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

Purposes: To discuss whether radiologic parameters are closely related to posterior ligamentous complex (PLC) injury identified by magnetic resonance imaging (MRI).
Methods: 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.
Results: Supraspinous ligament (SSL) rupture versus intact was not only associated with the occurrence of AEIEA <70°, LK >25° and BFOFV, but also with increased AED (9.89 ± 3.12 mm and 9.34 ± 3.36 mm, P = 0.034), RA (9.52 ± 3.93° versus 7.91 ± 3.99°, P = 0.042), and LK (23.98 ± 5.88° versus 15.55 ± 5.28°, P = 0.021). The indications for interspinous ligament (ISL) injury included AEIEA <75°, AEIEA <70° (P = 0.004 and P < 0.001, respectively), increased AED (P = 0.010), LK >25° (P = 0.024), AVH (P < 0.001), and BFOFV (P < 0.001). Multivariate logistic regression analysis revealed that AEIEA <70° 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 >25° were also related to either ISL rupture (P = 0.035 and 0.001, respectively) or SSL rupture (P = 0.014 and 0.008, respectively).
Conclusion: 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 <70°, BFOFV, LK >25°, and increased AED, are correlated with ISL or SSL rupture, while RA, CA, SI, A/P ratio, and AVH ratio are not.