Evaluation of stainless steel surgical instruments subjected to multiple use/processing

Background: To determine the effect of multiple use and processing cycles on instrument quality over the life of stainless steel, complex designed clinical surgical instruments. Methods: Steam sterilised surgical instruments due to be discarded from Australian hospitals, because of loss of functionality, were assessed for contaminating protein and bacteria using the bicinchoninic acid protein assay and microbial culture, respectively. Biofilm presence and instrument damage were visually confirmed by scanning electron microscopy (SEM). Instruments were categorised into hinged/serrated, screw, cannulated, flexible, and irregular surfaced (but not hinged) according to their design. Results: Protein contamination ranged from 24 μg on the new screw to 3,756,046 μg contaminating a discarded forceps. The more complex the instrument design the higher the protein contamination. All samples were culture negative, however, biofilm was visually confirmed on 4/8 instruments tested using SEM. SEM also detected soil, holes or black stains on all the instruments. Conclusion: "Ready to use" surgical instruments that underwent multiple uses and processing cycles were contaminated with high amounts of protein, and microscopy revealed the presence of soil, structural damage, black stains and biofilm. While less affected new but multiply processed screws also showed soil and biofilm contamination. These findings highlight the need for further research into determining what is the "life" of stainless steel instruments and development of standard criteria for evaluating when to "retire" an instrument.