In vitro testing of Al(2)O(3)-Nb composite for femoral head applications in total hip arthroplasty

Alumina (Al(2)O(3)) bearings in total hip arthroplasty lead to low wear rates, but catastrophic failure of Al(2)O(3) femoral heads, while rare, remains a concern. In the present work, a composite of Al(2)O(3) and niobium (Nb) was tested in vitro for potential use as an alternative femoral head material in vivo. Dense composite laminates of Al(2)O(3) and Nb were fabricated by hot pressing, and their microstructure and mechanical properties were evaluated. The flexural strength of Al(2)O(3)-Nb laminates in four-point loading was 720+/-40MPa, compared with a value of 460+/-110MPa for Al(2)O(3). Scanning electron microscopy and X-ray diffraction showed a well-bonded interface between the Al(2)O(3) and Nb without measurable formation of an interfacial reaction phase. The interfacial shear strength between Al(2)O(3) and Nb, measured by a double-notched specimen test, was 290+/-15MPa. The feasibility of fabricating prototype femoral heads (32mm in diameter), consisting of an Al(2)O(3) surface layer (2-3mm thick) and a Nb core, by hot pressing was shown. The composite femoral head combined the low wear of an Al(2)O(3) articulating surface with the safety of a ductile metal femoral head.