"We found there is a relationship between vertebroplasty and the development of new fractures," says Andrew Trout, first author of the paper describing the study's findings. "People should be made aware of the fact that despite the positive benefits of vertebroplasty, there is a risk of new fractures with this procedure."
The researchers discovered that following vertebroplasty, which involves injecting bone cement into the vertebrae to stabilize fractures, patients' risk for new fractures in vertebrae adjacent to those treated was 4.62 times the risk for nonadjacent vertebral fractures. In addition, they found that new fractures occurred in adjacent vertebrae sooner than in nonadjacent vertebrae: a median of 55 days following vertebroplasty for adjacent fractures and 127 days for nonadjacent vertebral fractures. This is the largest study ever to address the risk of new fractures post-vertebroplasty and the first study to examine whether there is a difference in time course between the development of new fractures adjacent and nonadjacent to the original fracture after treatment with vertebroplasty.
"Previous studies of vertebroplasty in cadavers and using computer simulation suggested that inserting cement in one bone weakens adjacent bones," explains David Kallmes, M.D., Mayo Clinic neuroradiologist and senior study investigator. The weakening effect is possible due to the overall cushioning effect of the spine, where stiffening one part puts greater stress on another, he says.
"Everyone involved in vertebroplasty research is concerned about the possibility that placement of cement into fractures will actually increase the risk of fractures in other bones nearby," says Dr. Kallmes. "Of course we do not want to cause new fractures by treating existing fractures, so we are studying treated patients to see if their bones are fracturing sooner or more frequently than would otherwise be expected."
Dr. Kallmes explains that though this study points to a significant association between vertebroplasty and new fractures occurring in adjacent vertebrae, it is not absolute proof of cause and effect.
"We consider the findings of the current study provocative," he says. "Our findings suggest vertebroplasty speeds -- and possibly facilitates -- the fracture of adjacent vertebrae. This is not definitive evidence, but should be considered when discussing risks with patients before embarking on vertebroplasty."
At this point in the research, Dr. Kallmes still practices vertebroplasty and believes the potential advantages outweigh the risks.
"I still have an open mind about the true risk of new fracture after vertebroplasty," he says. "Vertebroplasty most likely is a good procedure, and it is still probably prudent to help relieve pain with vertebroplasty. We need to be aware of potential long-term risks, however."
Dr. Kallmes recommends that patients considering vertebroplasty for unhealed vertebral fractures consider all potential risks with their physicians, including risks of new fractures in adjacent vertebrae, prior to undergoing the treatment.
The increased risk of adjacent vertebral fractures post-vertebroplasty in some patients could be due to throwing off the biomechanics of the spine by introducing cement, or it could relate to the especially weakened nature of the bones in some patients or the type of cement used in the procedure, say the researchers.
"It may be prudent to develop new cements that may be friendlier to the spine," says Dr. Kallmes. He also cites the importance of optimizing other aspects of care for osteoporotic patients, especially regarding drug therapies aimed at overall bone health.
This study involved a retrospective analysis of the risk and timing of subsequent fractures in 432 Mayo Clinic patients previously treated with vertebroplasty. From this group, 186 new fractures occurred post-vertebroplasty in 86 patients; 77 of the fractures were located in vertebrae adjacent to the vertebroplasty-treated vertebrae.
Vertebroplasty is used to treat patients with osteoporosis or a similar condition who have suffered compression of their spines with no or minimal injury. Osteoporotic patients can fracture their vertebrae with simple, everyday movements such as bending over to tie their shoes or turning over in bed, because their bones are weakened. Each year, 700,000 people suffer this injury. For four out of five patients, the fracture heals and the accompanying pain goes away in approximately four weeks with bed rest and analgesics. However, for the other one out of five patients, the fracture does not heal and the pain persists, requiring treatment. Surgery is not an option for these patients, as their bones are too weak. Vertebroplasty is the only available treatment option for patients in this condition. Vertebroplasty is not appropriate for patients with back pain due to ligament injuries, joint disease or narrowing of the spinal canal, says Dr. Kallmes.
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