A Comparative Biomechanical Analysis of the Impact of Different Configurations of Pedicle-Screw-Based Fixation in Thoracolumbar Compression Fracture

Abstract

The aim of this experimental study was to analyze the impact of applying different configurations of the transpedicular fixation system on selected mechanical parameters of the thoracolumbar spine under conditions of its instability (after simulated fracture). Five study groups were tested: physiological, with compression fracture of the vertebra, with two-segment fixation, with three-segment fixation, and with four-segment fixation. Each of the analyzed study groups was subjected to axial compression, flexion, and extension. Based on the conducted experimental tests, the mechanical parameters, i.e., stiffness coefficient and dissipation energy, were determined for all groups under consideration. The stiffness value of two-segment fixation is significantly lower than the physiological value (during flexion and extension). The use of long-segment fixation considered in two configurations (three- and four-segment fixation) may result in excessive stiffness of the system due to the high stiffness values achieved (approx. 25–30% higher than the physiological values in the case of compression and on average 60% higher in the case of flexion). The use of long-segment fixator design shows better results than short-segment fixation. Considering both biomechanical and clinical aspects, three-segment fixation seems to be a compromise solution as it saves the patient from more extensive stiffening of the spinal motion segments.

Biomechanical Analysis of the Impact of Transverse Connectors of Pedicle-Screw-Based Fixation on Thoracolumbar Compression Fracture

“…It was observed that a PFS design with a short-segment configuration does not offer sufficient stability, particularly during flexion-extension movements. Such a PFS design may lack the necessary rigidity, resulting in an excessive range of motion at the thoracolumbar junction [1]. In line with these findings, McDonnell et al [2] and Bolesta et al [3] reported immediate stabilization of the affected segment when implementing LSF, along with achieving higher stiffness values compared to those seen in physiological systems.…”

“…The experimental tests were conducted in a manner similar to the test procedure presented in a previous study that analyzed the impact of the length of fixated segments on the damaged thoracolumbar spine [1]. Loading was performed using an MTS 858 Mini Bionix testing machine (MTS Systems, Eden Prairie, MN, USA), and the specimens were subjected to forces simulating typical activities of daily life.…”

“…Despite the commonly used techniques for surgical treatment of vertebral compression fractures in the thoracic or lumbar spine, the selection of the appropriate type of fixation is still open to debate. Prior experimental research conducted by the authors has demonstrated that employing long-segment fixation (LSF) in the design of a posterior spinal fixation system (PFS) yields superior outcomes compared to short-segment fixation (SSF) [1]. It was observed that a PFS design with a short-segment configuration does not offer sufficient stability, particularly during flexion-extension movements.…”

Biomechanical characteristics of 2 different posterior fixation methods of bilateral pedicle screws: A finite element analysis

“…[58] The pedicle screw fracture observed in the clinic is mostly concentrated near the lowest nail tail cap. [59] Therefore, to reduce the risk of internal fixation failure, we can try to take a variety of methods: on the one hand, fusion is necessary. After fusion, the internal fixation stress can be reduced, and the possibility of fatigue fracture caused by long-term nonfusion fretting can also be reduced to a certain extent.…”

Impact of short segment fixation on Spinopelvic Sagittal Alignment in Thoracolumbar Fracture Cases

“…Surgical management of thoracolumbar burst fractures is to correct kyphosis and provide adequate biomechanical stability for early mobilization while reducing surgical invasiveness and associated complications [6]. Biomechanically, having two or more xation levels above and below the fracture is a better option for thoracolumbar burst fractures, providing greater mechanical stiffness and reducing the likelihood of segment collapse and implant failure [7]. However, in addition to the interruption of spinal motion segments, long-stage immobilization was associated with more severe surgical invasiveness [8].…”