Short-segment stabilization techniques for burst fractures of the thoracolumbar junction: a finite element study under lateral flexion

Introduction: Burst fractures of the thoracolumbar junction (TLJ, T10–L2) are common spinal injuries associated with a high risk of neurological complications. Transpedicular fixation is one of the most effective treatment methods; however, the optimal choice of fixation configuration remains unresolved. This study aims to analyze the stress-strain state of various short-segment transpedicular fixation configurations for Th12 vertebra burst fractures under lateral flexion loading. Materials and methods: A finite element model of the Th9–L5 spinal segment with a simulated Th12 burst fracture was created. Four fixation configurations were considered: M1 – short screws in Th11 and L1 (without intermediate screws), M2 – long screws in Th11 and L1 (without intermediate screws), M3 – short screws in Th11 and L1 with intermediate screws in Th12, and M4 – long screws in Th11 and L1 with intermediate screws in Th12. The models were analyzed using CosmosM software, assessing equivalent von Mises stress at 18 control points. Loads simulated physiological lateral trunk bending. Results: Models with long screws (M2, M4) demonstrated lower maximum stresses in connecting rods (315.5–321.0 MPa) compared to short screws (324.8–324.9 MPa). The inclusion of intermediate screws (M3, M4) significantly reduced stress in the fractured Th12 vertebra (by up to 28%), in adjacent vertebral endplates (by 18–25%), and at screw entry points into vertebral arches (up to 28%). The lowest fixation screw stresses were observed in the model with long and intermediate screws (up to 38% lower compared to the baseline model M1). However, intermediate screws minimally influenced stresses in the connecting rods (up to 1.2%). Conclusions: The optimal short-segment transpedicular fixation configuration is the use of long screws in adjacent vertebrae combined with intermediate fixation in the fractured vertebra (M4). This approach provides optimal load distribution, reduces the risk of construct failure, and preserves mobility of adjacent segments. Long screws improve overall system stiffness, while intermediate screws effectively stabilize the damaged segment and significantly unload critical areas of the construct and adjacent anatomical structures.