Biomechanical effects of processing bulk allograft bone with negative-pressure washing

The best method for processing allograft bone to prevent disease transmission without compromising its biomechanical function is not yet determined. We evaluated the biomechanical effects of processing bulk allograft bone segments with negative-pressure washing. Specimens were prepared from matched pairs of adult cadaveric femurs. The experimental femur underwent routine processing, followed by negative-pressure washing, whereas its matched control underwent routine processing only. Each specimen was tested to failure, and maximal stress values were determined. No differences were found in yield stress comparisons between groups for the following specimens and tests: compression of machined femoral heads, screw push-out testing in cortical bone, and 4-point bending of cortical beams. Compression testing of diaphyseal ring struts provided varied results. Negative-pressure-washed half-ring strut grafts were statistically stronger (9.6%) than their matched controls (P = 0.018). Negative-pressure-washed full-ring strut grafts were statistically less strong (-12.2%) than their control counterparts (P = 0.003). We studied 5 different allograft types (designed with clinically relevant geometries) subjected to 3 modes of testing (representative of loading in typical clinical situations). Our data show that processing of large, essentially intact allograft bone segments with negative-pressure washing had little, if any, biomechanical effect relative to frozen controls.