Conclusion: The IOM window size is of utmost importance in trans-membrane TP transfers, given that if equal or smaller than the transposed tendon oblique diameter, a high entrapment risk exists. A membrane window of 5 cm or 2.5 times the size of the tendon diameter should be performed in order to theoretically diminish this complication. (C) 2015 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.