The radiologic assessment of posterior ligamentous complex injury in patients with thoracolumbar fracture

To discuss whether radiologic parameters are closely related to posterior ligamentous complex (PLC) injury identified by magnetic resonance imaging (MRI). One hundred and five thoracolumbar fracture (T11-L2) patients were retrospectively analyzed in the study. The patients were divided into different groups by the status of the PLC on MRI: intact, incompletely ruptured and ruptured. The radiographic parameters included the anterior edge-inferior endplate angle (AEIEA), the anterior edge displacement (AED), the Cobb angle (CA), the region angle (RA), the sagittal index (SI), local kyphosis (LK), the anterior/posterior vertebral height ratio (A/P ratio), the anterior vertebral height ratio (AVH ratio), and bony fragment in front of the fractured vertebra (BFOFV). T test, Pearson's Chi-square and multivariate logistic regression were calculated for the variables. Supraspinous ligament (SSL) rupture versus intact was not only associated with the occurrence of AEIEA < 70A degrees, LK > 25A degrees and BFOFV, but also with increased AED (9.89 +/- 3.12 mm and 9.34 +/- 3.36 mm, P = 0.034), RA (9.52 +/- 3.93A degrees versus 7.91 +/- 3.99A degrees, P = 0.042), and LK (23.98 +/- 5.88A degrees versus 15.55 +/- 5.28A degrees, P = 0.021). The indications for interspinous ligament (ISL) injury included AEIEA < 75A degrees, AEIEA < 70A degrees (P = 0.004 and P < 0.001, respectively), increased AED (P = 0.010), LK > 25A degrees (P = 0.024), AVH (P < 0.001), and BFOFV (P < 0.001). Multivariate logistic regression analysis revealed that AEIEA < 70A degrees and BFOFV were high risk factors for SSL rupture [standard partial regression coefficients (betas) were 0.439 and 0.408, P = 0.003 and 0.001, respectively] and ISL rupture (betas were 0.548 and 0.494, P = 0.028 and 0.001, respectively). Increased AED and LK > 25A degrees were also related to either ISL rupture (P = 0.035 and 0.001, respectively) or SSL rupture (P = 0.014 and 0.008, respectively). Our data may prove useful in a preliminary assessment of the PLC integrity based on plain radiographic imaging. We show that radiologic indications, such as AEIEA < 70A degrees, BFOFV, LK > 25A degrees, and increased AED, are correlated with ISL or SSL rupture, while RA, CA, SI, A/P ratio, and AVH ratio are not.