New Mexico's Pet Resource SPRING 2004


CANINE CORNER

ANTERIOR CRUCIATE LIGAMENT SURGERY

by Nancy Marano

Amber, a 14-year-old Golden Retriever from British Columbia, loved accompanying her owner on hikes over the trails around her home. Then her left hind leg started causing her consider able pain and she could no longer walk.

Jojo, an 11-year-old, overweight Yorkshire Terrier, experienced a traumatic injury when he jumped from a window ledge in an attempt to catch a squirrel.

Amber and Jojo have never met, but they are soul mates. Both were older dogs who experienced lameness due to a torn anterior cruciate ligament (ACL) in the stifle joint (canine for knee) and both underwent successful surgery for the problem.

ANATOMY

The stifle joint in a dog is similar to the human knee. Within it are the femur, tibia, and patella (kneecap) bones, the medial and lateral collateral ligaments, which run on either side of the joint, and the cranial and caudal cruciate ligaments, which cross inside the joint. There are also menisci that act as shock absorbers between the bones and perform the duties of cartilaginous ligaments.

Unlike the hip, which is a ball-and–socket joint, the stifle is an articulated joint where the femur (thigh bone), fibula and the tibia (shin bone) meet and are held together by the ligaments. The function of the cruciates is to stabilize the joint. They limit the internal rotation and the movement of the tibia and help prevent the joint’s hyperextension.

“If any of those five ligaments is broken, the joint becomes unstable,” says Dr. Michael Riegger, D.V.M. and Diplomate, American Board of Veterinary Practitioners. “When it becomes unstable, the internal movement chews up the joint and arthritis sets in.”

DIAGNOSIS

Injury to the anterior cruciate ligament (ACL), also known as the cranial cruciate ligament (CCL), is the most common cause of hind-limb lameness. Such an injury can result from trauma, poor conformation, obesity or degenerative joint disease.

Traumatic injury most often occurs in younger dogs and is tied to a specific traumatic event. The usual cause of the problem is chronic degeneration of the joint through the wear and tear of the aging process. It is much more likely this injury will be found in older dogs, aged seven years and up. It is also true that a ligament weakened by degenerative disease is more easily ruptured.

If the ligament ruptures, the body makes an effort to heal it. For a while the dog will seem to get better, but then the lameness will return. This is usually the result of damage to the meniscus or the total rupture of an already torn ligament.

When lameness, with accompanying pain, occurs, the veterinarian performs a cranial drawer test on the affected limb. This test is done by placing the fingers on either side of the affected joint. If movement or instability can be detected within the joint during palpation, it is a sure indication the joint is damaged. Often, this test must be done while the dog is sedated because it can increase the pain in the joint. Also, dogs have a tendency to guard an injury. This is particularly true when testing a larger dog. The veterinarian will follow up with x-rays to determine the extent of the problem.

TREATMENT

Several factors must be taken into consideration in determining treatment. What is the dog’s age and general physical condition? What is the dog’s lifestyle? Is he a working dog or does he lead a sedentary life? What about the economic considerations? These might be a factor since the surgery costs from $250-$800. How conscientiously will the owner follow post-operative care instructions?

Conservative treatment consists of limited exercise, anti-inflammatory medications, weight reduction and some physical therapy but no surgery. This may help some dogs, especially those weighing less than 15 pounds. But most veterinarians prefer to stabilize the joint via surgery to lessen the chance of further degenerative joint disease. Surgery also decreases the likelihood that the other stifle will be damaged, something that commonly occurs because of the extra strain put on the healthy joint to compensate for the painful one.

Several surgical procedures are available to stabilize the joint. These surgeries can be categorized into three different types. One procedure is intracapsular ligament replacement, which means transplanting tissue or synthetic ligament replacements into the dog’s knee in order to put the ligament into the correct position. Another surgical technique is called extracapsular stabilization. This uses internal tissue, suture material or stainless steel wire to stabilize the joint so that it acts as if the cranial cruciate ligament weren’t damaged. This technique is done outside the knee joint. A third technique, called Tibial Plateau Leveling Osteotomy® (TPLO), is a patented procedure that veterinarians must be trained to use. Then they are licensed by the developer to perform the surgery. TPLO does not try to simulate the action of a healthy ligament. Instead it eliminates the need for the ligament. The surgery actually changes the anatomy of the knee joint by using a cut in the tibia and placement of a bone plate inside to change the stifle’s configuration in order to eliminate the need for the ligament. TPLO is usually used on large dogs weighing 40 pounds or more.

All of these procedures produce good results and none has been demonstrated to be overwhelmingly superior to the others. The choice of which one to use is made by the veterinarian and depends on the circumstances and type of dog.

Dr. Riegger often uses fibular transposition, an extracapsular technique. “I take the fibula and the lateral collateral ligament and move them. Ordinarily, the orientation of the ligament is straight up and down. By moving the fibula and the lateral collateral ligament forward, we change the orientation of the head of the fibula and the ligament to do the work of two,” he said. “Instead of having five ligaments stabilize the joint, we now have four.”

If the ligament were severely weakened, he would not use this procedure. Then he would choose an imbrication technique in which a suture is passed through the connective tissue and then tightened to prevent rotation within the joint, essentially forming an additional ligament.

All remnants of the broken ligament and any pieces of damaged cartilage or meniscal tissue are cleaned out of the joint before the procedure to repair the ligament is done.

RECOVERY

No matter which procedure is used to stabilize the joint, the results of this surgery are quite successful. Eight-five to 95% of the patients regain good to excellent function in the affected limb.

Depending on the type of procedure performed, and the surgeon’s preference, the dog may leave with no bandage or with a Robert Jones bandage, which is a soft cast that immobilizes the joint to some degree. The dog’s activities are severely restricted the first week following surgery. The dog is confined and allowed outside on a leash for eliminations only. Gradual resumption of normal activity over a six- to twelve-week period is the standard.

Dr. Riegger says, “For one week, the dog gets to sit around and watch Oprah! Over the next six to seven weeks, the dog returns to his normal life pattern. We do check-ups at one, two, four and eight weeks. Usually the recovery rate at these visits is 24%, 50%, 75%, perfect. Ninety-five percent of the dogs regain 95% use of their leg within eight weeks.”

Amber and Jojo both left the hospital with soft bandages. Amber suffered depression during her recovery because she was a very social dog and missed her contacts with people. The depression ended once she regained her strength and ability to move around. Owners are urged to do range-of-motion exercises with their dog during recovery to help strengthen the joint and muscles. This is particularly true with large dogs.

The best reward for doing this surgery is seeing a dog who was lame and in constant pain running, playing and hiking without difficulty.


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