Dogs are considered a part of the family for many people and when they get injured, it can be tough to see them in pain. Anterior Cruciate Ligament (ACL) tears are one of the most common injuries in dogs and can be difficult to recover from without surgery. A completely ruptured cruciate ligament in dogs weighing greater than 10 lbs ultimately requires surgery to regain the proper function of their knee. There are a few different procedures that can be used for cruciate repair in dogs, each with its own benefits and drawbacks. Here we will discuss the three most common procedures: extracapsular or lateral suture technique, tibial plateau levelling osteotomy (TPLO) and tibial tuberosity advancement (TTA).
What is the ACL in dogs and what are its functions?
The ACL, or cruciate ligament, is one of the major stabilizing structures in the canine knee joint. It is located in the stifle joint (the equivalent of the human knee) and attaches the femur (thigh bone) to the tibia (shin bone). The ACL's main function in dogs is to prevent the tibia from sliding forward relative to the femur during weight-bearing.
What causes a torn ACL in dogs?
A ruptured, or partially ruptured ACL is one of the most common causes of hindlimb lameness in dogs. Interestingly, very few torn ACLs in dogs are a result of a single traumatic incident which is much different compared to ACL tears in people. Affected dogs undergo a degenerative process in which the fibres of the heavy ACL ligament are weakened. Once there is considerable weakness and instability of the fibres of the cruciate ligament, a simple activity such as jumping or chasing a squirrel can subsequently result in the complete rupture of the ACL in dogs.
Although the initial degenerative process's underlying cause is unknown, age, genetics, and obesity are potential sources. There are certain breeds of dogs which have an increased risk of developing a torn ACL. These breeds include larger breed dogs such Labrador retrievers and golden retrievers and smaller breed dogs such as the Bichon Frise.
Symptoms of a torn ACL in dogs
The most common symptom of an ACL tear is hindlimb lameness. This is often sudden in onset and is frequently associated with an audible 'pop' or 'snap'. As the condition progresses, you may notice that your dog becomes increasingly lame and may even avoid using the affected leg altogether. In some cases, dogs with a torn ACL will hold the affected leg up while standing but may attend to using it when walking or running.
Surgical options for a torn ACL in dogs
A completely ruptured cruciate ligament in dogs weighing greater than 10 lbs ultimately requires surgery to regain the proper function of their knee. The most common surgical repair options for a torn ACL in dogs include the extracapsular or lateral suture technique, tibial plateau levelling osteotomy (TPLO) and tibial tuberosity advancement (TTA). Below, we will discuss each option in detail and the pros and cons of each procedure so that you can help make the best decision for your dog.
Extracapsular or Lateral Suture Technique
A completely ruptured cruciate ligament in dogs weighing greater than 10 lbs ultimately requires surgery to regain the proper function of their knee. The most common technique used is the extracapsular technique (band, tightrope procedures, lateral suture). This procedure involves the installation of 2 surgical grade nylon bands around the knee to mimic the functions of an intact ACL. This procedure is very successful with success rates of greater than 90%.
The main advantage of this technique is that it is less invasive that the other procedures and is relatively quick and easy to perform. In addition, this procedure can be done without the need for special instruments, making it a more cost-effective option. The main disadvantage of this technique is that it is not very effective for large dogs (>35-40kg). Additionally, if the procedure is not performed correctly, such as having the bands too loose, or too tight, can be problematic for the dog and contribute to complications.
A study that looked at data from multiple centers found that 94% of dogs who received the extracapsular ACL repair had good to excellent outcomes, with a 9% major complication rate. Complications included implant failure, infection, and meniscal tears.
Tibial Plateau Leveling Osteotomy (TPLO)
The tibial plateau levelling osteotomy (TPLO) is one of the most common ACL surgery procedures in dogs. The goal of this procedure is to change the biomechanics of the knee joint so that the forces that would normally be placed on the cruciate ligament are redirected.
This is achieved by making a cut in the tibia (the larger of the two bones that make up the lower leg) and rotating it so that the plateau is level. The cut bone is then held in place with a metal plate and screws. This changes the angle at which the femur (thigh bone) and tibia meet, effectively taking the tension off of the cruciate ligament.
The main advantage of this technique is that it has a very high success rate, with some studies reporting up to a 95% success rate. Additionally, this procedure can be performed on dogs of all sizes but is typically reserved for larger dogs. The main disadvantage of this technique is that it is a more invasive procedure and requires special instruments which can make it a more costly option. The TPLO procedure is typically only performed by board-certified veterinary surgeons.
Tibial Tuberosity Advancement (TTA)
The tibial tuberosity advancement (TTA) is a newer ACL surgery procedure in dogs. The TTA procedure is used to stop cranial tibial thrust by changing the position of the patellar tendon so that it is perpendicular to the weight-bearing force through the stifle and therefore eliminating cranial drawer and tibial thrust.
This is achieved by making a cut in the tibia and advancing the tibial tuberosity (a bony protrusion on the front of the tibia) so that it is closer to the femur. This effectively changes the angle of the patellar tendon and prevents it from pulling the tibia forward. The cut bone is then held in place with a metal plate and screws.
The advantages and disadvantages parallel that of the TPLO surgical procedure but can be performed by your veterinarian provided that they have had additional training on the procedure. As this procedure is a relatively new procedure, long-term data on success rates and complications are not yet available, although the overall complication rate of the TTA in dogs is 25-60%. The complication rate will likely reduce with time and as more procedures are performed.
Can dogs recover from a torn ACL without surgery?
A completely torn ACL is a common dog injury. In some cases where the ACL is partially torn, whereas the dog continues to have stability within the knee, or if the dog is small (less than 10lbs) conservative management may be successful. A completely torn ACL however requires rehabilitation, immobilization or surgical procedures. In dogs, ACL tears will be repaired successfully using the surgical techniques mentioned above. Some dogs' healing is accomplished through surgery alternatives such as orthopedic braces and supplements. You will want to consult your veterinarian to see if your dog will require surgical treatment and whether it could require surgical alternatives to surgery. While there are braces available for torn ACLs in dogs, they are often not successful and have low owner satisfaction rates. The braces can be uncomfortable for your dog and would require to be worn at all times during weight-bearing.
How can I prevent another ACL tear in my dog's other knee?
As a torn ACL in dogs is a result of a chronic degenerative process of the cruciate ligament, there is an approximately 50% chance your dog will tear their other ACL after tearing their first. Sometimes this is inevitable, however, make sure your dog is in its ideal weight range and is well exercised to help build muscle and provide extra support to the knee. Unfortunately, there are no supplements or medicines available to prevent your dog from tearing or injuring its ACL.
There are a few different options for repairing a ruptured ACL or cruciate ligament in dogs. The most common procedures include the extracapsular or lateral suture technique, tibial plateau levelling osteotomy (TPLO), and tibial tuberosity advancement (TTA). Each of these procedures has its own advantages and disadvantages, which should be taken into consideration when deciding which procedure is best for your dog. The success rates of each procedure vary, but all have high success rates overall. The main disadvantage of some of these procedures is that they are more invasive and require special instruments which can make them a more costly option. FI you have any questions or are concerned about a torn ACL in your dog, please reach out to your veterinarian.