What’s the best veterinary surgery procedure for my dog’s cruciate ligament injury?

WestVet’s Chief of Staff, Jeff D. Brourman, DVM, MS, DACVS, outlines best practices for ACL, or knee TPLO treatment in dogs,

Rupture of the cranial cruciate ligament, equivalent to the anterior cruciate ligament (ACL) in people, is one of the most common orthopedic injuries in dogs. The rupture may occur from trauma or from the gradual deterioration of the ligament. Why this “cruciate disease” occurs in some dogs remains a mystery, however, a combination of heritable and environmental factors–such as conformation and obesity–likely play a role.

Many dogs that tear the cruciate ligament will often have a concurrent injury to their meniscus, the “cushion” of cartilage in between the bones of the knee. About half of the dogs that tear their cruciate ligament in one knee will end up tearing the cruciate ligament in the other knee.

Dogs with partial or complete cranial cruciate ligament rupture rarely improve without surgical intervention. Instability and inflammation in the knee joint will usually continue until stability is restored. The concurrent meniscal injury also needs to be addressed at the time of surgery.

When it comes to surgery, owners of dogs with cruciate ligament injury are often faced with difficult decisions. A variety of surgical procedures have been developed to deal with this injury and discussions with veterinarians and other pet owners may only lead to further confusion.

The first step in surgically addressing a dog or cat knee with a cruciate ligament injury is to properly explore the joint, confirm the ligament tear, and identify any other injuries within the joint. This exploratory can be achieved through a variety of ways. The least invasive and most complete method is by arthroscopic exploratory. Similar to what’s done in people, a small scope, connected to a camera and video monitor, is inserted through a small (~1cm) incision. This allows good visualization of all structures inside the joint.  It also allows various treatments such as cleanup of the torn ligament and repair or removal of the meniscus to be accomplished through a very minimally invasive approach. Other non-arthroscopic techniques can be used, however, require either a larger incision in the joint (arthrotomy) or a more limited approach which confines visualization to only the medial meniscus. A meniscal release procedure (cutting the meniscus or ligament holding the meniscus) remains controversial. The theory is that it helps prevent a meniscal tear in the future. Concerns, however, have arisen that the meniscal release may lead to instability and possibly an increase in osteoarthritis.

Once the structures within the knee have been adequately addressed, a stabilization procedure is performed. In people, this is most often accomplished by replacing the cruciate ligament with a synthetic graft, autograft, or allograft. These graft procedures have been performed in dogs, however, issues with deterioration of the graft continued instability, and additional osteoarthritis has led to less than satisfactory results. Extracapsular stabilization procedures (lateral suture and tight-rope) or geometric modification procedures such as the tibial plateau leveling osteotomy (TPLO) and the tibial tuberosity advancement (TTA) have been used more commonly to stabilize the canine and feline knee. Recent studies have shown that the geometric modification procedures such as the TPLO and TTA are superior to the traditional extracapsular procedures with regards to improvements in weight-bearing and reduced development of osteoarthritis. Controversy remains, however, on which geometric procedure (the TPLO or TTA) is better.

The surgeons at WestVet have tried to answer this question through an extensive, comparative clinical study. Sixty dogs with cruciate ligament injury were enrolled in our study and randomly assigned to receive either a TPLO or TTA procedure. All dogs had an arthroscopic exploratory of the knee at the time of surgery and were then followed for 2 years.  A brief summary of the results is as follows:

• Both TPLO and TTA will lead to significant improvements in the usage of the injured leg.
• Dogs that receive the TTA procedure get back to using their operated limb approximately 2 weeks faster than dogs that receive a TPLO. Long-term (at 6 months and 1 year), however, the dogs receiving the TPLO procedure did better than dogs receiving the TTA procedure. While the difference was small, it was statistically significant. The difference was larger for dogs with certain anatomic variations (steeper tibial slope).
• Dogs that had the TTA procedure had a higher rate of meniscal tears after surgery.

Based on our study, the surgeons at WestVet (Drs. John Chandler, Sean Murphy, and myself) recommend the following:

• Ideally, an arthroscopic exploratory of the knee should be performed.  This allows the ligament, lateral, and medial meniscus to be evaluated and treated through a very small joint incision.
• If a dog is having a TTA procedure, the meniscus should be released.
• If a dog is having a TPLO procedure, the meniscus should be preserved and not released.

Based on our study and some recent studies emerging from Dr. Peter Boucher in Germany, the TPLO is our preferred stabilization procedure.  Further studies in this area, however, are needed and will continue to be beneficial in determining the best procedure for treating cranial cruciate ligament disease in animals.