Biomedical Engineering Reference
In-Depth Information
Table 6.1
Main characteristics of orthopaedic metallic implant materials
Advantages
Disadvantages
Primary uses
Stainless steels
Low cost;
High modulus
Temporary devices (plates,
availability of
screws) and hip stems
processing
Co-base alloys
Wear resistance;
High modulus;
Dentistry castings;
corrosion;
availability
hip and knee joints
resistance;
fatigue strength
Ti and Ti-base
Biocompatibility;
Wear resistance; Modular total hip replace-
alloys
corrosion; fatigue
low shear
ment (THR) (stems); dental
strength; low
strength
implants; maxillofacial and
modulus;
craniofacial implants;
low density
permanent devices (nails,
pacemaker cases);
fixation elements (screws,
staples)
Titanium alloys were developed in the 1950s for aerospace applications
but it was not until the 1960s they were used as surgical implant materials.
nowadays, about 2% of the total production of titanium tonnage is used for
biomedical applications. Their attractiveness is primarily based on an excellent
combination of corrosion resistance, biocompatibility, osseointegration and
biofuntionality. Their low wear resistance, however, is the limiting factor
for their application in articulating components.
The driving force in the development of new metallic biomaterials for
surgical implants is an ageing population that demands implants with both a
longer service life and greater reliability. The success of new designs depends
upon knowledge of the properties that determine the interactions with living
tissues, without the need for trial and error. nowadays it is accepted that
biocompatibility strongly depends on the interactions between the implant
surface and physiological environment which can be extremely hostile and
sensitive. Therefore, the physicochemical properties of the implant surface
are relevant. surface parameters that have been demonstrated to play an
important role for
in vitro
and
in vivo
biocompatibility are frequently
grouped in three categories: geometrical, chemical and electrical. Geometrical
properties (roughness, topography) are related to the surface finishing or to
surface modification techniques and, therefore, are out of the scope of this
chapter. electrical and chemical properties are related to properties of the
passive films developed on the surface that obviously are linked to chemical
composition of the bulk.
