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Cruciate Ligament Injury in Dogs: Treatment options

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In dogs, as in people, the knee joint is a frequent site of injury. In fact, tearing (or "rupture,'' as it's technically called) of the cranial cruciate ligament (CCL) is the most common orthopedic injury in dogs. The good news is that there are a number of surgical procedures that -- together with good post-operative care and rehabilitation -- can restore function to the ruptured ligament and return your dog to "active duty.''

Understanding the CCL

A dog's rear knee joint (or "stifle joint,'' as it's called in veterinary lingo) is a complex piece of bioengineering, no less so than its human counterpart. You can think of it as nature's solution to the problem of connecting the femur, or thighbone, to the tibia, the large bone of the lower leg. A system of ligaments links the two bones so that they can function as a unit. A cushion of cartilage called the meniscus prevents the bottom of the femur from rubbing directly against the top -- or plateau -- of the tibia.

The CCL prevents the tibia from sliding forward, away from the femur, when a force is applied to the leg. If the CCL is torn, the stability of the joint is compromised and lameness results, accompanied by pain. Left untreated, CCL can cause irreversible arthritis, which will eventually result in permanent damage to the joint, worsening pain, and lameness.

What's the cause of CCL rupture?

CCL rupture can be chronic or acute in its origin. Pamela Schwartz, FACVS, staff surgeon at the Animal Medical Center in New York, explains: "A chronic rupture of the CCL is typically the end result of a number of degenerative changes to the stifle joint. Over time, these changes cause the CCL to fray or loosen, which will eventually lead to a partial or complete tearing of the ligament.''

Obesity and certain anatomical abnormalities of the leg or knee joint may predispose some dogs to CCL rupture. Chronic CCL rupture is more common than the acute variety.

An acute rupture usually results from a sudden, severe twisting of the joint as may happen, for example, if the dog steps in a hole while running or turns while its paw is fixed in position. This results in a sudden hyperextension and internal rotation of the leg. An acute CCL rupture can also occur when a dog jumps and the force exerted on the CCL is just too much for the ligament to bear.

Certain factors place a dog at increased risk of CCL rupture:

  • Being of a large or giant breed, such as Rottweilers, Labrador Retrievers, and Golden Retrievers
  • Obesity
  • "Weekend warriors'', i.e. dogs who -- like their owners -- are sedentary most of the time, with intermittent periods of intense athletic activity, may be at increased risk, according to some studies.

Signs of CCL rupture: what to look for

The signs and symptoms of CCL rupture in dogs vary depending on whether the rupture is acute or chronic, partial or complete. In the case of an acute CCL rupture, circumstances and your dog's behavior will usually tell you that there's a problem. Lameness may be subtle and only evident when the dog is engaged in vigorous activity; in the case of a complete rupture of the ligament, the dog may be unable to bear any weight on the affected limb.

Your vet can make a definitive diagnosis of CCL rupture by palpation (physical manipulation) of the affected limb, x-ray, and range-of-motion examination. She or he will also make sure to rule out other possible causes of lameness, such as fractures, tendon rupture, as well as a number of other orthopedic conditions.

Treatment: Surgical and non-surgical options

In the case of small dogs (under 20 lbs.), Schwartz explains that a non-surgical approach is sometimes sufficient. She recommends conservative management for these dogs for a roughly one-month period, with surgery reserved for those who have not improved. If the dog is kept completely inactive during that time, enough scar tissue may be produced within the joint to provide adequate stabilization. However, surgery is recommended for all dogs weighing more than 20 lbs.

The two most common surgical procedures are the TPLO and the TTA:

  • TPLO, or Tibial Plateau Leveling Osteotomy, is a procedure in which the top of the tibia -- which ordinarily is sloped sharply downward -- is leveled. This prevents the femur, which is normally held in place by the now-torn CCL, from sliding downward and forward. Without that sliding, the knee joint is stabilized even though the CCL is still torn. A metal bone plate is attached with screws to allow healing.
  • TTA, or Tibial Tuberosity Advancement, is a procedure in which a portion of the tibia is cut, thrust forward, and fixed in place with a metal plate and screws. The result is that the downward-forward force of the femur is now opposed by the repositioned upper portion of the tibia.

Other surgical procedures

Both TPLO and TTA are extracapsular surgical techniques. This means that the surgeon does not have to go inside the knee joint -- or capsule -- itself. With intracapsular techniques, the surgeon stabilizes the knee by going inside the capsule and replacing the ruptured CCL with a graft of either synthetic material or with tissue taken from elsewhere in the dog's body. There are a number of intracapsular procedures referred to as "Over-the-top," "Under-and-over," as well as arthroscopic procedures.

In the case of smaller dogs, another surgical option, called lateral imbrication, which involves the use of sutures to stabilize a ruptured CCL, may provide good results.

Which surgical procedure is right for my dog?

The number and variety of procedures for the surgical treatment of CCL rupture can present the dog owner with a difficult choice. How do you know what the correct procedure is for your dog?

Which procedure is best is a matter that even experienced veterinary surgeons disagree about. However, some generalizations are possible:

  • TPLO is a more surgically challenging procedure than TTA and has a longer "learning curve" for the surgeon;
  • In medium to large or very active dogs, both TPLO and TTA are preferable to intracapsular procedures;
  • If the slope of the tibial plateau is excessive, TPLO is preferable;
  • TTA is a more recently developed procedure than TPLO, and so has less of a long-term `track record;'
  • TPLO and TTA are more expensive than lateral imbrication;
  • Which procedure a surgeon recommends is usually a matter of the surgeon's professional experience, training, and personal preference.

Most importantly of all: when properly performed by a qualified veterinary surgeon, all of the various techniques generally have excellent outcomes. Schwartz advises dog owners to seek out a surgeon certified as a "Diplomate" by the American College of Veterinary Surgeons (ACVS). The ACVS maintains a 'Diplomate Search feature on its Web site, making the task of finding a qualified specialist much easier. Ask the surgeon about his or her experience with this type of injury.

The bottom line: choose the surgeon, not the surgery!

Credit: Reviewed by Amy I. Attas, V,M.D.
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