Bioceramics are not bioinert

Are there arrows in the innovation quiver?

In an era of laboratory-grown human replacement cells and programmable therapeutic genes, it is astonishing that prosthetic joints have not even remotely considered incorporation of similar advanced approaches for enhanced healing. Since its inception in the 1960s, the modern artificial hip joint has solely been seen as a bionic mechanical object (see Fig. 1). Instead of innovation, the past several decades have seen scientific stagnation. Manufacturers have released variations of alumina-based bioceramics (some of different colors, cf., see Fig. 1); but all possessing essentially the same properties. Far from a holistic engineering approach, which could have defined biomaterial interactions with the surrounding biological environment, mechanistic paradigms have prevailed based on strength, friction, and sliding wear. Accordingly, new products have essentially been mainly ‘me-too’ devices. The unfortunate consequence is that key perspectives from the disciplines of physical chemistry and biology are missing. Perhaps this mechanistically centered methodology may have been excusable in an earlier era due to a lack of advanced biological engineering technologies. However, given the availability and quality of scientific tools today, it appears that the short-sighted approach by prosthetic joint manufacturers is predominately based on revenue preservation, governmental regulations, and the fear of recalls or litigation. However, the current paradigm is slowly giving way to a new concept of the ‘healing’ joint. Within this paradigm, biomaterials are selected not only for their mechanical or friction characteristics, but also for their ability to provide beneficial remedies within the human milieu. In this commentary, scientific criteria are identified which hopefully will trigger advanced research into artificial joints to take advantage of new potential ‘medicinal’ materials.