Quantitative Raman Spectroscopy of Biomaterials for Arthroplastic Applications - Emerging Raman Applications and Techniques in Biomedical and Pharmaceutical Fields - page 410

Fig. 17.7. Photograph of an alumina femoral head in (a) , on which we have drawn
the surface stripe wear zone. In the center of the figure, a schematic draft is given of
the different degrees of wear observed on the femoral head surface. Maps of residual
stress collected on the sample surface by Raman piezo-spectroscopy are also given
for zones affected by different amounts of wear fatigue. In (b )and (c) , two scanning
electron micrographs are shown, which give the surface morphology of the femoral
head surface worn to grade 3 and grade 5 + wear

using scanning electron microscopy, which merely visualize the morphology of
the surface. On the other hand, Raman microprobe maps reveal the presence of
microscopic residual stresses that remain stored onto the material surface due
to severe impingement and microseparation promoted by the bulky implant
design. In other words, the micromechanics of wear can be traced back by an-
alyzing hyperspectral residual stress images collected by Raman microprobe
spectroscopy on the surface of joint retrievals. Raman analysis was performed
in a highly confocal probe configuration on a retrieved alumina femoral head,
which was donated from Professor Sedel's series in Paris (Ceraver-Osteal,
Roissy CDG, France). Although the confocal configuration was selected in
order to single out the residual stress field on the very surface of the material,
thus minimizing the influence of the sub-surface, the need to screen large ar-
eas necessarily imposed a limitation on the lateral resolution achievable by the
Raman probe (i.e., a 20 optical lens was selected). Such a lack in resolution

might reflect in the detection of a lower value of the absolute magnitude of
residual stress. At revision, the head, which was employed against an alumina
liner, has been marked for orientation. The implantation time in vivo was as

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