The novel transsacral fusion system AxiALIF allows stabilization of the lumbosacral junction. The system consists of a screw with two different diameters. With additional facet screws or internal fixation devices 360° fusion can be achieved. The effects of different parameters such as length, diameter combination and material of the transsacral screw, type of additional fixation and stiffness of the bone are unknown. In a probabilistic finite element analysis, the input parameters were randomly varied. The rotational angles and the axial forces in the various implants were calculated for four different load scenarios. In a subsequent sensitivity study the influences of single input parameters on the variance of the results were calculated. A transsacral screw significantly reduces the motion in the treated segment, except for axial rotation. An additional fixation has a strong effect on the variance of rotation angles. The other parameters usually explain less than 10% of the variance. The novel lumbosacral fusion system allows good stabilization of the segment, especially when additional fixation via facet screws or fixators is performed.