TABLE 3.

Definitions and descriptions of bone morphometric data.

Abbreviation	Variable	Description	Standard unit
TV	Total volume	Volume of the entire region of interest	mm3
BV	Bone volume	Volume of the region segmented as bone	mm3
BS	Bone surface area	Surface of the region segmented as bone	mm2
BV/TV	Bone volume fraction	Ratio of the segmented bone volume to the total volume of the region of interest	%
BS/TV	Bone surface density	Ratio of the segmented bone surface to the total volume of the region of interest	mm2/mm3
BS/BV	Specific bone surface	Ratio of the segmented bone surface to the segmented bone volume	mm2/mm3
Conn.D	Connectivity density	A measure of the degree of connectivity of trabeculae normalized by TV	1/mm3
SMI	Structure model index	An indicator of the structure of trabeculae; SMI will be 0 for parallel plates and 3 for cylindrical rods	-
Tb.N	Trabecular number	Measure of the average number of trabeculae per unit length	1/mm
Tb.Th	Trabecular thickness	Mean thickness of trabeculae, assessed using direct 3D methods	mm
Tb.Sp	Trabecular separation	Mean distance between trabeculae, assessed using direct 3D methods	mm
Tb.Th.SD	Standard deviation of trabecular thickness	Measure of the homogeneity of trabecular thickness, assessed using direct 3D methods	mm
Tb.Sp.SD	Standard deviation of trabecular separation	Measure of the homogeneity of trabecular separation, assessed using direct 3D methods	mm
DA	Degree of anisotropy	1 = isotropic, >1 = anisotropic by definition; DA = length of longest divided by shortest mean intercept length vector	–
MIL	Mean intercept length	Measurements of structural anisotropy	–

The variables highlighted in bold are the minimal set of variables that should be reported when describing trabecular bone morphology.