The balloon trepan is used in minimal invasive surgery in order to create or maintain the area required for an operation by dilation of tissue or dissection of layers of tissue. The connection between the balloon and the sleeve of the trepan must be easily and securely produced without enlarging the outer diameter of the balloon trepan. The balloon must be secured against slipping and must be able to resist pressure during inflation. The balloon surrounding the distal end of the trepan is pressed against a peripheral step formed on the sleeve of the trepan by a clamping element in order to fix it to the sleeve of the trepan. The clamping element is displaced by rotation of at least one part of the clamping element about a longitudinal axis of the sleeve of the trepan in a longitudinal direction in relation to the said sleeve.