MATERIALS FOR ORTHOPEDIC APPLICATIONS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 84

3.6.3 Co-Cr-Mo, Ni or Ta-Based Alloys
In an interesting study, Plotz et al. 114 described the technique of cementless pros-
thesis using spongy metal surface. The shaft and metal cup of the prosthesis are
made of a Co-Cr-Mo alloy and are completely covered by spongy metal surface.
They summarized the results, after implanting this type of metal on 100 patients.
After one year, 82% of patients were pain-free with the prosthesis fi xed by bony
ingrowth, 8% were pain-free with the prosthesis fi xed by dense fi brous tissue, and
10% were not pain-free, but did not desire revision surgery. Ni and Ni-based
alloys are widely used in different medical treatments and devices. Also, it can be
present as a contaminant in fl uids for intravenous administration or released
from surgical implants and other medical devices.
Fell 115 described the risk of intravenous injection of human albumin solu-
tions contaminated with Ni causing Ni-sensitive subjects and patients to have
impaired renal function. This investigation showed that the concentration of Ni
in human albumin solutions, recently produced in two European countries (the
United Kingdom and Italy), is substantially reduced in comparison with previous
reports.
Tantalum is highly resistant to chemical attack and shows little adverse bio-
logical response. Metals coated with tantalum and tantalum itself does not
degrade in extraction media during exposure to body fl uid media. Tantalum has
been widely used in clinical applications for more than 50 years in the following
areas 116 :
a) radiographic marker for diagnostic purposes, due its high density,
b) material of choice for permanent implantation in bone,
c) vascular clips, with the particular advantage, that since tantalum, being
anti-ferromagnetic, is highly suited to MRI scanning,
d) for repair of cranial defects,
e ) fl exible stent to prevent arterial collapse,
f) stent to treat biliary and arteriovenous (haemodialyzer) fi stular stenosis,
g) for fracture repair and
h) for dental applications.
Aronson et al. 117 undertook a specifi c study of tantalum markers in radiogra-
phy with pin and spherical markers, being implanted into bony and soft tissues of
rabbits and children. No signifi cant macroscopic and microscopic reaction was
noted around the markers and those implanted into bone were fi rmly fi xed,
exhibiting close contact with adjacent bone lamellae.
In a review article, Semlitsch and Willert 118 reported various applications of
metals and metallic alloys in THR prosthesis. The ball head of THR can be made
either of Fe - 18Cr - 14Ni - 3Mo, Fe - 20Cr - 10Ni - 4Mn - 3Mo - Nb - N, or Co - 28Cr - 6Mo -
0.2C, Co - 28Cr - 6Mo - 0,08C, Ti - 6A1 - 7Nb/TiN, Ti - 6A1 - 7Nb/ODH, or Co - 28Cr -
6Mo-0.2C; whereas the cup can be made of UHMW-polyethylene, Al 2 O 3 , and