Pet Surgery Topics

Meniscal injuries in dogs are a common occurrence secondary to cranial cruciate ligament injury.  Isolated meniscal injuries without a torn cruciate ligament are very rare, however.

The menisci are two C-shaped structures within the knee that play a role in distributing the force of weight-bearing from the femur to the tibia as well as act in stabilizing the femur on the tibia. The idea is that the bottom part of the femur is made of two round structures called condyles. The area that they contact on the tibia called the tibial plateau is a relatively flat surface. The menisci help allow a round surface to have more stability on a flat surface and increase the area available for weight-bearing.

Dog Meniscal Tear

Almost all of the time for the meniscus in the dog to be injured there has to be some laxity or tearing of the cranial cruciate ligament. When the cranial cruciate ligament is torn, this allows the femur to slide off the back edge of the tibia and then as it comes forward, grab a portion of the meniscus in the back of the joint and drag it forward, resulting in the torn piece sitting between the femur and tibia. The torn portion of the meniscus is almost always on the back half of the medial (inner) side of the joint.

Clinically, dogs with a torn meniscus show lameness, often severe, to the point of almost nonweight-bearing. Some of these dogs may have had a mild lameness before it suddenly worsened because the cruciate may have been slowly tearing long before the meniscus got injured. Another sign of a meniscal tear is a “popping” or “clicking” noise, called a meniscal click, when the dog walks. This is due to the torn portion of meniscus sliding around during movement of the joint.

Diagnosis of a meniscal tear is usually made by visual inspection at surgery. There are no known nonsurgical methods of repairing a meniscal tear and most dogs will ultimately not use the leg unless the torn portion is removed. Inspection of the meniscus can be performed using arthroscopy or via an arthrotomy (opening of the joint). Most of the time, the meniscus is being visualized along with some surgery to stabilize the torn cranial cruciate ligament. In dogs, attempts to repair the torn meniscus have not proven success. Therefore, removal of the torn portion of the meniscus is the standard of treatment.  Other procedures like ultrasound and MRI of
the knee have been studied and may be effective at diagnosing a meniscal tear, but are rarely performed since surgery is usually indicated to repair the torn cruciate ligament anyway.

Meniscal injuries can also occur after a dog has had their knee repaired for a cranial cruciate ligament tear. This occurs in about 1 out of every 15-20 dogs and can occur months to years after the knee has been repaired. udden onset of lameness that does not improve with time or rest is the typical sign. These dogs will return to good use of the leg in most cases with surgical removal of the torn piece of meniscus.

Prognosis for dogs with meniscal tears is typically thought to not be as good in the long term as for dogs without meniscal injuries. Because the menisci play a role in stability and force distribution within the knee, an increase in post-op arthritis is expected after removal. Which procedure is performed to stabilize the knee may also play a big role in arthritis post-op. Clinically most dogs still do very well after meniscal removal and stabilization of the knee for the cruciate tear and if severe arthritis does occur, it is usually much later in life.

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.

Tightrope Procedure

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.

TPLO surgery is one of the many different methods of stabilizing a dog’s knee after a cranial cruciate ligament tear. The TPLO surgery involves cutting the top of the tibia and rotating the bone then putting a plate on the bone to hold it in the new position while it heals. Sounds pretty radical just to make the knee stable but it is a very effective way of stabilizing a dog’s knee. I’ll go further into exactly what is happening in a minute.

First, to understand why we cut the tibia, you need to understand the anatomy within the dog knee. In a human, the top part of the tibia where the femur comes into contact with the tibia, called the tibial plateau, is flat. Because of this, when a person has a torn cruciate ligament, they can get around pretty well without the ligament. What the cruciate ligament does is stop the knee from turning inwards, called internal rotation, and hyperextension, in a person, the knee bending backwards. A person, as long as they don’t want to twist and turn on their leg, can get around pretty well without their cruciate. The dog’s anatomy is different. Dogs have a slanted tibial plateau. On average, the slant is about 25 degrees (see diagram). The consequence of this slant is that when all the muscles around the knee joint contract, the tibia tries to move forward compared to the femur. This movement is what the cranial cruciate ligament in the dog has to stop. Consequently, the cranial cruciate ligament in a dog is stressed every time the dog takes a step on the leg. Like I discussed in the post about CCL disease in dogs, we think this is a big reason why dogs tear their cruciate ligaments with little to no trauma. Just slowly over time becoming lame on the leg because the ligament keeps tearing more and more over time.

