Assuming a 68% closure rate with TheraSkin, and a 47% closure rate, with a desired alpha value of p<0.05 and a power of 80%, 64 subjects would be needed. However, if a difference in closure rate is assumed to be only 10%, with a closure rate of 68% with TheraSkin and 47% with Apligraf, the power calculation predicts that 142 subjects would be needed. A compromise difference of 13% was used to predict that 84 subjects would be needed. If we assume a 20% dropout rate due to lack of compliance or adverse events, we will need to enroll a total of 100 subjects.