Estimation of bone matrix apparent stiffness variation caused by osteocytelacunar size and density

The role of osteocyte lacunar size and density on the apparent stiffness of bone matrix was predicted using a mechanical model from the literature, La cunar size and lacunar density for different bones from different sender an d age groups were used to predict the range of matrix apparent stiffness va lues for human cortical and cancellous tissue. The results suggest that bon e matrix apparent stiffness depends on tissue type (cortical versus cancell ous), age, and gender, the magnitudes of the effects being significant but small in all cases. Males had a higher predicted matrix apparent stiffness than females for vertebral cancellous bone (p<10(-7)) and the difference in creased with age (p = 0.0007). In contrast, matrix apparent stiffness was n ot different between males and females for femoral cortical bone and increa sed with age in both males (p<0.0001) and females (p <0.0364). Osteocyte la cunar density and size may cause significant gender and age-related variati ons in bone matrix apparent stiffness. The magnitude of variations in matri x apparent stiffness was small within the physiological range of lacunar si ze and density for healthy bone, whereas the variations cart be profound in certain pathological cases. It was proposed that the mechanical effects of osteocyte density be uncoupled from their biological effects by controllin g lacunar size in normal bone.