Disclosed is a medical device (9) comprising a porous structure (1), wherein a configuration of the porous structure (1) varies in dependence on a load applied to the porous structure (1), such that the porous structure (1) has a first configuration when the load is of a first magnitude, and has a second configuration when the load is of a second magnitude greater than the first magnitude. The porous structure (1) comprises a first surface portion (2) and a second surface portion (3). The first surface portion (2) is disengaged from the second surface portion (3) when the porous structure (1) has the first configuration, and is engaged with the second surface (3) portion when the porous structure (1) has the second configuration.