Goat study cements vertebroplasty’s efficacy

Vertebroplasty appears to be safe for people in their golden years. But as the range of applications expands and the age of eligibility grows ever younger, will the procedure materials stand the test of time? A study of goats suggests they will.

Vertebroplasty, which involves injection of cement into the vertebral body under fluoroscopic guidance, is typically performed to relieve painful spinal lesions. Potential problems with the cement over time include disc degeneration and damage to surrounding bone tissue.

Candidates for vertebroplasty have traditionally been older patients (aged 70 to 90 years) who were successfully treated for osteoporotic fractures. Now, however, surgery is being considered for younger people - some in their thirties - with other conditions.

Polymethylmethacrylate (PMMA) has been the cement most commonly used in vertebroplasty, and its properties are well known from hip arthroplasty. In hip surgery cases, however, PMMA particles have been shown to form after tens of thousands of load cycles, potentially causing osteolysis in surrounding bone. Consequently, most radiologists and orthopedic surgeons are reluctant to use PMMA for vertebroplasty in young patients. Instead, they use calcium phospate cement (CPC) or similar materials in this patient group.

Researchers from the University Medical Center Utrecht in the Netherlands specifically examined the effect of PMMA and CPC in traumatic fracture treatment, a more common use in younger patients. They presented their findings at the European Congress of Radiology meeting in March.

To assess the risks, the researchers performed a study of 30 mature goats, including six control animals. Intravertebral holes were drilled or reamed into the vertebral bodies of the animals in the treatment group.

All animals in the treatment group underwent bilateral transpedicular vertebroplasty at two lumbar levels. Animals were injected with one of the two types of cement, with and without direct contact with intervertebral material.

After surgery, the goats were examined at six weeks and six months, which is probably long enough to detect early signs of degeneration in humans or animals.

No signs of disc or endplate degeneration were seen in any of the animals, and there was no decrease in the mean disc height. A mild inflammatory reaction was found in some animals who received PMMA, however, both with and without direct contact with cement. Ultimately, it's possible that this reaction could lead to osteolysis within the vertebral body or degenerative changes.

The study suggests slightly better biocompatibility with CPC. But that advantage comes at a price, because CPC is inferior to PMMA when it comes to mechanical properties, Verlaan said.

Overall, the study results are reassuring, given that vertebroplasty has been booming in popularity. The number of search engine page hits for the procedure has risen from about 900 in 2001 to 8700 in 2003 and 171,000 in 2006, Verlaan said.

Vertebroplasty's success has made it difficult to perform randomized controlled safety trials, because participants are reluctant to be placed in a nontreatment group.

"A lot of promising techniques are being introduced into the clinic without appropriate trials. We should be very careful. Applications are rapidly expanding for vertebroplasty without any data on long-term effects," he said.

A range of possible applications now exists for people in their thirties. In patients with traumatic facture, for example, cement is injected not in the vertebral body for pain relief, but for reinforcement of the anterior column. In this application, it prevents the intervertebral disc from entering the center of the vertebral body through the fractured endplate.

Vertebroplasty could become a treatment option for patients with osteogenesis imperfecta, which causes the collapse of almost all vertebral bodies in the third or fourth decade of life. It could also bring relief from painful Schmorl nodes in the younger population, Verlaan said.

"Vertebroplasty is a new and powerful tool, but the procedure is not without risks and should be applied with some consideration," he said.

For more information from the Diagnostic Imaging archives:

Kyphoplasty, vertebroplasty proponents reach detente

Vertebroplasty spells relief for back pain

Vertebral fracture identification rounds out osteoporosis diagnosis