CRANIAL CRUCIATE LIGAMENT RUPTURE
The cranial cruciate ligament (CrCL) is the main stabilizing structure of the canine knee. This ligament prevents forward shifting of the tibia (shin bone) in relation to the femur (thigh bone). It also prevents excessive internal rotation of the tibia. Rupturing of the CrCL is one of the most common causes of hind limb lameness in the dog. It is the most common orthopedic injury that Front Range Mobile Surgical Specialists performs surgery for. The cause of rupture of the CrCL is from excessive force applied to the CrCL from excessive tibial thrust, excessive internal rotation, hyperextension of the knee, or more rarely external direct trauma. Many studies suggest there is a degenerative process that occurs in the CrCL and factors are present which exacerbate the process. The exact cause and mechanism is unknown and consequently the term Cruciate Disease is often used. This may explain why a majority of the animals we perform surgery on have advanced arthritic changes present at the time of surgery, even with the history of a more recent lameness. Also, many if not most of the dogs begin with a partial tear of the CrCL resulting from progression of the degenerating ligament which is not capable of withstanding normal stresses and eventually a complete tear develops. A vicious degenerative cycle of events can occur with the unstable mechanism resulting in the progression of osteoarthritis and a complete failure of the ligament occurs. Some animals will continue long term with partial tears. Spontaneous healing of a partial tear of the CrCL to its normal pre injury function has never been reported.
The complexity of the biomechanics of the canine knee and the CrCL is hard to mimic or replace with various surgical methods. There have been over 100 techniques described to repair the knee which has sustained a ruptured or torn CrCL. All methods have some advantages and disadvantages and even within surgeons performing the same procedure, results may be variable. However, we can expect approximately 85-90% of the dogs can be returned to good functional pet quality activity with surgery. Mild lameness may still be noticed and it may be more prominent after strenuous activity. Smaller breeds of dogs weighing less than 15kgs are more likely to return to a very good function after surgery. The larger the dog, the predictability for return to a very good functional result decreases somewhat. All dogs that have a ruptured CrCL will develop arthritis and it will be progressive. The pet is more likely to obtain a better result if surgery is performed, especially if the dog is over ~40 lbs. Surgery is recommended sooner than later.
The methods of repair for a CrCL deficient knee can be divided into Extra-articiular stabilization techniques using synthetic materials to substitute the function of the ligament (variation of the placement of the extra-articular stabilizing sutures have been described and given different names for the procedure e.g. Tight Rope, Lateral Fabellar Tibial Suture, etc); Intra-articular stabilization using synthetic materials as well as the patients own natural tissues placed within the joint (currently not performed commonly) Tibial Tuberosity Advancement (TTA); and Tibial Plateau Leveling Osteotomy (TPLO). Surgeon discretion and case load selection drives the decision amongst surgeons but the decision is mostly based on personal experience. Clearly the TPLO and TTA techniques are most popular. Over the past 25 years having performed many techniques, I prefer the TPLO in most all of my patients, and especially those larger than 15 kgs. Although we have performed many extra-articular stabilizations in smaller dogs in the past with good results, we are currently performing TPLOs in most of the smaller patients as well (10 lbs and larger). Consequently, we are performing TPLO’s on most all dogs, over 300 per year. It is my experience that the TPLO has provided us with a very versatile surgical technique that has increased the predictability of returning our patients to a very good functional result in 90% of the cases. This innovative TPLO technique developed by Dr. Barclay Slocum has moved the bar higher with our expectations for improved outcomes.