Along with cartilage degeneration that occurs in arthritis, an MRI of the knee may also show a bone marrow lesion (BML). In recent years, injecting bone cement into these BMLs (a new procedure called a subchondroplasty) in arthritic knees has become a trend. While we’ve seen favorable outcomes reported on this procedure at conferences, in practice, we’ve also seen actual patients with real disastrous results after this procedure. Let’s take a look at this new procedure on the block and give you the information you need to help you decide if it’s worth the risk to have your arthritic knee injected with bone cement.
What Is a Bone Marrow Lesion?
A bone marrow lesion can be seen on MRI (usually in arthritis patients) as either a dark spot or a bright spot (the shade of the spot is determined by the type of MRI sequence) in the bone. Also known as bone marrow edema (BME), in years past, these we incidental findings that didn’t really concern physicians. However, in recent years, we’ve found that these BMLs represent weak or damaged bone as well as swelling and that these are associated with the patient’s arthritis. In addition, while degenerated cartilage and meniscus tears may not cause pain, BMLs are the most common MRI finding associated with pain, so it may be a good idea to treat BMLs as part of a treatment plan for arthritis pain.
Subchondroplasty and Bone Cement Injection
Bone cement is a paste-like substance that once injected hardens up, like cement. The idea is for it to substitute for missing bone but then broken down and eventually replaced by bone. Last month, if you’ll recall, we talked about cement injections (called a vertebroplasty) for backbone fractures.
Bone cement can be exothermic, meaning it heats up once it has cured (though this can damage local cells), or it can be endothermic, meaning it doesn’t heat up. BMLs are usually treated with an endothermic cement made of calcium phosphate. The actual procedure that involved injecting the cement is called a subchondroplasty. Broken down, the medical term subchondroplasty means surgery below the cartilage. The idea is that treating the damaged bone (the BMLs) in knee arthritis is more effective than just treating the joint.
Indeed we have seen studies showing BMLs, in hips for example, are more reliably associated with pain in arthritis. In addition studies have long since determined that cartilage degeneration in arthritis is not the cause of arthritic pain. So turning the focus to BML treatment certainly seems like the way to go, but is subchondroplasty, a surgical procedure that involves injecting a foreign and synthetic substance into the bone, the answer? Unfortunately, we’ve seen some bad results from this one. Let’s review a patient case.
A knee arthritis patient made his way to use earlier this year who had previously undergone a subchondroplasty for his BMLs. The orthopedic surgeon had performed an arthroscopic debridement of his knee and also injected bone cements into his bone marrow lesions (a first for this surgeon). This not only didn’t address the patient’s pain, but he, in fact, got much worse. We obtained his MRIs showing his BMLs before and after the procedure (shown above).
The “before” images are actually the two images on the right, with the BMLs (the bright spots on the MRI) circled in yellow. The “after” images, the two on the left, had the cement injections worked, should show dark, or normal bone, inside the red circles. Unfortunately for this patient, this is not even close to what we are seeing. There are instead gaps and holes, the bright spots, so it appears that the bone, while attempting to heal, has actually died off. Adding to this disaster, the patient has also lost a lot of cartilage in the nine months between the before and after. This patient’s subchondroplasty has actually made things worse, not better.
Stem Cells Instead of Bone Cement
In the 1990s, European physician Philippe Hernigou was the first to use bone marrow concentrate (BMC) stem cell injections to treat bone. Clearly, using the patient’s own stem cells to treat their BMLs makes more sense than introducing a foreign material into the body by injecting patients with cement.
We have knee arthritis research (a match case-control series) that we are readying to publish that shows BMLs injected with BMC is beneficial to patients also receiving a same-day stem cell treatment in the knee joint. In other words, we’ve seen that knee arthritis patients’ function is better when both the joint and bone are treated rather than just the joint alone.
So while subchondroplasty is an option, injecting bone cement into the bone comes with risks. Whether it’s an allergy to the synthetic and foreign substance being injected, or an infection, or damage to stem cells and bone, or something else, right now there simply aren’t enough right answers or data to give a thumbs up to having your arthritic knee injected with bone cement to treat BMLs.