This article was updated in April 2016, to reflect advances in treatment options.
Anybody who follows sports will know that athletes, particularly football players, will sometimes injure their ACL, the anterior cruciate ligament, putting them out of action for weeks or months.
Your dog can suffer a similar injury — Cranial Cruciate Ligament rupture, or CCL. It’s a painful, acute or chronic degenerative injury, usually of the anterior cruciate ligament, that results in partial or complete instability of the knee joint.
In the dog’s knee, or stifle, there are two cruciate ligaments — the anterior and the posterior. As they pass between the two main bones of the leg, the femur and tibia, they cross, hence the ‘anterior’ and ‘posterior names. If the knee is subjected to twisting when under load the anterior cruciate ligament can tear, destabilising the knee joint. The tear may be partial or complete.
As with athletes, the cause can be trauma related but that is not actually a common cause in dogs. More often, cruciate ligament rupture is a gradual process resulting from chronic inflammation in the knee joint. Obesity, age-related changes, poor conformation and immune-mediated diseases — where the body’s defence mechanism starts attacking the body instead of protecting it — are some of the more common causes of CCL in dogs. Whatever the cause, CCL is always painful and debilitating for the animal, and often distressing for the owner.
CCL ruptures are the most common cause of hind limb lameness in dogs. Dogs of any breed, sex or age can suffer a CCL injury but it tends to be more common in large and giant breeds, and in obese dogs. If the damage has occurred due to conformation problems of the joint, there is a strong chance of the other knee becoming injured at some stage.
The type of cruciate ligament injury that shows as an inability to bear weight on a leg, with the animal holding the affected limb off the ground, is generally caused by athletic or traumatic events.
Signs of degenerative types of cruciate ligament injuries are much more subtle, showing as marked intermittent lameness that continues for weeks or months. Bilateral cruciate disease, where both knee joints are affected, is also common.
In some cases degenerative changes in the ligaments may predispose a dog to injury, resulting in partial ligament tears that, over time, can progress to full tears, so there is a chance that the opposite knee joint may have a similar type injury in the future.
How is a torn cruciate ligament diagnosed?
An initial physical examination can often reveal a suspected cruciate ligament rupture. With the stabilising action of the anterior cruciate ligament ‘out of action’, the femur and tibia will move in an abnormal fashion in relation to each other, demonstrating instability. This kind of physical exam can sometimes be done when the dog is conscious but, besides being painful, the muscles of the dog’s joint will probably be in spasm, making diagnosis difficult. Usually the dog requires sedation or general anaesthesia to allow proper examination of the joint.
Tentative diagnosis of CCL is based on gait, lameness and palpation of the affected joint. There can be increased fluid in the joint, loss of definition around the ligaments or bony changes on the inside surface of the joint and pain on full extension. Movement of the joint is often increased due to a reduction in stability because of the loss of the CCL, so two different techniques can be used to ascertain joint strength — cranial tibial thrust and cranial drawer. Many dogs with CCL damage have no palpable joint instability due to muscle mass of the hind limb and swelling within the joint, particularly in acute injury. In these cases, radiographs (x-rays) are taken to determine the degree of joint effusion.
While an x-ray will not detect the damaged ligaments in your pet when they occur, they will pick up arthritic changes as they later develop in the unstable joint.
We may also use ultrasound to help confirm a diagnosis, or, in some cases, insert an arthroscope into the joint, allowing us to see if the cruciate ligament is torn or the meniscal cartilage is damaged, and the full extent of the damage.
A CCL can be treated either by medical management or by surgery.
Medical management is most suited for smaller, lighter dogs but larger breeds can show improvement as well.
A conservative medical management program essentially lets nature take its course, with a little help from us. It uses a planned regime of rest, restriction of strenuous exercise, planned diet and weight loss programs, hydrotherapy, anti-inflammatory medications, and time.
At Alpine Animal Doctors, where examination does not fully confirm CCL damage, we opt for a ‘wait and see’ approach. These patients are routinely placed on a four week course of Pentosan Polysulphate (either via injection or capsules), joint supplements (Glyde or Sasha’s Blend) and sometimes pain relief, depending on the dog’s nature. The owner must then keep their pet very quiet with no exercise for the next 4-8 weeks to ensure the joint is given every chance to resolve the possible damage, rarely an easy thing to achieve.
Most dogs will show some degree of improvement with this regime, but few will return to full knee function.
The difficulty with this type of conservative management is that it is not fixing the underlying problem and, if instability of the knee remains, it will normally lead to arthritic changes in the joint, which cannot be reversed, leading to ongoing pain for the patient.
Surgery to repair the ligament and stabilise the knee joint is generally the only way in which CCL ruptures can be permanently improved. There are a number of surgical techniques available, all of which attempt to improve joint stability and reduce the progression of osteoarthritis.
Intra-capsular techniques insert devices used to stabilise the knee and require opening the joint. Extra-capsular techniques are designed to add strength to the structures surrounding the joint to compensate for the torn cruciate.
