## 5 Conclusions  
The design requirements of a hip implant are challenging due to many variables that have to be considered, such as the biocompatibility of the materials, the geometry, the bone anatomy, and the patient age; these variables play an important role in the generation of stress and strain in the implant. Designing a new prosthesis by doing a geometry modification or using an optimal biomaterial can be a solution to reduce potential problems, such as aseptic loosening or a fracture of the implant.  
This work evaluated sixteen different hip implant configurations found in the literature under multi-objective analysis using a common standardized condition and considering the potential and daily activities performed by the patients. In conclusion, by comparing all the stems using the same criteria, the advantages and disadvantages between the stems can be evaluated. It was found that the use of softer profiles (with a longer radius on the lateral part of the implant) and rigid materials provided better distribution of the stresses and generated less deformation. However, the risk of micro-movements could increase due to the lack of edges that increase the contact area. If this problem needs to be reduced, a trapezoidal cross-sectional area is recommended.  
The new geometry was proposed using a multi-objective analysis, based on a trapezoidal cross-section, with a stress reduction in the proximal area and a strain decrease in the whole stem. The hybrid proposal presented a stress reduction of 9.6% compared with the reference stem (P2-T) in activity 4 using the titanium alloy (Ti6 Al4V) as material. In addition, using ASTM F2996-13 and ISO 7206-4:2010(E) standards, a stress reduction of 9.98% was obtained using the same material. This reduction was achieved by following the assessment conditions described in the work of [PERSON] et al. [28]. The results show both methods comply with the design requirements.  
Stress/strain reduction is a potential advantage for patients with osteoporosis. In terms of materials, SS316L showed the lowest strain results. However, the modulus of elasticity was still very high compared to cortical bone, which could cause various problems such as wear and micro-movement. In contrast, titanium is a better option in terms of stress. Although it is a more expensive option and its modulus of elasticity is lower than SS316L, it is still high compared to cortical bone.  
This leads researchers to continue searching for a material that performs an optimal function in the interaction of bone-implant and generates a better design depending on the morphological needs and health problems that the patient may present (such as osteoporosis or fractures) when performing the surgery.  
**Author Contributions:** Formal analysis, M.S. and L.G.; Methodology, I.S.; Project administration, E.D.; Validation, D.J.; Writing--review & editing, M.G. and A.O. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This research received no external funding.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** Not applicable.  
**Acknowledgments:** [PERSON] and [PERSON] thank the [PERSON], [PERSON], and [PERSON] The technical support of [PERSON], [PERSON], [PERSON], [PERSON], [PERSON], and [PERSON] is also acknowledged. [PERSON] thanks the scholarship 327470 from CONACyT.  
**Conflicts of Interest:** The authors declare no conflict of interest.