Home | Surgical Info | Cruciate Ligament Repair in Dogs

Cruciate Ligament Repair in Dogs

Jul 18 2022

Cranial cruciate ligament repair, also known as ACL repair, is a surgical procedure that aims to stabilize the knee joint in dogs. It is a common orthopedic procedure that involves the replacement of a damaged ligament in the knee joint with a synthetic substitute. This surgical intervention is often used to treat dogs that suffer from knee instability, lameness, or arthritis caused by a ruptured or torn ACL. The procedure has four surgical treatment options, including extracapsular (RMIT), tibial plateau leveling osteotomy (TPLO), tibial tuberosity advancement (TTA), and tightrope technique, each tailored to the individual patient's needs. Effective post-operative care is critical to the successful outcome of this surgery.

“In dogs, the most common knee injury is a rupture or tear of the cranial cruciate ligament. Most dogs with this injury cannot walk normally and experience pain. The resulting instability damages the cartilage and surrounding bones and leads to osteoarthritis (OA) in the knee joint. “

What is the Cranial Cruciate Ligament?

The word cruciate means 'to cross over' or 'form a cross. The Cranial Cruciate Ligament (CCL), also sometimes called the Anterior Cruciate Ligament, is a tough band of tissue that connects the two main bones of the knee (stifle) joint. Specifically, the upper part of the joint is called the Femur and the lower part of the joint is called the Tibia. The Cranial Cruciate Ligament connects the posterior (rear area) of the lower Femur, to the anterior (front area) of the Tibia. This ligament helps prevent excessive motion between these two bones. Rupture of this ligament is the most common orthopedic injury in dogs and results in a painful, unstable joint. If left untreated, this injury leads to degenerative joint disease (arthritis).

What happens when a Cruciate Ligament tears?

When a cruciate ligament tears, the dog experiences sudden pain and often holds his leg up. The dog may put the leg down and start using the leg again within a day or so but will continue to limp for several weeks. Normally, at the end of several weeks, the initial pain subsides and the dog is willing to use its leg more; however, the joint will stay unstable.

Longer term, when your dog puts his weight on the leg, the tibia (shin bone) slides forward in relation to the femur (thigh bone). As you can imagine, this can be painful as the joint cartilage wears down, leading to arthritis. This motion can also put excessive stress on the menisci (C-shaped pieces of cartilage within the knee joint), causing damage or tearing. Not a fun place for Max to be.

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How does a cranial cruciate rupture occur?

Although this is the most common orthopedic injury in dogs, it is still not completely understood why this ligament ruptures. Many theories have been proposed. Certainly, trauma can cause the ligament to rupture - this is the most common reason for ligament rupture in humans. In dogs, however, this does not seem to be the most important cause. It is known that some dogs have excessive Tibial Plateau Angles (TPA), but research has shown that this, by itself, is not enough to cause the ligament to rupture.

Some researchers think that under normal circumstances, the muscles of the knee joint are the main forces that control movements and that the cruciate ligaments are there as a safety factor to prevent excessive motion in certain directions. If there is a defect in this muscular control, as is postulated by these

researchers, then the cruciate ligaments will be under more continuous stress than in a normal dog, which will lead to their deterioration. Indeed, most of the ruptured ligaments that we see are not sudden ruptures. Instead, they are partial ruptures that lead to full ruptures.

In most cases when the joint is opened, even in a “fresh rupture”, there is obvious evidence that there has been ongoing arthritis in the joint, indicating abnormal movement (and wear and tear) for a prolonged period of time. This previous deterioration is what ultimately leads to the final rupture of the cruciate ligament.

  1. Traumatic Injury: most often the ligament is injured when the stifle is rotated rapidly with the joint in 20 to 50 degrees of flexion or when the joint is forcefully hyperextended. Acute or traumatic cruciate rupture is caused by a twisting injury to the knee joint. This occurs most often when the dog (or athlete) is running and suddenly changes direction. This place the majority of the body weight on the knee joint, and excessive rotational and shearing forces are placed on the cruciate ligaments. Hyperextension probably occurs most frequently by stepping into a hole or depression at a fast gait. This injury usually affects the anterior or cranial (front) ligament. A cruciate ligament rupture is usually extremely painful and the knee joint becomes unstable, resulting in lameness.

