Scott P. Hammel,
DVM, MS, Diplomate ACVS
Decision making for pets with ACL (Cranial Cruciate Ligament) tears
Anterior (Cranial) Cruciate Ligament Tears
Tears of the anterior (cranial) cruciate ligament or ACL are the most common orthopedic injury in dogs. They also occur in cats, with less frequency. The reason for this common injury is not entirely known, but genetics, patient weight, and activity all likely play a role.
Treatment for ACL injury- Extracapsular Repair
City of Lakes Veterinary Surgery performs three techniques for pets with a torn ACL. For cats and small dogs (less than 25-35 pounds), a surgery called an extracapsular technique (also called a fishing line repair or lateral suture imbrication) works well. This surgery involves placement of one or two heavy monofilament sutures that hold the knee in the correct position, preventing the abnormal movement that occurs when the ACL is torn. Proper recovery from this surgery relies on the body creating fibrous or scar tissue to hold the knee stable long-term. The scar tissue has to form before the suture is stretched for it to work. Essentially, this becomes a race between scar tissue formation and the repair stretching out. But for small pets, we generally win the race. For larger dogs who might stretch the repair out before enough scar tissue forms, we recommend a different approach. That brings us to the other two options:
TTA and TPLO- An Overview
TPLO, or tibial plateau leveling osteotomy, and TTA, or tibial tuberosity advancement, are two biomechanically similar surgical techniques used to treat medium and large dogs (more than 25-35 pounds) with a torn cranial cruciate ligament (CrCL or ACL). Both the TPLO and TTA create stability within the dog stifle by altering the forces in the knee. They both involve making a surgical cut in the tibia (shin bone) and using implants to hold the bone in place while the it heals in a new position. The new position allows knee stability to be provided by other knee structures, without the need to create a new ACL or repair the old one. The TTA procedure is essentially a modified version of the TPLO procedure, using a different location for the bone cut that is less invasive. Both TTA and TPLO are great procedures that have a very high rate of success, and each is likely to return the patient to normal or near-normal function.
So which is better, TPLO or TTA?
This is one of the most debated topics in small animal veterinary orthopedic surgery. Most dogs are a candidate for either TTA or TPLO. There is no reputable literature that categorically shows one procedure is better than another. That having been said, most surgeons have a preference. Dr. Hammel performs both TPLO and TTA, but prefers TTA due to earlier use of the leg following surgery, less common complications, and less frequent need to remove the metal implants later in life. TTA has the advantage of being modified to treat patella luxation, occasionally seen with torn ACL in dogs. The most important factor for a good outcome that your pet’s surgeon is experienced in the technique chosen. Dr. Hammel is a board certified surgeon, and has been performing TPLO since 2003, and TTA since the procedure was developed in 2005. He has performed thousands of each of these procedures during this period of time.
Which is less invasive?
The TTA is surgically slightly less invasive than the TPLO. The amount of weight-bearing bone shift that takes place during a TTA is minimal when compared to that of a TPLO, where the weight bearing part of the tibia is surgically cut and altered. In the TTA, the osteotomy is made in the tibial tuberosity (not a weight bearing part of the leg). This appears to make TTA patients more comfortable earlier following surgery.
Which has a shorter recovery time?
Both surgeries rely on the bone for healing, so exercise restrictions are similar- in most cases, 8 weeks. However, because it is a surgically less invasive process, TTA usually allows weight bearing earlier than TPLO. This means less time losing muscle, and more time building it during the recovery period. While most TTA and TPLO dogs are able to begin weight bearing within the first 24 to 48 hours after surgery, TTA dogs tend to weight bear a bit earlier. Physical therapy will speed use of the leg and improve long term outcome with either surgery.
Which has less risk of complications?
TTA appears to have less risk of surgical and post operative complications, including infection and surgical failure. TTA uses titanium implants, which carry less risk of infection and rejection than the stainless steel implants used in TPLO. Also, because TTA is a quicker procedure to perform, there is less time spent in the operating room, which means lower chance for infection or anesthesia-related complications.