A trocar fixation device, comprising: a cannula having a first, interior surface, a second, exterior surface, a first, proximal end, a second, distal end, a lumen defining a working channel for a surgical instrument extending between the proximal end and the distal end, a first, proximal-end region, a second, distal-end region, and a central region that is positioned between the proximal-end region and the distal-end region; an elongate tube that is mountable onto the exterior of the cannula, the elongate tube having a first, proximal end, a second, distal end, a lumen extending between the first, proximal end and the second, distal end, a first, interior surface, a second, exterior surface, a first, proximal-end region, a second, distal-end region, a central region positioned between the first, proximal-end region and the second, distal-end region, and a plurality of slits positioned about a periphery of the central region of the elongate tube, wherein the plurality of slits are arranged in a plurality of rows of slits, the fixation device in use being activated through rotation of the proximal end of the elongate tube in a first direction such that material of the elongate tube positioned between adjacent slits is compressed and forced radially outward to form ridges in the exterior surface of the elongate tube and the fixation device being deactivated by rotation in a second direction opposite the first direction such that the exterior surface of the elongate tube returns to a substantially smooth condition, the trocar fixation device being characterized in that the thickness of the elongate tube varies along its length such that at least one row of slits is positioned within a region of the elongate tube having a first thickness and at least one other row of slits is positioned within a region of the elongate tube having a different, second thickness; a cannula having a first, interior surface, a second, exterior surface, a first, proximal end, a second, distal end, a lumen defining a working channel for a surgical instrument extending between the proximal end and the distal end, a first, proximal-end region, a second, distal-end region, and a central region that is positioned between the proximal-end region and the distal-end region; an elongate tube that is mountable onto the exterior of the cannula, the elongate tube having a first, proximal end, a second, distal end, a lumen extending between the first, proximal end and the second, distal end, a first, interior surface, a second, exterior surface, a first, proximal-end region, a second, distal-end region, a central region positioned between the first, proximal-end region and the second, distal-end region, and a plurality of slits positioned about a periphery of the central region of the elongate tube, wherein the plurality of slits are arranged in a plurality of rows of slits, the fixation device in use being activated through rotation of the proximal end of the elongate tube in a first direction such that material of the elongate tube positioned between adjacent slits is compressed and forced radially outward to form ridges in the exterior surface of the elongate tube and the fixation device being deactivated by rotation in a second direction opposite the first direction such that the exterior surface of the elongate tube returns to a substantially smooth condition, the trocar fixation device being characterized in that the thickness of the elongate tube varies along its length such that at least one row of slits is positioned within a region of the elongate tube having a first thickness and at least one other row of slits is positioned within a region of the elongate tube having a different, second thickness;