Effects of Structure Characteristics of Osteocyte Lacunae on Squeeze Damage Resistance of Osteons.

Scanning electron-microscopic observations show that there are many osteocyte lacunae between the circumferential lamellae, which are nonuniform in distribution. The lacunae are elliptical, and their major axes are along the circumferential direction of the osteon, which can be denoted as circumferential elliptical lacunae (CE). The observations also show that there are many circumferential microcracks in the osteons, and these microcracks are initiated from 2 endpoints of the major CE axis. To investigate the effects of the structural characteristics of osteocyte lacunae on the crack-propagated route and squeeze damage resistance of oste-ons, 3 different osteon models - CE, radially elliptical lacunae (RE), and circular lacunae (CL) - were created. The microcrack initiation and propagation of the 3 different osteon models were calculated and simulated based on progressive damage analysis. The results show that the crack-propagated route of the CE osteons is along the circumferential direction of the osteon, which is consistent with experimental observations, while those of the RE and CL are in the radial direction of the osteon. CE around the osteon in the bone is the result of long-term natural evolution, which is an important factor for bone to have strong fracture toughness.