A system and method for treating bone abnormalities including vertebral compression fractures and the like. In one vertebroplasty method, a fill material is injected under high pressures into cancellous bone wherein the fill material includes a flowable bone cement component and an elastomeric polymer component that is carried therein. The elastomer component can further carry microscale or mesoscale reticulated elements. Under suitable injection pressures, the elastomeric component ultimately migrates within the flowable material to alter the apparent viscosity across the plume of fill material to accomplish multiple functions. For example, the differential in apparent viscosity across the fill material creates a broad load-distributing layer within cancellous bone for applying retraction forces to cortical bone endplates. The differential in apparent viscosity also transitions into a flow impermeable layer at the interface of cancellous bone and the flowable material to prevent extravasion of the flowable bone cement component.