INTRODUCTION: Although surgery for high-energy traumatic thoracolumbar spine injuries can be performed minimally invasively using percutaneous pedicle screws (PPS), cases of significant corrective loss are often experienced. In recent years, there have been scattered reports of intervertebral disc injuries being a risk factor for corrective loss, however, there are no reports regarding the optimal range of fixation. The purpose of this study was to classify the results of PPS fixation for thoracolumbar spine injuries according to the degree of disc injury and to investigate the optimal range of fixation.
METHODS: 56 cases and 66 vertebrae (40 males and 16 females, mean age 56.8 ± 16.5 years) who underwent PPS fixation for thoracolumbar spine injury between October 2018 and September 2021, with AO classification Type B2 or less, fusion extent of 2 above 2 below and observable for at least 2 years were included. Intervertebral disc injuries on the cephalocaudal side of the fractured vertebra were evaluated using Sander's classification and divided into two groups, Grade 3 injury: infraction of the disk into vertebral body or annular tears (G3 group) and Grade 0-2: minor injury or no injury (G0-2 group). Each group was compared in terms of age, gender, AO classification, LSC (Load Sharing Classification), range of fixation, wedge shaped deformation angle of fractured vertebra and local kyphosis angle at the time of injury, immediately after surgery, and at the last observation, and their correction loss. The G3 group was further divided into two groups with fixed ranges of 1 above 1 below (group S) and 2 above 2 below (group L), and the same analysis was performed.
RESULTS: The G0-2 group had 39 vertebrae and the G3 group had 27 vertebrae. There were no differences in age or gender, but the G3 group had more AO classification Type B, larger LSC, and longer fixation range. There were significant differences in wedge shaped deformation angle (G0-2 group: 7.4 degrees, G3 group: 12.1 degrees) and local kyphosis angle (G0-2 group: 6.5 degrees, G3 group: 10.8 degrees) at the time of injury, but not immediately after surgery and correction loss. However, in the analysis of the G3 group alone, corrective loss was significantly greater in the S group for both wedge shaped deformation angle (S group: 11.9 degrees, L group: 2.8 degrees) and local kyphosis angle (S group: 11.9 degrees, L group: 3.2 degrees).
DISCUSSION: In the analysis of the G3 group alone, 1 above 1 below fixation resulted in significant corrective loss, and therefore, in thoracolumbar spine injuries, intervertebral disc injuries should also be evaluated to determine the extent of fixation.