## 4 Discussion  
The performed analysis of the impact of using transverse connectors in PFS designs made it possible to assess the mechanical parameters of the thoracolumbar spine under conditions of its instability (in the case of a compression fracture of a single vertebra). The obtained results can be used in clinical studies associated with the introduction of novel implant solutions for the stabilization of thoracolumbar spine injuries and the feasibility of minimally invasive surgery as an alternative to open surgery. The tests carried out showed that the introduction of transverse elements in a PFS design results in a slight increase in stiffness compared to fixation without connectors. A similar relationship was observed in experimental research by [PERSON] et al. [36], who assessed the biomechanical properties (range of motion and stability) of LSF used in the thoracic spine (Th4-Th10). The researchers showed that transverse connectors do not increase stability during flexion, extension, or lateral bending. However, they observed that both one transverse connector (regardless of location) and two transverse connectors improve stability during axial rotation of such a long fixated spinal segment. Also, [PERSON] et al. [37] showed that the use of transverse connectors (one or two) in the cervical spine should be reserved only for unstable injuries involving the posterior column of the spine and laminectomy procedures because they increase the stiffness of the fixated cervical spine (C2-T1), especially during axial rotation. Numerous in vitro experimental studies indicate that the insertion of implants changes the system of load transmission through the spinal structures. The literature shows that lumbar spine mobility increases above and below the fixated area, especially in the segments directly adjacent to the implantation region [38; 39; 40]. Similar relationships were observed by [PERSON] et al. [41], who conducted in vitro experiments assessing the mobility of segments adjacent to the damaged thoracolumbar spine, within which transpecicular fixation was inserted. Their biomechanical and radiological tests showed that in the segments adjacent to the fixated segments, there is increased mobility as well as increased pressure withinthe IVDs. However, it is uncertain whether the increase in these parameters can lead to degenerative changes in the structures of adjacent segments. [PERSON] et al. [41] also showed that during the transmission of loads through the implant-stabilized lumbar spine (Th12-L2), the mobility of the Th11-Th12 segment, located above the fixated region, increases significantly. The authors of the present study observed that the introduction of transverse connectors in a PFS design results in a slight increase in mobility and pressure in the IVD (statistically insignificant differences) compared to fixation without connectors. This result indicates that transverse connectors in such configurations do not bring about a visible change in the overall fixation of the damaged spine, as is often assumed. In addition, it was noted that the choice of LSF may result in excessive stiffness of the considered spinal region below the fracture site, as evidenced by the limited mobility of the last three segments in the analyzed spinal region compared to the physiological system. It was also shown that the use of LSF significantly increases the pressure in intervertebral disks above the fixation site, which may lead to the development of degenerative changes in these elements. It should be remembered that excessive stiffness of the evaluated spinal area may consequently lead to increased mobility of the segments immediately adjacent to the implantation region. This elevated mobility may subsequently increase the curvature of the thoracic kyphosis, potentially leading to issues like pedicle screw breakage or loosening [38,40]. It, therefore, appears that LSF with the use of transverse connectors may be justified primarily in the treatment of spinal deformities, such as scoliosis.