4:25 Repair of osteoporotic vertebral compression fracture by transpedicular injection of bioactive calcium phosphate cement into the vertebral body

Abstract

Purpose of study: Percutaneous vertebroplasty (VP) and kyphoplasty (KP) have been successfully used for the treatment of osteoporotic vertebral compression fractures (VCFs). Although polymethylmethacrylate has been exclusively used and seems to be useful in the clinical series of VP and KP, it seems not to be an optimal material because of several potential disadvantages. We have developed transpedicular injection of bioactive calcium phosphate cement (CPC) into the vertebral body for repair of osteoporotic VCFs and pseudarthrosis without neurological involvements. We report the clinical experience of this new treatment for painful VCFs.Methods used: We prospectively followed up 38 patients with 41 vertebrae treated with this procedure, including 19 fresh fractures, 3 delayed unions and 19 vertebral pseudarthroses. The average age of the patients was 71 years old, and the follow-up period was 15 months on average (3 to 70 months). Radiological examinations are performed for all patients to evaluate progression of collapse, radiolucent line around the CPC, vertebral height change at flexion-extension lateral views. Wedging rate is defined as a percentage of the anterior vertebral height to the posterior one in a lateral view and is evaluated in all patients before and after the surgery and at final follow up. Preoperative and postoperative pain was assessed using a 10-point scale.of findings: All patients had significant pain relief. The average 10-point pain scale was 8.4 preoperatively and improved to 0.9 postoperatively. Radiological examinations 3 months after treatment to the final follow-up demonstrated no progression of vertebral collapse, no radiolucent zone around the CPC and also no detectable changes of the vertebral height at flexion-extension views in all cases of fresh VCFs and delayed union, and in 18 of 19 vertebrae of pseudarthrosis. In case of fresh fracture, the wedging rate is 66% before treatment and 84% immediately after treatment. Seventy-nine percent were maintained up to the final follow-up at 30 months after surgery. No loss of correction was observed after 1 month. As for pseudarthrosis, the rate is 28% preoperatively, 61% postoperatively and 49% at final follow-up of 13 months after surgery. The correction loss, which is not associated with back pain, occurred within 3 months postoperatively, but afterward never. Two patients had asymptomatic complications. One was minor intracanal leak, and the other was extravertebral migration of fragmented CPC 1 month after surgery, which suggested the failure of repair. There were no other significant complications in this series.Relationship between findings and existing knowledge: The CPC we used is injectable, nonexothermic, self-setting, is bioactive cement with osteoconductivity and sets by hydration to change composition into carbonated hydroxyapatite. Direct bonding of CPC to the surrounding bone and new bone formation around the CPC were described in the literature. Its compressive strength increases over time and reaches the maximum in about 7 days after injection. The maximum value is over 80 MPa, which is strong enough to reinforce the collapsed vertebrae. The clinical and radiological outcomes in this study suggest that the fractures have been successfully repaired by the injection of the CPC, except one case of pseudarthrosis.Overall significance of findings: The transpedicular injection of CPC is safe and effective for pain relief and stabilization of the fractured vertebral body and might have potential advantages over the VP and KP because of the excellent biocompatibility of the CPC.Disclosures: Device or drug: calcium phosphate cement: Biopex, Mitsubishi Materials Corporation, Tokyo, Japan. Status: not approved.Conflict of interest: No conflicts.