IT REALLY WORKS: Percutaneous Vertebral Augmentation

Naveen Kumar, MD

At first blush, the term vertebral augmentation sounds suspect. Nonetheless, the procedure has the potential to greatly improve the lives of those afflicted with spinal compression fractures. Vertebral augmentation is a catch-all phrase that encompasses two procedures: vertebroplasty and kyphoplasty. 

Vertebroplasty involves injecting bone cement (polymethylmethacrylate—PMMA) into a fractured vertebral body under fluoroscopic guidance to provide internal fixation and pain relief from a compression fracture. Kyphoplasty is basically the same procedure except that it involves initial inflation of a balloon within the vertebra to create a cavity for cement deposition. The two different names for variations of the same procedure are confusing, and in reality kyphoplasty should be considered balloon-assisted vertebroplasty. These procedures are performed by several specialties including radiologists, surgeons and pain specialists. In my practice it is typically done under moderate sedation and does not require a hospital stay. Complications are extremely rare and generally involve cement leakage into areas that can compress nerves or the spinal cord. However, most cement leakage is asymptomatic. On rare occasions, cement has been reported to enter the venous system and can even lead to PE. However, meticulous technique and careful fluoroscopy during injection can prevent this. 

The vertebroplasty procedure was developed in France in 1984 and began to gain popularity in the U.S. in the 1990s. However, it became the subject of controversy following the August 2009 publication of negative articles in the NEJM ^1,2 claiming that vertebroplasty provided no more pain relief than a sham procedure. The sham procedure was identical to vertebroplasty with the important exception that instead of injecting cement into the vertebral body, lidocaine and bupivacaine were infiltrated along the periosteum of the involved pedicle. Both study groups showed equivalent decrease in pain following the procedures and up to 2–3 months later.  

Careful review of both articles reveals several flaws in the study, which were addressed in letters to the editor.³ One flaw was the large number of patients who refused participation in the study. Another was a high crossover rate from the placebo group to the treatment group. 

Poor patient selection was an additional and highly critical flaw. The key to any successful procedure is patient selection. In one of the studies the mean age of the fractures was 4–5 months. Treating an already healed fracture is unlikely to provide benefit. 

In recent fractures, bony edema is evident on MRI. While there are numerous causes for back pain including disc disease and facet arthropathy, the target for vertebral augmentation is the relief of painful bony edema and inflammation related to the fracture. In our practice we generally require a spine MRI with STIR (fluid-sensitive) imaging to determine if a patient is a candidate for vertebral augmentation. A patient may have multiple compression fractures of different ages, and MRI can tell us which are new enough to be more likely to respond favorably to vertebroplasty. (Figure 1 below shows two compression fractures. T9 [long arrow] is acute and shows edema. L1 [short arrow] is an older fracture and does not show edema.) 

Neither NEJM article used MRI findings for inclusion in or exclusion from the study. Most fractures treated were not acute. In addition, the study included patients with mild pain even though it is patients with moderate to severe pain who are most likely to benefit from the procedure. Two larger studies published in Lancet in 2009 (randomized trial with 300 patients) and 2010 (randomized trial with 431 patients) did show benefit from vertebral augmentation. These trials required fractures to be acute with edema on MRI and moderate to severe pain.^4,5 Figures 2 and 3 show a vertebroplasty success in a recent fracture. Figure 2, a fluoroscopic spot image, shows the patient from Figure 1 with the T9 compression fracture before vertebroplasty. Figure 3 shows same spot after T9 vertebroplasty with good cement fill. The patient had an excellent response with good pain relief. 

In this day and age, personal experience no longer seems to count for much, particularly when compared to clinical trials. However my nearly 10 years of performing the procedure ought to lend a certain degree of credibility to my views and experience. In Marin County we have many elderly patients with osteoporosis who are susceptible to vertebral compression fractures. These fractures can occur spontaneously—just from bending over to pick something up, for example. Many of the patients I see are older women who live alone and have previously been able to care for themselves independently. Their fractures can be very painful and often trigger a visit to the ED, following which they are sometimes admitted for pain control. They become immobilized by pain, and opiates result in sedation and/or delirium. The fracture can wind up setting off a downward spiral. While many will improve slowly over months, there is a risk of permanent pain and disability, not to mention the deformity and kyphosis that arise from multiple fractures.

In my experience, patients with acute fractures in severe pain are ideal candidates for the procedure. I have seen bed-bound, delirious patients who suffer severe pain with any movement transformed in a single day. I recall being on rounds the day after a vertebroplasty. I went to the patient’s room and could not find her. To my surprise, I spotted her down the hall, smiling and already able to participate in physical therapy. She was even wearing lipstick. Vertebroplasty can get people out of the hospital and back home sooner.

Osteoporosis can lead to multiple spinal compression fractures, and we have several patients who come back when they suffer a new fracture. Some critics feel that strengthening one vertebral body may lead to fractures of adjacent weak vertebrae. There is no data to support this because we know that patients with osteoporosis continue to fracture multiple vertebrae with or without vertebroplasty having been performed. The fact that patients come back for repeat vertebroplasty speaks volumes about the benefits they derive. 

To end this article, allow me to turn to the end (except for the coccyx) of the spine, the sacrum. This bone too is susceptible to osteoporotic fractures. We call them sacral insufficiency fractures. Being at the base of the spine, the sacrum can literally buckle under the weight above. I have done a number of “sacroplasty” procedures that are really nothing more than vertebroplasty of the sacrum. The anatomy of the sacrum, however, is very different from other vertebrae. Its unique flat, broad shape requires placement of the needles under direct CT rather than fluoroscopic guidance to ensure that the cement fills the sacrum appropriately. It is with great satisfaction that I watch the cement fill the porous bone, strengthening it and providing internal fixation of the fracture lines. Comic book fans will understand how this reminds me of the way the character Wolverine had his bones strengthened by the injection of a fictional metal alloy called Adamantium. Unfortunately we do not have such a liquid metal. However, PMMA, which is chemically identical to Plexiglass, works pretty well.

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Dr. Kumar is a diagnostic, vascular and interventional radiologist at Kaiser San Rafael.

Email: naveen.n.kumar@kp.org

References 
1. Kallmes, et al, “A randomized trial of vertebroplasty for osteoporotic spinal fractures,” NEJM, 361:569-579 (2009). 
2. Buchbiner, et al, “A randomized trial of vertebroplasty for painful osteoporotic vertebral fractures,” NEJM, 361:557-568 (2009). 
3. Clark, W, Letter to the editor. “Trials of vertebroplasty for vertebral fractures,” NEJM, 361:2097-2100 (2009). 
4. Wardlaw, et al, “Efficacy and safety of balloon kyphoplasty compared with non-surgical care for vertebral compression fracture (FREE): a randomised controlled trial,” Lancet, 373:1016-24 (2009). 
5. Klazen, et al, “Vertebroplasty versus conservative treatment in acute osteoporotic vertebral compression fractures (Vertos II): an open-label randomised trial,”  Lancet, 376:1085-1092 (2010).