Comparison of failure characteristics of a range of cancellous bone-bone cement composites.

Over the past decade, orthopedic surgery has embraced an increase in the depth of cement penetration into the adjacent cancellous bone structure. The resultant interdigitation transforms this zone into a thick layer of continuous interpenetrating composite material. The failure behavior of the composite formed with a number of potential bone cements with different bonding ability was investigated. The cancellous bone-cement composites exhibit considerable resistance to crack extension, and in situ optical observation indicates that the contribution of the cancellous bone is analogous to that of a typical fiber bridging process. The critical stress intensity factor and the work of fracture have been used to quantify the failure characteristics of the cancellous bone-cement composites. The nature of the crack propagation through these cement-bone composites was also captured via optical microscopy, and scanning electron microscopic images were taken of the failure surfaces. The R-curve behavior, or crack extension characteristic, of the cancellous bone-cement composite was also determined. The interesting outcome is that the cancellous bone-PMMA (poly-methylmethacrylate) composite, despite the absence of chemical bonding with bone, required the highest energy to fracture. In addition, the dimensional stability of the cement has a great effect on the interface.