## 1 Introduction
Conventional methods for predicting the AL failure risk and assessing the safety of the implant devices preoperatively include in vitro experiments, animal experiments, and clinical trials. However, each approach has its limitations. One notable weakness of in vitro experiments is their inability to fully replicate the conditions of cells or tissues in a living organism [18]. Animal experiments can maintain biological conditions, but they may not be equivalent to clinical conditions in human patients [19]. Clinical trials are time consuming, costly, and limited in this long-term failure risk investigation. One promising alternative to traditional methods is represented by the use of computer modelling and simulation. In particular, Finite Element (FE) modelling, has been demonstrated to be a powerful numerical tool that allows for generating information supporting the device's safety and/or efficacy. It holds promise for assessing whether subtle modifications in orthopaedic devices can enhance existing designs while accounting for patient and surgical variability [20; 21; 22]. A virtual cohort of simulated patients can be used to optimise implant design, including material selection, geometry, and surface features (In Silico Trials) [23; 24]. Also, with patient-specific models, surgeons can create a virtual replica of a patient's anatomy (Digital Twins), personalise the planning, and optimise the surgical outcome [25]. A large body of literature has used FE modelling to investigate the biomechanical interaction between bone and cementless femoral implants in the context of AL failure. This literature covers a broad range of topics and can be categorised into subsets based on the various aspects related to AL that have been specifically analysed. Some researchers simulated the complex interactions between the implant and surrounding bone by quantifying parameters such as stress distributions, micromotion, ossee-integrated area, and bone remodelling [26; 27; 28; 29; 30; 31; 32]. Most of the studies focused on mitigating the risks of AL from various perspectives. For instance, some have evaluated the mechanical performance of stems with different parameters, such as geometric features and materials [27; 28; 30; 31; 32; 33; 34; 35; 36; 37; 38; 39]. Others have examined the effect of bone quality [40; 41], surgical variability, and patients lifestyles [29; 32; 34; 41; 42] on the risk of failure. While some articles have attempted to review the literature on numerical simulation of orthopaedic devices [21; 43], including in some cases analyses on post-operative bone growth and long-term bone adaptation [44], to the best of the authors' knowledge, none provide a comprehensive overview of the use of FE simulations to specifically investigate AL failure risk in cementless femoral stems. The aim of this paper is to address this gap by providing a comprehensive overview of the main modelling procedures for predicting AL risk in cementless femoral stems due to a lack of long-term stability. The review will assess papers based on several criteria, including bone and implant geometry modelling, loading patterns considered, contact models, and output quantities analysed. For most of these criteria, the main limitations and effects of the different modelling assumptions on the simulation results will also be discussed.