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Part Two: The Cruciatus Cure

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“Cure” is hopeful term. Unfortunately, a cruciate-deficient knee can never truly be returned to normal because the knee was never truly normal in the first place. The degenerative process that ultimately leads to rupture of an anterior cruciate ligament doesn’t go away when the ligament is repaired. These knees are arthritic and their arthritis is promoted to some degree by surgical trauma.

The length of time between the initial cruciate injury and surgical stabilization of the joint plays a huge role in determining the functional outcome of a repair (and the later functionality of the “good” knee). The animal’s weight is another powerful determinant of success. Like everything in medicine, there are 100 billion factors involved. We control nearly a dozen of these. I consider a cruciate repair successful when I don’t have to fix the opposite knee later!

The Tibial Plateau Leveling Osteotomy (TPLO) was developed about 20 years ago. The procedure involves cutting a circular fracture in the tibia that allows adjustment of the angle of the tibial plateau (the flat weight-bearing surface of the lower leg bone) under the theory that a level tibial plateau eliminates the knee’s need for a cruciate ligament. This was a radical departure from earlier techniques, which were primarily based upon lateral stabilization and was seized upon by many specialty surgeons as a superior method of cruciate repair.

The Tibial Tuberosity Advancement (TTA) procedure was developed more recently (~2000). This method of cruciate stabilization also modifies the geometry of the knee joint in a way that eliminates the need for a functional cruciate ligament. The TTA surgery has recently come into greater favor than TPLO among some specialty surgeons.

Both TPLO and TTA surgeries create fractures in the tibia which are used to modify the geometry and weight bearing characteristics of the knee joint and are widely claimed to result in less long-term arthritic change to the knee. Both procedures rely on metal implants and bone screws to stabilize the fracture over a 12 to 16 week (normal bone fracture) healing period.

The Lateral Stabilization technique has been around ‘forever.’ This approach replaces the function of the cruciate ligament by placing a lateral tension band on the outside of the knee joint parallel to the ligament’s interior course. High Strength Lateral Stabilization (HSLS), based on the use of modern materials, generates a much more reliable repair than older versions of the surgery and continues to be a practical, lower-cost alternative to TPLO and TTA.

Which ACL repair technique is best? The answer depends on whom you talk to. Surgical specialists who perform the TPLO and TTA procedures believe these methods produce better, more reliable results with less long-term arthritis in the repaired knee.

TPLO surgery is generally agreed to have the greatest risk of catastrophic failure of the repair, and it is often said that a pet owner should not undertake a TPLO unless they are prepared to pay for it twice. Complications include loosening of the screws or bone plate used to stabilize the repair fracture or opening of the surgical wound. Complications of one form or another have been reported to occur in as many as 15% of patients.

TTA surgery tends to generate fewer complications but reliable statistics are difficult to locate because the technique is relatively new. A figure of up to 7% has been reported. It is generally agreed that TTA complications tend to be less serious and less costly than complications of TPLO.

Complications of High Strength Lateral Stabilization are typically the result of implant failure. The heavy nylon monofilament used to replace ACL function can fatigue and break, and the stainless steel tubes used to crimp the nylon loops at the proper tension can slip and allow unwanted instability of the knee. However, because the repair does not involve creation of a bone fracture, the severity of HSLS complications is much lower than complications of TPLO or TTA.

I use the HSLS technique for my patients. I have performed hundreds of HSLS surgeries over the years with very few problems, though I have replaced the lateral stabilization sutures in a couple of patients due to failure. I look forward to a controlled study comparing the benefits of these three techniques among the many different kinds of patients requiring ACL repair surgery. Given the much greater cost of TPLO and TTA surgery, I believe HSLS technique continues to offer a viable alternative to newer methods because no published evidence has demonstrated the superiority of TPLO or TTA over HSLS.

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