The most common orthopedic condition seen in dogs is rupture of the cranial cruciate ligament. The causes of the condition are thought to be due to old age, obesity, trauma,
breed and an increased tibial plateau angle. Rupture of the cranial cruciate ligament leads to inflammation of the stifle (knee) and subsequent degenerative osteoarthritis. Many procedures have been developed to correct the ruptured cranial cruciate ligament; however, no one has demonstrated superior results until the introduction of the tibial plateau leveling osteotomy (TPLO).
The key to understanding this lameness is an understanding of the forces generated in the knee. The tarsal tendon within the Achilles tendon is a fixed length between the hock and the femur; therefore, all the forces of the foot (during weight bearing) are transmitted through the tibia. The top portion of the tibia (the tibial plateau) is sloped. The slope causes the tibia to slide forward unless it is restrained by an intact cranial cruciate ligament. The force that the cranial cruciate ligament opposes is called the cranial tibial thrust or cranial drawer. When the force is too great, it ruptures the ligament. Ruptures can be partial or complete which will affect the severity of the lameness.
Clinical signs associated with cranial cruciate ligament injury can vary with the severity of the rupture. With partial ruptures of the ligament, most dogs have an intermittent weight bearing lameness that is often worse after exercise or after lying down for long periods of time. With complete ruptures most dogs exhibit a non-weight bearing lameness, with a reluctance to use the affected leg at any time.
The diagnosis of a partial or complete cranial cruciate ligament injury is made with a full orthopedic exam and radiographs (x-rays). The affected knee is often painful when flexing and extending. Typically, the knee becomes thickened and develops a hard swelling on the inside surface known as the medial buttress. The exam also reveals a certain amount of instability within the joint. Radiographs exhibit swelling within the joint and usually some degree of arthritic changes, which generally coincide with the duration of the injury.
The tibial plateau leveling osteotomy (TPLO) is used to overcome the effects of the cranial tibial thrust. This procedure levels the tibial plateau and neutralizes the cranial tibial thrust. Thus, the need for the cranial cruciate ligament is eliminated as a restraint to the cranial tibial thrust. All patients are radiographed before surgery to determine the preoperative slope at the top of the tibia. A surgical cut is made in the tibia using a special saw, and the newly cut piece is then rotated counter-clockwise a predetermined number of millimeters. A specially designed plate is then applied to hold the two pieces of bone together so that they can heal in their new position. More radiographs are taken after surgery and new measurements are taken to determine the new angle of the slope at the top of the tibia. The radiographs to the left demonstrate what the joint looks like after surgery.
The recovery time for the surgery is 12 weeks. During the first 8 weeks there is no running, jumping, rough play or excessive stairs; only short leash walks to urinate and defecate. We re-evaluate your dog's progress at 4 and 8 weeks. At the 8 week re-check we will re-radiograph the leg to monitor healing of the bone. The last 4 weeks are a gradual return to normal activity.