Background: It has been stated that care must be taken not to scratch the m
etal components during total knee arthroscopy; however, this concern has no
t been studied. Clinical observation during arthroscopy of total knee repla
cements suggested the possibility of damage to the femoral component by the
arthroscopic cannula; there-fore, a bench test was performed to study this
potential risk.
Methods: Cobalt-chromium femoral components were tested to determine the su
rface damage that resulted from moving a stainless-steel arthroscopic cannu
la and a plastic arthroscopic cannula across the components under a variety
of applied loads. Scanning electron microscopy and surface-roughness measu
rements of the prosthetic surface were used to evaluate the damage.
Results: The stainless-steel cannula produced observable alterations to the
surface of the femoral component at loads as small as 8 N. The majority of
these alterations were deposits of stainless steel from the cannula onto t
he component. The plastic cannula did not appear to produce alterations on
the component surface. Surface roughness increased with increasing loading
of the stainless-steel cannula, but there was no noticeable change with inc
reasing loading of the plastic cannula. These forces did, however, severely
damage some parts of the plastic cannula.
Conclusions: Alterations to the surface of cobalt-chromium femoral componen
ts can occur during arthroscopy with stainless-steel cannulae but not with
plastic cannulae. The results of this study support a recommendation to use
plastic cannulae during arthroscopy of total knee replacements.
Clinical Relevance: Arthroscopy of total knee replacements is increasing in
the clinical setting, and damage to the prosthesis should be avoided whene
ver possible. This study provides evidence that damage to the femoral compo
nent is possible with a stainless-steel cannula and that use of a plastic c
annula may reduce this risk.