The most abundant cell in bone, osteocytes form an interconnected system upon which the regulation of healthy bone relies. Although the complete nature of the role of osteocytes has yet to be defined, they are generally accepted to play a part in the sensing of load and the initiation of damage repair. A previous study conducted by our group identified variation of up to 30% in osteocyte lacunar density and morphological parameters between regions of a single cross-section of human femoral shaft; that study, however, was limited to a single individual. The aim of the current study was to determine whether this pattern consistently occurs in healthy young male femora. Anterior, posterior, medial and lateral blocks were prepared from the proximal femoral shaft of seven males and synchrotron radiation micro-CT imaged. Average lacunar densities (AE SD) from the anterior, posterior, medial and lateral regions were 23 394 AE 1705, 30 180 AE 4860, 35 946 AE 5990 and 29 678 AE 6081 lacunae per mm 3 of bone tissue, respectively. These values were significantly different between the anterior and both the medial and posterior regions (P < 0.05). The density of the combined anterior and posterior regions was also significantly lower (P = 0.006) than the density of the combined medial and lateral regions. Although no difference was found in predominant orientation, shape differences were found; with the combined anterior-posterior regions having lacunae that were significantly more elongated and less flat than the combined medial-lateral values (P < 0.001). As expected, in this larger study, there was a dramatic difference in lacunar density between the medial and anterior region (up to~54%). The study clearly demonstrates that the high variation seen in osteocyte lacunar density as well as other lacunar parameters, noted in a number of biomechanical, age and pathology studies, are well within the range of normal variation; however, the reasons for and consequences of this variation remain unclear. Lacunar parameters including abundance and shape are being increasingly incorporated into computational modeling of bone biology and this paper represents a more comprehensive description of normal healthy lacunae.

We previously reported considerable intra‐element variation in osteocyte lacunar properties, with density differences up to 30% across a cross‐section of the male (20 yrs) femoral cortex related to the biomechanical axes. The purpose of this research was to determine whether this pattern of variation occurs in a larger sample. Anterior (A), posterior (P), medial (M) and lateral (L) blocks (2×2 mm) were prepared from the proximal femoral shaft of 7 healthy males aged 20–34 and synchrotron micro‐CT imaged. Average lacunar density (± sd) from the APML regions were 22,961 ± 1991, 28,264 ± 4186, 32,082 ± 7731 and 30,525 ± 1977 per mm3 of bone, respectively. Consistent with the pattern observed in the previous study, density was significantly different between the A and the L region (p<0.05). The density of the combined A and P regions was also lower (p=0.006) than that of the combined M and L regions. The differences in density were mirrored by shape differences; with the combined AP region having more elongate (p=0.004) and flattened (p=0.001) lacunae, than those of the ML region. The consistent appearance of this pattern of variation in a larger sample suggests considerable normal variation occurs in the lacunar properties of healthy young males. The underlying functional significance of the observed differences likely relates to localized variations in loading conditions as the pattern corresponds well with mechanical axes.Grant Funding Source: Saskatchewan Health Research Fund