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THE CHARACTERIZATION OF PARTICULATE DEBRIS OBTAINED FROM FAILED
ORTHOPEDIC IMPLANTS:
Chapter 10
10Discussion
of Results
Debris Generation and The Role of Hydrogen
Many of the titanium particles observed are very thin and exhibit
jagged and brittle fracture-like surfaces. The particles observed
for these specimens are more aptly termed lens-shaped since their
thickness was on the order of tenths of microns when viewed edge
on. The fact that these particles exhibit a white fringe at their
outer extremes indicates that the edges of these particles are
less than 500Å thick. This extremely thin nature of debris
tends to implicate hydrogen in the generation process. These lenticular
plates are probably hydrogen stabilized b
phase that existed as the thin b component
of Widmänstatten a + b regions
of the stem-mesh interface where the acicular a
+ b phase is present.
On the other extreme, the particle shown in Figure 40 exhibits
very ductile behavior: wear marks are visible on its surface and
surface cracking is not evident. Thus, hydrogen does not appear
to play a major role in the debris generation within the joints
of some patients. Clearly, variation in the chemistry of the patient's
synovial environment and loading conditions are very important
factors in terms of how much and what kind of titanium debris
is generated.
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