Due to an ageing population and increased sedentary work, many back problems exist. Severe cases have to be stiffened by surgical therapies with screw-rod systems. However, due to the complex biomechanics of the spine, the screws implanted in the vertebrae often loosen. Additive manufacturing and new modeling methods mean complex lattice structures can now be designed for medical implants. This would make it feasible for the bone not only to grow onto the implant but even into it, thus improving the stiffness of the screw-bone bond and preventing premature loosening. However, this design poses a challenge to the design process of medical implants, as for screws with cellular-designed functional areas, the loads during implantation must be calculated. Therefore, all the calculation procedures were carried out in this work to predict intraoperative loads. For this purpose, the maximum torsional moment and the torsional moment curve were determined analytically according to Wilkie et al. and using explicit dynamic screw-implantation simulations and compared with experimental data. The analytical model showed an apparent overestimation of the torsional moment compared to the numerical model and the experimentally determined data. Based on this, a simulation process for calculating intra-operative loads during implantation and the feedback of the simulation data into the modeling was described.