Damage to cobalt-chromium surfaces during arthroscopy of total knee replacements

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.