Origin
Tibial plateau leveling osteotomy (TPLO) is a procedure developed in Eugene, Oregon, in the early 1990s. It was the first procedure designed to address the active biomechanics underlying cranial cruciate ligament disease (Source 1). Dr. Slocum introduced the new surgical technique to interested small animal surgeons in the 1990s and presented impressive successes with TPLO. For example, sled dogs successfully returned to competing in extreme sled dog races in Alaska after the surgery, and knee osteoarthritis was cured.
theory
The basis of TPLO is that it prevents the instability known as "tibial translation / drawer sign" which occurs when the anterior cruciate ligament in the knee joint is torn.
Unlike humans, dogs have a sloped articular surface. This inclination of the tibial surface is usually between 20° and 30°, but in extreme cases can even exceed 40°. Like a cart on a slope, the femoral condyle tends to slide down this incline. However, a healthy anterior cruciate ligament prevents this.
The anterior cruciate ligament (ACL) is under tension with every step a dog takes. If the ACL is injured while jumping or running and begins to tear, it can no longer heal itself due to the constant tension. A cruciate ligament injury causes inflammation in the knee joint. Inflammatory enzymes (metalloproteinases), which are produced in large quantities during joint inflammation, attack the already damaged ACL and the articular cartilage. The ACL is then further weakened, and osteoarthritis develops. Like a ship's rope rotting under tension, the ACL eventually tears completely, usually during normal stress on the knee joint (a "minor injury"). At this point, advanced osteoarthritis in the knee joint may already be observed.
For information on the symptoms of a cruciate ligament tear, please refer to these chapters.
TPLO – Surgical Method
During the operation, a quarter-circle incision is made in the bone at the upper end of the tibia. The articular surface of the tibia is then rotated posteriorly according to a pre-calculated measurement. In this new position, it is fixed with a bone plate and screws.
Rotation reduces the inclination of the articular surface. The goal is a postoperative inclination of 5°. The angle between the patellar ligament and the articular surface is then approximately 90°. Studies have shown that at this inclination, anterior tibial translation is neutralized and the tension on the anterior cruciate ligament (provided it is not yet completely torn) is significantly reduced. Subsequent arthroscopies performed two years after TPLO showed that in 16 out of 17 dogs, the torn cruciate ligament was still intact, and that the articular cartilage, menisci, and all other joint structures were completely normal and healthy.
To avoid severe osteoarthritis of the knee joint, surgery should not be delayed until the cruciate ligament is completely torn. Ideally, TPLO is performed even with a partial cruciate ligament tear to prevent further joint damage (osteoarthritis, meniscus tear).
Procedure of the TPLO operation
The most important factors for a successful TPLO operation are the veterinarian's experience as a surgeon with this method and very precise planning. Furthermore, meticulous surgical hygiene is essential for an uncomplicated wound healing process.
On the day of surgery, the dog should be fasted, meaning it has not eaten for 12 hours, and should have successfully completed its walk and relieved itself. After a brief general examination, paying particular attention to the dog's suitability for anesthesia, an intravenous catheter will be inserted. Following premedication with diazepam and painkillers, anesthesia will be induced with a short-acting anesthetic (propofol).
The sleeping dog is then taken to the preparation area of the operating room, where, after intubation, it is connected to inhalation anesthesia, anesthesia monitoring, and an intravenous infusion. The affected limb is then x-rayed from various angles. This is necessary for planning the surgery.
After the X-ray examination, the patient is carefully shaved and washed. Depending on the dog's size, approximately two hours pass before it is transported to the operating room. In the operating room, the dog is restrained and placed on the operating table, and connected to the anesthesia system with artificial ventilation. A special intravenous antibiotic is then administered. The aseptically prepared surgical team drapes the dog with sterile surgical drapes, covers the skin of the affected limb with sterile films, and prepares the instrument table with all necessary instruments.
The operation now begins:
First, the knee joint is inspected. Particular attention is paid to meniscus tears, articular cartilage damage, or other soft tissue injuries. The joint is then closed. Next, the skin on the inside of the knee, just below the joint, is incised, and the TPLO procedure is performed.
The dog is now moved from the operating room to the X-ray or CT scanner, where follow-up X-rays are taken to measure the postoperative angle of the tibial plateau. Finally, the animal patient is transferred to the inpatient ward, where we will care for him during his recovery. He will typically receive strong pain medication for the next 12 hours, and the surgical wound will be cooled with cold compresses.
The dog can be picked up by the owner in the evening – of course, we will explain the course of treatment, the next steps and medication in a detailed final consultation.
Duration of the TPLO healing process
In our experience, patients recover with better long-term results than with conventional passive stabilization techniques such as extracapsular lateral suture overlap. As early as one month after surgery, patients are able to bear weight well and make progress with home physiotherapy.
Possible complications of TPLO
Implant complications Complications such as infections or screw loosening occur in a small percentage of cases and are treated with appropriate antibiotics and removal of the implant after healing.
Among the serious complications These include: postoperative patellar dislocation, tibial fracture, implant loosening/failure and implant-related infections and meniscal tears (if the original meniscectomy/meniscal release was not performed).
Among the minor complications belong: Infection/inflammation of the incision (interface), seroma and wound dehiscence (separation of the wound edges).
TPLO surgery in the video
References
1 B Slocum, TD Slocum. Tibial plateau leveling osteotomy for repair of cranial cruciate ligament rupture in the canine. Vet Clin North Am Small Anim Pract (1993) 23:777–795.