## 5 Conclusions  
In conclusion, the present study provides a comprehensive analysis of the main FE models predicting the AL failure risk induced by the lack of long-term stability. The main modelling assumptions, including bone and implant geometry, materials, boundary conditions, and the bone-implant interface, were summarised and presented. The limitations of various modelling assumptions and their impact on the simulation results were also discussed. Technical differences and trends in methodology evolution have been observed. Specifically, the modelling of long-term stability in femoral stems has progressed from macroscopic direct contact models to more advanced indirect models integrating interface layers. Microscale or hybrid models, focusing on localised regions at the interface, have grown in complexity, incorporating detailed surface porous structures and sophisticated tissue differentiation algorithms. This progress has been made possible thanks to the growth of available computational resources.  
Although several important improvements in computational modelling have been made, it is evident that further advancements are needed. In particular, more rigorous step-by-step clinical validation for osseointegration models would be crucial for translating computational methodologies into clinical practice. Failure criteria used to determine loosening of the implant should be clearly defined, and effort should be made to identify the appropriate limit of tolerable conditions (e.g., maximum micromotion at the interface) considering implant, patient, and environmental factors, as also suggested by [84].  
Extra attention should also be paid to the terminology used to present FE studies on AL. Terms such as \"bone ingrowth\", \"bone remodelling\" and \"bone adaptation\" are often used interchangeably to define the osseointegration process since they all include the bone formation description.  
Conceptualisation, C.C. and M.V.; methodology, X.S., C.C. and M.V.; formal analysis, X.S. and C.C.; investigation, X.S. and C.C.; resources, X.S.; data curation, X.S. and C.C.; writing--original draft preparation, X.S. and C.C.; writing--review and editing, C.C. and M.V.; visualisation, X.S. and C.C.; supervision, C.C. and M.V.; project administration, M.V.; funding acquisition, M.V. All authors have read and agreed to the published version of the manuscript.  
This study was partially founded by the European Commission through the H2020 project \"In Silico World: Lowering barriers to ubiquitous adoption of In Silico Trials\" (topic SC1-DTH-06-2020, grant ID 101016503) and by the National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.1, Call for tender No. 104 published on 2 February 2022 by the Italian Ministry of University and Research (MUR), funded by the European Union--NextGenerationEU--Project Title \"IST4 HR--In Silico Trials for Hip Replacements\"--CUP J53D23002330006- Grant Assignment Decree No. 742 adopted on 30 May 2023 by the Italian Ministry of Ministry of University and Research (MUR).  
Not applicable.  
This research was supported by the Italian Ministry of Health--Ricerca Corrente and by the China Scholarship Council PhD fellowship (CSC No. 202206020079). The authors would like to thank [PERSON] for the illustrations.  
The authors declare no conflicts of interest.