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

Background 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 6 groups according to different defatting treatments, which were high pressure washing for 10 seconds (10S group), 20 seconds (20S group), 30 seconds (30S group), gradient alcohol immersion (Alcohol group), acetone immersion (Acetone group), and non-defatted (Fresh group). The appearance of 6 groups was observed, comparing the appearance difference between defatted bone and fresh bone. 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. No difference in residual lipid content among the three groups under high pressure washing (1.45 ± 0.16%, 1.40 ± 0.13%, 1.46 ± 0.11%, respectively) ( p = 0.828). No difference in residual lipid content among the 10S, alcohol, and acetone groups (1.45 ± 0.16%, 1.28 ± 0.07%, 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. No difference in residual lipid content among the three groups under high pressure washing (4.53 ± 0.23ug/ml, 4.61±0.18ug/ml, 4.66 ± 0.25ug/ml, respectively) ( p = 0.645). No difference in residual lipid content among the 10S, alcohol, and acetone groups (4.53 ± 0.23ug/ml, 4.29 ± 0.24ug/ml, 4.27±0.29ug/ml, respectively) ( p = 0.247). The maximum stress of the bone decreased significantly with the increase of the washing time (9.95 ± 0.31Mpa, 9.07 ± 0.45Mpa, 8.17 ± 0.35Mpa, respectively) ( p = 0.003). The elastic modulus of the bone decreased significantly with the increase of the washing time (116.40 ± 3.54Mpa, 106.10 ± 5.29Mpa, 95.63 ± 4.08Mpa, 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 ± 0.67Mpa, 9.95 ± 0.31Mpa, 10.11 ± 0.07Mpa, 10.09 ± 0.39Mpa) ( 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 ± 4.94Mpa, 116.40 ± 3.54Mpa, 118.27 ± 0.85Mpa, 118.10 ± 4.52Mpa) ( p = 0.737). Conclusion The results of this experiment indicate that the defatting efficiency was satisfactory at a time of 10 seconds under high pressure washing. High pressure washing and gradient alcohol were similar to conventional acetone solvent extraction defatting.