Cranial Cruciate Ligament Stabilization Surgery

Cranial Cruciate Ligament Stabilization Surgery

By Dr. Ed Mapes
Stonebridge Animal Hospital
McKinney, Tx

The cranial cruciate ligament (CrCL) is the most important supportive structure in the knee joint, and is subject to the most damage and failure. There is no surgical procedure that repairs the ligament; that is not possible. There are, however, a number of surgical techniques available to stabilize the knee in lieu of a functional CrCL. Each technique has its advantages and disadvantages regarding stability, return to function, post-operative complications, consequences of failure, control of pain, and rate of arthritic development.

new4Complete tears of the CrCL allow the tibia to slide forward with respect to the femur. This is called the positive drawer sign. During the orthopedic examination, recognizing the sometimes-subtle difference in complete versus partial tears of the ligament is important because they call for different treatment plans. Partial tears can be given time to heal (I usually recheck the patient after one month of exercise restriction), while totally ruptured ligaments call for surgical stabilization.

Joint instability from a torn CrCL causes a series of events that further damage the joint, leading to progressive osteoarthritis and tears of the meniscus. Surgical cases should be done as soon as possible to minimize joint pathology that leads to chronic soreness. It is important to note that arthritic joints can cause discomfort even after surgical stabilization

All of these damaged joints require incision through the joint capsule to expose the joint. Fragments of the torn ligament are removed and the meniscal horns inspected for possible damage that can accompany CrCL tears. Once completed, the joint is flushed and capsule sutured for closure. At this point the procedure for stabilization is begun.

Surgical techniques can be categorized as either Osteotomy-based (requiring bone to be cut) or Extracapsular (no bones are cut and specialized suture material is positioned to compensate for lost cruciate support).

Two techniques used to accomplish extra-capsular stabilization are the longstanding Modified Retinacular Imbrication Technique (MRIT) and the newer Tightrope CrCL methods. I have used the MRIT since graduation from Michigan State due to the fact that Dr. Gretchen Flo, developer of the method, taught me surgery there. It is a popular procedure and has always been successful for me. Risks of catastrophic failures are non-existent, and the procedure is faster and less involved than osteotomies.

 

new5MRIT Surgical Technique
The surgery (at left) consists of looping specialized suture material behind the medial fabella (a small bone behind the distal femur) and extending it through an opening through the front of the proximal tibia (the tibial tuberosity). The suture is secured with a clamp, and provides stabilization in exactly the same plane as the ruptured ligament. I have used this procedure for a lot of years in small and large dogs with equally successful outcomes.

Shortcomings are rare with this procedure; limited mainly to possible breakage or stretching of the suture material in the larger dogs. I have found that ensuring adequate tensile strength of the suture material – doubling strands if necessary – has obviated that problem.

 

new3The Tightrope (right, Courtesy of ArthrexVet Systems) and SwiveLock procedures replace function of the ligament as well, but secure the suture in a different manner than the MRIT. The material provided is stronger than other sutures previously available, and this technique provides very good stability in dogs up to 250# body weight.

 

 

 

 

 

 

 

new1Tibial Plateau Leveling Osteotomy (TPLO) and Tibial Tuberosity Advancement (TTA) are the two osteotomy-based techniques. TPLO is probably the best known of the osteotomy procedures. The technique involves sawing the tibia into two sections via a crescent-shaped cut and then rotating the upper segment to a more favorable orientation within the knee. This creates a more stable joint in the absence of the CrCL, controlling abnormal motion within the joint.

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new2Tibial Plateau Leveling Osteotomy (TPLO) Technique

Courtesy of ArthrexVet Systems

A crescent-shaped cut through the tibia is done to permit rotation of the tibial plateau during TPLO procedure (left). Here, a bone plate secures the cut sections of bone into position.

Tibial Tuberosity Advancement (TTA) Technique
Courtesy of ArthrexVet Systems

The TTA technique (right) involves a longitudinal cutting of the tibia bone. The resultant flap segment is pulled forward, and a prosthetic device (bridging bone plate) is fixed beneath it to maintain proper positioning. The cut in the bone needs to be stabilized by the use of a plate and bone screws. The prosthetic device must stay in place forever; the bone plate and screws are usually left in position as well.

Both procedures require bone plates with multiple screws to maintain proper positioning and alignment. These techniques are relatively new and are preferred by universities and specialty referral surgical practices. They require more involved, radical, and time-consuming procedures than extra-capsular stabilization. Since large sections of bone are cut, there is greater risk of infection within the bones.

As with any bone fracture repaired with bone plates and screws, failure can occur due to screw loosening, infection, or other causes. These incidents of plate failure are of serious consequence, since they then require extensive surgical efforts to repair, with long recovery periods – in other words failure of these procedures can be catastrophic.

Since the implants and equipment necessary for these procedures are very expensive, costs for osteotomy-based surgeries are also substantially more than the aforementioned techniques.

The goal of all surgical techniques performed to regain joint stability following cranial cruciate ligament rupture is to return the patient to as near normal function as possible with minimal pain on a long term basis. Surgeons also aim to hasten recovery with a minimum of discomfort and curtail the rate of arthritic development in the knee. The technique chosen must be based on the age and general health of the patient, ability of owners to oversee aftercare, and financial constraints.

I prefer the MRIT and Tightrope procedures for a number of important reasons. Primarily, the success rate of procedures I’ve done – in all sizes of dogs – has been very good throughout the years. I trust the procedures and have used them on my own dogs on two occasions. Healing has been augmented considerably by incorporation of post-op laser therapy sessions; which aids by decreasing pain, inflammation, and swelling. Healing times are reduced and return to function is usually within the first month post-surgery. The patients are often placing weight on the leg two weeks after the procedure, when we remove sutures and perform the last laser treatment.

It is difficult for me to adopt osteotomy-based procedures since the less radical techniques deliver at least equivalent results without the risks of serious consequences in the event of failure. Also, since osteotomies take much longer to perform and are roughly double the expense, the increased risk to the patient and owner expense seems unwarranted.

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