Resource Library: Cranial Cruciate Ligament Rupture (CCLR)

CRANIAL CRUCIATE LIGAMENT RUPTURE
The most common cause of rear limb lameness in the dog is rupture of the cranial cruciate ligament (CCLR). This leads to degenerative changes in the knee joint including cartilage damage, meniscal injury and osteophyte production.

CCLR can occur in several different ways. There may be a single incident which causes a sudden complete rupture of the ligament with severe pain and non-weight bearing lameness. Anterior cruciate ligament ruptures can also occur in small increments or a little bit at a time. These are known as partial ruptures of the anterior cruciate ligament. These partial ruptures cause a small amount of pain and a mild lameness. When partial ruptures proceed to complete ruptures, the transition is often gradual. Two other important structures in the knee are the medial and lateral menisci. The menisci cartilage pads between the femur and the tibia. They are prone to injury when the stifle joint is unstable from a cruciate ligament tear and can be removed if they are damaged.

Clinical Signs
Once the cranial cruciate ligament ruptures, the tibia can slide forward and the femur is free to ride down the slope of the tibial plateau. The meniscus is often damaged as the femur rides over the top of it. When the ligament tears, pain, swelling, and marked lameness will occur. If not stabilized, the joint will become dramatically arthritic over time. Rest and anti-inflammatory medications have little effect upon the pain and lameness the dog experiences.

Diagnosis
Diagnosis is made upon eliciting forward motion of the tibia (cranial drawer sign) or via the presence of tibial thrust. This is easy in acute, complete ruptures but may be more subtle in chronic or partial tears. Mild sedation to allow muscle relaxation and radiographs to demonstrate arthritic changes and swelling may be necessary to obtain a diagnosis.

Methods of repair
There are many ways to repair a ruptured cruciate ligament. The best surgical method for you pet will be determined by evaluating age, activity, size, temperament, and weight. Some common methods we use to repair ruptured cruciate ligaments are TPLO's, TTA's, lateral sutures, and the tight rope procedure. Meniscal injuries are also corrected during the all stifle surgery in order to prevent further arthritic changes in the joint.

TPLO Surgery
The tibial plateau leveling osteotomy is used to neutralize the effect of cranial tibial thrust. The procedure levels the tibial plateau, changing the biomechanics of the knee thereby eliminating the need for the cranial cruciate ligament as a restraint against cranial tibial thrust. The TPLO procedure is an excellent choice for larger active dogs due to the stability it provides under extreme repetitive stress.

TTA
The Tibial Tuberosity Advancement is another option to repair a CCLR. The objective of the TTA is to advance the tibial tuberosity, which changes the angle of the patellar ligament to neutralize the tibiofemoral shear force during weight bearing. By neutralizing the shear forces in the stifle caused by a ruptured or weakened CrCL, the joint becomes more stable without compromising joint congruency.

Extracapsular Stabilization/Lateral Suture Procedure
There are many technical variations of the lateral suture, but all are the same in that the stifle joint is stabilized with placement of a non-absorbable suture material, typically monofilament nylon such as fishing leader line, around the lateral fabella and through a hole in the tibial crest mimicking the pattern of the CCL. Although often referred to as an "artificial ligament", the suture provides only temporary stabilization and will loosen over time. This technique relies on scar tissue to ultimately stabilize the joint. Recovery time following the Extracapsular Stabilization is approximately 3 to 5 months. While this technique can be successful, it is more likely to fail in large breed dogs as the prosthetic ligament can stretch or rupture.

Tight Rope
The newest procedure for repairing a ruptured CCL by ligament replacement is the TightRope Ligament technique. As with the other procedures the TightRope CCL counteracts the forward tibial thrust and inward rotation resulting from CCL damage, while providing optimal joint range of motion. A tunnel is drilled in the femur and a second tunnel is drilled in the tibia. The TightRope Ligament is passed through the femoral tunnel, then through the tibial tunnel. The prosthetic ligament is now in place, very secure and mimics very closely the function of the natural cranial cruciate ligament. Complications of the tight rope can require removal of prosthetic ligament and repair of the CCLR via another method. This technique is not idealy suited for a young large breed active dog.

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