Quantifying how altered lacunar morphology and perilacunar tissue properties influence local mechanical environment of osteocyte lacunae using finite element modeling.

Previous studies have demonstrated that osteocyte lacunar morphology and perilacunar bone tissue properties undergo alterations due to physiological and pathological processes such as aging, lactation, diseases, and treatments. However, the influence of these alterations on the apparent mechanical properties of the bone and the local mechanical environment of osteocyte lacunae has not been evaluated in detail. The goal of this study is to quantify the influence of osteocyte lacunar morphology and perilacunar tissue properties on local mechanical environment around lacunae and the apparent mechanical properties of the bone using three-dimensional FE models of lacunae networks with varying lacunar morphology and perilacunar properties based on previously reported experimental data. To attain this goal, a parametric study using models with different lacunar/perilacunar properties, including lacunar density (Lc.D), orientation (Lc.Φ), volume (Lc.V), and equancy (Lc.Eq), as well as perilacunar modulus (Pl.E), and size (Pl.S) was carried out. In addition, a specific case study using models derived from aged and young bone specimens was performed. Our results showed that the highly strained tissue around lacunae increased linearly with increasing Lc.D and Lc.V, reduced exponentially with decreasing angle of major axis of lacunae from the loading direction and with increasing Pl.E, and increased exponentially with increasing Pl.S. The change in apparent elastic modulus with modifications in lacunar morphology was very small whereas the change in perilacunar modulus had a more substantial influence on the apparent elastic modulus. Lacunar strain amplification was reduced by increasing Lc.Φ, and Pl.E and increased with increasing Lc.V within the range of 1.5 and 2.3. No significant difference was seen in the apparent elastic modulus of models derived from young and aged bone models. However, young bone showed substantially larger amount of highly strained tissue around lacunae compared to the aged bone. This difference was amplified when the perilacunar tissue property modifications were incorporated in the models. In summary, the results indicate that modifications in the osteocyte lacunar morphology and perilacunar tissue properties can significantly alter local tissue deformation around lacunae which may impact osteocyte mechanosensitivity.