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My interest in this new procedure not only stems from my involvement in cruciate ligament repair, as I have been actively been repairing CCLs for over 30 years in private practice, but also from my new found passion in Labrador field trials. I have been waiting for a procedure like this for years and when I learned of the procedure, our practice hosted the first clinical presentation, with Dr. Cook, and seven board certified surgeons who also had interest in adding another procedure to their armamentarium for CCl repair.
Jeffrey Schuett DVM, Diplomate American Board of Veterinary Practitioners Certified in Canine and Feline Practice
“He took a great line to the mark, and then I heard him yelp as he stumbled. He came up lame, not wanting to use his hind leg. I got this sick feeling as I ran into the field to stop him. His leg didn’t seem to be broken, but I rushed him to the local veterinarian anyway. I was told that he had completely torn his CCL. What should I do? Will this be a career-ending injury?”
Does this scenario sound familiar? I have heard it dozens of times as I consult with owners of field trial dogs, hunting dogs, agility dogs or backyard pets.
In dogs the most common back leg injury is the tear or rupture of the Cranial Cruciate Ligament (CCL). In humans the ligament is named the Anterior Cruciate Ligament.
You may have heard of football players injuring the ACL - this is the same ligament that is affected in dogs, however, in dogs it is most often associated with a degenerative process in the ligament and arthritis in the stifle (knee). A traumatic injury to the CCL may occur in athletes such as field trial or agility dogs, however dogs of all sizes and “occupations”, and cats, get CCL problems.
The more common presentation that I see is the overweight dog that gets limited exercise. Then he gets thrown a tennis ball or chases a squirrel and the hind quarters are not synchronized with the rest of the body. The knee takes a quick twist and the CCL bears the brunt of the momentum. The ligament cord may fray or it may become fully detached from the bone. Lameness is usually immediately observed. If the injury is a partial tear (fray) the dog may improve with prescription anti-inflammatory medications, nutritional support, weight loss, rehabilitation and rest. This is now a weakened area of the body and often gets reinjured and eventually tears completely...
Unlike in humans with the traumatic tear injury the canine CCL tears and damage generally takes place over a period of months or years, rather than being associated with a single traumatic event.
There is current work at the University of Wisconsin College of Veterinary Medicine by Dr Peter Muir that has determined that degenerative CCL rupture is a type of rheumatic disease He has identified certain bacteria by genetic testing and believes that this is one thing responsible for the degeneration in the stifle that leads to the eventual tear of the CCL. The ongoing research has a long-term goal to develop a new medical therapy that targets key pathways and leads to a blocking of the progressive joint degradation that precedes degenerative CCL rupture. Successful treatment of dogs with early disease and stable knees should prevent the need for knee surgery.
Other investigators have provided early evidence for genetic, degradative enzyme, or collagen disorders playing important roles in CCL disease in dogs.
The canine knee is a complex joint. The knee contains 13 ligaments which articulate the joint. Ligaments attach from bone to bone providing static stability to the joint. Muscles and tendons contribute a dynamic component to joint stability and function. If the CCL is deficient, the knee is not fully functional because of the associated pain, inflammation, and loss of a primary stabilizer. In addition, the other rear leg may now be overworked and can experience the same injury.
50-70% of dogs that have one CCL injury are at risk of the opposite stifle needing surgery at some point in their lives. The general conformation can contribute greatly to knee wellbeing. A dog with poor hip conformation may walk differently to compensate and hold the knees at a more stressed angle and therefore be more prone to CCL injury.
The diagnosis of CCl injury involves a complete lameness exam and radiographs. In most cases sedation is helpful to evaluate the presence of a drawer sign on palpation of the stifle. In certain cases you may elect to postpone surgery if the CCL is partially torn but often surgery is needed several months later.
Every year, veterinarians perform over one million knee surgeries on dogs in the United States. This exceeds the numbers of knee surgeries performed on humans. Unlike human ligament injuries the dogs’ ligament are not reattached or permanently replaced by surgery.
In all surgeries the joint is evaluated to check for meniscus trauma and ligament fragments. This can be done either by arthrotomy (cutting into the joint) or by arthroscopy (using a scope to examine the joint structures). Joint assessment and “clean up” via arthrotomy or arthroscopy is a critical part of comprehensive surgical treatment for CCL disease in dogs.
