## 1 Introduction and General Background
The study demonstrates a potential reduction in stress shielding by 70% and bone mass loss by 60%, suggesting a viable alternative to the generic solid implant. The study presented by [PERSON] et al. [11] evaluates mechanical behavior under idealized and physiological loading conditions to compare the femoral fracture risk classifications with metastatic bone disease using different finite element simulation approaches, demonstrating that the incorporation of physiological muscle forces significantly affects local deformation. The strategy based on topological optimization in hip prostheses allows a reduction in stress shielding, an increase in the strength-to-weight ratio and an improvement in dynamic behavior, which leads to greater implant durability due to a reduction in aseptic loosening [12]. Optimization algorithms allow the best bone-implant stability to be determined [13]. In the study [PERSON] et al. [14], a martensitic TiNi biomaterial with a low modulus and mechanical behavior mimicking human bones is studied. The bioinspired structure exhibits both strength and ductility. Additionally, it is shown that post-processing heat treatments alter the microstructure, resulting in a hierarchically reinforced multiscale behavior, offering one of the highest specific strengths (around 70 kN m/kg) among porous biomaterials. [PERSON] et al. [15] analyzed the criticalities in the contact between the femoral head and the stem neck, showing that in proximal contact, the stress levels can exceed 500 MPa in certain areas of the prosthesis. [PERSON] et al. [16] studied the changes in stress distribution in the femur after total hip replacement by providing simulated in vivo loading and boundary conditions. The loading and boundary conditions were generated using the musculoskeletal modelling software 'AnyBody'. The results showed considerable variations in the stress distribution pattern in the femur before and after total hip replacement, with the metallic implant taking major loads and transferring very little load to the femur. [PERSON] et al. [17] investigated the stress-strain and force displacement at the bone-implant interface using the finite element analysis of implant models. This study demonstrated that the maximum principal stress generated in the solid hip stem, both with and without the femoral bone, remains below the safe limit, exhibiting good mechanical properties and strength. [PERSON] et al. [18] showed that a musculoskeletal multibody simulation framework was capable of virtually characterizing the knee joint dynamics for different TKR designs. [PERSON] et al. [19] proposed a parallel optimization method to study the topological structure of a type A femoral stem. [PERSON] et al. [20] compared a rational inner scaffold and the topology optimization design of an implant by considering the clinical design requirements, patient customization, weight reduction, and mechanical stability. [PERSON] et al. [21] provided a comprehensive overview of the modelling procedures for predicting the aseptic loosening risk, focusing on cementless femoral stems. A femur fixed with different osteosynthesis plates was simulated using the finite element technique and a statistical analysis of a region of interest placed in the femur diapphysis showed that the biomechanical effect of using the dual plate system was smaller in the osteotomy region than at the femur head [22]. Implant stress, bone atrophy and loosening are related to the use of a material with a Young's modulus much higher than that of cortical bone. This failure of a joint is known as stress shielding, and to mitigate this effect, the adequate design optimization of hip prostheses is required. Stress shielding occurs when the alloy inserted into the bone has a different elastic modulus, and therefore, the stresses are not uniformly distributed over the bone-implant interface; regions of stress concentration can then lead to inflammation in the bone, reducing its ability to remodel.