New procedures are continually being developed. The most recent, developed by Dr. James Cook of the University of Missouri in 2010, is the Arthrex Tightrope CCL repair system, which uses a very strong synthetic ligament anchored directly to the bones on either side of the joint.
In all cases there is no absolute guarantee that surgery can ensure the affected joint will function normally. Arthritis can still develop in the affected joint following surgery, but usually to a significantly lesser extent than if no surgery were performed.
Techniques that surgically alter the function of the stifle joint are the most widely used. These have been developed in an attempt to reduce complications and poor outcomes of ligament replacement techniques, particularly in very large dogs. They are designed to change the anatomy of the stifle joint so that the tibia does not slide forward when weight bearing. There are four ways this can be achieved.
- A Tibial Wedge Osteotomy (TWO) procedure reduces the tibial plateau angle by cutting a wedge of bone from the shaft of the tibia and securing the osteotomy with a bone plate and screws.
- In a Tibial Plateau Levelling Osteotomy (TPLO) the angle of the tibial plateau is reduced by making a semicircular cut below the stifle joint. The cut bone is then rotated to a new position to reduce the tibial plateau angle, and secured with a bone plate. The procedure requires a purpose built semicircular saw blade.
- A Tibial Tuberosity Advancement (TTA) is a procedure involving a vertical cut down the front of the tibia. The cut piece of bone is moved forward a measured distance to neutralise the forces that cause the femur to slide down the tibial plateau. The Tibial Tuberosity is secured with a purpose designed plate, comb and a spacer basket. The procedure requires specialised instruments for plate application and ready access to a complete set of plates, combs and spacer baskets.
- The Triple Tibial Osteotomy (TTO) is a procedure that combines the TWO, the TPLO and the TTA. A vertical cut down the front of the tibia enables the Tibial Tuberosity to be advanced. A small wedge of bone is removed from the tibia behind the first cut, allowing the tibial plateau slope to be reduced. The wedge osteotomy is secured with a bone plate and screws.
- The Tightrope Cruciate Ligament Repair system is a relatively new and minimally invasive method for extra-capsular stabilisation of the CCL. This technique does not require cutting of the bone. Instead, small holes are drilled in the femur and tibia to allow a synthetic biomaterial that closely mimics the properties of a natural ligament to be passed through a small incision to provide bone-to-bone stabilisation during healing.
The Kevlar-like synthetic material used has properties which make it stronger and less prone to failure than any other suture materials being used for CCL reconstructions and is used extensively in human joint surgery, including the repair of ACL sports injuries.
The method used to repair your pet’s CCL injury will often come down to the preferences, experience and the level of skill of your chosen veterinary surgeon. At Alpine Animal Doctors we use the technique we think most suited to a specific patient.
More recently, however, we have begun to lean toward using the Tightrope system wherever we can. As effective as they are, the other techniques described above do have a downside; because the bone has been cut there is increased risk of infection or repair breakdown, and the results of such complications can be serious. They are also significantly more expensive.
The Tightrope procedure allows treatment of larger dogs who would normally require an osteotomy, but with reduced cost and risk of side effects. Our experience with this system has been that the procedure is easier and faster, with a reduced risk of both infection and/or catastrophic failure. The Tightrope system is also more easily reversed in the event of complications.
It can also be used in dogs of all sizes and both recovery rates and long term benefits appear to be comparable with other, more invasive, procedures. Importantly, because it takes less time to complete, it is also cheaper than other forms of CCL surgery.
The surgical repair of a Cranial Cruciate injury must always be carried out with care and precision and is often a long and arduous procedure for both the patient and the veterinary surgeon.
Currently (2016) few vets in Australia are trained in the Tightrope procedure. Dr. Bek has been fully trained in its use. The use of the Arthrex Tightrope Cruciate Ligament Repair System means we can reduce the operative and post-operative stress on our patients, and reduce the cost to pet owners. Savings will vary but the Tightrope procedure will generally cost between $800 to $1,000 less than other surgical methods.
How successful is CCL surgery?
There has always been some debate about the long term effectiveness of surgery for the repair of cruciate ligament ruptures. One study has found that the number of dogs who return to full normal leg function after surgery is little more than those who recover with conservative medical management.
We use both conservative management treatments and surgery, depending on the patient and the owner’s wishes.
With a substantial number of surgical procedures under our belt, our experience over the years has been that, in almost all cases, our surgical patients experience a better long term outcome than those treated without surgery. Significantly, dogs who have undergone surgery for CCL appear to be far less likely to go on to develop arthritis in the affected knee, and consequently suffer less long term pain.
We will discuss with you the various treatment options available, and fully explain the pros and cons of each but, in the end, the decision on treatment options is always left to the pet owner.
It’s worth noting that overweight and obese dogs are much more prone to cruciate ligament tears. The best way to prevent a CLR in your dog is to ensure their diet is matched to their size and level of exercise.