## 5 Conclusions  
In this research, a hip implant was designed in accordance with relevant standards to facilitate numerical simulation. The main goal was to optimize the design by applying lattice structures in three distinct variations to the middle stem area of the hip implant stem. The lattice configuration was implemented as a shell with multiple thicknesses, offering structural flexibility and mechanical efficiency. In order to evaluate the performance of the design variations, numerical compression tests were performed under the established standards for hip implant compression testing.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**1 mm Lattice**} & \multicolumn{2}{c}{**2 mm Lattice**} & \multicolumn{2}{c}{**3 mm Lattice**} \\ \hline \multirow{2}{*}{**Model**} & **Normal** & **Surrogate** & **Normal** & **Surrogate** & **Normal** & **Surrogate** \\  & **Model** & **Model** & **Model** & **Model** & **Model** & **Model** \\ \hline Time (s) & 1580 & 17 & 7363 & 20 & 9683 & 24 \\ \hline Maximum memory used (MB) & 1878 & 116 & 1924 & 124 & 2293 & 140 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Deviation in results between geometrically latticed model and the surrogate model.  
One good aspect of this research was the introduction of a surrogate model with properties identical to those of the geometrically latticed model. This substitute model helped simplify the complex geometry while preserving the necessary mechanical behavior. The simulation results revealed that the application of lattice structures led to a significant reduction in equivalent stress values, indicating an improvement in the implant's structural performance. Additionally, the computational time required for the simulation was greatly reduced, leading to considerable cost savings. This reduction in computation time, however, did not affect the accuracy of the results, which remained within an acceptable margin of error (within 5%).  
Another benefit to be noticed of using the substitute model was the reduction in RAM usage. Due to the simplification of the simulation process, the model was run efficiently even with a medium-performance computer, thus enhancing accessibility and practicality for research.  
For future research, it is planned to validate these numerical findings through laboratory experiments on 3D-printed hip implants. This experimental verification could confirm the reliability of the proposed design optimizations and support the practical implementation of lattice structures in hip implant manufacturing. In general, this study presents a promising approach to the optimization of hip implant design while reducing computational demands and maintaining high accuracy and performance standards.  
Conceptualization, T.M. and R.A.; methodology, T.M.; software, R.A.; validation, T.M. and R.A.; resources, R.A.; writing--original draft preparation, R.A. and T.M.; review and editing, T.M.; visualization, R.A.; supervision, T.M.; project administration, T.M.; funding acquisition, T.M. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the University of Debrecen Scientific Research Bridging Fund (DETKA) and the OMAA 117 ou9--Experimentelle und numerische Untersuchung massgeschneiderter, zel-lullarer Implantate, hergestellt mit AM-Technologie project.  
Not applicable.  
Data availability Statement: Data is unavailable due to privacy regarding future publication.  
The authors declare no conflicts of interest.