Table 1 Possible experiments to investigate paradox associated with sarcomas and Millipore filters

What aspect of the implant is responsible for sarcomas?

2 × 2 × 2 × 2 factorial design involving surface area, roughness, electrostatic charge, pore size

A factorial design allows investigation of many factors at once.

How does the implant affect cellular changes?

Primary study: no implant versus small pore implant that induces sarcoma

Looking for salient differences in gene expression using multiple random validation and signatures with few genes

Secondary study: no implant versus large pore implant that does not induce sarcoma

Control study to determine if differences in gene expression could reliably be associated with histological changes