Metals foams for biomedical applications: Processing and mechanical properties

Abstract

Optimized structures found in nature can be sometimes imitated in engineering structures. The recent interest in functionally graded metallic materials makes bone structures interesting because bones are naturally functionally graded1. The cellular structure of foam metals (Fig.1) is very similar to that of the cancellous bone; therefore, these metals can be considered as potential candidates for future implant applications if porosity level, size and shape, strength and biocompatibility aspects satisfy the design specifications of implants. Foam metals based on biocompatible metallic materials (e.g. Ti and Ti-6A1-4V) are expected to provide better interaction with bone. This is mainly due to higher degree of bone growth into porous surfaces and higher degree of body fluid transport through three-dimensional interconnected array of pores2 (open cell foam), leading to better interlocking between implant and bone and hence reducing or avoiding the well-known implant losening. Furthermore, the elastic modulus of foam metals can be easily tailored with porosity level to match that of natural bone, leading to a better performance by avoiding the high degree of elastic mismatch which currently exists between conventional solid metallic implants and bone.