniscus is checked for damage and any damaged portion is removed. The next step is to stabilize the joint to eliminate the instability caused when weight is applied. This is where the surgical technique may vary from case to case.

Extracapsular Imbrication Technique:
A heavy suture(s) is placed across the joint, following the same direction as the CCL. This CCL replacement, however, is outside the joint capsule (containing the joint fluid). Over a period of several months, scar tissue forms around the suture(s) and the joint gradually becomes strong enough to support full weight.

Fibular Head Transfer Technique:
The fibula is a small bone on the outside of the stifle joint which has the lateral collateral ligament attached to it. The other end of the lateral collateral ligament crosses the stifle joint and is attached to the femur. When the fibula is moved forward, the lateral collateral ligament will replace the function of the CCL. A pin and wire are used to hold the fibula in the new position. This technique is usually combined with the extracapsular imbrication technique described above. This technique is typically used for dogs over 40 pounds and is seldom perform at TBVS.

Tibial Plateau Leveling Osteotomy:
This technique changes the slope of the tibial plateau (the surface of the tibia where the femur rests). When the CCL is torn, the femur has a tendency to slide off the back of the tibia. The objective of this technique is to change the slope of the tibia to a more neutral angle so the femur will not slide off the tibia when weight is applied to the joint. Biomechanically, this eliminates the need to tether the femur and tibia with a CCL or CCL substitute. This technique allows for early motion and limited use of the operated leg within a few days of surgery. The tibial plateau leveling osteotomy (TPLO) offers working dogs and very active pets the best chance of regaining full stifle function. This technique is also used for dogs over 10 pounds.