  2. Degeneration of the ligaments within the joint. The more common injury scenario is thought to be a progressive degenerative process that leads to a partial or full ligament tear. A more chronic form of cruciate damage occurs due to the progressive weakening of the ligaments as a result of repeated trauma or arthritic disease. Initially, the ligament becomes stretched or partially torn and lameness may be only slight and intermittent. With continued use of the joint, the condition gradually gets worse until a complete rupture occurs. Obese dogs appear to be more predisposed to developing a cruciate rupture. In these dogs, the injury may occur with minor trauma to the knee, such as stumbling over a rock while walking. Dogs with other knee problems such as a luxating patella (“Luxating Patella in Dogs") may also be predisposed to rupturing their cruciate ligaments. Concurrent patellar luxation is seen fairly often in toy breeds of dogs. Dogs who rupture one cranial ligament are more predisposed to rupturing the cranial cruciate ligament in the other knee. Approximately 40% to 50% of dogs sustaining a cruciate ligament rupture will rupture the opposite ligament within 2 years. Concurrent bilateral problems are even more common in young adult dogs (1 to 2 years) of specific breeds, particularly the Newfoundland, Rottweiler, and Labrador retriever.

Why does my dog need surgery?

Unfortunately, if your dog ruptures the Cranial Cruciate Ligament, surgery is the only real option.  When the ligament is torn, there is a shearing force that results when your dog tries to bear weight on the leg. This shearing force makes the femur slide backward on the surface of the tibial plateau. This abnormal movement sets up excessive wear and tear on the cartilage surface, which induces a further arthritic change in the joint.  Additionally, this abnormal motion frequently damages the cartilage pads in the joint, known as the menisci.  Damaged menisci also lead to further arthritic change.  Many dogs develop such severe arthritis that their leg is in constant pain.  Pain is certainly not what we want for our pets!

Why do different surgeons recommend different procedures?

For many years, various surgeons have proposed different procedures to repair a ruptured cranial cruciate ligament. Several procedures have fallen by the wayside as they have been shown to be inferior to newer procedures. As the researchers have analyzed follow-up data, it has been shown that certain procedures are not as good as they initially were thought to be. This is a normal event in medicine (both human and veterinary). This does not mean that the surgeries proposed 20 years ago, or even 5 years ago, were wrong. It simply means that as good surgeons, we are constantly striving to present what we feel (at the time) to be the best alternatives available.

What surgeries are currently being done for Torn ACL?

The four most common techniques done today in Veterinary Practices:

  1. The extracapsular suture (MRIT)

  2. Tightrope CCL

  3. Tibial tuberosity advancement (TTA)

  4. Tibial plateau leveling osteotomy (TPLO)

These techniques can be broken down into three groups: extracapsular, intracapsular, and tibial osteotomy:

  • Extracapsular methods embrace a wide variety of stabilization techniques for the cruciate-deficient stifle joint. Most of these involve the use of heavy-gauge sutures to decrease joint instability.

  • Intracapsular methods usually involve anatomical (or near-anatomical) replacement of the cruciate ligament with autogenous or autologous grafts or synthetic materials.

Tibial osteotomy techniques are thought to provide dynamic stabilization by neutralizing the shear forces (cranial tibial thrust) seen in the stifle during weight bearing. EG TPLO and TTA Extraarticular methods work well in smaller breeds but have often been considered less satisfactory in larger, athletic animals with a cranial cruciate ligament rupture.

