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	Christopher Bono, a MED assistant professor of orthopedic surgery, is using a new procedure called kyphoplasty to treat fractured vertebrae and straighten out curved spines. Photo by Kalman Zabarsky

By Tim Stoddard

With bones made brittle by osteoporosis, about half a million Americans — most of them women over 50 — every year suffer a vertebral compression fracture, where a crack in the spine causes one or more vertebrae in the spine to collapse. These painful fractures are slow to heal, and cause the spine to slump forward in a hunchbacked posture called kyphosis. Until recently, the treatment options for vertebral compression fractures were either six weeks of bed rest with painkillers, or a major operation to resculpt the spine with screws, plates, and cadaver bone. But now there’s a better alternative: a minimally invasive spine surgery called kyphoplasty that’s becoming popular at medical centers around Boston.

Christopher Bono, a spine surgeon and a MED assistant professor of orthopedic surgery, introduced kyphoplasty at Boston Medical Center when he joined the MED faculty in September 2002. In the procedure, a surgeon or a radiologist inserts a needle into the broken vertebra and inflates a balloon to expand the bone to its former height. An acrylic cement is then injected into the hollow created by the balloon to stabilize the vertebra and correct the hunched-over posture.

The results are often swift and dramatic. “If patients are going to have pain relief,” Bono says, “it’s going to be immediately after the surgery. They’ll be up and walking around the same day, and that’s extremely satisfying. There are very few operations that we do in orthopedics, let alone spine surgery, where the patient tells you, ‘My pain is gone.’ And you can do it with only a drop of blood being lost.”

Only about 3,600 kyphoplasties have been performed to date, but so far, surgeons are reporting that about 90 percent of patients experience significant pain relief within days of the 45-minute operation. In the procedure, the patient lies facedown on an operating table under general anesthesia or with sedation and a local anesthetic. Bono makes a small incision and inserts a hollow needle into the large part of the vertebra called the vertebral body, carefully guiding it into place using two X-ray machines. This is the most delicate part of the procedure: a misguided needle can stray into the spinal cord, blood vessels, or the nearby lungs. Bono then slips a guy wire down the center of the needle, and replaces the needle with a tiny drill bit that he gently twists to create a pilot hole for the balloon.

If the fracture is recent enough, the expanding balloon restores the collapsed vertebra to its original shape, a process that orthopedists call fracture reduction. Bono then injects a cement called polymethylmethacrylate, which oozes into the void like toothpaste and hardens within 10 to 20 minutes. The cement prevents the tiny bone fragments from rubbing against each other, bringing about almost immediate pain relief.

Before the balloon

Kyphoplasty is an offshoot of a similar procedure called vertebroplasty, which was pioneered by the French physician Hervé Deramond in the mid-1980s. In vertebroplasty, Deramond inserted a needle into the fractured vertebra and injected cement, which permeated the porous bone like water filling a sponge. The procedure stabilizes fractures and provides almost immediate pain relief, but problems arise when the cement leaks out of the vertebral body into the spinal canal or into veins. If it enters the bloodstream, the cement clumps together and travels to the lungs, causing a potentially fatal event called a venous thrombosis. If it impinges on the spinal cord, it can cause paralysis.

While vertebroplasty has a high rate of success — about 90 percent of patients experience significant pain relief — Bono says that studies have shown that the cement leaks in 20 to 70 percent of those cases. This high complication rate was part of the impetus that led the California-based orthopedic surgeon Mark Reilly to develop kyphoplasty in the late 1990s. By creating a pocket inside the bone, surgeons can inject a thicker mixture of cement at a lower pressure. “That has dramatically decreased the rates of extravasation, the leaking of the cement, which happens at a high rate in vertebroplasty,” Bono says. “In kyphoplasty, rates of extravasation have been less than 10 percent.”

Kyphoplasty can also reduce compression fractures, restoring the crumpled vertebra to its original height and straightening the hunched-over posture, known as dowager’s hump. Correcting a kyphotic spine is important not just from a cosmetic standpoint: one collapsed vertebra will put stress upon neighboring vertebrae, causing a domino of fractures that make breathing and walking difficult.

Family feud

As interest in vertebroplasty and kyphoplasty has exploded across the country, there has been rising disagreement over which procedure is safer and more effective. Some doctors say that kyphoplasty is inherently more dangerous because it uses a larger surgical instrument and is more complicated. Some vertebroplasty aficionados say that patients need pain relief, not height, and that the pressure from a balloon may create new cracks in a brittle bone and send fragments into the spinal canal or blood vessels. Vertebroplasty is also cheaper — about $1,500 per procedure; kyphoplasty can run as high as $4,000 to $7,000.

Since both procedures are relatively lucrative, there’s a turf war brewing over who should do them: orthopedic surgeons or interventional radiologists. Orthopedic surgeons initiated and developed kyphoplasty, Bono says, but neurosurgeons and interventional radiologists now perform them, too. “It’s not exactly clear why they are doing these,” he says, “but one of the original doctors to do this was an interventional radiologist at the University of California, San Diego.” The first physician to perform a vertebroplasty in the United States was also an interventional radiologist.

In the future, kyphoplasties may be offered on a more acute basis, meaning that patients won’t have to wait for several weeks following a fracture before having the procedure done. Most doctors, including Bono, first recommend bed rest, however, because about two thirds of all vertebral compression fractures will heal on their own. But if the fracture clearly isn’t mending after a month, or if the patient is becoming dangerously weak in bed, then Bono recommends that his patients consider the balloon. “I think the procedure has a very good track record, with a peer-reviewed series of good results,” he says. “I think kyphoplasty has already proven itself.”

5 September 2003
Boston University
Office of University Relations