Compositions for use in treating and repairing orthopedic defects are provided. The compositions are especially useful for performing percutaneous vertebroplasty, percutaneous kyphoplasty and other procedures. When cured, the compositions are relatively solid but compressible, and prior to curing are viscous liquids with a low enough viscosity to fill voids in cavities such as voids within fractured vertebrae. Optionally, the properties of a composition according to the invention can be adjusted taking into account the hardness and density of the orthopedic structure to be repaired. Also disclosed are devices and methods for using the compositions, and a kit containing components for forming and utilizing the composition.