Iranian Journal of Orthopedic Surgery

Abstract Abstract The healing of bone fractures is a multifaceted process that ultimately leads to the creation of new bone tissue. A significant factor influencing this process is the mechanical environment present at the site of healing. Computational models that employ mechanobiological algorithms are capable of simulating the impact of mechanical stimuli on the differentiation of stem cells into various tissue types during the bone healing process. This paper provides a review of the domain of computational mechanobiology, particularly concerning bone healing, and evaluates the existing mechanobiological models. Furthermore, it discusses recent developments and the current challenges faced in this area. Recently, there has been a growing interest in integrating mechanobiological algorithms with a more comprehensive depiction of cellular and molecular events. A primary challenge in this domain is the validation of these models through their comparison with experimental data. Such models can enhance our understanding of the bone fracture healing process and improve the design of implants and treatment analyses. However, existing mechanobiological models are still in their early stages and require ongoing updates and refinements to keep pace with the continuous advancements in the field of stem cell mechanobiology.

Abstract Background: Most reports on the underlying problem of complete hip replacement are related to its loosening. Several important factors such as the implant features, the replacement process, the use and amount of bone cement, and the patient's lifestyle affect the loosening. The aim of this study was to provide an analysis of the dynamic stresses and strains at the interface between the bone and the implant in different phases of walking in order to determine and develop biomechanical parameters of loosening.

Methods: A two-dimensional model including femur and its artificial joint has been used in numerical simulation with ADINA software based on finite element method. There is a dynamic load applied to the joint head corresponding to the normal walking cycle of a person with 75 kg weight.

Results: The results show a difference between stress and strain in the medial and lateral edge of the bone-implant interface, which indicates a risk area for loosening. The amount of strain difference at the interface with about 1.6% and stress reaches about 5.7 MPa.

Conclusion: The greatest strain difference occurred in the lowest area of the implant stem, which indicates the possible occurrence of separation in implant loosening. This information can also be used in surgical strategies for hip replacement and is also important for optimal mechanical design of the implant.