A method and instrumentation particularly adapted for disc space preparation from an anterior approach to the spine. It concerns a method of high-rate directed mutagenesis, that is the formation of numerous directed mutants in reduced time and with reduced number of steps. In particular, the amount of enzyme mRNA detected in tissue sample correlates with disease status such that enzyme levels can be used to predict the presence of, as well as the metastatic potential of cancer. A second foam disc is adhered to an adhesive face of the first foam disc and has an outer diameter greater than the plastic disc.