The mechanism of thoracolumbar burst fracture may be related to the basivertebral foramen

Background Context The basivertebral foramen (BF), located in the middle posterior wall of the vertebral body, may induce local weakness and contribute to the formation of a retropulsed bone fragment (RBF) in thoracolumbar burst fracture (TLBF). We hypothesize that the mechanism of TLBF is related to the BF. Purpose This study aimed to clarify the relationship between RBFs and the BF in TLBFs, and to explain the results using biomechanical experiments and micro-computed tomography (micro-CT). Study Design A comprehensive research involving clinical radiology, micro-CT, and biomechanical experiments on cadaveric spines was carried out. Patient Sample A total of 162 consecutive patients diagnosed with TLBF with RBFs, drawn from 256 patients who had reported accidents or injuries to their thoracolumbar spine, comprised the patient sample. Outcome Measures Dimensions and location of the RBFs in relation to the BF were the outcome measures. Materials and Methods Computed tomography reconstruction imaging was used to measure the dimensions and location of RBFs in 162 patients (length, height, width of RBF and vertebral body). Furthermore, micro-CT scans were obtained of 10 cadaveric spines. Each vertebral body was divided into three layers (superior, middle, and inferior), and each layer was divided further into nine regions (R1–R9). Microarchitecture parameters were calculated from micro-CT scans, including bone volume fraction (BV/TV), connectivity (Conn.D), trabecular number (Tb.N), trabecular thickness (Tb.Th), and bone mineral density (BMD). Differences were analyzed between regions and layers. Burst fractures were simulated on cadaveric spines to explore the fracture line location and test the relationship between RBFs and BF. Results Retropulsed bone fragment width was usually one-third of the width of the vertebral body, whereas RBF length and height were approximately half of the corresponding vertebral body dimensions. Measures of trabecular bone quality were generally lowest in those central and superior regions of the vertebral body which are adjacent to the BF and which are most affected by burst fracture. In simulated TLBFs, the fracture line went across the vertex or upper surface of the BF. Conclusions The most vulnerable regions in the vertebral body lie within or just superior to the BF. The central MR2 region in particular is at risk of fracture and RBF formation.