Properties related to the mechanical response of the PMMA cements used in present study.

E: Modulus of elasticity; Φ: rule of mixture constant. The cements were selected from a range of commercial products (Simplex P; Stryker Howmedica Osteonics, Mahwah, NJ. Vertecem; Synthes GmbH, Solothurn, Switzerland. Active OS; Kyphon, Sunnyvale, CA), where the liquid phase was modified in our lab, in some cases, for the purpose of getting a wide range of stiffness for the cements used in the study; A: modified Simplex P. B: modified Simplex P. C: Modified Vertecem. D: Vertecem. E: Simplex P. F: Active OS.