## 1 Introduction  
Total hip arthroplasty involves replacing the acetabular surface and the femoral head with prosthetic implants, known as total hip replacement (THR), to recover the joint functionality after suffering mechanical damage or a degenerative disease [1; 2; 3; 4]. Prosthesis selection for THR depends on the type of fracture/pathology, the surgeon's preference, and the availability and the cost of the prostheses in the market [5; 6; 7]. There is also an increasing demand for THR in younger people, so the aim is to reach longevity of 20 to 25 years after being implanted, with an expected average lifespan of 15 years for the used stems [7; 8].  
The prosthesis used in THR has particular components; the main ones are the acetabular head and the stem. These components are usually made of metal alloys, despite that they are prone to loose particles, the CoCr alloys, stainless steel alloys (SS 316L), and titanium alloys (TI6 Al4V) being the most frequently used [9; 10; 11; 2]. Those materials have high elasticity moduli compared to the elasticity modulus of the human bone (12-30 GPa) [2; 3; 8; 12; 13; 14; 15; 16; 17; 18; 19; 20; 21], and when implanted, represent a critical factor in the stress and strain distribution. Along with the materials, improvement in the stem design is essential. A balance between the distribution of the stress and strain along the implant's length is crucial in keeping the functionality and securing the implant's bonding to the bone structure.  
During stem design, a multi-objective analysis was carried out to investigate the different types of failures that can occur in a hip implant. Applications of these studies using the multi-objective analysis can be found in fracture analysis [22; 23], stress shielding [24; 25; 26], micro-movements [2; 27], and also in studies aiming to improve the performance of a hip implant by modifying its profile or cross-sectional area [2; 9; 28]. The variables typically studied in this analysis are the principal stresses, von Mises equivalent stress, total deformation, and von Mises equivalent strain. Multi-objective analysis has been used to develop and improve stem geometries, using different loads [2; 9; 28; 29; 30; 31; 32; 33; 34; 35; 36; 37]. Then, FEM is the tool used to analyze different variables (as reported previously [38; 39; 40]), and it is regularly used to analyze the implants, allowing the evaluation of critical factors. Those analyses mainly focus on stress and strain by combining different profiles and cross-sectional areas [2; 9; 10; 28].  
We aimed to develop a new implant (hybrid implant) based on assessing sixteen implants with different profiles and cross-sections by comparing their advantages and disadvantages using the same base for the analysis. Multi-objective analysis was used to evaluate different implants. First, the cross-sectional area with the best performance was selected. Then, a new profile design was generated by analyzing various points on the medial and lateral region of the implants. Finally, combining the section area with the new profile design, a hybrid implant was developed to demonstrate that the new design has better mechanical performance than the previous implants, resulting in lower stresses and strain at the points analyzed.