Biomedical Engineering Reference
In-Depth Information
Fig. 5.2
Materials Properties Chart. E modulus (
left
) and fracture toughness (
right
)vs.yield
strength. (1) Al
2
O
3
,(2)ZrO
2
, (3) steels, (1) Ti alloys, (5) glasses, (6) PMMA, (7) nylons, (8)
HDPE, (9) LDPE, (10) polymer foams, (11) elastomers (more on the polymers 6-11 in Chap. 11).
Adapted from Ashby [61, 184]
Thus, scratch ceramics from the shopping list?
Ye s
for use in bending,
no
for example in compression. But read more about ceram-
ics in Chap. 9, because development does not stand still and a new generation of
ceramics is arriving. Applicability of materials from other classes in the materials
properties chart is either marginal like foams or subject of other chapters. Wood
might be another story. Present as a biomaterial in 3000 years Chinese orthopedics
and traumatology, it never disappeared completely from the scene: Ezerietis and
colleagues used Juniperus communis in fracture healing with considerable success
over a period of 55 years [185, 186].
For the time being however, metals still have a future!
5.2
Zirconium, a Newcomer?
Zirconium is not quite a newcomer. In a general paper on oxidized zirconium,
Hunter refers to the use of Zircaloy with promising results for orthopedic screws
and bone plates by at least one center in England in 1950 [187, 188]. The metal
was made unavailable soon after that year due to the priority given in those days to
nuclear power programs. When it became available again at the end of the 1950s,
the interest in zirconium vanished in favor of the less costly and clinically estab-
lished titanium alloys. The interest reappeared in the 1990s. For example, Smith &
Nephew filed a patent on the use of oxide nitride-coated zirconium prostheses in
1992 (US patent 5152794).
