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Cruciate Ligament Rupture A ruptured cranial (or anterior) cruciate ligament is one of the most common causes of hind limb lameness in dogs. The cruciate ligaments are the two most important stabilisers of the knee joint. Although the knee joints of dogs and humans look similar, in humans the hip, knee and ankle joints are parallel to each other and perpendicular to the weight-bearing surface (foot). This allows us to stand easily without stress on any ligaments. Dogs, however, stand on their toes with their ankles up in the air and their knees bent forward. The top weight-bearing surface of the tibia (shin bone) slopes backwards. Weight bearing creates forces that push the femur back down the sloping tibial plateau. The main structure stopping the femur from moving back is the cranial cruciate ligament. With every step the dog takes stress is applied to the ligament. Over time, dogs with a steep slope, especially when combined with an upright stance, place enormous stress on the ligament, often resulting in the tearing of the ligament. The ligament can also tear with the twisting of the knee. When this ligament ruptures the whole joint becomes unstable, causing damage to the meniscus cartilages and eventually leading to osteo-arthritis. However, due to progressive damage to the meniscus and the osteo-arthritis that will develop in the knee, the leg will get progressively lame again. The cruciate ligaments never heal, therefore surgery is indicated for most patients. Until recently all surgical techniques to treat this condition have attempted to replace the function of the cranial cruciate ligament by using materials such as wire, nylon or tendon to prevent the femur moving backwards down the tibial plateau. This is often still the preferred method of treatment for smaller dogs with acute tears of the cruciate ligament. Because of inconsistent results, a couple of new techniques for treating cranial cruciate rupture have recently been developed. Rather than trying to restore function of the ligament, the forces acting on the joint are changed. . There are two main types of surgery that are recommended for medium and large breed dogs that have cranial cruciate ligament tears: the Tibial Tuberosity Advancement (TTA) or the Tibial Plateau Leveling Osteotomy procedures (TPLO). The TTA is a somewhat less invasive surgery and gives similar results. These techniques are also advised for very active smaller dogs like Staffordshire Bull Terriers. Before embarking on any surgical treatment, it has to be remembered that surgery is aimed at stabilising the forces in the joint and slowing down the osteo-arthritis (OA) that develops in a joint, if the joint has been injured. Most dogs will recover very well, but some degree of OA will always be present. Some dogs have advanced osteo-arthritis by the time that the diagnosis of cruciate disease is made and will have less dramatic improvement with surgery. Tibial Tuberosity Advancement (TTA), Tibial Plateau Levelling Osteotomy (TPLO), and These techniques have advantages over the ligament replacement techniques in that they allow the dogs to regain good range of motion of the knee, keeping good muscular development as well as slowing the progression of osteo-arthritis. Most importantly they allow the return to good function, depending on the pre-operative degree of degenerative joint disease. At the moment we mostly do the Tibial Tuberosity Advancement (TTA) procedure or, when there is an excessive tibial plateau slope, one of the Tibial Plateau Levelling Osteotomy procedures (TPLO), either by wedge osteotomy, or by radial osteotomy. Your dog’s surgeon will make a decision on which procedure is the best option. We will give a sedation to allow us to do a thorough examination of the knee and to take the necessary radiographs. The radiographs are assessed by the surgeon and the angles of the tibia are calculated.
This will seem complicated when you look at the forces that are applied to the knee, but let me try to explain. There are opposing forces that affect the stability of the knee. The forces that come from the patellar ligament (from the pull of the quadriceps muscles), oppose the other forces applied. Because the patellar ligament is angled more than 90 degrees to the top of the tibial slope, when the dog puts full weight on the limb during weight bearing, there is a resultant shear force that causes the tibia bone to slide forward; this force is normally opposed by the cranial cruciate ligament. However, when the cruciate ligament is torn, this force causes the knee ‘give out’ with every weight-bearing stride. After the TTA procedure has been completed, the angle of the patellar ligament approaches 90 degrees to the tibial slope and the opposing forces become cancelled. Thus the tibia bone remains in place when weight is placed on the limb. Tibial Plateau Levelling Osteotomy This technique involves cutting the top of the tibia, tilting it and fixing it in a new position so that there is virtually no slope The biomechanical effect of the Tibial Plateau Levelling Osteotomy procedure (TPLO), is that the femur will no longer slide backwards on a steep slope, but will butt against a perpendicular surface, thereby taking away the need for the cranial cruciate ligament. There are different techniques to achieve a level tibial plateau. We use either the cranial wedge resection technique, or the radial cut technique, depending on the individual need. The surgery Morphine, nonsteroidal painkillers and antibiotics are given at the time of surgery. The anaesthetic agents we use, namely propofol and Sevoflurane are the safest drugs available. Complications are possible following TTA or TPLO surgery, but are rare. Under the care of trained personnel anaesthetic reactions are extremely uncommon and rarely result in mortality. Although infection may develop in the surgical site, this is uncommon, as strict sterile technique is used during the surgery. If your dog is receiving medications such as chemotherapy or steroids the bone may not heal well. Therefore it is imperative that you inform the surgeon prior to surgery that your dog is receiving these medications. Over-activity in the post-operative period may also result in poor bone healing, loosening of the screws or breakage of the implant. In addition, if your dog falls, the tibia may fracture. Arthritis (bone spurs) is usually present at the time of diagnosis of a cruciate ligament rupture and in all likelihood will progress, regardless of surgical procedure performed. If the arthritis symptoms progress, medications can be used to help relieve these signs. Reports indicate that there is about a 9 to 10% risk of developing a meniscal tear after TTA surgery. Although some surgeons do a meniscal release to prevent this complication from happening, we prefer to keep the meniscus intact, as it is an important structure in the knee function. Any dog that develops a sudden deterioration of symptoms, or has an audible click sound during movement of the knee, should be examined by the surgeon. Post operative care and rehabilitation After the surgery you can continue to give your pet a prescribed pain reliever to minimise discomfort. Many dogs will soon use the leg, as the fixation is very stable. However, although the fixation is stable, it is not strong enough to withstand heavy use of the leg. Severe restrictions, therefore, have to be imposed for six to eight weeks post-operatively during the bone healing process, to avoid complications that could compromise the final results. Although some movement is good for maintaining joint mobility, the dog must be controlled at all times. No playing, jumping or running is allowed. When the dog is left unsupervised it must be in a confined area, small room, cage or kennel. When outside, it must be on a lead. Rehabilitation After the initial six-week period, the dog’s exercise and rehabilitation can begin. During this time a gradual increase in the duration of exercise will help build muscle. Be careful to observe the reaction to the exercise. While your dog remains comfortable you can gradually increase the duration of exercise, but if there are any signs of pain and discomfort you must allow rest and then return to the last comfortable level of exercise. Extra-capsular stabilisation using polypropylene or poly-amide Although this method is probably not the ideal method of stabilisation in heavier dogs, it has been successfully used in dogs as big as 60kg. It is especially effective in dogs with an acute rupture of the cranial cruciate ligament, without a severe slope of the tibial plateau. It is not indicated in dogs with chronic degenerative joint disease. The advantages of this technique are the following: The technique:
The disadvantage of this technique is that it does not address the forces acting on the joint, and may result in more osteo-arthritis developing in the joint. The post-operative care of this procedure differs in that the dogs only have to be restricted for two weeks after surgery until the wound has healed. The polypropylene that stabilises the knee is effective immediately and the dogs can use the leg quite soon. Some dogs take a couple of weeks to use the leg properly again, due to wound healing and the osteo-arthritis.
© Cruciate Rupture © Extra-articular Stabilization © Wedge Resection © Flat Tibial Plateau
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