Today we present an interview with Mike Grafinger, DVM. Dr. Grafinger ('Graf') is a Diplomate of the American College of Veterinary Surgery and one of the owners of TVEC.
We know that people get injuries to their cruciate ligaments (like athletes who damage their ACL), but we were surprised to learn that dogs suffer the same problems. What are the cruciate ligaments?
Cruciate means "crossed" or "X" in Latin. There are two cruciate ligaments that form an “X-shape” within the stifle (AKA, knee) joint. There main function is to stabilize the knee joint. The caudal cruciate ligament prevents the tibia from caudal instability (tibia moving independently towards the tail), and the cranial cruciate ligament prevents independent movement of the tibia in the cranial direction (towards the head). The cranial cruciate is more commonly injured.
Why is the stifle so likely to be injured?
The knee joint is one of the weakest joints in both dogs and humans because it is composed of multiple ligaments which stabilize it. The elbow and hip joints have interlocking bones and ligaments which make these joints more stable. The femur sits on top of the tibial plateau, while the cruciate ligaments keep it there. Some dogs have a steep tibial plateau (e.g. Rottweilers, Labradors, etc) which can predispose the cranial cruciate ligament to injury. Think of the tibial plateau as a table top and the femur as a ball sitting on top of it. An excessive slope can result in the ball sliding off or down the table which places strain on the supporting cranial cruciate ligament. Eventually the ligament can rupture which results in acute lameness. Other causes of cranial cruciate ligament injury include: excessive internal rotation of the lower leg and hyperextension of the knee joint.
How is cruciate rupture diagnosed?
The most reliable means of diagnosing the injury is to move the femur and tibia in a “front to back” direction to demonstrate the instability. This movement is called the “drawer sign”. Imagine dresser drawers (stifle joint) and pulling one drawer (tibia) partially out. This is analogous to the tibia moving forward independently of the femur secondary to cruciate injury. Also, the tibial compression test is used to determine if the upper tibia will move forward (tibial thrust) when the hock or ankle is flexed. Tibial thrust causes pain when elicited. A positive drawer sign and tibial thrust can only occur once the the cranial cruciate ligament has been ruptured.
Will my dog require sedation for an orthopedic exam or for other diagnostics?
Most often cranial cruciate rupture can be diagnosed while the dog is awake. However if the dog is experiencing severe pain, has very strong muscles, or is uncooperative, he or she may require sedation in to order examine the joint thoroughly. Usually about half of the patients require sedation. Therefore, withhold food from your pet the morning of the appointment.
Your pet will also have specific radiographs taken of the stifle joint and associated upper/lower leg bones. These radiographs will be used to evaluate if there is osteoarthritis in the joint, if there is another unexpected problem in the joint or bones and for potential surgical planning.
How is cranial cruciate ligament injury treated?
Most dogs are very painful and reluctant to use the affected limb, and most dogs require surgical stabilization. Triangle Veterinary Emergency Clinic stabilizes these joints using two different techniques. Extracapsular stabilization is used to stabilize knees in small to medium or less active dogs. A heavy nylon suture anchors the lower femur to the upper tibia simulating the cranial cruciate ligament and alleviating the cranial drawer sign. This technique is performed outside of the joint compartment or capsule (e.g. extracapsular).
A tibial plateau leveling osteotomy (TPLO) neutralizes tibial thrust in larger, active dogs with cranial cruciate ligament injury. This technique involves cutting the bone associated with the tibial plateau and leveling the table so the ball will not slide off the back. Then a plate and screws are used to fix the tibial plateau osteotomy in a flat tabletop position.
Patients who are managed conservatively usually develop osteoarthritis, persistent pain, decreased range of joint motion and are likely to develop meniscal injury if surgery is not performed. The purpose of surgery is to stabilize the joint, alleviate discomfort and to the slow the progression of impending osteoarthritis.
I have heard of torn cartilage. Does this also occur in dogs?
There are two cartilaginous discs called menisci which lie between femur and tibial surfaces. These structures function as shock-absorbers or cushions between these bones. Occasionally the meniscus can damaged because it becomes entrapped between the unstable surfaces of the bone. Entrapment may cause a tear or crushing injury. Injury to the meniscus can be extremely painful. These structures are examined at the time of surgery and are partially or completely excised depending on the extent of damage.
My dog is overweight. Does that relate to injury?
Obesity or excessive weight gain can be a strong contributing factor in cruciate rupture, as well as, exacerbating pre-existing osteoarthritis. The ligament may become weakened because of the excessive force and tension generated with each step. Obesity will also increase your pet’s period of convalescence post-operatively. It will make your pet’s other knee more susceptible to a cruciate injury post-operatively; especially if there is pre-existing osteoarthritis. In fact, dogs with osteoarthritis in the opposite stifle have 50-60% chance of rupturing the cruciate some time in their life. Excessive weight increases this percentage. Therefore, it is strongly recommended to decrease your pet’s caloric consumption prior to surgery and during his/her period of convalescence.
Weight loss can be achieved with prescription diets which are lower in calories and higher in fiber. Also consider feeding your pet multiple smaller portioned meals throughout the day or feeding less during periods of decreased activity (e.g. feed less at night before your pet goes to bed).
What is involved with surgical stabilization for cruciate injury?
As in human medicine, general anesthesia is used to make sure the animal is unconscious for muscle relaxation and pain control. This will involve using a pre-anesthetic analgesic (alleviates discomfort), a brief intravenous anesthetic in order to place an endotracheal tube followed by gas anesthesia for the remainder of preoperative preparation and surgery.
The entire leg is shaved up to the middle of the back. The shaved area is disinfected with surgical scrub and alcohol in preparation for a sterile operating field. Once sterile, the surgeon will perform the operation. Preoperative preparation can take approximately 20 to 30 minutes to perform.
Once in the operating room, the operation takes about 1 ½ hour to 2 hours plus to perform, depending on whether there is concurrent meniscal injury. The animal will have an IV catheter placed and be on IV fluids throughout the surgery and after surgery. He or she will also receive post operative analgesics to maintain pain control. A bandage will be placed over the limb to help reduce swelling and provide comfort. The bandage usually remains in place for about 2-3 days.
What are the risks and complications of cranial cruciate stablization?
During surgery patients are placed on a blood pressure monitor, respiratory ventilator , and a multi-parameter monitoring device to measure respirations, ventilation and heart beat to name a few. The nurse anesthetist is responsible for closely monitoring the patient, managing anesthesia and communicating any concerns to the surgeon. There are risks associated with anesthesia and we do see anticipated side effects to organs including the brain, kidneys, liver, heart and lungs. Occasionally side effects can be life-threatening in critical patients however generally the risk of anesthesia is less than 1 %.
Complications for extracapsular cranial cruciate stabilization include: deep infection of the nylon leader line, crimps or bone, implant failure, fracture of the tibial crest, meniscal injury and/or a superficial infection The most common complication is a superficial infection of the incision line and meniscal injury. Approximately 10-15% of cases will have secondary meniscal injury at some point in their life, which requires surgical intervention.
The complication rate for a TPLO is less than 10%. Complications include: superficial infection, deep infection of bone and implant, patellar tendonitis, tibial tubercle fracture, tibial fracture, implant failure, nonunion of the bone (bone not healing) and/or meniscal injury/impingement. The most common complications are patellar tendonitis and a superficial infection. Both of these can be managed conservatively with medical therapy. Fractures and implant failures are usually attributed to too much activity during his or her convalescent period. Meniscal injury has to be addressed surgically.
For more information, call TVEC to schedule a consultation with Dr. Grafinger.
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