Load adaptation through bone remodeling: a mechanobiological model coupled with the finite element method.

This work proposes a novel tissue-scale mechanobiological model of bone remodeling to study bone's adaptation to distinct loading conditions. The devised algorithm describes the mechanosensitivity of bone and its impact on bone cells' functioning through distinct signaling factors. In this study, remodeling is mechanically ruled by variations of the strain energy density (SED) of bone, which is determined by performing a linear elastostatic analysis combined with the finite element method. Depending on the SED levels and on a set of biological signaling factors ([Formula: see text] parameters), osteoclasts and osteoblasts can be mechanically triggered. To reproduce this phenomenon, this work proposes a new set of [Formula: see text] parameters. The combined response of osteoclasts and osteoblasts will then affect bone's apparent density, which is correlated with other mechanical properties of bone, through a phenomenological law. Thus, this novel model proposes a constant interplay between the mechanical and biological components of the process. The spatiotemporal simulation used to validate this new approach is a benchmark example composed by two distinct phases: (1) pre-orientation and (2) load adaptation. On both of them, bone is able to adapt its morphology according to the loading condition, achieving the required trabecular distribution to withstand the applied loads. Moreover, the equilibrium morphology reflects the orientation of the load. These preliminary results support the new approach proposed in this study.

A mathematical biomechanical model for bone remodeling integrated with a radial point interpolating meshless method.

Bone remodeling is a highly complex process, in which bone cells interact and regulate bone's apparent density as a response to several external and internal stimuli. In this work, this process is numerically described using a novel 2D biomechanical model. Some of the new features in this model are (i) the mathematical parameters used to determine bone's apparent density and cellular density; (ii) an automatic boundary recognition step to spatially control bone remodeling and (iii) an approach to mimic the mechanical transduction to osteoclasts and osteoblasts. Moreover, this model is combined with a meshless approach - the Radial Point Interpolation Method (RPIM). The use of RPIM is an asset for this application, especially in the construction of the boundary maps. This work studies bone's adaptation to a certain loading regime through bone resorption. The signaling pathways of bone cells are dependent on the level of strain energy density (SED) in bone. So, when SED changes, bone cells' functioning is affected, causing also changes on bone's apparent density. With this model, bone is able to achieve an equilibrium state, optimizing its structure to withstand the applied loads. Results suggest that this model has the potential to provide high quality solutions while being a simpler alternative to more complex bone remodeling models in the literature.

Radial scar of the breast: Is it possible to avoid surgery?

INTRODUCTION: Breast radial scar (RS) management remains controversial. The need for surgical excision is supported by the concern of an associated high-grade lesion missed in the biopsy. The aim of this study was to assess histologic upgrade rate after a percutaneous biopsy, to determine if vacuum assisted biopsy prevents the need for subsequent RS surgical resection and to evaluate the upgrade risk factors. PATIENTS AND METHODS: This was a uni-institutional retrospective study of consecutive patients with RS histologically diagnosed from January 2010 to December 2015. RESULTS: A total of 113 cases of RS were diagnosed. We verify that there was a histologic upgrade in 22 (19.5%) cases. The upgrade risk factors were the type of biopsy performed, the presence of atypia, the presence of calcifications and the number of fragments obtained in the biopsy (p < 0.05). The biopsy type was vacuum assisted in 25 (22.1%). The upgrade rate in the vacuum assisted biopsy group was 4.0%, whereas in the standard core needle biopsy group was 23,9% (p = 0.041). DISCUSSION AND CONCLUSION: We demonstrated that the risk of upgrade after a RS diagnosis depends on the type of biopsy performed, the presence of atypia, the presence of calcifications and the number of fragments obtained. When a standard core biopsy is performed the risk of upgrade and malignancy is not negligible, and surgery is indicated. When the biopsy is vacuum assisted, the risk of upgrade and malignancy is significantly decreased and so the indication for excisional biopsy seems not to be so imperative.