In order to study the properties of retrieved orthopaedic prosthetic implan
ts, microtomy is often used to produce pieces suitable for examination. How
ever, the cut made with the microtome can change the characteristics of the
material to be studied and thus give an incorrect picture of some of its a
ctual properties. This paper is based on a thorough investigation of the ef
fects of different cutting depth, cutting velocity and cutting angle on the
orientation and crystallinity of ultra high molecular weight polyethylene.
It was found that the orientation decreases with greater cutting depth and
cutting velocity and increases slightly with a greater cutting angle. The
degree of crystallinity as measured by FTIR and calculated from the first D
SC heating was found to increase with greater cutting depth. The crystallin
ity calculated from the second heating, however, always gave an average val
ue of 50.5 +/-0.5%. Cutting angle and cutting velocity did not influence th
e crystallinity. Two different knives were used ii the investigation. One w
as old and left scratch marks on the film while the other had recently been
sharpened. The main difference between the two knives, apart from the scra
tch marks, was that the films cut with the old knife had a lower degree of
crystallinity than the ones cut with the new knife when measured immediatel
y after cutting. The crystallinity did, however, increase during ageing in
ambient atmosphere, and after about 2 months it was the same as for the sam
ples cut with the new knife. (C) 2001 Elsevier Science Ltd. All rights rese
rved.