In vitro testing of Al2O3–Nb composite for femoral head applications in total hip arthroplasty

Alumina (Al2O3) bearings in total hip arthroplasty lead to low wear rates, but catastrophic failure of Al2O3 femoral heads, while rare, remains a concern. In the present work, a composite of Al2O3 and niobium (Nb) was tested in vitro for potential use as an alternative femoral head material in vivo. Dense composite laminates of Al2O3 and Nb were fabricated by hot pressing, and their microstructure and mechanical properties were evaluated. The flexural strength of Al2O3–Nb laminates in four-point loading was 720 ± 40 MPa, compared with a value of 460 ± 110 MPa for Al2O3. Scanning electron microscopy and X-ray diffraction showed a well-bonded interface between the Al2O3 and Nb without measurable formation of an interfacial reaction phase. The interfacial shear strength between Al2O3 and Nb, measured by a double-notched specimen test, was 290 ± 15 MPa. The feasibility of fabricating prototype femoral heads (32 mm in diameter), consisting of an Al2O3 surface layer (2–3 mm thick) and a Nb core, by hot pressing was shown. The composite femoral head combined the low wear of an Al2O3 articulating surface with the safety of a ductile metal femoral head.