No double-blind, randomized controlled studies of the effectiveness of vertebroplasty have been performed. However, this reflects less the effectiveness or safety of the procedure than it does the difficulty involved in conducting randomized controlled trials of any treatment for a pain disorder.
The son of an elderly patient calls you to say that his mother has severe back pain that began suddenly just a few days earlier. The pain prevents her from walking and is exacerbated by even slight movement. Because your patient has a history of osteoporosis, you strongly suspect a vertebral compression fracture, and you arrange for radiographs to investigate. The films confirm your suspicion; they reveal a compression fracture at T12. What do you do next?
Not long ago, there were few options for elderly patients such as this woman. Too frail to be candidates for surgical fixation, they were prescribed narcotics and bed rest, were perhaps fitted for a back brace, and were told that their pain would gradually resolve-if they were lucky, within a few weeks, but possibly not for several months.
With increasing frequency, however, physicians are recommending vertebroplasty for such patients. This relatively new, minimally invasive procedure has been touted as providing dramatic pain relief in patients with vertebral compression fractures.
But is the procedure really as easy, effective, and safe as is claimed? And are the claims backed by solid evidence? Which patients stand to benefit most from the procedure? Are there any hidden risks? I will attempt here to answer these and other questions.
HOW VERTEBROPLASTY WORKS
The mechanics of the procedure are simple and straightforward. With the patient consciously sedated and in the prone position, 2 needles are inserted into the fractured vertebra under fluoroscopic guidance. Cement is then injected through each needle into the vertebra, where it fills in the spaces in the bone. The patient remains prone until the cement has hardened (about 2 hours); he or she is then usually discharged.
What has proved less simple is determining how the procedure relieves pain. Some experts have postulated that pain relief results from the cement's stabilization of the fracture, others that the procedure destroys the endings of nerves that transmit pain. Or, pain may be relieved by a combination of these 2 mechanisms of action.
EFFECTIVENESS OF VERTEBROPLASTY: WHAT THE EVIDENCE SHOWS
No double-blind, randomized controlled studies of the effectiveness of vertebroplasty have been performed. However, this reflects less the effectiveness or safety of the procedure than it does the difficulty involved in conducting randomized controlled trials of any treatment for a pain disorder. It is almost impossible to find patients in severe pain who are willing to risk being randomly assigned to the placebo arm of such a study. A randomized placebo-controlled trial under the auspices of the Mayo Clinic (the Investigational Vertebroplasty Efficacy and Safety Trial [INVEST]) is currently enrolling patients; however, it will be some time before results are available.
Still, there are a great many case studies, a number of prospective case-controlled series, and one nonrandomized prospective control study. Across the board, these show positive short-term outcomes-significant reduction in pain in about 90% of patients-often within just a few days.1,2 Although unaccounted-for biases (eg, regression toward the mean, placebo effect, and the natural tendency for compression fractures to heal on their own) may be a factor in these results, most physicians who have witnessed a patient's almost overnight recovery from incapacitating pain following vertebroplasty are convinced of the procedure's effectiveness.
Risks of vertebroplasty. The rate of complications associated with vertebroplasty is low: overall risk of severe complications, less than 1%, and risk of cement embolism, less than 0.1%. However, the procedure is not risk-free. The principal risks associated with vertebroplasty are:
Iatrogenic injuries, such as pneumothorax or spinal stenosis, occur in less than 1% of patients who undergo vertebroplasty.
Cement can enter the bloodstream through the vasculature of the vertebral body and can potentially make its way to the pulmonary system. However, the use of fluoroscopic guidance and contrast mixed in with the cement, which enables the operator to see whether any cement has entered the bloodstream, helps make this a very rare occurrence. The rate of cement extravasation is also significantly lower in vertebroplasties performed in osteoporotic compression fractures than in those performed in fractures associated with malignancy.
One way to guard against the cardiotoxic effects of the cement is to limit the number of vertebroplasties that are performed in a patient in a single sitting. Although there is no official guideline, I recommend that no patient have more than 3 vertebroplasties at one time-and ideally no more than 2.
The risk of fractures in adjacent vertebrae is increased because a vertebroplasty alters the biomechanics of the spine; it changes the way loading forces are transmitted through the vertebrae. The pressures increase in the area surrounding the cement; this, in turn, increases the risk of fracture in the adjacent vertebrae.
How great is this risk? In a recent study, Kim and colleagues3 observed for 3 years 106 patients in whom 212 vertebroplasties had been performed. After 1 year, 93.1% of vertebrae near the repaired vertebrae were fracture-free. By the end of the 3-year observation period, 72 new fractures had been observed in monitored vertebrae; the mean fracture-free interval was 32 months (95% confidence interval, 32 to about 33 months). The investigators noted that greater degrees of height restoration in the cemented vertebra, location at the thoracolumbar junction, and proximity to the originally treated vertebra were all associated with increased risk of fracture in adjacent vertebrae. In addition, it is worth keeping in mind that the results of this study have not been compared with the risk of a second osteoporotic compression fracture in patients who are not treated with vertebroplasty.
Risks of alternative treatments. When you weigh the pros and cons of vertebroplasty for a patient, it is helpful to consider the risks associated with the alternative to the procedure-immobilization and, probably, prolonged use of pain medications. Most patients in whom vertebroplasties are performed are elderly and typically have other comorbidities. Prolonged immobilization in such patients is associated with increased morbidity and even mortality. Immobility has numerous adverse effects, including heightened risk of deep venous thrombosis, pulmonary embolism, and-ironically-acceleration of the osteoporosis cascade. In addition, for each day of immobility, patients generally require 3 days of exercise to restore the aerobic muscle conditioning, anaerobic conditioning, cardiovascular conditioning, and cardiopulmonary conditioning they lost during that 1 day in bed.
The extended use of narcotics also carries many risks for elderly patients. Such agents can interfere with the ability to defecate, create GI distress and nausea, and adversely affect the patient's mental state.
There are no official guidelines for patient selection. First, of course, it is essential to confirm that a compression fracture is the cause of a patient's pain. After that, clinical intuition plays an important role. The risks of the procedure (which are slight but still real) must be weighed against the risks of possible prolonged pain and immobility. There is no scientific way to determine whether a particular patient's pain will subside quickly over a few weeks or persist for several months.
A related procedure, called kyphoplasty, may be more appropriate for certain patients. Kyphoplasty involves inserting a balloon into the fracture, inflating it to restore the prefracture shape of the vertebra, and then injecting cement into the inflated balloon. Kyphoplasty has been marketed as being more effective than vertebroplasty in patients who have significant loss of vertebral body height; however, recent studies demonstrate that vertebroplasty and kyphoplasty are similar in their ability to restore vertebral body height and reduce kyphotic deformity. Still, kyphoplasty may be preferable in patients with metastatic disease.
SELECTING A SPECIALIST
A variety of specialists perform vertebroplasties. Of primary importance is to select someone who not only does procedures but also evaluates patients with back pain of various kinds. In some patients with compression fractures, a concurrent condition causes their pain. Unnecessary vertebroplasties are occasionally performed in such patients. Thus, it is essential to select a physician who will evaluate your patient properly beforehand-and follow up with him or her afterward.