Interface structure

An interface structure for detachably interfacing a surgical robot arm to a surgical instrument, the interface structure comprising:

• a main body;
• and
• a plurality of drive transfer elements, each comprising a first portion and a second portion, the first portion being releasably engageable with a respective portion of the surgical robot arm and the second portion being releasably engageable with a respective portion of the surgical instrument;
• each of the drive transfer elements being linearly movable relative to the main body so as to transfer linear drive between the surgical robot arm and the surgical instrument, wherein the main body defines a plurality of linear paths, at least two of which are of differing lengths, along a respective one of which a respective one of the drive transfer elements is movable to transfer the linear drive;
• wherein the main body comprises a first side for facing the surgical robot arm and a second side for facing the surgical instrument, the first portion being disposed towards the first side and/or the second portion being disposed towards the second side;
• wherein the main body comprises an aperture connecting the first side and the second side, the plurality of drive transfer elements being configured so as to obstruct fluid flow through the aperture so as to maintain a sterile barrier between the surgical robot arm and the surgical instrument;
• and
• wherein the plurality of drive transfer elements covers the aperture.