Cranial cruciate ligament tears are the most common cause of hindlimb lameness in dogs
Instability of the stifle is corrected with either the TPLO surgery or the Lateral imbrication technique (extracapsular)
The extracapsular procedure is best suited for small dogs
What is it?
The canine knee (also called the stifle) is similar to a human's knee in many regards.
The joint is made of the femur (thigh bone), tibia (shin bone), patella and supporting tendons and ligaments. Of great importance are the cruciate ligaments.
The cranial cruciate ligament (also known as the anterior cruciate ligament or ACL in humans) which is most commonly torn ligament in dogs results in lameness due to pain and instability of the joint.
When the ligament is torn, the femur slides down the sloped top portion of the tibia called the tibial plateau.
The cause of cruciate ligament tear is unknown, but conformation of the limbs and genetics may play a role.
In about one third of the patients that are operated for a torn cruciate ligament also have a tear of the meniscal cartilage on the inner side of the joint (medial meniscus) - the two illustrations (right and below) demonstrate the dynamic displacement of a torn medial meniscus - this is very painful.
Anatomy
The knee is correctly termed the stifle joint in animals
Ligaments hold the stifle joint together
Ligament tears are common in dogs and cats
The cranial cruciate ligament is one of the main stabilizing structures of the stifle joint. The cranial cruciate ligament serves to prevent forward movement of the tibia bone (shin bone) relative to the femur bone (thigh bone), to prevent internal rotation of the tibia bone, and to limit hyperextension of the stifle.
Two meniscal cartilages (medial and lateral meniscus) located inside of the joint are crescent-shaped pads that serve as cushions and provide some stability to the joint.
Clinical signs
Most dogs are middle-aged or older when the rupture occurs, however young dogs can also have a similar injury.
Breeds commonly affected include Labrador Retrievers, Rottweilers, Akitas, Border collies, Huskies, German Shepherds, and Mastiffs.
Many small breeds also develop cruciate ligament tears which include poodles,
Common signs include:
stiffness on the limb after resting for a period of time
varying degrees of lameness
not bearing weight on the limb
if the meniscus is torn sometimes a clicking noise is heard from the stifle when the pet walks on the limb or when the stifle is flexed (see animations above and right)
Diagnosis
Physical examination will frequently reveal the following:
lameness on the limb
instability of the knee (called drawer movement)
swelling of the knee joint
X-rays will show signs of swelling in the stifle joint, arthritis, and in some cases displacement of the femur bone down the slope of the tibia
Contralateral cruciate tears
about one third of the dogs will tear the cruciate ligament in the opposite limb within 1 to 2 years
these dogs frequently have arthritis in the knee joint even before the tear in the cruciate is obvious on physical examination, but early changes such as mild joint swelling may be detected with x-rays.
an x-ray may show subtle changes of cruciate ligament disease that may not be obvious on physical examination.
Treatment
Candidates for the lateral fabellar surgery
We use this technique primarily for small dogs and cats.
Some dogs have a steep tibial slope which will place a tremendous amount of stress on the lateral fabellar sutures. It is our opinion, that regardless of size of dog, those having a steeply sloped tibial plateau should strongly consider the TPLO.
Prior to surgery, a side view x-ray of the stifle joint should be made to measure the tibial slope so that the owner can make an informed decision whether they chose the TPLO or the lateral fabellar suture technique.
Surgery
The initial part of the surgery is joint "house keeping". The remnants of the torn ligament are removed and the joint is inspected for other damage. If damage to the meniscus is found, the torn portion is removed.
Two very strong sutures are passed around the small bone (lateral fabella) on the back side of the femur bone and then passed through a hole drilled in the top of the tibia bone. The sutures are placed in the same orientation as the cranial cruciate ligament (not drawn on illustration). The sutures are tied to the appropriate tension to tighten the stifle joint.
Scar tissue will develop on the side of the stifle joint which will ultimately serve to keep the stifle stable.
The illustration (above right) of the stifle joint demonstrates the placement of the suture bands that stabilize the joint.
Aftercare
Give prescribed medications that control pain and reduce swelling in the stifle joint.
Check the incision for signs of infection daily which include swelling, pain, discharge and redness.
A cold compress should be applied to the stifle three times daily, 10 minutes per session for the first 2 days to help reduce the swelling.
Starting on the third day after surgery, a warm compress is applied to the stifle in order to soften the connective tissues. This should be done 10 minutes per session prior to passive range of motion exercises of the joint. Passive range of motion of the joint involves flexing and extending the stifle joint, and should be done 10 minutes. This therapy should be done until your pet is using the limb well.
Exercise should be limited to to short leash walks for two months. During the third and fourth months after surgery, exercise should be gradually be increased to normal.
Running, jumping, and rough play are not allowed during the first four months after surgery.
Potential complications
Infection at the surgical site is uncommon as sterile technique is implemented.
Reaction to the suture bands is possible and may necessitate removal of these bands.
The nylon suture bands may tear, necessitation reoperation. If this is the case we typically recommend the TPLO procedure.
The meniscus may develop a tear in the postoperative period and this may require surgery.
During the surgery the peroneal nerve could get trapped in the nylon bands which results in severe pain; additional surgery would be needed to relieve the nerve entrapment.
Anesthetic reactions are uncommon and rarely result in mortality under the care of our trained specialists.
Prognosis
With the lateral fabellar technique, about 85% of the operated dogs are significantly improved from their preoperative state. It is expected that 50% of all dogs operated will have some degree of lameness that may be associated with weather changes or heavy activity.
MVS Surgery Team
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