There are some commonalities between these techniques.  All strive to achieve stability of the stifle joint.  The keys to having a successful outcome with any of these techniques are:

  •  Case selection

  •  Knowledge of anatomic landmarks used for the technique

  •  Knowledge and proper application of the technique

  • Appropriate postoperative and home care

  • Appropriate rehabilitation

Potential complications that can be seen with any of these techniques include: Infection (incisional or implant-related)

  • Failure of repair

  • Persistent instability

  • Implant Failure

  • Progression of arthritis

  • Ongoing Lameness

What is the lateral suture procedure (MRIT) for the stabilization of an ACL tear in a dog?

The lateral suture procedure involves using suture material to replace the torn ligament in a different position that where it normally is. Although it mimics the function of the original ligament, it does not have the same biomechanical properties as the ligament, thus the knee is not capable of performing like it originally did. Some of the normal range of motion is lost. Eventually, this temporary ligament will also eventually break. The theory is that your dog will build up scar tissue around the temporary ligament in the knee to act as a long-term stabilizer. This scar tissue will result in decreased range of motion of your pet's knee long term.

What are the advantage and disadvantages of the Lateral Suture Procedure?

There are many variations of the Lateral Suture Procedure, but they are basically all similar. They involve the placement of an artificial fiber on the outside of the joint to try to stabilize its abnormal motion. When done correctly, this procedure will frequently work in small-breed dogs. This procedure is more likely to fail in larger breed dogs. In this procedure, there is a tendency to overtighten this artificial ligament to eliminate all of the excessive joint motion. In the process, there is often excessive joint compression, leading to damage to the cartilage and to a decrease in a normal range of motion. Most people feel that these artificial ligaments all will break with time, so their real benefit may be to keep the leg in a forced rested position, while the dog’s body builds up enough scar tissue around the joint, limiting its abnormal motion. While this procedure has been around for a long time, many surgeons are drifting away from this procedure to newer procedures.

What Tightrope CCL Procedure for Torn ACL?

The Tight Rope Procedure is a variation of the lateral suture procedure. The artificial ligament that is used is VERY strong, but it has the disadvantage of being a braided material. All braided materials have the unfortunate risk of harboring bacteria.

If contamination occurs during the surgical procedure, the resulting infection can be a major disaster.

What is the TPLO procedure?

TPLO stands for tibial plateau leveling osteotomy. In the normal knee, the top of the tibia slants at a backward angle. This allows the femur to slide back down this tibial slope. It is this sliding that causes the pain once the ligament tears. TPLO removes this backward slant of the tibia and stabilizes the knee. Removal of this slant of the tibia changes the way the quadriceps muscle pulls on the tibia and allows the muscle to assume the job of the torn ACL.

What are the advantage and disadvantages of the TPLO procedure?

The TPLO procedure is designed to alter the slope of the Tibial Plateau. As previously mentioned, the Tibial Plateau has a downward slope to it. The advocates of this procedure claim that excessive slopes are the cause of the rupture of the cruciate ligament. Unfortunately, research has not backed this up. Research into the Tibial Plateau Angles (TPA) of both dogs and wolves, has shown that the degree of the TPA has not been correlated with the rupture of the ligament. Therefore, would changing that angle be the appropriate surgery? That question is currently being actively debated. During this surgery, the top of the tibia (the weight-bearing surface) is cut and rotated a few degrees to decrease the slope of the Tibial Plateau. This cut bone is then re-attached with a heavy-duty stainless-steel plate and numerous screws.

It has been shown that dogs will bear weight on the leg quickly after the surgery. But it has also been shown that some additional arthritis does still occur after surgery, indicating that there may still be some abnormal motion in the leg. A search of the literature indicates that some abnormal motion may remain in the form of a Pivot Shift. Some of these dogs seem to be in discomfort in cold weather. It is possibly the thick Stainless-Steel plate that is responsible. Since the cut made into the bone is on the weight-bearing surface of the tibia, the use of a thick plate is essential to help the two bones heal back together.

What is the TTA procedure?

TTA stands for tibial tuberosity advancement. The procedure involves moving the patellar tendon attachment on the tibia forward which allows the quadriceps muscle to assume the normal job of the torn ACL by pulling forwards on the tibia to oppose the torn ACL.

