Cement Leakage More Likely With Severe Vertebral Compression Fractures
Compression fractures are the most common type of fracture affecting the spine. A compression fracture of a spine bone (vertebra) causes the bone to collapse in height. A special surgical procedure called percutaneous vertebroplasty (PVP) has been used to treat painful vertebral compression fractures. But there have been some problems with that treatment from leakage of the cement used to repair the break.
In this study from the Netherlands, surgeons try to identify risk factors for cement leakage. If patients could be screened before surgery and identified as high risk for cement leakage, then perhaps the surgeon could do something different to change that. Or maybe patients at high risk just aren’t good candidates for this particular procedure. Let’s take a look and see what they found.
There were 177 cases of painful osteoporotic vertebral compression fractures in 89 patients. Everyone had MRIs taken before surgery to look at the type of fractures and areas affected. CT scans were done after surgery to look for cement leakage. The procedure itself involves placing a needle into the fractured vertebral body and then injecting a bone cement into the fractured area.
To perform vertebroplasty, the surgeon uses a fluoroscope to guide the needle. A fluoroscope is a special X-ray television that allows the surgeon to see the spine and the needle as it moves. Once the surgeon is sure the needle is in the right place, bone cement, called polymethylmethacrylate (PMMA), is injected through the needle into the fractured vertebra.
A reaction in the cement causes it to harden within 15 minutes. This fixes the bone so that it does not collapse any further as it heals. More than 80 percent of patients get immediate pain relief with this procedure. But this problem of cement leakage can cause problems of its own (e.g., paralysis, tears of the heart, and even death). Leakage must be prevented if percutaneous vertebroplasty is going to continue being a helpful treatment for this problem.
The researchers involved in this study gathered all kinds of information about each patient looking for potential risk factors. For example, they considered age, sex (male versus female), type and location of fracture(s), and severity of fracture.
They also used the pre-operative MRIs to look for any disruption of the disc called cortical disruption. Tears or disruption of the disc could make it possible for cement to seep into the disc. A hard disc would create even more problems since these are the spine’s shock-absorbers and must remain soft and pliable.
They found three major risk factors for cement leakage when using percutaneous vertebroplasty for osteoporotic vertebral compression fractures. First, leakage was more likely in the severe fractures. The presence of disc (cortical) disruption was another important risk factor. The surgeon doesn’t have control over either of those variables.
But the third risk factor is one surgeons can change and that is how viscous (thin or thick) the cement is. Low viscosity cements flow easily (they are less resistant to flow) so they fill in all the cracks in a bone fracture. This effect is good but the low viscosity also allows the fluid to seep into other areas. A higher viscosity cement clumps more and doesn’t spread as much so there is less leakage.
As the authors point out, the surgeon can see the consistency of the cement before injecting it so there is some control over how viscous it is. They recommend using cement that is “doughy” in consistency. A higher viscosity cement may be needed to avoid cement leakage when there is a more severe fracture or there is documented cortical disruption.
In summary, the findings of this study highlight what surgeons have observed clinically about percutaneous vertebroplasty. Cement leakage occurs most often with severe vertebral compression fractures and when the disc has been compromised. With the evidence available from this and other studies, it looks like the problem of cement leakage can be better managed. The surgeon can control the cement viscosity by selecting the cement with the best viscosity for the problem before injecting it into the bone.
Reference: Marc J. Nieuwenhuijse, MD, et al. Cement Leakage in Percutaneous Vertebroplasty for Osteoporotic Vertebral Compression Fractures: Identification of Risk Factors. In The Spine Journal. September 2011. Vol. 11. No. 9. Pp. 839-848.