Table 1.

(Unshaded) Properties of regularly oriented 600, 900, and 1200 μm porous titanium bases: Apparent density (n = 11–12); true density (i.e., density of titanium or tantalum, n = 11–12); metal volume fraction (n = 11–12); porosity (n = 11–12), pore side length (n = 6 pores per 4 bases per top and side), strut thickness (n = 6 pores per 4 bases per top and side); and pore area fraction (n = 4–6 per top and side). (Shaded) Properties of additional bases: randomly oriented 600 μm porous titanium (n = 11–12 for apparent density, true density, metal volume fraction, and porosity; n = 4 per top and side for pore area fraction) and porous tantalum (n = 6 for apparent density, true density, metal volume fraction, and porosity; n = 4 per top and side for pore area fraction). Data are expressed as mean ± standard deviation. Letters indicate significantly different groups (p ≤ 0.001). The final column summarizes obtained the linear regression value and R₂ obtained from testing acellular samples on bases or on an impermeable platen (see Fig. 4). Slopes for 600-random and tantalum groups stem from n = 15 to n = 9 points, respectively. Each linear regression slope is significant (p < 0.001). Slopes for the 1200 μm and tantalum groups are each significantly different from all other groups. The slope for the 900 μm group is not significantly different from that of either 600 μm group, however the 600 regular and random groups have significantly different slopes (p < 0.05).

Group	Unit Cell Pore Size (μm)	Apparent Density (g/cm3)	True Density (g/cm3)	Metal Volume Fraction	Porosity	Pore Side Length (mm)	Pore Cross-sectional Area (mm2)	Strut Thickness (mm)	Pore Area Fraction	Eosteochondral/Echondral Slope
600-Regular	600	1.59±0.03A	4.34±0.12A	0.37±0.01A	0.63±0.01A	0.25±0.03A	0.65±0.01A	0.18±0.02	0.26±0.03A	0.87, R2=.93
900-Regular	900	0.78±0.02B	4.28±0.21A	0.18±0.01B	0.82±0.01B	0.44±0.03B	0.20±0.02B	0.18±0.02	0.42±0.04B	0.78, R2=0.98
1200-Regular	1200	0.45±0.02c	4.47±0.49A	0.10±0.01c	0.90±0.01c	0.64±0.04c	0.41±0.05c	0.18±0.01	0.54±0.03c	0.54, R2=.91
600-Random	600	1.56±0.03A	4.30±0.13A	0.36±0.01A	0.64±0.01A	N/A	N/A	N/A	0.26±0.02A	0.73, R2=0.96
Tantalum	N/A	3.96±0.18D	14.7±1.6B	0.27±0.03D	0.73±0.03D	N/A	N/A	N/A	0.29±0.06A	0.85, R2=0.96