Wj. Maloney et al., ISOLATION AND CHARACTERIZATION OF WEAR PARTICLES GENERATED IN PATIENTS WHO HAVE HAD FAILURE OF A HIP-ARTHROPLASTY WITHOUT CEMENT, Journal of bone and joint surgery. American volume, 77(9), 1995, pp. 1301-1310
Wear particles from thirty-five membranes obtained during revision hip
-replacement operations were studied after digestion of the soft tissu
e with papain. The particles were isolated and were characterized with
use of light and scanning electron microscopic techniques, x-ray micr
oanalysis, and an automated particle analyzer. The mean size of the po
lyethylene particles was 0.5 micrometer, and the metal particles were
a mean of 0.7 micrometer, as determined with scanning electron microsc
opy. The automated particle analyzer revealed a mean particle diameter
of 0.63 micrometer (more than 90 per cent of all particles were less
than 0.95 micrometer) and a mean of 1.7 billion particles per gram of
tissue, compared with only 143 million per gram of tissue for the cont
rol samples. X-ray microanalysis revealed metal debris in sixteen (46
per cent) of the thirty-five membranes after digestion. Thirteen (50 p
er cent) of the twenty-six membranes surrounding a titanium-alloy stem
contained metal particles, compared with three of the nine membranes
surrounding a chromium-cobalt stem. Metal debris was present in only o
ne of the twelve membranes surrounding a titanium-alloy stem without a
porous coating, compared with twelve of the fourteen membranes surrou
nding a titanium-alloy stem with a porous coating. This tenfold differ
ence in prevalence was significant (p < 0.005). On the average, the to
tal number of particles (expressed in millions per gram of tissue) ass
ociated with the bipolar acetabular components was twice that associat
ed with the fixed acetabular components. In addition, there was a tren
d toward a larger mean size of the polyethylene particles in associati
on with the bipolar cups. Our data indicate that particulate prostheti
c debris in the tissues around failed femoral components that have bee
n inserted without cement constitutes a class of particles that are pr
edominantly less than one micrometer in size and are present in amount
s of more than one billion particles per gram of tissue. Routine histo
logical methods did not detect this class of wear debris and led to a
gross underestimation of the amount of debris in these membranes. CLIN
ICAL RELEVANCE: Characterization of wear particles, as performed in th
e current study, will permit a better assessment and understanding of
the biological response in vivo. Our data also demonstrate the relatio
nship between the design features of implants and the generation of pa
rticles. It is important for surgeons who perform joint-replacement op
erations to be cognizant of factors that may influence the production
of wear debris and thus affect the fixation of the implant and limit t
he longevity of the reconstruction.