Correlations between posterior longitudinal ligament status and size of bone fragment in thoracolumbar burst fractures.

This study aim to determine the correlation between the size of bone fragment and injury of posterior longitudinal ligament (PLL). In this study retrospectively analyze medical chart of patients with thoracolumbar burst fractures from June 2010 to December 2012. Patients were divided into two groups (Intact group and Disrupted group) according to the result of MRI assessing status of PLL. All the fractures were classified according to the Arbeit Fuer Osteoosynthese (AO) classification system. Neurological status was classified according to American Spinal Injury Association (ASIA). Mimics measured the height and width of bone fragment (HBF and WBF), transverse canal diameter (TCD) and calculate the height of posterior wall of the injury vertebrae, ratio of height of bone fragment occupying height of posterior wall of vertebrae body (RHBF) and ratio of width of bone fragment occupying transverse canal diameter (RWBF). The results indicated that 52 patients were included in the study. There are 31 patients with intact PLL and 21 patients with disrupted PLL. There was significant difference on the HBF (t = -3.646, P = 0.001), WBF (t = -3.615, P = 0.001), RHBF (t = -4.124, P = 0.000) and RWBF (t = -3.305, P = 0.002) between the intact group and injury group. There was a significant correlation between injury of PLL and ASIA grade (OR = 7.851, P = 0.005), and AO classification (OR = 6.401, P = 0.011), and RHBF (OR = 6.455, P = 0.011), and HBF (OR = 5.208, P = 0.022). In conclusion, the results of this study indicate that AO classification, ASIA grade, HBF and RHBF could act as the predictors of injury of PLL.