Frequently Asked Questions Regarding Tibial Tuberosity Advancement (TTA) For Surgical Repair of Ruptured Cranial Cruciate Ligaments(CCL/ACL) in Dogs
Q: What exactly is a cranial cruciate ligament in dogs?
A: The cranial cruciate ligament is what is called the anterior cruciate ligament in humans or ACL. It is a ligament located in the back of “stifle” (or knee) joint, and its function is to give stability to this joint (knee) by keeping the tibia from sliding forward (tibial thrust) as well as preventing the knee from turning inward (internal rotation).
Q: How does a CCL rupture occur, and why does it cause lameness in my pet?
A: Injuries to this ligament is the MOST common cause for rear leg lameness in dogs, and can be acute or chronic in nature. Acute injuries can be traumatic sports injuries in active dogs, and most commonly occurs due to hyperextension and internal rotation of the leg (often occurring when a dog steps in a hole or any type of force stressing the ligament that exceeds its breaking strength while the pet is active). Proposed underlying causes for chronic disease of the CCL include age-related deterioration of the ligament, obesity, conformation abnormalities of the rear limb, and immune-mediated disease.
Q: What are the signs and symptoms of a ruptured CCL in dogs?
A: This is going to depend if the injury is acute or chronic, and whether it is a complete or partial rupture of the ligament. Symptoms can vary from a sudden lameness associated with exercise, to a full non-weight bearing injury.
Q: How does my veterinarian diagnose a ruptured CCL in my pet? And what are pre-surgical radiographs used for if the ligament can’t be visualized? What are they looking for?
A: A CCL rupture in most cases can be diagnosed on physical and orthopedic examination by obtaining a positive cranial drawer movement or “cranial tibial thrust” during manipulation of the knee. This abnormal motion is diagnostic and specific for this condition. Partial ligament tears are more difficult to detect and can be negative for this sign. Ligaments can not be seen on x-rays of the knee joint, but x-rays are valuable to screen for joint effusion (swelling of the joint), presence of osteoarthritis in the joint, and also to rule out other orthopedic conditions.
Q: Ok, my pet has already been diagnosed with a torn CCL, what are the treatment options?
A: There are two types of treatment options: conservative vs. surgical. Conservative treatment consists of rest, non-steroidal anti inflammatories, as well as pain medications, weight management, and other supportive medical options (i.e. laser, nutritional supplements, acupuncture, etc). Conservative treatment is best tolerated by smaller less active patients, and is less reliable in larger breeds. Small dogs treated conservatively may eventually appear to function normally on the injured leg; however, instability from the torn CCL within the knee continues to exist and development of osteoarthritis is inevitable.
Q: What is a TTA?
A: TTA stands for tibial tuberosity advancement, and is one of the techniques available for stabilization of cranial cruciate ligament deficiency in dogs. This technique was invented by Dr. Slobodan Tepic and Dr. Pierre Montabon in Zurich, and was launched by Kyon in 2004 following three years of clinical testing.
TTA involves an osteotomy of the non-weightbearing portion of the tibia. This section of the bone called the tibial tuberosity is moved forward so that the patellar ligament is aligned on a 90 degree angle with the tibial plateau. By doing this, you change the angle of the forces applied to the knee during stride which gives stabilization to the joint.
Implants used to keep the tibial tuberosity in place (as seen in this radiograph of a CVSS patient), includes a cage which is placed on the end of the osteotomy closer to the joint and is secured by two titanium screws to keep the space between the tibial tuberosity and the tibia. Also, a tension band plate secures the tibial tuberosity to the tibia and is secured by an an pronged implant called a fork and additional cortical screws.