Histological and Radiological Findings After Balloon-Assisted Endplate Reduction with Tricalcium Phosphate Bone Cement and Short-Segment Instrumentation for Thoracolumbar Burst Fractures

BACKGROUND CONTEXT: Balloon Assisted Endplate Reduction (BAER) is a relatively new and promising treatment modality for thoracolumbar burst fractures. Combined with pedicle fixation, central elevation of the corpus and reduction of the segmental kyphosis is possible. Consequently preventing anterior column insufficiency, because of migration of the disc tissue through the central endplate of the fractured vertebra. Theoretically, Tricalcium Phosphate bone cement (TCP) is an attractive bone filler due to its assumed biocompatibility and osteoconductive properties. To our knowledge, no histological findings have been reported in humans. No reports on the behaviour of the fractured vertebra after removal of the instrumentation were found. PURPOSE: Histological and radiological evaluation of BAER with TCP and short-segment instrumentation for thoracolumbar burst fractures. STUDY DESIGN/SETTING: Retrospective cohort study. METHODS: Fourteen patients with traumatic thoracolumbar burst fractures were operated on with BAER using TCP combined with shortsegment instrumentation. None of the patients had neurological deficits, pre-existing spinal deformity, spinal stenosis, osteoporosis (criteria WHO) or had previous spinal surgery. Instrumentation was removed as intended aproximally nine months after the initial surgery. Transpedicular biopsies were taken for histological and histochemical analysis. Roentgenograms before to after the surgery and after removal of the instrumentation were taken to evaluate endplate reduction and correction of the segmental kyphosis. Furthermore CT-scans were taken before and after the initial surgery to evaluate spinal canal encroachment, cement leakage and malposition of the instrumentation. RESULTS: Analysis of the biopsies confirmed a variable degree of bone remodelling. Most samples contained remnants of the TCP and showed incorporation of this material into newly formed bone matrix. Average follow up was 2.6 years, wedgeand kyphosis angle improved from an average of 19 and 9 before surgery to 9 and 0 after surgery (p50.00). Anterior-posterior and central-posterior vertebral body height ratio improved from an average of 0.4 and 0.6 before surgery to 0.8 after surgery (p50.00). After removal of the instrumentation no significant differences in endplate reduction were seen, whereas the initial correction of the segmental kyphosis was reduced by four degrees. However when the segmental kyphosis before the initial surgery was compared with the segmental kyphosis after removal of the instrumentation, a significant improvement of five degrees could still be observed (p50.00). Aside from screw breakage in one patient no other adverse events occurred. CONCLUSIONS: In this small patient group, BAER with TCP and shortsegment instrumentation showed significant correction of the fractured vertebra. This correction was maintained after removal of the instrumentation. Histology confirmed the biocompatibility and osteoconductive properties of TCP. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.