Calcium phosphate cement improved kyphoplasty results

The cement helped provide good correction of deformity in two studies.

Issue: Issue 3 2004

This 79-year-old woman had an L1 osteoporotic vertebral pseudoarthrosis. After the CPC injection, the wedge deformity of the collapsed vertebral body was corrected, and a filling with the CPC was observed (right).

COURTESY OF RYUICHI TAKEMASA

SAN FRANCISCO — Japanese and German researchers reported that bioactive calcium phosphate cement can be an excellent alternative to polymethylmethacrylate, or PMMA, in kyphoplasty for the treatment of vertebral fractures.

In a study of 20 fractured vertebrae (10 acute fractures and 10 pseudarthroses) in 19 patients with a minimum follow-up of two years, Ryuichi Takemasa, MD, of Kochi Medical School in Kochi, Japan, found that calcium phosphate cement (CPC) used with kyphoplasty is effective for osteoporotic vertebral fractures.

Takemasa and his colleagues have been using bioactive CPC for kyphoplasty since 1995. “It is non-exothermic, self-setting, radiopaque, bioactive and osteoconductive. The CPC consists of dry elements and solution that are mixed together to form an injectable paste. The paste gradually sets and hardens by hydration to form hydroxyapatite,” said Takemasa at the American Academy of Orthopaedic Surgeons 71st Annual Meeting.

“We evaluated the pain intensity using a 10-point pain rating scale and deformity correction using a wedging rate,” or the anterior vertebral height as a percentage of the posterior vertebral height, he said.

Patients’ average preoperative score was 7.5, which significantly improved to 1.0 immediately postsurgery. Pain relief lasted to the two-year follow-up.

The preoperative wedging rate was 46%, which improved to 73% postoperatively and was maintained at 63% at final follow-up.

Takemasa reported one case of asymptomatic epidural leak and one case of CPC fragmentation, but there were no other significant complications.

“In in vitro studies, we have already confirmed direct binding of the CPC to the surrounding bone and osteogenesis around the CPC,” he said.

Acute vertebral fractures

“These results demonstrated that the CPC vertebroplasty is minimally invasive and safe, and can provide highly significant pain relief and good correction of the deformity. This procedure might have potential advantages over PMMA vertebroplasty and kyphoplasty because of the excellent biocompatibility of the cement.”

In Heidelberg, Germany, orthopaedic researchers reported success using kyphoplasty with an injectable CPC to treat acute vertebral fractures.

“We already had very good results with kyphoplasty in treating osteoporotic fractures. We wanted to see if the results would be just as good in younger patients,” said lead investigator Joachim S. Hillmeier, MD.

He said that the gold standard treatment for younger patients with acute traumatic fractures has been osteosynthesis with internal fixation. However, “Kyphoplasty seems to be an excellent alternative minimally invasive technique, which requires a shorter operative time and [provides] excellent height restoration.”

In their prospective study, the surgeons used balloon kyphoplasty to treat 25 patients (average age 57 years) with acute traumatic vertebral fractures. Patients were randomized to receive either PMMA cement or Calcibon (Biomet Merck) for vertebral body augmentation.

A bioactive bone cement, Calcibon received the CE mark in Europe.

Deformity Correction

chart
Takemasa evaluated the deformity correction. The wedging rate defines the anterior vertebral height as a percentage of the posterior vertebral height. The preoperative wedging rate was 46%, and it was corrected to 73% postoperatively. In 63%, the correction was maintained at the final follow-up. The correction loss occurred up to 3 months, none after 3 months.

SOURCE: RYUICHI TAKEMASA

Pain, function improved

The investigators reported a significant improvement in pain and function in 23 of the 25 patients, who presented with type A fractures according to the AO classification system. There was no significant difference in results among the patients who received either PMMA or Calcibon. There was also no evidence of retropulsion of the fractured dorsal vertebral wall post-kyphoplasty. Patients returned to work between the fourth and eighth week.

A few audience members questioned the use of the bone cement in young patients and the high risk of younger patients eventually developing avascular necrosis. They also cited the potential risk of bone collapse in patients in their 40s and 50s and questioned whether the cement is totally resorbed.

Hillmeier said that uncontrolled resorption of Calcibon has not happened in any cases. His group is starting a multicenter, prospective randomized study to determine the most effective course of treatment for acute vertebral fractures in younger patients, including the value of conservative treatment. He also said the progressive loss of vertebral body height in some patients could be attributed to the settling of the cement in the cancellous bone.

For more information:

Takemasa R, Yamamoto H, Tani T, et al. Kyphoplasty using bioactive calcium phosphate cement for osteoporotic vertebral fractures. #184.
Hillmeier JS, Meeder PJ, Kasperk HC. Kyphoplasty for acute vertebral fractures with an injectable calcium phosphate cement. #187.
Both presented at the American Academy of Orthopaedic Surgeons 71st Annual Meeting. March 10-14, 2004. San Francisco.