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The most common orthopedic injury in dogs is the rupturing of the cranial cruciate ligament (CCL), also known as the anterior cruciate ligament (ACL). The cruciate ligament is located within the stifle (knee). This joint is similar to a human knee in that it is made up of the femur (thigh bone), tibia (shin bone), patella (knee cap) and supporting tendons, ligaments and cartilage. The cruciate ligament is one of the main stabilizing structures of the stifle because it prevents forward and backward movement of the femur and tibia. When the cruciate ligament tears or ruptures, these bones slide against each other, damaging other structures in the knee and causing chronic arthritis.
Cruciate ruptures may occur during a single traumatic event, but are more likely caused by a slow breakdown of the ligament due to a predisposing factor, such as anatomical abnormalities or excessive slope of the top of the tibia. Clinical signs of early cruciate disease include stiffness and mild lameness. As the disease advances, lameness becomes more pronounced. A complete cruciate tear initially results in a pet who cannot bear weight on the affected leg. As time passes, the pet may use the leg, however, the lameness will not completely subside without surgery.
Our veterinarians diagnose cruciate tears during physical examinations by using a cranial drawer test. If the ligament is ruptured, they can feel the femur slide across the tibia. Radiographs are also used to ensure no bones are broken and also to assess the extent of damage of the joint.
In most cases of ACL rupture, we recommend a surgical procedure known as a TPLO (Tibial Plane Leveling Osteotomy), a state-of-the-art procedure developed and patented by Dr. Barclay Slocum of Eugene, Oregon. In order to perform this procedure, veterinarians must complete Dr. Slocum’s certification course. Compared to other ligament repair procedures, patients undergoing TPLO surgery usually experience a more rapid recovery, a better range of motion, less arthritic development and more athletic performance ability.
The basis of the TPLO procedure is to level the tibial plateau, which eliminates the use of cruciate ligaments. In dogs, the top of the tibia is sloped and is known as the tibial plateau. The cruciate ligaments stabilize the joint, causing the femur to slide down the tibial plateau when the ligament ruptures. This sliding motion causes the tibial plateau to thrust forward with each weight-bearing step, resulting in pain and excessive wear on the cartilage pad (the medial meniscus), as well as other structures in the joint.
During a TPLO procedure, a special radial saw is used to make a curved cut in the tibia bone. Next, the tibial plateau is rotated along the curved cut to obtain a more level slope. The amount of rotation varies from pet to pet. To determine the appropriate amount for each pet, we use digital radiographs in conjunction with a detailed software program. After the tibial plateau is rotated, a metal plate, which is manually contoured by the surgeon to fit each pet, and six screws are used to hold the bone together so that it may heal in its new position.
After surgery, owners must restrict their pets’ movements to ensure the bones heal normally. Although the plate is extremely secure, quick movements or severe strain on the leg could cause too much pressure on the healing bone and result in a fracture. Ideally, the pet should be confined to a crate and activity should be limited to walking on flat surfaces, meaning the pet cannot climb stairs or jump up on anything.
A fentanyl patch is applied prior to surgery to help ease the pet’s pain. Additional pain medication and prophylactic antibiotics will also be sent home with the owner. In some cases, pets may also be prescribed a mild sedative, such as acepromazine. Along with administering medications, owners will also need to periodically apply ice packs to the leg. After the bandage is removed, the leg will also need to be gently massaged and placed through a range of motion exercises three times daily. While short walks three to four times daily are allowed, no long walks or strenuous exercise is recommended during the first four weeks of recovery. Throughout the recovery process, our doctors will examine the leg and monitor the pet’s progress. Radiographs will also be repeated eight and 12 weeks after the surgery to ensure the metal plate and screws are in place and that the bone is healing correctly.