On the basis of the results of the two published retrospective cohort studies comparing the balloon and hormone therapy group (control group) in the prevention of adhesion reformation, the investigators estimate that the adhesion reformation rate in the immediate balloon group to be 30% and in the delayed balloon group to be 10%. Accepting a type 1 error of 0.05, and a type 2 error of 0.10, the number of subjects in each arm of the randomized, controlled trial would be 79. Assuming that the dropout rate to be 20%, the total number of subject to be recruited would be 90 in each arm.