S. Bobo Tanner MD
Divisions of Rheumatology, Allergy, & Immunology
Vanderbilt University Medical Center
Nashville, TN 

Techniques of Vertebroplasty and Kyphoplasty (Table1)

The percutaneous technique of treating osteoporotic VCF evolved from the use of the bone cement, polymethylmethacrylate (PMMA), along with surgical decompression in patients who had spinal pain and/or instability due to metastatic malignancies and spinal hemangiomas, as well as in patients with fractures due to benign tumors of long bones. 

Gallibert first described the use of cement augmentation of the vertebral body in France in 1984 (11). The goal of this technique was directed at pain relief in patients with spinal tumors and hemangiomas. PMMA, which is a low-viscosity bone cement, was injected into the damaged vertebral body under radiological guidance using a percutaneous approach. In 1997, the use of this technique was reported in North America in a patient with malignant disease as well as in patients with non-malignant osteoporotic fractures (4). 

The technique of vertebroplasty begins with the placement of an 11- to 15-gauge needle into the involved vertebral body. Most patients are in prone position on an appropriate table for CT scan and/or fluoroscopic guidance. Usually local anesthesia and IV sedation are used, although general anesthesia may be needed if the patient is unable to lie in the prone position. The typical procedure is performed through a 1-cm paramedian incision leading to a transpedicular approach to the vertebral body. A special mix of PMMA is used with increased radiopacity so that the cement can be seen more easily with radiological guidance during and after the procedure. The PMMA is injected into the vertebral body under pressure, but usually not enough pressure to restore or change vertebral height. Sometimes bilateral injections of the vertebral body are performed in order to achieve more uniform cement application, but the current use of curved needles often allows a unilateral approach. The posterior vertebral cortex must be intact during vertebroplasty in order to avoid cement leakage into the spinal canal (12). 

Kyphoplasty grew out of vertebroplasty and follows a similar procedure with an additional step (Figure 1). A tract for a larger gauge needle is drilled into the vertebral body through the pedicle followed by an inflatable balloon (bone tamp). The balloon serves to create a cavity when inflated. The balloon inflation step can re-expand the vertebral body and, thus, increase the height of the vertebral body. The balloon is then deflated and withdrawn from the vertebral body prior to the injection of the PMMA cement. The use of a large gauge needle and the creation of the cavity in the vertebral body allows for a more viscous PMMA mixture to be injected under relatively low pressure. This increased viscosity cement and low-pressure injection has the advantage of reducing cement leakage. The average volume of the injected PMMA is about 7 ccs. Kyphoplasty is typically done bilaterally for each vertebral body fracture. As many as 6 levels have been done at once, although usually just 1 or 2 vertebral bodies undergo the procedure during a single setting (4,12). 

With either vertebroplasty or kyphoplasty, the patient remains in a supine position for 1 to 2 hours after the procedure in order for the PMMA cement to “cure.” During this curing, there is an exothermic reaction that polymerizes the cement. Local tissue damage due to the heat has been reported but only anecdotally, and it is not clear if this can result in unwanted side effects or perhaps be a mechanism of pain relief due to changes in sensory nerve fibers (4). During the 1 to 2 hours of curing, radiological evaluation of the spine is undertaken with CT scan and/or fluoroscopy to look for leakage of cement outside of the vertebral body. Cement leakage can be associated with complications from the procedure such as nerve damage.