The cranial cruciate ligament is a strong ligament within a dog’s knee or stifle which connects the femur to the tibia and provides stability to the knee when a dog bears weight. If it is non-functional, then the femur slides backwards over the tibia during weightbearing. This instability is painful and leads quite rapidly to degenerative joint disease or arthritis.
Cruciate ligament rupture in dogs is usually the result of degeneration of the ligament rather than trauma. So, although a rupture may appear to happen suddenly while a dog is exercising, this is the end result of an already weakened ligament. Unfortunately, this means the joint usually already has signs of arthritis by the time surgery becomes necessary. This degenerative joint disease will progress with or without surgery but will be slowed by surgical stabilisation. Cruciate ligament degeneration can be present in both stifles, and many dogs will suffer rupture of the cruciate ligament in the opposite knee within 18 months.
Treatment
There are quite a few different treatment options for cruciate ligament rupture. Non-surgical treatments seldom lead to a good outcome. All surgical techniques include a small arthrotomy to examine the inside of the knee joint. Any remnants of the torn ligament are removed and the meniscal cartilages are also inspected and treated if needed.
Our surgical treatment of choice is called a tibial tuberosity advancement or TTA. The bone below the knee is called the tibia and the front part of the tibia is called the tibial tuberosity. If this part of the tibia is advanced forward after making a cut in the tibia, the resultant change in the joint angles leads to stability of the stifle. In essence this procedure renders the cranial cruciate ligament unnecessary as there is no longer a tendency for the femur to slide backwards over the tibia during weightbearing. The cut piece of bone is maintained in the new position by means of a spacer (called a cage) as well a plate and screws.
Extracapsular nylon repair
This is an older technique which can be successful especially in smaller, lighter animals. A strong nylon loop is passed between the femur and the tibia on the outside of the joint and joined by means of a small metal tube called a crimp. This technique provides stability to the joint until such time as the body can provide long term stabilisation by means of fibrosis or scar tissue. Recovery does tend to take longer than techniques such as a TTA and there is a risk of the implant breaking leading to failure of the repair.
Postoperative care
Aftercare is a very important part of a successful outcome after cruciate surgery. The body needs time to recover and in the case of a TTA, the cut bone also needs time to grow together again in the new position. For some animals these exercise restrictions may necessitate cage confinement.
Prognosis
Most dogs will return to a similar physical level compared to their pre injury state. Existing degenerative joint disease is still present after surgery and the improvement is due to the elimination of instability. Some dogs will require ongoing or intermittent analgesia in the form of anti-inflammatory drugs.
Complications
As with any surgery, complications can occur.
The most common complication is meniscal injury. Dogs (and humans) have menisci, which are thin semi-circular cartilages, within their knee joints. Up to 10% of dogs suffer meniscal injury some weeks or months after surgery. Typically, this is seen as a recurrence of lameness in a dog that had been doing well after surgery. Treatment for this so called late meniscal injury requires a further, smaller surgery to examine the joint and remove the damaged tissue.
Other complications are less common but include infection, implant breakage, tibial fracture and patellar luxation. We take extensive precautions to limit the incidence of infection but nonetheless a 3% incidence is anticipated. Infection may require the removal of implants.