A fractographic analysis of in vivo poly(methyl methacrylate) bone cement failure mechanisms

Cementing with poly(methyl methacrylate) (PMMA) is a common means of fixing total hip prostheses. Bone cement fails mechanically, and subsequent loosening frequently requires correction via revision surgery. An initial step in optimizing bone cement properties is to establish which properties are critical to the material's in vivo performance. The objectives were to discern the critical in vivo failure mechanisms of bone cement. Fracture surfaces of bone cement specimens that failed in vivo were compared with fatigue and rapid fracture surfaces created in vitro. In vivo fracture processes of bone cement were positively identified and explained by the elucidation of PMMA fracture micromechanisms. The ex vivo fracture surfaces are remarkably similar to in vitro fatigue fracture surfaces. The fractographic data document that the primary in vivo failure mechanism of bone cement is fatigue, and the fatigue cracks grow by developing a microcraze shower damage zone. Agglomerates of BaSO4 particles can be implicated in some bone cement failures, large flaws or voids in vivo can lead to a rapid, unstable fracture, pores in the PMMA mass have a clear influence on a propagating crack, and wear of the fracture surfaces occurs, and may produce PMMA debris, exacerbating bone destruction.