The injection is safe when performed by physicians experienced with the technique, and pain reduction is both swift and sustained, according to the one-year, multi-center cohort study.
Among the 25 patients enrolled in the uncontrolled study, the mean pain score on a 10-point visual analog scale was 7.3 at baseline, 2.7 immediately post-procedure, 1.4 at two weeks, 0.5 at 24 weeks, and 0.3 at 52 weeks, according to Michael Frey, MD, a NASS member and physiatrist at Advanced Pain Management and Spine Specialists in Fort Myers, FL.
There are currently no treatments for sacral insufficiency fractures. Recovery is typically slow, and pain may linger for up to a year. In some cases, symptoms and disability last longer.
To calm the pain, physicians often prescribe bed rest, painkillers, corsets, or other measures. However, these can put patients at increased risk of thromboembolism, skin breakdown, pressure ulcers, constipation, depression, progressive osteoporosis, and reduced muscle strength and cardiac function.
"These patients are miserable," said Frey, who has performed sacroplasty on nearly 50 patients.
To explore better alternatives, Frey and others have adapted techniques developed for vertebroplasty in the lumbar spine. In vertebroplasty, physicians use fluoroscopic guidance to inject polymethylmethacrylate (PMMA) into osteoporotic compression fractures. After injection the acrylic bone cement hardens. The technique was designed to stabilize the fracture, reduce pain, and improve function.
Frey and colleagues reported on consecutive patients with osteoporosis who had incapacitating low back or gluteal pain and a sacral insufficiency fracture documented on MR imaging or CT scan, and who failed or could not tolerate conservative care. The authors excluded patients with fractures caused by malignancies.
About one in seven patients experienced complete relief of pain within 30 minutes, said Frey. Approximately one-fourth were pain-free at two weeks and about one-third at four weeks. Frey said there were no complications associated with the procedure at any time, though one patient died of what was deemed unrelated pulmonary disease within four weeks of undergoing the procedure. Excluding this patient, all but two patients reported 75% to 100% satisfaction at one year.
"Sacroplasty is a dramatic leap forward," said Frey.
Most previous reports about sacroplasty have been small case series with short followup. They suggested that the procedure is technically feasible and leads to short-term pain relief. But there is scant prospective evidence on the safety and efficacy of sacroplasty in larger cohorts followed for longer periods of time.
Frey says the procedure can be technically demanding, and recommends physicians have extensive experience in vertebral augmentation. Potentially, cement can leak outside the sacrum and compromise the sacral nerve root, the sacral spinal canal, or sacroiliac joint.
Several years ago, the FDA issued a surprisingly sharp warning about the risks associated with vertebroplasty, including pulmonary embolism, respiratory and cardiac failure, and death. (FDA Public Health Web Notification: Complications related to the use of bone cement in vertebroplasty and kyphoplasty procedures, October 31, 2002; http://www.fda.gov/cdrh/safety/bonecement.html.)
Frey noted that sacroplasty is an off-label use of PMAA, and there is no Medicare code for the procedure, so reimbursement is problematic. His cost for one kit is about $400. He said he performs the service at no charge and receives no industry funding for his research.
Frey would like to see controlled trials to compare sacroplasty to a sham procedure. It is conceivable, he said, that sacroplasty is no better than placebo. In his study, none of the patients who declined sacroplasty was pain free at 12 weeks, though at six months and one year their pain had subsided to a level comparable to that of patients who received sacroplasty.