Cranial Cruciate Ligament Repair: Extracapsular Repair

What is a cranial cruciate ligament injury?

One of the most common injuries to the knee (stifle) in dogs is tearing of the cranial cruciate ligament (CCL). This ligament is like the anterior cruciate ligament (ACL) in humans.

There are actually two cruciate ligaments inside the knee: the cranial cruciate ligament and caudal cruciate ligament. They are called cruciate because they cross over each other inside the middle of the knee.

When the CCL is torn or injured, the shinbone (tibia) slides forward with respect to the thigh bone (femur). This movement is known as a positive drawer sign. 

Most dogs with this injury cannot walk normally and they experience pain. The resulting instability damages the cartilage and surrounding bones and leads to osteoarthritis (OA).

What options are there for repairing my dog’s torn CCL?

When the cranial cruciate ligament is torn, surgical stabilization of the knee joint is often required, especially in larger or more active dogs. Surgery is generally recommended as soon as possible to reduce permanent, irreversible joint damage and to relieve pain.

Several surgical techniques are currently used to correct CCL rupture. Each procedure has unique advantages and potential drawbacks. Your veterinarian will guide you through the decision-making process and advise you on the best surgical option for your pet. 

This handout describes two types of CCL surgery: extracapsular lateral suture (ECLS) stabilization and another type of extracapsular repair, the TightRope® procedure.

What does ECLS surgery involve?

The traditional ECLS technique is the oldest surgical correction for cruciate ligament injury in dogs. The name of the procedure originates from the fact that the joint is stabilized outside the joint capsule (externally).

CCL repair surgery typically begins with an initial examination of the inside of the knee. This examination may be done by opening the joint capsule and looking inside or by using an arthroscope. Any damaged or torn portions of the CCL may be removed. 

The shock absorber, or cartilage meniscus, that cushions the knee and sits between the femur and tibia is examined. If the meniscus is torn or damaged, that part will be repaired or removed. After the joint capsule has been examined and any cartilage or ligament fragments are removed, the joint capsule is sutured closed.

In the ECLS procedure, a loop of a special type of suture material (an artificial ligament) is placed from the back of the knee joint around to the front, where it is anchored just below the knee. This suture material stabilizes the joint and prevents the tibia from slipping back and forth after the cruciate ligament has torn. 

The suture is anchored in two spots:

• Around a small bone (fabella) behind the femur, in the back of the knee. The suture passes through a strong tendon that can hold it tightly. 
• A small channel drilled in the front of the tibia.  

The suture is then tightly connected to the other end on the outer aspect of the knee.

There have been several innovations in external capsular repair during the past decade. New materials, anchoring devices, and tools have allowed veterinary surgeons to perform this surgery more successfully than ever before.

Perhaps the biggest advancement in CCL surgery has been in how the suture material is joined together. In the past, veterinarians relied on bulky knots that could come undone or irritate the surrounding tissues. 

Today, there is a variety of suture connectors that are much more reliable, effective, and less irritating. The use of bone anchors and modified bone drills and bits for varying sizes of dogs has also improved ECLS. Strong, specialized knee suture materials have also been developed that make the surgery simpler, more effective, and less risky than in the past.

What does the TightRope® procedure involve?

The TightRope® procedure involves different materials and a slight variation in the traditional extracapsular repair. This method uses a customized needle and a special suture material affixed to bone anchors.

The TightRope® procedure requires drilling two bone channels (resulting in four holes) to run the suture material through. One bone channel is drilled from side to side through the tibia and the other is drilled from side to side through the femur, thereby stabilizing the joint. These unique bone anchors help reduce the need for additional suture material in the joint.

Is one of these procedures better than the other?

Both the traditional ECLS and the Tight Rope® procedure are considered extracapsular or external repairs of CCL injury. Both yield similar results with similarly low risks. The two primary risks of extracapsular surgical repairs are infection and failure. With either type of extracapsular repair, success rates are found to be at least 85% to 90% in smaller dogs, with overall complication rates reported to be between 5% and 8%.

Both the traditional ECLS and the Tight Rope® procedure are considered extracapsular or external repairs of CCL injury. The procedures are nearly identical in their respective potential risks, so it is up to the surgeon to determine which procedure they are most confident will give your dog the best chance of full recovery.

Both the traditional ECLS and the TightRope® procedures are considered adequate for most small to medium-sized dogs and for cats. No matter which technique is used, extracapsular repair is designed to stabilize the knee as scar tissue develops.  Over time, the suture can stretch, weaken or break.  Stability in the knee will then rely on the strength of the remaining scar tissue.  Larger dogs may benefit more from tibial plateau leveling osteotomy (TPLO) or tibial tuberosity advancement (TTA) procedures. Your veterinarian will discuss your dog's condition and which procedure is best. 

What else do I need to know about CCL repair surgery?

Pain management during and after stifle surgery is critical, so be sure to give all medications as prescribed and use them until they are gone. Physical rehabilitation post-operatively can improve healing and speed up the time it takes your dog return to their normal activities. Ask your veterinarian about incorporating rehabilitation into your dog's recovery plan.