The concept behind the TPLO surgery is to remove the slant to the tibial plateau. Essentially, what we accomplish by doing this is we put the tibial plateau at a 90 degree angle to the dog’s patellar ligament. This is an important concept that comes up again in another surgery to stabilize the dog’s knee called the TTA (tibial tuberosity advancement). With the TPLO, a semicircular cut is made completely across the tibia using a special saw.  Once the tibial plateau is free, it is rotated a certain distance (7-9mm for most dogs) until the plateau now has about a 5 degree slant to it. In studies, around 5 degrees was found to be the optimal angle where everything is stable within the knee during a full range of motion. Once the plateau is at the appropriate angle, a bone plate is attached to it to keep it in that position until the bone heals (see diagram). Effectively, what we are doing is making so that the dog does not need his cruciate ligament anymore. In actuality, we do not replace the cruciate ligament at all. We inspect the joint to assess how torn the ligament is, remove the damaged portion of ligament, and make sure other structures within the knee like the menisci are okay. But, as far as doing anything to replace the torn ligament, we don’t. The whole effect in the end is that when a dog bears weight on the leg after a TPLO procedure, and all the muscles around the knee contract, there is no shifting of the two bones, effectively removing the need for the cruciate ligament. Why the dog can run, twist, turn, and do other things that they should need a cruciate ligament for without a problem, we don’t fully understand that. Probably other ligaments surrounding the knee take up that job. We do know though, from having performed this surgery on hundreds of thousands of dogs that they recover and do very well with the TPLO procedure.

Complications with the TPLO surgery mainly involve the bone plate and screws that we use to stabilize the bone and the fact that we have essentially fractured the bone and need to get it to heal. Breakage of the bone plate or screws is a concern but is a rare problem. Infection is a problem that occurs in about 10% of dogs.  The plate, unfortunately, is right below the skin and has little tissue covering it so it is at risk of infection. Infection manifests as swelling, discharge, lameness, and fever. It can occur close to surgery (5-7 days) or can manifest as a low-grade mild infection that appears even months post-surgery. Delay in bone healing can occur and is usually either associated with infection or with breakage of screws that hold the plate on. With most TPLO surgeries, the tibia is completely healed around 8 weeks, 12 weeks at the latest. This is somewhat age dependent, with older dogs taking longer to heal, and activity dependent, with the more active dogs post-surgery taking longer. Another common problem we see are dogs licking their incision open so your vet should always send you home with an e-collar (lamp-shade) for your pet to wear for the first two weeks. There are some other more rare complications that your surgeon should mention to you also when you discuss the procedure.

TPLO recovery varies depending on the surgeon. In my hands, I have the owners restrict their pet’s activity for a full 3 months. Restricting activity is mainly the dog needs to be on-leash whenever outside and otherwise no running, jumping, playing with other dogs, and for the early recovery, no stairs. Dogs are encouraged to take leash walks once they are willing to put the surgery leg down. This is usually one week post-op. Owners can start with 5-10 minute leash walks and gradually increase the duration from there. After 3 months, if radiographs show the bone has healed, the dog has had no complications that set back the recovery, and the dog is using the leg well, they can return to their normal, off-leash activity.

So who is the TPLO procedure for? I recommend the TPLO procedure for any dog over about 40lbs. Dogs below 40lbs. can till have a TPLO surgery, but other techniques that are less expensive can lso be done in those size dogs. The more the dog weighs, though, the more a technique like the TPLO should be considered. Also, very active dogs, I usually recommend the TPLO or similar type of surgery. As far as what is the best surgery for your dog, that is something that depends on the surgeon doing the surgery, what you can afford, and many other factors. There is really no right and wrong answer to which surgery is the best for any specific case. This is still something that is hotly debated across the field of veterinary medicine. The key for owners is to take the initiative and become educated about the options for their pet.

Did you know that your dog’s knee, or stifle as we call it, is pretty similar to your own knee. Dogs have similar structures and ligaments within their knee  is humans. Unfortunately, they are also prone to tearing or rupturing their cruciate ligament, just like people.

Dog cruciate ligament injury is a very common injury that veterinarians see. It is by far the most common disease that veterinary surgeons perform surgery for. A study in 2005 looked at the estimated economic impact of dog cruciate ligament injury for the year of 2003 and found it to cost pet owners $1.32 billion (JAVMA, 2005) and the incidence of dog cruciate ligament tear hasn’t really changed since 2003 except costs of repair have gone up.

