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Dog: Cranial Cruciate Ligament Rupture

General information

Other common/scientific names: ACL rupture or tear, CCL rupture or tear, anterior cruciate ligament rupture or tear

The most common cause of hind limb lameness in the dog is rupture of the cranial cruciate ligament (CCL). The stifle or knee in a dog is made up of two bones: the femur which is the thigh bone and the tibia which is the shin bone. The end of the femur has an indentation called the trochlear groove. The patella or kneecap sits in this groove. The knee is a hinge joint and is stabilized by two ligaments inside the joint which cross each other called the cranial and caudal cruciate ligaments. These ligaments prevent abnormal forward and backward sliding of the tibia. The joint is also stabilized by two crescent shaped pads of cartilage called menisci. The medial (inside) meniscus and the lateral (outside) meniscus act a shock absorbers and aid in lubrication of the joint.

When the CCL is torn, the tibia slides forward and the femur slides backward. When the femur becomes displaced backward this can also cause pressure on the medial meniscus resulting in a painful meniscal tear. If left untreated, the unstable joint causes excessive wear of the cartilage, bone and other ligaments of the joint. This leads to chronic, debilitating arthritis. Left untreated, it also places additional stress on the opposite knee. Dogs with a CCL tear in one knee have a higher chance of developing the same problem in the other knee.

Abb. GFTD59R1
Abb. GFTD59R1: This is an illustration of the anatomy of the knee.
The drawing on the left is a normal knee. The drawing on the right illustrates the instability which results from a tear.

Causes

Obesity, poor conformation, repeated minor trauma and normal aging can result in weakening of the ligament. These ligaments are then prone to tearing or rupture. Genetic factors are also thought be involved in a cause. Dogs with straight hind legs are more prone to CCL ruptures. Dogs can also tear the CCL when the joint is rotated or overextended.

Cardinal symptom

Hind limb lameness

Symptoms

Varying degrees of lameness can be seen with CCL tears. Initially, the lameness may be severe and the dog may not bear any weight on the leg. The dog will resist flexing the leg. If the meniscus is torn, a clicking noise may be heard when the dog walks. Joint swelling may be present.

Diagnosis

Diagnosis of CCL rupture can be made from clinical signs and physical examination. The key to diagnosing a CCL rupture is the demonstration of an abnormal knee motion called the drawer sign. The veterinarian stabilizes the femur with one hand and manipulates the tibia with the other. If the tibia moves forward more than normal, a CCL tear is diagnosed. Most dogs will resist this test making it difficult to interpret. Sedation may be required for an accurate response. Radiography is used to assess the stifle joint for arthritis and displacement of the femur.

Treatment

Conservative treatment can be used in the form of NSAIDs (non-steroidal anti-inflammatories), rest, chrondroprotective supplements and physical therapy. However, without surgery, arthritis will develop and most dogs will never be pain free or have complete use of the leg.

There are three recognized surgical procedures for repairing a torn CCL. The technique used will depend on the dog’s size, age and the financial resources of the owner. These include:

Extracapsular Repair

With this procedure, the knee joint is opened and inspected with either an incision or an arthroscope. Any torn ligament or meniscus are removed to minimize arthritis. A prosthetic ligament made of nylon is placed to mimic the CCL. In addition, the tissue outside the joint is tightened to provide additional stability to the joint. With this technique, a dog may carry the leg for two weeks or more post surgery.

Tibial Plateau Leveling Osteotomy (TPLO)

Using this technique, the tibia is cut and rotated in such a way that the natural weight bearing of the dog stabilizes the joint and the CCL is not needed. Specially designed bone plates and screws are used to stabilize the cut tibia. As before, the joint is opened and any torn ligament or meniscus are removed. This surgery is complex, involves special training and is much more expensive than the extracapsular repair. However, most experts believe this is the best method of CCL repair and it does allow the dog to return to normal function much quicker. Typically, most dogs are touching their toes to the ground by 10 days after surgery. Many surgeons recommend following up with aquatic physiotherapy using an underwater treadmill for rehabilitation and strength building.

Abb. GFP6IF0B
Abb. GFP6IF0B: Tibial Plateau Leveling Osteotomy.
This is a radiograph taken of a dog’s knee after TPLO.

Tibial Tuberosity Advancement (TTA)

This is a relatively new procedure developed in Switzerland which also alters the biomechanics of the knee by changing the position of the tibial tuberosity (the front of the tibia). It is anchored in its new location with a titanium basket, bone plate and screws. A bone graft is used to speed the healing process. This technique also requires specialized equipment and expertise.

As with the other procedures, the joint is opened and any torn ligament or meniscus are removed.

Abb. GFP6KPS3
Abb. GFP6KPS3: Tibial Tuberosity Advancement.
This is a radiograph taken of a dog’s knee after TTA. The arrow points to the space between the tibial tuberosity and the tibia which is filled with a bone graft. (A) femur (thigh bone) (B) patella (kneecap) (C) Tibia (D) fibula.

Prognosis

The prognosis can be good for a torn CCL if diagnosis and treatment is implemented before arthritic changes occur in the joint. However, it is vital that dog owners follow the aftercare instructions provided by their veterinarian. Exercise restriction is mandatory for several weeks after surgical repair. Follow up veterinary examinations, radiographs and physiotherapy are also important. Not providing the proper care to your dog following a CCL rupture can result in chronic, painful arthritis.

Prevention

Maintaining a healthy weight for your dog is most important in preventing a CCL tear.

Tips

For dogs undergoing surgery, it is very important that the dog does not lick or pull at the sutures. A special collar (E-collar or Elizabethan collar) is worn by the dog to prevent this. Incisions should be observed daily for swelling, discharge or redness.

CAUTION

If you notice your pup or dog is lame, contact your veterinarian. Early diagnosis of orthopedic problems is the key to successful treatment.

Update version: 4/24/2014, © Copyright by www.enpevet.de
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