Cranial Cruciate Ligament (CCL) Rupture
The most common knee injury in the dog is rupture of the Cranial Cruciate Ligament (CCL), also referred to as the Anterior Cruciate Ligament (ACL). This condition is the number one cause of severe hind limb lameness in dogs.
What and where are the cruciate ligaments?
There are two bands of fibrous tissue called the cruciate ligaments in each knee joint. They join the femur and the tibia (the bones above and below the knee joint) together so that the knee works as a hinged joint.
They are called cruciate ligaments because they “cross over” inside the knee joint. One ligament connects from the inside to the outside of the knee joint and the other outside to inside, crossing each other in the middle. Humans have the same anatomical structure of the knee.
How does a cranial cruciate injury occur?
The knee joint is a hinged joint and only moves in one plane, backwards and forwards. Traumatic cruciate damage is caused by a twisting injury to the knee joint. This is most often seen in dogs and athletes when running and suddenly changing direction so that the majority of the animal’s weight is taken on this single joint. This injury usually affects the anterior or cranial (front) ligament. The joint is then unstable and causes extreme pain.
How is it diagnosed?
With traumatic cruciate rupture, the usual history is that the dog was running and suddenly stopped or cried out and was then unable to bear weight on the affected leg. Many pets will “toe touch” and only place a small amount of weight on the leg. During the examination, the veterinarian will try to demonstrate a particular movement called a “drawer sign” which indicates laxity in the knee joint.
Is other joint damage common?
Inside the knee joint are pieces of cartilage called “menisci”. They act as shock absorbers between the femur and tibia. Many times these cartilages are also damaged when the cruciate ligaments rupture. They are usually repaired at the same time as the surgery to address the torn ligaments.
Is an operation always necessary?
An injured Cruciate Ligament can only be corrected with surgery. There are numerous surgical corrections currently being performed:
- External Capsular Repair (LFS for Lateral Fabellar Suture)
- Tibial Plateau Leveling Operation (TPLO)
- Tibial Tuberosity Advancement (TTA)
What do these surgeries involve?
In this surgery the knee joint is opened and inspected. The torn or partly torn cruciate ligament is removed. Any bone spurs of significant size are bitten away with an instrument. If the meniscus is torn, the damaged portion is removed. A large strong suture is passed around the fabella behind the knee and through a hole drilled in the front of the tibia. This suture tightens the joint to prevent the drawer motion, effectively taking over the job of the cruciate ligament. The suture will often loosen or break 2 to 12 months after surgery and the dog’s own healed tissue will hold the knee.
The dog may carry the leg up for a good 2 weeks after surgery but will increase knee use over the next 2 months, eventually returning to normal. The dog will require 8 weeks of exercise restriction.
Tibial Plateau Leveling Osteotomy (TPLO) (Osteotomy means cutting the bone)
A fresh approach to the biomechanics of the knee joint is used in this surgery. This surgery addresses the lack of long term success with the extra capsular repair in large dogs. With this surgery, the tibia is cut and rotated in such a way that the natural weight bearing of the dog actually stabilizes the knee joint. The knee joint must still be opened and the damaged meniscus removed. The surgery is complex and involves special training. Many radiographs are necessary to calculate the angle of the osteotomy. It has been shown that the TPLO procedure can still allow rotational instability (pivot shift) in the knee joint, and this may lead to the progression of arthritis as the dog ages.
Most dogs are touching their toes to the ground 10 days after surgery, although that can take up to 5 weeks. 8 weeks of exercise restriction are needed with return to full function in 3 to 4 months.
Tibial Tuberosity Advancement (TTA)
This is the newest procedure and probably the best repair for most dogs. The idea is that when the cruciate ligament is torn, the tibial plateau (top of the tibia) and the patellar ligament should be repositioned at 90 degrees to one another to combat the shear force generated as the dog walks. To make this happen, the tibial tuberosity (front of the tibia where the patellar ligament attaches) is separated and anchored in its new position by use of a titanium cage, fork and plate. A bone graft is used to assist healing. Rotational instability does not appear to be a problem with the TTA because it results in more control of rotation by the large quadriceps muscle which pulls on the Patellar Tendon.
The TTA has gathered tremendous support over the last 5 years due to the following advantages:
- Increased joint stability
- Much faster recovery time, typically 6 weeks with patients usually weight bearing within 24 hours of surgery
- Decreased complication rate and severity of complications
- Decreased surgical time and therefore anesthetic risk
- Return to excellent long-term function while minimizing the progression of degenerative joint disease in the affected joint
Procedures offered at Our Clinic:
Our veterinarians have special training in both the Extracapsular Repair and the Tibial Tuberosity Advancement (TTA) surgery. We utilize our Laser Therapy with each surgery to help speed recovery.
The drawing above shows a view from the front with the muscles removed. It is important to note that the Patellar Tendon, a vital structure in the joint has been removed, so that you can see “behind” it. The Patellar Tendon is a thick, tough band that runs from the Patella (green dot) to the Tibial Tuberosity (red dot).
Surgery description (in detail with diagrams)
See below for a description of the normal joint, the typical joint angle, the corrected angle and the surgical appearance once the knee has been stabilized by the titanium implants.
The normal joint, viewed from the side, shows the upper bone, the femur and the lower bone, the tibia. The Tibial Plateau is the actual point of contact between the femur and the tibia. In this diagram the Patellar Tendon is clearly visible. It is this structure that must offset the abnormal forces that are created with a rupture of the cranial cruciate ligament
Typical Joint Angle
In the typical joint, the angle formed between the Tibial Plateau and the Patellar Tendon is about 115 degrees when the leg is in a normal standing position.
The abnormal motion that occurs in a knee with a torn cruciate ligament is called Tibial Thrust. After the TTA Surgery, the corrected angle is now 90 degrees, which will offset the forces in the knee that tend to make it unstable.
This diagram shows the knee once it has been stabilized with the appropriate Titanium implants. These implants are very lightweight and are designed to stay in permanently.
The above information includes excerpts and pictures from the web sites of Upper Canada Animal Hospital (Dr. Jim Turpel) and Sechelt Animal Hospital (Dr. Lorne Carroll) who both are currently performing the TTA surgery.