In the past 25 years two procedures have been developed for use in the larger and more active dog. They are the Tibial Plateau Leveling Osteotomy (TPLO) that decreases the tibial thrust in the knee, and Tibial Tuberosity Advancement (TTA) that counteracts the abnormal cranial thrust by helping the muscles rebalance the joint. These surgeries attempt to address the CCL deficient stifle by shifting of workload of joint stability to other healthy ligaments, muscles, and tendons and require that the shin bones, or tibia, be cut, shifted and stabilized with plates and screws to compensate for these mechanical changes.
Traditionally, the most commonly performed technique to address CCL injuries has been the Extra Capsular Suture Repair. Until recently the best choice for large highly active dogs might have been one of the more invasive bone-geometry-altering procedures TPLO or TTA. This was because the usual synthetic monofilament suture (similar to fishing line) used in the conventional extracapsular procedure would be likely to fail with a large very active dog. Currently advanced suture materials are much stronger and more resistant to stretching and abrasion when used in stifle stabilizations than the standard monofilament suture material. Improved bone anchors and improved methods of securing the suture material also lessen the chance of stabilization failure.
The Tightrope CCL surgery is the newest surgical option available for dogs with cranial cruciate ligament injury.
Recently at the University Of Missouri College Of Veterinary Medicine, Dr. James Cook worked with Arthrex Inc. to develop and test the less invasive Tightrope procedure for dogs as an alternative to the current options employed by orthopedic surgeons.
Because of the nature of the CCL injuries, and their degenerative process over time, this new procedure focuses on a technique used in human ankle joints using bone to bone fixation in a minimally invasive way.
The Tightrope CCL surgery uses a unique fiber tape secured in small holes that are drilled in the femur and tibia to isometrically stabilize the joint using an extracapsular method.
The Tightrope CCL seeks to optimize the lateral suture stabilization technique by employing bone-to-bone fixation, utilizing an implant with superior strength and stiffness designed specifically for ligament repair, and a method for consistent isometric implant placement.
The Tightrope procedure is a less invasive technique that replaces the damaged CCL with the fiber tape suture, immediately stabilizing the stifle joint. The objective of TightRope CCL is to counteract cranial tibial thrust, drawer, and internal rotation while providing optimal joint range of motion. Results in surgical outcomes are equal to or better than more invasive surgeries.
Compared to other surgical options the Tightrope procedure can be:
Certainly, complications still occur - Dr James Cook says. “Arthrex and I are 100% committed to continually monitoring and reporting all outcomes and complications associated with TR – we work very hard to gather data from every center doing TR that will send it to us so that we can report it publicly – we know of no other group doing this for any other CCL procedure. From this constant monitoring (data on over 500 cases collected), we are seeing a worldwide success rate of 95.1% and an overall major complication rate of less than 9% including an infection rate of 3.1% for major infections and 2.2% for minor infections – this compares very favorably to reported rates for TPLO, TTA, and lateral suture or any major orthopedic procedure done in dogs.”
Oral medications are used to control pain and inflammation for the first week after surgery. All of the procedures have extended post-operative procedures for optimal recovery. Dogs may not use their leg fully for several weeks and need extended rest and a schedule for physical therapy at home or at a veterinary rehabilitation facility in order to gain the needed strength and confidence for full long term function. Maintaining proper body weight nutritional support and regular exercise are important for complete success.
“In my experience, approximately fifty percent of the success for any of the surgical corrections is dependent on what is done after the surgery is completed,” states Dr. Cook. He stresses how important rehab is for the eventual outcome. “Compliance to incision care, activity restriction, and progressive and controlled muscle building activities is absolutely vital for consistently returning dogs to high level pain-free function!”
Dr James (Jimi) Cook, can be contacted at the University of Missouri.
James L. Cook, DVM, PhD, Diplomate ACVS
William C. Allen Endowed Professor for Orthopedic Research Director, Comparative Orthopedic Laboratory
University of Missouri 900 East Campus Drive Columbia, MO 65211
Following are illustrations describing the TightRope Ligament replacement procedure for ruptured or partially torn cranial cruciate ligaments.
The illustration below shows the canine knee from a front view with the knee cap removed in order to illustrate the femoral tunnel with more clarity. A tunnel is drilled in the femur beginning at a very precise anatomical point on the inside of the bone, at an upward angle, exiting on the inside surface of the shaft of the femur.
The illustration below shows the canine knee from the outside surface with the TightRope Ligament in place. Note that the TightRope Ligament is placed under the long digital extensor tendon, allowing it to function normally and to prevent any damage to the tendon.
The illustration below shows the canine knee from the inside surface with the TightRope Ligament in place. The tibial toggle button and the femoral button are both securely anchored against the surface of the bone to prevent movement.