Erratum to “Relationships of loading history and structural and material characteristics of bone: Development of the mule deer calcaneus,” DOI: 10.1002/jmor.10167

Abstract

The authors of the above article would like to apologize for an error and an omission contained within the text of the original article. This omission/error relates to the definition and quantification of osteocyte lacuna population density, and is twofold in nature: 1. The Materials and Methods section of the original article did not elaborate on methods employed for the quantification of osteocyte lacuna population density. These methods should have appeared under the subheading “Microstructure” on page 285. The methods, as applicable to our study, are as follows: The population density of osteocyte lacunae (N.Lac/B.Ar) was manually quantified in each 100× backscattered electron image. The N.Lac/B.Ar was defined as the total number of osteocyte lacunae (N.Lac) divided by the total area of bone (B.Ar; area of bone per image area minus nonlacunar porosity). The N.Lac/B.Ar is meant to represent the concentration of osteocytes, although no differentiation could be made between empty lacunae and those containing viable osteocytes at the time of animal death/tissue harvesting. 2. There is some confusion in our study as to the rigorous definition of osteocyte lacuna population density, and what the numbers we provided actually represent. The methods reported above in #1 are accurate, and reflect the original intent of our study—to report the number of lacunae per bone area. A subset of data provided in the original, however, did not reflect this intent. Data for the young fawns, as reported in the original study, showed a relatively lower N.Lac/Ar compared to older animals. In this case, the N.Lac/Ar was erroneously calculated as total number of osteocyte lacunae (N.Lac) divided by the total image area (Ar), without the subtraction of nonlacunar porosity. In all other age classifications, the above methods (i.e., calculation of N.Lac/B.Ar) were employed. Thus, in young fawns the data represent “N.Lac/Ar,” and reflect the number of osteocyte lacunae per total area, rather than per bone area. Therefore, for definitive clarification of the original submission, all instances of the abbreviation “N.Lac/Ar” should be revised to the more accurate abbreviation “N.Lac/B.Ar”. Furthermore, this clarification requires some adjustments to figures and tables containing N.Lac/B.Ar data, including some descriptive statistics and correlations. Revised tables and figures are provided herewith (revised Tables 4, 5a,b, revised Figs. 3f, 9b). In young fawns there are no significant N.Lac/B.Ar differences. In older fawns there are significantly more osteocyte lacunae in the caudal cortex compared to the cranial cortex. In subadults and adults, the cranial cortex has significantly more lacunae than the other cortices (*P < 0.01). There were no significant differences in N.Lac/B.Ar between medial and lateral cortices in any age group. The adult bones contained significantly fewer osteocyte lacunae when compared with all other groups (P < 0.001). The section on page 288, entitled Osteocyte lacuna population density (N.Lac/Ar) should read as follows: Osteocyte lacuna population density (N.Lac/B.Ar) (Table 4; Fig. 3f). There are significantly more osteocyte lacunae per bone area in younger and older fawns when compared to adults and subadults (P < 0.001). In adult bones, the cranial cortex has the greatest N.Lac/B.Ar. The cranial cortex contains significantly more osteocyte lacunae than the caudal cortex in subadults and adults (P < 0.05), but is similar to the caudal cortex in the young fawn group and lower than the caudal cortex in older fawns (P < 0.05). This difference is further illustrated in revised Figure 9b. There were no significant differences in N.Lac/B.Ar between medial and lateral cortices in any age group. The adult bones contained significantly fewer osteocyte lacunae when compared with all other groups (P < 0.001). The revised figure legend for Figure 3f should also read as follows: In young fawns there are no significant N.Lac/B.Ar differences. In older fawns there are significantly more osteocyte lacunae in the caudal cortex compared to the cranial cortex. In subadults and adults, the cranial cortex has significantly more lacunae than the other cortices (P < 0.01). Despite the confusion in the original study, there is some utility in the calculation of N.Lac/Ar, as was originally erroneously reported for the young fawns. Vashishth et al. (2002) used calculations of osteocyte lacunar number per tissue area (similar to N.Lac/Ar) to show correlations between osteocyte number and bone volume fraction in compact and cancellous bone. The corrected values for N.Lac/B.Ar show lacunar density to differ by ∼32% when comparing values for the young fawns vs. adults (679.9/mm2 for young fawns vs. 465.6/mm2 for adults). These values reflect trends recently reported in the literature, which describe osteocyte lacuna density to be ∼40–100% greater in woven bone than in lamellar bone (Hernandez et al.,2004). This is important, since the histology of the young fawns in the present study resembled woven bone morphology.