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Cranial Cruciate Rupture
Cranial cruciate ligament (CCL) rupture of the stifle is a common cause of hind leg lameness in dogs. The ligament supports the knee to prevent cranial separation of the tibia (distal bone) from the femur (proximal bone). When the CCL ligament is ruptured, increased cranial displacement and medial rotation of the tibia occurs. This results in stretching of the surrounding soft tissue and also increased abnormal wearing of the joint cartilage. See pictures below for illustration.
Small animals that have ruptured their CCL typically present with lameness of one rear leg, although both the left and right can rupture at the same time. Diagnosis can often be made on physical examination of the knee joint and palpating a cranial instability of the tibia (called cranial drawer motion). Some patients that only have a partial tear of the CCL may not have a palpable instability making diagnosis more difficult. Pain upon extension of the knee is often a reliable indicator of CCL trauma in partial tears. Radiographs are beneficial to confirm no other concurrent lesions are present, and can diagnosis degrees of fluid and arthritis in the joint. MRI and Arthroscopy can be beneficial in patients that have an undetermined cause of lameness.
Repair of the joint is usually performed by removing any diseased or abnormal tissue from the joint that results in inflammation. The ligament can not simply be sutured back together as it will not heal correctly to function. The joint is then flushed and the joint capsule closed. Sometimes, a tiny "C" shaped piece of tissue called the meniscus is torn or displaced and also needs to be removed. It is only removed if damaged as it provides a "Cushion" effect and is difficult to remove if not damaged. Over 60 methods of repair for the CCL have been described in the literature since the early 1900’s, but currently stabilization of the joint is accomplished by one of several methods, the most common are listed:
Retinacular imbrication (MRIT)- A strong suture is placed around the outside of the joint in a plane resembling that of the original ligament. Suture ligaments or bone "Anchors" are generally not used within the joint in canines as they have been found not to do well. This external stabilization suture will generally last for 6 months or longer, but often eventually breaks. The joint capsule and surrounding tissues will have healed well by this time and the suture is generally no longer required. This is the most common procedure used. Very large dogs tend to have more complications than smaller dogs, but this is with any procedure.
Fibular head transposition- This procedure involves displacing the lateral collateral ligament of the knee cranially (forward) to approximate the alignment of the cruciate ligament. This procedure is often combined with other forms of stabilization, and usually reserved for large dogs. It is a more involved procedure and may not be of great benefit in many cases.
TPLO- Tibial Plateau Leveling Osteotomy is a procedure that is quite involved. In theory the angle of the tibia is greater in dogs that rupture their cruciate ligament, thus putting more stress on the ligament. The procedures goal is to change this angle by breaking the proximal tibia and rotating the articular surface to a more level angle. In theory this creates less cranial "thrust" force on the tibia. Subjectively, this procedure is reported to work well. Very large dogs that may break down other implants may respond more favorably to this procedure. In this authors opinion, dogs over 100# and certain breeds should strongly consider this procedure.
Tibial Tuberosity Advancement (TTA) is a procedure where the tibial tuberosity (bony attachment of the patellar tendon on the tibia) is fractured and then an implant is placed that moves the tendon cranially. This creates more tension on the patellar tendon in an effort to stabilize the joint. This procedure does show promise but some concerns would be breakdown of the implant and that additional stresses are not placed on the patella and patellar tendon. In the authors experience, these patients will have a “mechanical” gait on the repaired limb but seem to cope well.
CCL tear in the dog can be very debilitating. Approximately 40% of dogs that rupture one ligament will proceed to rupture the CCL in the other knee at some time in the future. The goal of any therapy is to preserve as much function of the joint as possible and maintain comfort of the patient.
Medical therapy consists of NSAID’s (anti-inflammatories), Tramadol, Adequan, glucosmine and other medications to maintain health of the joint and reduce pain and inflammation to the pet. Weight control is essential in these patients not only for recovery of the current lesion, but to prevent future trauma to other joints.
Although some pets may heal without surgery by developing fibrosis (scar tissue) around the joint, many do not. It also takes months for the fibrosis to develop and in the meantime abnormal wear and arthritis develop within the joint. Along with prolonged pain, some pets will tear the Meniscus (a “C” shaped cushion in the back of the joint) that will result in chronic pain and lameness that will not resolve without surgery.
Regardless of the surgical procedure used, about 90% of patients will return to good function of the limb. Pain and weight control are essential. Pets that are severely obese or have other limb abnormalities (ie bow-legged, concurrent hip dysplasia, etc) will tend to not do as well. About 5% of patients will later tear the meniscus cartilage if not already removed, necessitating further surgery. Again, it is not recommend to remove the meniscus at the original surgery unless already torn. Breakdown of the implant and infection are possible complications as well.
It is imperative to keep your pet on a leash and activity restricted or this increases the risk of meniscal tear or implant breakdown in addition to soft tissue trauma. Patients licking at an incision can cause an infection or even chronic irritation that pet wants to lick at long-term. Physical therapy, range of motion exercise and laser therapy treatments can assist your pet recover more quickly and completely as well.