What are the advantage and disadvantages of the TTA Procedure? The TTA or Tibial Tuberosity Advancement Procedure is based on the research that the Patellar Ligament can stabilize the joint if it is at a 90-degree angle to the Tibial Plateau. The Patellar Ligament is one of the toughest ligaments in the body, and it is completely controlled by one of the biggest muscles in the body, the quadriceps muscle on the front of the leg. By advancing the Tibial Tuberosity, we can overcome the abnormal front-to-back motion called Tibial Thrust and tend to overcome the tendency for Pivot Shift. The current thought is that this procedure leads to a less arthritic change in the joint. This procedure can be successfully done on any size dog and is currently the treatment of choice by many surgeons.

Why do some surgeons continue to do TPLO surgeries when the TTA has been shown to be a better procedure?

There are several answers to this question, First, it is not universally accepted that one procedure is better than another. It appears that the TTA procedure will be the best procedure available, but we will know for sure twenty years from now! The second reason is the surgery requires the purchase of very specialized equipment, and consequently, a fair amount of investment has been made on the part of the surgeon. It is quite hard to give up a procedure that you have invested time and money in. A third reason is that most of the TPLO surgeons report “good” results. The fact the TTA research looks better than the TPLO does not mean that the TPLO surgery is wrong. Similarly, surgeons doing many of the older procedures for cruciate repair also reported good results. As I have mentioned, twenty years from now the results will be more evident.

Is the TTA procedure only for large-breed dogs?

The TTA procedure can be successfully performed on almost any size dog.  Implants are made for dogs as small as 10 lbs to dogs over 120 lbs.

I have been told that my dog may have the same problem later on in the opposite leg. Is this true?

The statistics tell us that 35-40% of the dogs will suffer a rupture of the cruciate ligament in the opposite leg.  It is probable that the underlying arthritic change that led to the first rupture has already started in the opposite leg.

What can I do to lower the chance that my dog will need surgery on the opposite leg?

To avoid this, restrict exercise during recovery, work on rehabilitation, and reduce your pet's weight.

What is the "best" surgery for a torn ACL in the canine?

There is no one best surgery. What is important to remember is that NO surgical procedure will completely heal the dog. Treatment of ACL injury in the dog is a lifelong process, involving rehabilitation, nutrition (weight control), and chronic/intermittent use of pain control medications and/or nutraceutical products. Dogs that have had TPLO or TTA surgery can and often do have intermittent periods of stiffness and lameness for the rest of their lives because no procedure can stop and/or reverse the osteoarthritis that is present in the knee. Ligament, muscle, and scar tissue strain in the knee are an infrequent problem for the rest of your dog's life. Despite our best efforts, some dogs never return to their pre-injury athletic status due to the chronicity of the initial injury to their leg.

Why do veterinarians recommend one surgical procedure over another?

Many veterinarians are confident in performing the lateral suture procedure for your dog. Complications are more easily dealt with compared with TTA or TPLO, and the TTA or TPLO can be used to replace the lateral suture if something should go wrong. TTA and TPLO are better at more closely restoring the normal biomechanics of the canine knee. A veterinarian will tend to recommend the procedure they are most comfortable with, and have the most success with.

Why is my doctor NOT recommending a TTA over the TPLO?

TPLO is only indicated over TTA if your dog has a steep tibial plateau angle (the top of the tibia) or if your dog has crooked legs There are no other reasons to perform TPLO over TTA except for comfort in performing (or recommending) one procedure over the other for the doctor. Many doctors do not understand the TTA yet.

My dog recently had a TTA done, and now the leg is swollen a lot. What should I do?

The swelling is usually located just past the surgery site. This is usually due to extensive bleeding from the bone grafting site in the tibia to fill the grafted area. This can be avoided by using a bone graft from somewhere else in the body, or by using a synthetic product such as Velocity(R). If you see this swelling, make sure your pet stays off the leg as much as possible for a few days, and that you ice the leg 3-4 times a day for the next week. The swelling will go away. If it gets to be too much, it could cause the incision to swell.


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