Another diagnostic tool in thoracolumbar posterior ligament complex injury: interspinous distance ratio

The increased interspinous distance ratio (ISDR) at the fracture site in plain X-ray is useful as an indicator of injury of the posterior ligament complex in thoracolumbar fractures.

154 patients of thoracolumbar junctional fracture (T12, L1, L2) were subjects for this study. The sensitivity, specificity, accuracy of MRI was measured by comparing the surgery findings for the two analysis groups: one in which indeterminate cases were included in the intact group and another in which the indeterminate cases were included in the ruptured group. Sensitivity, specificity, accuracy of ISDR (measured in lateral decubitus X-ray) were measured after dividing patients into 3 groups (110, 120, 130 % increased).

MRI's sensitivity, specificity and accuracy were 70.8, 100, and 80.5 %, respectively, when the indeterminate was assumed to have intact PLC. After assuming the indeterminate to have ruptured PLC, sensitivity, specificity and accuracy were 99.1, 52.4, and 85.7 %, respectively. In 53 cases with indeterminate MRI reading, sensitivity, specificity and accuracy were 81.2, 76.2, and 79.2 % %, respectively.

In this study, in cases where it was difficult to make a diagnosis of the injury in the posterior ligament complex, based on the interspinous distance ratio (ISDR) of 120 % measured in plain X-ray in a lateral decubitus position, the sensitivity was 81.3 %, the specificity was 76.2 %, and the accuracy was 79.2 %. Therefore, measuring the ISDR will be helpful in determining whether surgical treatment is required in patients with thoracolumbar injury.