A biomaterial´s perspective viewed from a specific design: the hip total prosthesis

The total hip implant, characteristic design of a functional articulation, has suffered extensive modifications since the first arthroplasty implanted by John Charnley, at 1950, using a cement bone paste of methilmetaacrilate (PMMA). Today, the state-of-the-art of such a design includes a series of biomaterials in different presentations, in order to obtain the maximum fiability. These biomaterials typically employs metallic alloys such as Ti 6Al 4V, stainless steel ASTM F138 or cobalt-chromium for the areas in which it requires a maximum mechanical strength and toughness, ceramic materials when a maximum abrasion resistance and chemical inertness is required (the ceramic head is made in toughened zirconia or doped alumina), in conjunction with materials with a high load capacity but a very low friction coefficient (such as UHMWPE). In order to ensure good adhesion of the implant to cortical bone, hydroxiapatite (in the non cemented prothesis) and PMMA (in the cemented ones) are commonly used. This review shows the typical mechanical and chemical properties, the relevant processing parameters and general characteristics of such biomaterials.