Medical apparatus (100) is provided for insertion into a mammalian body. The apparatus (100) includes structural stent elements (110), at least a portion of which are shaped so as to define (a) a t least one generally circumferential band (112), and (b) a plurality of engagement members (114) that are joined to and extend radially inwardly from the band (112). The apparatus (100) further includes an elongated latch member (118) which is threaded through the engagement members (114), thereby physically latching the engagement members (114). The band (112) and the engagement members (114) are configured such that (a) when the latch member (118) is threaded through and thus physically latches the engagement members (114), the engagement members (114) retain the band (112) in a radiallycompressed state, and (b) when the latch member (118) is removed from the engagement members (3.14), the band (112) assumes a radially-expanded state. Other embodiments are also described.
