Pet caretakers who have dogs who have had TPLO surgery for cruciate ligament injuries, whose dog later on developed bone cancer at the site of the surgery, have been asking if there is a connection between the two.  The standard answer is that there is no evidence that shows that there is a connection.  But, human research done this year shows that this in not likely true.  Since bone cancer is a malignancy that leads to death of the pet, it is something that we need to know.

TPLO (tibial plateau leveling osteotomy) is the current method for surgical repair for dogs and cats who have ruptured their anterior cruciate ligament.  This condition is very common in large and medium sized dogs but can also be found in small breed dogs and cats as well.  Surgical repair has been the go-to treatment in order to re-stabilize the joint in order to reduce pain and slow down the development of arthritis in the joint.

Throughout the history of surgical repair for CCL ruptures, a variety of surgical techniques have been used.  Orthopedic surgeons love new techniques and in the forty plus years that I have been a small animal vet and have done many cruciate surgeries, I have watched the techniques morph from on procedure to the next.  But, the TPLO surgery is not only the latest surgical technique for CCL repair but it also has a sketchy history.

About 25 years ago, a veterinary orthopedic surgeon in Oregon secretly developed the technique he called the TPLO.  His theory was that most dogs have a slope in their tibial plateau (flat surface of the tibia bone where the thigh bone rests) which causes the center of gravity going through the knee joint to be forced forward creating excess stress on the cranial cruciate ligament.  His surgical technique corrected that anomaly.  He would cut the bone and take a wedge out of it so the it would create a horizontal tibial plateau in order for the center of gravity to move straight downward as it should.  This meant that he would measure the angle that created the slope, tsurgically fracture the tibia, remove the wedge of bone that would correct the slope and then repair the fracture that was created by placing a bone plate across the fracture site.

This turned out to be a very successful surgical protocol and many dogs returned to normal function quickly if all went well with the surgery.  The interesting history about Dr. Slocum is that all his research and experiments for this protocol were kept secret.  At the point that he felt he was ready and prepared for his plan, he placed a legal patent on his protocol.  This was the first time that a legal patent was created for surgical procedure.  It meant that no one could do this surgery without his permission.  And, he was not willing to give his permission unless the veterinarian would come to his school and pay to learn the technique and buy his equipment in order to perform the surgery.  Ah, capitalism at its finest.  Karma decided to step in and within a year after teaching the vets the new protocol, he died of a heart attack.  His wife eliminated the patten and allowed any vet who wanted to do the surgery to do so.  The entire orthopedic community jumped on this and the TPLO became the gold standard for cruciate repair.

Everyone was happy in the orthopedic world.  They were all doing TPLO surgery on any and all pets who ruptured their cruciate ligament.  They loved it and the income wasn’t bad either.  The TPLO surgery cost about $3000 whereas the other surgical protocols were around $1000.  As I mentioned, all was happy, until Dr. Bartles at Tennessee vet college decided he wanted to study the long term effects on the dog’s knee with the different surgical protocols that were used for CCL ruptures.  His extensive research, including strike force plates, imaging, etc., revealed that no matter what surgical procedure was done, the knee would eventually end up in the same condition, degenerative joint disease and no difference in function.  Oops, there went the one of the primary reasons to do the TPLO, to prevent arthritis in the knee.

The orthopedic community scrambled to figure out how they would handle this report.  At their annual convention, they decided to only recommend the TPLO for dogs weighing 80 pounds or more.  This made sense because the previous technique gave the dog about 80 pounds of strength in the surgically repaired knee.  Their reasoning was that the bone plate could withstand any amount of weight.  This self-imposed guideline lasted a couple of years and then the surgeons drifted back to doing TPLO surgery on all pets.  Remember, the cost difference?  Nowadays, at the vet colleges, they are only teaching the TPLO to vet students and not performing any other procedures for surgical repair of the CCL injury.  So, when your pet has a ruptured CCL, the only option for repair is going to be the TPLO.  There are still a few gray-haired vets who do the other techniques and as always the pet performs well and the end result is the same for the TPLO.

As time went by, some dogs who had had a TPLO done were developing bone cancer at the site of the surgery and pet caretakers started asking questions.  Unfortunately, the surgeons, had a typical response.  “I do hundreds of TPLO surgeries and only a few dogs end up with bone cancer. Also, there are many dogs who get bone cancer who have never had a TPLO done.”  Good answer, but it assumes that bone cancer is a “one variable” disease.

It appears that the same thing is going on in the human world.  Many people who have had fractures the were repaired using bone plates are developing bone cancer.  Research done this year, 2022, gave strong evidence that there is a connection between the bone plates and bone cancer.  When bone plates were first used to repair fractures, it was standard protocol to remove the bone plate after the fracture healed.  In time, surgeons decided to leave them in place to avoid having to do another surgical procedure to remove the plate and give the fracture site some additional support.  Since there was no long-term research, it was assumed that all would be fine.

According to the latest research by several research groups, “With implantation of a surgical bone plate, the innate immune system recognizes the device as a foreign pathogen and begins the first stage of defense.  Pathogenic recognition receptors localized at the cellular level induce the immune and inflammatory genes and activate signaling pathways leading to a release of inflammatory cytokines which creates a persistent state of inflammation to the surrounding tissues.  Other reports state that in time, the oxidation process (corrosion) of the metal plates begin to release their metallic elements into the tissue creating a toxicity to the bone in which the plate is adhered.  The combination of the inflammatory immune response and metal toxicities affect the genetics of the bone cells, creating the potential for bone anomalies, including cancer.  The research did state that titanium plates were preferred over the commonly-used stainless steel plates, but in time they both created the same response.  Stainless steel plates are the primary plates used by vets due to the cost difference between stainless steel and titanium.

We cannot forget that a surgical TPLO is electively creating a fracture of the proximal end of the tibia and is repaired by using a bone plate and that the bone plate is left in the dog indefinitely, unless there are post-operative complications like infection, where the plate is removed. Research tells us that leaving the metal bone plates adhered to the bone has a real potential to create bone pathology, including bone cancer.  That leaves us pet caretakers who have pets with ruptured cruciate ligaments a couple of options.  Find a surgeon who will repair the knee using a different technique or having the surgeon remove the plate when the fracture is healed.  This will eliminate the potential for bone cancer down the road.  We can also opt for alternative modalities, like acupuncture, but that is for another blog.