Compressive fatigue properties of commercially available standard and low-modulus acrylic bone cements intended for vertebroplasty.

Abstract

Vertebroplasty (VP) is a minimally invasive surgical procedure commonly used to relieve severe back pain associated with vertebral compression fractures. The poly(methyl methacrylate) bone cement used during this procedure is however presumed to facilitate the occurrence of additional fractures next to the treated vertebrae. A reason for this is believed to be the difference in stiffness between the bone cement and the surrounding trabecular bone. The use of bone cements with lower mechanical properties could therefore reduce the risk of complications post-surgery. While intensive research has been performed on the quasi-static mechanical properties of these cements, there is no data on their long-term mechanical properties. In the present study, the in vitro compressive fatigue performance as well as quasi-static mechanical properties of two commercially available acrylic bone cements - a low-modulus cement (Resilience®) and a standard cement (F20) from the same manufacturer - were determined. The quasi-static mechanical properties of the low-modulus and standard cements after 24 h of setting were in the range of other vertebroplastic cements (σ = 70-75 MPa; E= 1600-1900 MPa). F20 displayed similar mechanical properties over time in 37 °C phosphate buffered saline solution, while the mechanical properties of the Resilience® cement decreased gradually due to an increased porosity in the polymeric matrix. The standard cement exhibited a fatigue limit of approx. 47 MPa, whereas the low-modulus cement showed a fatigue limit of approx. 31 MPa. In summary, the low-modulus bone cement had a lower fatigue limit than the standard cement, as expected. However, this fatigue limit is still substantially higher than the stresses experienced by vertebral trabecular bone.