P3F-4 Ultrasonic Consequence of Different Common Sterilization Treatments Applied to Human Bone Before Transplantation

The aim of this study was to evaluate the mechanical consequences of different common sterilisation treatments applied to human bone before transplantation. Ultrasound velocity measurements at low (LF) and high frequency (HF) were used as surrogate markers of structural (LF) and material (HF) elastic properties and failure stress. Cubic cancellous bone specimens (N=192) were obtained from human femoral heads originated from 14 donors. The elastic properties were assessed by measuring the sound velocity along three orthogonal directions at 60 kHz and 2.25 MHz before and after treatment. The samples were divided in four groups that were exposed to different treatments: Group 1: Powerful protein denaturants and gamma irradiation at 25 KGrays (TBFreg procedure). Group 2: Physical treatment with humid heat at 125 degC for 20 minutes (Toulouse bone tissue bank). Group 3: Chemical solvents for complete bone marrow cleaning and gamma irradiation of 25 KGrays (Tutogenreg, Germany). Group 4: Treatment with CO
₂
in supercritical phase for bone cleaning followed by chemical treatment. Samples were dried before undergoing 25 KGrays of gamma irradiation (Biobankreg, France). Group 5: Identical to group 4, but without irradiation. The utilisation of powerful protein denaturants (group 1, decrease in speed of sound of 8 and 10%) leads to a structural alteration of cancellous bone, probably modifying type I collagen and causing an important alteration in bone graft mechanical resistance. Prudence therefore must be taken with regards to graft choice in orthopaedic reconstructions requiring a strong graft mechanical resistance. The use of chemical solvents cleaning in group 3 causes intermediate but significant variation (2.5 to 5%). A physical treatment like heat in group 2 causes a measurable but weak alteration of 0.5 to 2%. The supercritical CO
₂
in group 4 showed also limited effects on the sound velocity, at the limit of least detectable change by the protocol used. In addition, no detectable effect was observed after irradiation of dried bone when included in the final step of group 4 protocol. Measurements of sound velocity were found to be useful for the comparison of different sterilisation treatment effects on the mechanical resistance of cancellous bone