What is Tibial Plateau Levelling Osteotomy – TPLO?
If your dog has been diagnosed with a torn cranial cruciate ligament, you will probably be considering surgical treatment options that may include a tibial plateau leveling osteotomy (TPLO).
What does Tibial Plateau Levelling Osteotomy – TPLO involve?
The top surface of the tibia (shin bone) that works together with the femur (thigh bone) at the knee joint had a tibial slope. Specifically, the top of the tibia slopes from front to back within the knee. The angle of this slope varies between dogs from degrees in the high teens to clearly abnormal slopes over 35 or 40 degrees. An average tibial plateau slope would be in the 21-24 degree range for most breeds. It was noted that the cruciate ligament ran between the femur and tibia and acted to hold the end of the femur in place atop the tibial plateau. This was characterized the ligament as “a rope tying a wagon to the top of a hill.” When the rope (ligament) is broken, the wagon (the end of the femur) tends to slide down the hill (the tibial plateau slope).
This instability, which had been named cranial tibial thrust, is the most important component of the dynamic instability that occurs in the stifle when the ligament tears. Surgeries had been attempts to “replace the rope” and had met with only fair success. The slope of the tibial plateau neutralises these forces in the knee and stops cranial tibial thrust.
Tibial Plateau Levelling Osteotomy – TPLO aims to neutralise this “cranial tibial thrust” force by levelling the top of the tibia (tibial plateau) so that on weightbearing it is perpendicular (at right angles) to the straight patella tendon which is under tension during load bearing.
As the straight patella tendon is under tension during weightbearing flattening the tibial plateau neutralises the cranial tibial thrust in the cruciate deficient stifle.
How is the TPLO performed?
Before surgery, an x-ray of the stifle is taken to measure the angle at the top of the shin bone, called the tibial plateau angle. The goal of the surgery is to reduce this angle so that dynamic joint instability (cranial tibial thrust) is eliminated. This is usually accomplished by creating a post-surgical angle of between 4 and 10 degrees, an angle not much different than is found in the human knee. In most cases the surgical procedure starts with an exploration of the inside of the stifle joint. The purpose is to assess the meniscal cartilages for any possible damage. Damaged cartilage must be removed if the dog is to regain normal pain-free function.
The TPLO procedure itself involves the use of a curved saw blade to make a curved cut on the inside, or medial, surface of the top of the tibia. The cut top portion is then rotated to create the desired tibial plateau angle. A stainless steel bone plate is then placed on the bone to hold the two pieces in their new alignment.
Q: Does my dog really need surgery? I read that they’ll do just fine without surgery.
A: Published data suggest that approximately 15% of dogs will recover reasonably good clinical function without surgery. Most of those dogs will be small breeds, under 15-20 pounds of body weight. Those that recover normal function tend to do so within 4-6 weeks after they first become lame. For the majority of dogs, surgery is the only way to return them to good function, not braces or medications or herbs or physical therapy or wishing or hoping!
Q: Which patients will benefit from TPLO?
A: Both small and large patients do well normally with a TPLO surgery.
Q: Why is TPLO so costly, especially when compared to other cruciate repair surgeries?
A: TPLO requires specialized equipment including a motorized bone saw with a specially-designed curved blade, a surgical stainless steel bone plate and 6-9 bone screws, between 4-6 x-rays, a significant investment in training on the part of the surgeon, and up to 2-4 hours of preparation, surgical and recovery time for each patient.
Q: Is TPLO really better than other surgical options?
A: If your dog is larger, younger and active the answer is yes. The data has not always been conclusive about this, however. Around 90% of referral surgeons prefer this technique to all of the other available procedures.
In the last few years, the research data is starting to confirm what surgeons have known all along: TPLO dogs return to function faster, they develop less joint arthritis, and they tend to return to better functional levels than is seen with other techniques.
Around 95% of patients get 90 % better with a TPLO surgery. Performance athletes will likely see a small drop in performance, but most pets make a “near normal” recovery.
- Implant failure – very rare and normally due to extreme activity.
- Bone fracture – very rare and normally due to extreme activity.
- Seroma– relatively common but insignificant fluid accumulation after surgery, normally improves with no treatment.
- Infected implants – This usually occurs due to the patient licking at the wound. This can also occur during surgery, recovery or through haematogonous spread (through the blood stream). 2. Delayed meniscal injury – as TPLO neutralises only cranial tibial thrust and not rotational forces acting on the stifle from time to time there can be tears of the cartilage (meniscus up to 6 months after surgery)
Signs to watch out for
- Sudden worsening of lameness that lasts for more than 12 hours.
- Smelly, yellow or abnormal discharge from the wound.
- Swelling more than 2 days after surgery, often seroma but worth having a check.
- Elizabethan (Buster) collar at all times for 2 weeks.
- Medications as prescribed, this is normally pain relief for 4-6 weeks and often antibiotics for 4-6 weeks.
- Restricted exercise. Your dog should be rested in a cage at all times except short lead walks to go to the toilet until the bone has healed. This normally takes 6-8 weeks.
- Any problems please contact your vet. It is better to have a recheck appointment when everything is normal than miss a problem. If everything is going as expected please schedule a recheck appointment with the regular vet 4-5 days and sometimes 14 days after surgery. If you are worried about the wound then please contact us. Signs to watch out for include redness, heat, pain or significant worsening of any lameness.
- A recheck appointment for radiographs under sedation at 6 weeks after surgery is highly recommended. Your dog will need to be starved for this from midnight as sedation will likely be needed.