The cranial cruciate ligament (or anterior cruciate ligament in a person) is the ligament that dogs usually tear. There are two ligaments within the knee joint that form a cross or x-shape, thus the name cruciate ligaments. The problem with these ligaments is that once they are torn, they do  not heal. The ligaments do not have a good blood supply and no mechanism for repairing themselves.

In humans, some form of injury or trauma is usually necessary to injure your cruciate ligament. Like football players getting tackled and injuring it, or skiers falling abnormally and tearing it. In dogs, we do see some dogs that are running around and suddenly tear the ligament. We also, however, see dogs that injure their cranial cruciate ligament without any trauma to the knee at all. There appears to be some degeneration of the dog cruciate ligament that occurs allowing the ligament to partially tear and then progressively continue to tear more over time with minimal trauma. Often these dogs present with just a progressively worsening lameness, usually exacerbated with exercise. These partial tears almost always go on and progress to complete tears given enough time.

The anatomy of the dog leg is thought to be partially responsible for why these partial tears occur. Studies have shown that when a dog bears weight on their hind leg and the muscles around the knee contract, there is a desire for the tibia to move forward compared to the femur. This movement, called cranial translation, is stopped by the cranial cruciate ligament. Since the dog cruciate ligament is stressed everytime the dog bears weight, it is thought that this is part of the reason behind the degeneration and gradual tearing of the cruciate ligament over time. This also is a big part in why dogs do not do well without their cruciate ligament.  Once the ligament is torn, every time the dog takes a step, the tibia and the femur shift on each other causing swelling and pain for the dog. It is a very rare dog that can get around well without their cruciate ligament and why most dogs end up needing surgery to  get them back to using their leg normally.

So how do you know if your dog has a cruciate ligament tear? The main sign you would see is lameness. Often with partial tears, the lameness is mild and most noticeable with exercise. The other sign you often see is lameness or soreness after resting. Usually the dog will use the leg for exercise but after laying down for a while, will have difficulty standing and show lameness when trying to walk around. As the torn ligament gets worse, the dog usually will show lameness more often and then progress to the point of holding the leg up. With acute (all of a sudden) tears of the ligament, the dogs tend to go “3-legged” lame, holding the leg up and not bearing any weight on it. The acutely torn ligament is also much more painful and dogs will often show  crying and whimpering because of the severe swelling that occurs when the ligament suddenly tears.

The diagnosis of a dog cruciate ligament tear is usually done by feeling the leg for abnormal shifting of the femur and the tibia. There are two tests in general that your vet can do to tell if the ligament is torn. The first is called a cranial drawer test and the  second is the tibial compression test. Both tests are trying to show abnormal shifting of the femur and tibia that the cranial cruciate ligament should prevent from happening. When the ligament is completely torn, both tests produce significant movement of the two bones. With partial tears, the movement between the two bones may be very subtle and sometimes just feeling the leg is not enough to tell for sure if the ligament is torn. In almost all cases, radiographs help to prove a diagnosis by showing swelling and possible arthritis within the knee to support some form of injury. Final diagnosis is made at surgery either with arthroscopy (using a camera on a scope) or arthrotomy (opening of the stifle) to visual the torn ligament.

Treating dog cruciate ligament injury almost always involves surgery. Like I said early, it is unfortunately a rare dog that will do well without having some form of surgery to stabilize the knee. There are some small dogs, maybe 10 lbs and under, that can get around without their cruciate ligament, but a majority of dogs, and definitely the larger the dog gets, will not use the leg without the cruciate being repaired. Because the ligament will not heal, the only hope a dog has without some form of repair is that the dog’s body can somehow lay down enough scar tissue around the joint to make it stable enough for the dog to use it. This may be enough for some small dogs, but usually it is not sufficient for medium to large sized dogs. Physical therapy and rehabilitation may help dogs to strengthen the musculature around the knee and possibly allow some dogs to do well without surgery.

There are multiple options for dog cruciate ligament surgery. Usually, the decision on which technique is done for dog cruciate ligament repair is based on the surgeon’s preference and the financial constraints of the owner. Because there are multiple techniques for repairing the cruciate, there is obviously no one surgery that is perfect. The techniques that are currently done for dog cruciate ligament repair include the lateral suture extracaspular repair, intracapsular reconstruction of the ligament, fibular head advancement technique, tibial plateau leveling osteotomy, tibial wedge osteotomy, tibial tuberosity advancement, and tightrope stabilization technique. I will leave discussing these different techniques with their advantages and disadvantages for another time.