Assessment of the Defatting Efficacy of Mechanical and Chemical Treatment for Allograft Cancellous Bone and Its Effects on Biomechanics Properties of Bone

Objective To assess the defatting efficacy of high pressure washing and gradient alcohol and biomechanical properties of defatted bone. Methods Fresh cancellous bone was obtained from the femoral condyle and divided into six groups according to different defatting treatments, which were: high pressure washing for 10 s (10S group), 20 s (20S group), and 30 s (30S group), gradient alcohol immersion (Alcohol group), acetone immersion (Acetone group), and non-defatted (Fresh group). The appearance of six groups was observed, and the appearance of defatted bone and fresh bone was compared. The residual lipid content and infrared spectrum were used to compare the efficacy of defatting, the DNA content was used to compare the cell content after defatting, and the maximum stress and elastic modulus were used to compare the effects of defatting treatment on biomechanical properties. Results The fresh bone was yellow and the pores contained a lot of fat. The defatted bone was white and the porous network was clear. There was no difference in residual lipid content among the three groups with high pressure washing (1.45% ± 0.16%, 1.40% ± 0.13%, and 1.46% ± 0.11%, respectively) (P = 0.828). There was no difference in residual lipid content among the 10S, alcohol, and acetone groups (1.45% ± 0.16%, 1.28% ± 0.07%, and 1.13% ± 0.22%, respectively) (P = 0.125). Infrared spectra showed that the fat content of the five defatting groups was significantly lower than that of the fresh group. There was no difference in residual lipid content among the three groups with high pressure washing (4.53 ± 0.23 ug/mL, 4.61 ± 0.18 ug/mL, and 4.66 ± 0.25 ug/mL, respectively) (P = 0.645). There was no difference in residual lipid content among the 10S, alcohol, and acetone groups (4.53 ± 0.23 ug/mL, 4.29 ± 0.24 ug/mL, and 4.27 ± 0.29 ug/mL, respectively) (P = 0.247). The maximum stress of the bone decreased significantly with the increase of the washing time (9.95 ± 0.31 Mpa, 9.07 ± 0.45 Mpa, and 8.17 ± 0.35 Mpa, respectively) (P = 0.003). The elastic modulus of the bone decreased significantly with the increase of the washing time (116.40 ± 3.54 Mpa, 106.10 ± 5.29 Mpa, and 95.63 ± 4.08 Mpa, respectively) (P = 0.003). There was no statistical difference in the maximum stress between the fresh group, the 10S group, the alcohol group, and the acetone group (10.09 ± 0.67 Mpa, 9.95 ± 0.31 Mpa, 10.11 ± 0.07 Mpa, and 10.09 ± 0.39 Mpa, respectively) (P = 0.963). There was no statistical difference in the maximum stress between the fresh group, the 10S group, the alcohol group and the acetone group (119.93 ± 4.94 Mpa, 116.40 ± 3.54 Mpa, 118.27 ± 0.85 Mpa, 118.10 ± 4.52 Mpa, respectively) (P = 0.737). Conclusion The defatting efficiency was satisfactory at a time of 10 s under high pressure washing. In terms of defatting efficiency and its effect on biomechanical properties of bone, high pressure washing and gradient alcohol were similar to conventional acetone solvent extraction defatting.