Step 5: Why Undergo TPLO Surgery
Step 5: Why TPLO
What exactly is the TPLO?
As seen in the Step 1 video, the femur (thigh bone) rests on the top of the tibia (shin bone). The top of the tibia, referred to as the tibial plateau has a slope to it (tibial plateau slope or TPS). In addition to the muscles surrounding the knee, there are 4 ligaments responsible for helping to stabilize the knee. The cranial and caudal cruciate ligaments, and the medial and lateral collateral ligaments. The cranial cruciate ligament is responsible for preventing the femur from sliding down the tibial plateau slope, which in a recent study of over 3,000 dogs with ruptured CCL, was found to average 29°.
The tibial plateau leveling osteotomy (TPLO) is one of the original osteotomy (bone cut) techniques and has been used in practice for over 20 years, with over 200 research articles published on the topic. This surgery requires making a semi-circular bone cut near the top of the tibia, which includes the weight-bearing portion of the bone, or the tibial plateau. Following the osteotomy, this small section of bone is rotated to allow a reduction of the tibial plateau slope (TPS) to approximately 5°. The two segments of bone are then stabilized with a plate and screws until the bone heals. In essence, we create a fracture and stabilize the bone in a new position. By rotating the tibial plateau and “leveling” it, the goal is to prevent the femur from sliding down the slope of the tibia and helping to stabilize the knee. Despite the perceived invasiveness of this procedure, dogs are generally comfortable enough to begin weight bearing on the limb within days of surgery.
For the first 8 weeks after surgery, we are completely relying on the implants (plate and screws) to stabilize the surgery site. Once the bone has healed, the plate and screws are no longer necessary, though in most cases implants are left in place unless there is a problem such as infection or irritation. Approximately 3% of patients who have a TPLO procedure will need to have the plate removed.
With the TPLO procedure, there is a reported 90-95% good to excellent outcome. An excellent outcome is one where your pet can run, jump, and play and you will not notice your pet has ever had a problem. With a good outcome, after heavy activity, your pet may have a transient period of being sore and may need a short course of anti-inflammatories. For one reason or another, 5-10% of patients will not return to a level of function that we hope for. It is important to note that even if your pet suffers a complication, such as an infection or a meniscal injury, they can still have a good to an excellent long-term outcome – there just may be some hiccups along the way.
Why TPLO over the other surgeries?
In a recent survey of Board Certified veterinary surgeons, TPLO was the most commonly preferred method for treating CCL injury in patients over 33 pounds (15kg), with approximately 79% of respondents preferring it over the other options. TTA was preferred by almost 14% of respondents, the extracapsular suture was preferred by just under 6%, and fewer than 2% preferred the Tightrope.
So why did most surgeons prefer the TPLO over the lateral suture, TTA, or Tightrope?
#1) TTA has been shown to have a rate of the persistent tibial thrust of approximately 80%. This means that in approximately 80% of patients, the femur continues to slide down the top of the tibia during weight-bearing. This is compared to a rate of 20% following TPLO. Though the reported success rate for TTA is often around 90%, the high rate of persistent tibial thrust seen in many patients is likely the reason for the higher risk of post-operative meniscal tears and progressive arthritis formation when compared to the TPLO.
A recent paper found long-term outcomes were better for TPLO compared to TTA when owners assessed outcome via the Canine Brief Pain Inventory (CBPI) and the Canine Orthopedic Index (COI). The study found that when considering how pain affected their pet’s function, pets with TPLO had less average pain, less interference with walking, less morning stiffness, and less pain with jumping and climbing, limped less during mild activities, and had a better overall quality of life.
Another reason why many surgeons prefer the TPLO over TTA is due to long-term limb use. One study found that following TPLO, dogs had limb function that was similar to a control population by 6-12 months at both a walk and a trot, while the TTA achieved normal function at the walk by 12 months, but like the lateral suture, never returned to normal during the study period at the trot.
Infections are possible at any surgical site. If infection occurs persistently following surgical placement of an implant, a second surgery may be required to remove the implants. Removing TPLO implants is straightforward and most dogs go on to activity very soon after the procedure. However, due to the presence of a cage placed during the TTA (the block that is placed in the bone to advance the front of the tibia), implant removal is much more difficult and there is likely a higher risk of complications following removal. In addition, due to persistent instability in many of these patients, further stabilizing procedures are often required. However, once the TPLO is performed, it is rare to ever have to place further implants after removing a
#2) Extracapsular techniques to address CCL injuries include the lateral suture procedure, the
Tightrope→, and the SwiveLock→.
The lateral suture procedure involves the placement of a nylon line secured around landmarks outside of the knee. The suture is responsible for stability in the near term, but long-term stability is reliant on the formation of scar tissue. The nylon is prone to stretching after the limb has gone through a range of motion, resulting in a loss of stability provided by the suture prior to the development of scar tissue. Due to this loosening of this suture persistent tibial thrust is as high as 100%. This means that almost all patients will develop some laxity in the joint. Due to the location of this suture, the range of motion in the knee can be significantly decreased. In addition, the suture can compress down on the underlying soft-tissues and may even enter the joint when appropriately passed. Though the surgery may be less invasive than osteotomy techniques, one study found that dogs achieve normal limb loading faster after TPLO than with the lateral suture, and most dogs with a lateral suture never reached symmetrical limb loading.
However, dogs with any of the extracapsular techniques have been found to have a faster progression of osteoarthritis when compared to patients receiving a TPLO. In dogs weighing over 33 pounds, these techniques, all together, were preferred by 8% of the surgeons surveyed.
For dogs under 30 pounds, the lateral suture can be an effective technique for returning your pet to a high level of activity. However, research is also published now supporting the use of TPLO in small breed dogs and some surgeons may prefer this technique over the lateral extracapsular suture, even in this subset of patients.
Other extracapsular repairs including the Tightrope→, and the SwiveLock→, attempt to stabilize the knee utilizing strong braided sutures secured either through bone tunnels in the femur and tibia or via bone anchors. The inherent strength of these sutures decreases the amount of stretching and resultant return of laxity when compared to the lateral suture.
One complication surgeons report when using the Tightrope→ is a widening of the bone tunnels that are created, which can lead to loosening. This may be eliminated by using the SwiveLock→ implant (bone anchors). Another potential risk of utilizing these sutures is infection. While infection can occur with any implant, the risk may be higher with these sutures due to their braided nature.
To see more information and different articles where we have pulled a lot of our information, visit our Literature page.
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"My dogs and I had a great experience at TPLO Chicago. I felt very confident that they were in the best of hands! Dr. Gendreau is a true veteran with his 40+ years of specialized orthopedic experience. His new facility is outstanding! All state-of-the-art equipment including “Indigo-Clean” for maximum sterility and maintenance of a germ-free environment is reassuring against harmful bacteria causing infections. It was a convenient, positive, successful experience. He’s the best! "
"My 8 1/2 year old English bulldog needed tplo surgery for over a year. After contemplating putting him through [the tplo surgery with TPLO Chicago] we eventually decided it was the best thing to do. Dr. Gendreau called me the night after the surgery and the next day to see how zeppelin was and handling pain meds. I cannot say enough about how well the surgery recovery and overall well-being of zeppelin has been. If your concerned about putting your dog through the surgery the amount of time you think about it will be greater than it will be for them to be moving better again. The first 3 days are hard but after the most difficult part is keeping him from doing things he couldn’t do before (stairs, walks, jumping on the couch,). After the 8 weeks it’s nice to see him back to normal."