Cranial cruciate ligament rupture in the dog is the most common orthopedic injury that veterinarians see. Although some dogs may do okay without surgery to stabilize the stifle joint, a majority of dogs will require surgery to get back to using the affected leg well. When we start talking surgery to stabilize the knee in dogs, there are multiple different techniques that are being done. Which technique that is chosen depends on many variables such as size of the dog, age of the dog, activity level of the dog, financial factors, and even surgeons preference.
As far as the question of is there one “right” technique to stabilizing the knee, the answer is definitively NO! I always tell owners that when there are multiple different surgeries advocated for doing the same thing, you know that there is no “best” way to do it. If there was, then there would only be one surgery recommended all the time.
The newest technique that has been introduced as a way to stabilize the cranial cruciate deficient stifle in dogs is the Tightrope Procedure. This procedure was introduced in 2008 by Dr. James Cook, PhD, Diplomate ACVS from the University of Missouri in collaboration with Arthrex Vet Systems, Inc. The idea behind the system is similar to the lateral retinacular suture that is regularly performed in small and medium sized dogs. With the lateral retinacular suture (also called the lateral fabello-tibial suture, lateral suture, lateral imbrication technique, and extracapsular repair) a couple of strands of heavy nylon suture are placed around the lateral fabella and through the tibial crest and tied in a figure-8 pattern on the outside of the knee to mimic the position of the cranial cruciate ligament within the joint and to stop cranial drawer otion within the knee. This technique works effectively in smaller and medium-sized dogs but tends to loosen in the larger breeds leading to less than optimum outcome long term.
The Tightrope procedure was developed as a less invasive method than the TPLO and TTA which require cutting the tibia (osteotomy), an easy to perform surgery, a technique that addresses all aspects of instability and which provides consistently good long term results, even in larger dogs. Anatomically, the Tightrope is similar to the lateral suture technique in that it is placing a heavy piece of suture outside the joint to stabilize the stifle. The difference is that the Tightrope procedure utilizes bone tunnels and toggles to attach the ligament directly to the bone rather than around other structures like the fabella. There is a thought that because the lateral suture wraps around the fabella which is held to the back of the femur by a ligament, that stretching or lateral displacement of the fabella or ligament holding the fabella occurs over time and leads to the lateral suture loosening, especially in the larger dogs. By attaching directly to the bone, there shouldn’t be loosening over time. The Tightrope procedure also utilizes a new product called FiberTape instead of heavy nylon suture. FiberTape, made by Arthrex Vet Systems, Inc, in studies has been shown to have dramatically better ultimate load and stiffness compared to nylon and less cyclical displacement. Because of this, FiberTape can be used in larger dogs with less chance of the suture material breaking and less chance of the material stretching and leading to laxity within the joint.
The Tightrope procedure involves drilling two holes, one across the femur and the other across the tibia. Landmarks for the hole placements are very specific so that once placed, the suture will be in the isometric (same or similar) position to the cranial cruciate ligament within the joint. The suture is passed through the holes and a toggle and button are used on the medial (inner) side of the leg to attach the material to the bone. The procedure is quick and technically easy to do. It works well with arthroscopy because it doesn’t require entrance into the joint. The benefit of this is a faster return to use of the leg post-op. Another advantage of the Tightrope procedure is that it should be less expensive than either the TPLO or TTA, since the surgery is quicker and there are less implants being used.
Recovery from the Tightrope procedure is similar to all of the other techniques done to stabilize the knee. The dog is able to use the leg when they are ready, hopefully the first week. Activity is restricted to on-leash only for a full 3 months post-op but leash walks are encouraged as soon as the dog is willing to use the leg. After 3 months of progressively longer leash walks, and if recovery has been without problems, the dog can return to normal, off-leash activity.
The Tightrope procedure is a relatively new technique so we unfortunately don’t have a ton of data to say complications and long term outcome. In the initial study performed by Dr. Cook, 24 dogs had the Tightrope procedure and 23 dogs had the TPLO procedure. The rates of complications were 12.5% for the Tightrope and 17.4% for the TPLOs which were statistically similar. Six month post-op evaluations showed as good or better outcomes in medium, large, and giant breed dogs with the Tightrope compared to the TPLO when it came to function on the leg and radiographic progression of arthritis.
Complications with the Tightrope procedure include infection of the FiberTape, loosening of the FiberTape, and subsequent meniscal injury post-surgery. Infection of the FiberTape can be a serious problem since once infected, it is very unlikely that the infection will be able to be eliminated from the FiberTape. Ultimately, this means the only solution for the infection may be to remove the FiberTape down the line. Loosening of the FiberTape has also been reported. This is usually caused by enlargement of the hole in the bone where the toggle or button are placed and then the toggle or button slipping into the bone itself. Sometimes this is associated with infection of the FiberTape also. Subsequent meniscal injury is a problem with any technique used to stabilize the stifle joint.