Tibial tuberosity advancement (TTA) is a surgical procedure that can be performed in animals to treat cranial cruciate ligament disease/rupture.

What is the Cranial Cruciate Ligament?

The cranial cruciate ligament (CCL) is a ligament in the back leg that stabilizes an animal’s knee. You may have heard it called the anterior cruciate ligament (ACL) in humans.

Ligaments are tissues that connect one bone to another and are an important part of keeping the knee strong. Two cruciate ligaments cross through the inside of the knee, making an “X” shape (which is where the name “cruciate,” meaning cross-shaped, comes from).

The first cruciate ligament, the cranial cruciate ligament, stretches from the front of the lower leg bone, called the tibia, to the back of the upper leg bone, called the femur. It keeps the tibia from sliding forward, where it would no longer be lined up with the femur and could cause weakness. The other cruciate ligament, the caudal cruciate ligament, stretches from the back of the tibia to the front of the femur and helps the cranial cruciate ligament to keep the knee strong. Of the two, the cranial cruciate ligament is more commonly affected.

Canine Knee Diagram

Cranial Cruciate Ligament Rupture

While the cranial cruciate ligament can rupture as a result of trauma, this is unusual. The most common cause of rupture is a gradual degeneration of the ligament over a period of months or years due to a condition we call “cruciate disease.”

When the ligament ruptures, the knee is less stable, causing excessive movement between the femur and tibia. This results in pain, which causes limping. This condition is seen in cats, but it is more commonly identified in dogs.

Diagnosis

Diagnosis of a CCL rupture is made following a physical examination where swelling or thickening is detected in the knee. Muscle wastage may also be seen in the upper aspect of the limb. In some cases, there may be abnormal motion of the knee, which you may hear your veterinarian refer to as a “drawer sign”; however, this is not seen in all cases. Pain is normally detected when the knee is manipulated. There are several tests your veterinarian can perform to check for this abnormality, with some of the most common being the cranial drawer test and the tibial compression test. (Ruptured Cranial Cruciate Ligaments in Dogs) X-rays are an essential part of the investigations to confirm the findings from the physical examination and eliminate other possible causes of knee pain.

TTA Surgery

Several surgeries are used to treat a CCL rupture, each with its own indications, advantages, and drawbacks. Your veterinarian will use your pet’s age, size, and activity level and will take several special measurements from X-rays of the affected knee to decide which is most suitable and to plan the surgery. While not an emergency, surgery is often recommended as soon as possible to prevent further injury to the joint, causing further damage. The TTA procedure is complicated and requires specialized training, so your pet will likely be referred to a veterinary orthopedic surgeon to perform the surgery.

During the TTA procedure, the front ridge of the tibia, called the tibial tuberosity, is cut and separated from the rest of the bone. A special orthopedic spacer is placed between this piece and the rest of the bone, which allows that portion to be reattached at a different angle, moving the lower portion of the knee forward and upwards (advancing it). Doing so realigns the patellar ligament, which runs vertically down the front of the knee to hold the patella (or kneecap) in place, creating more stability and eliminating some of the abnormal movement of the knee. This change is made so that when the pet puts weight on their knee, it pushes the femur backward to keep it aligned with the tibia below. This makes the knee joint more stable and reduces difficulty and pain during walking or standing. In effect, this surgery removes the need for the cranial cruciate ligament. An important part of this surgery is the assessment of the menisci (shock absorbers in the knee), as in approximately 60% of cases, they may be damaged as a result of the instability.

What to Expect After Surgery and During Recovery 

TTA offers a rapid return to normal function and natural range of motion. Most animals can bear weight quickly after surgery, usually within 10 days. Full function and return to normal activity are usually achieved within three to four months after surgery.

Your pet will be placed on restricted exercise for about eight to 12 weeks to allow for proper healing. This usually means short walks on a leash, no rough play, and no jumping on beds or other furniture. Your veterinarian may recommend pain management and rehabilitation during the recovery time. This can include anti-inflammatory medications, ice packs, and gentle leg manipulations.

Your pet will need to return to their veterinarian within 10 to 14 days after surgery for suture removal. Further rehabilitation exercises, such as light activity and the use of a water treadmill, may be recommended. The skin incision should heal within 10 to 14 days; however, the cut bone can take eight to 12 weeks to heal. It is important to prevent your pet from running, jumping, and stair climbing during the healing process to minimize the risk of complications. Complications may be mild or can be serious (infection, movement of the implants, fracture of the leg), so if you are concerned at all, it is recommended you seek advice from your veterinarian. Your pet will need further visits with their veterinarian for X-rays to ensure the knee is healing properly. You will be guided through this when your pet is discharged.