Methods of coupling a catheter to a stem are disclosed. In some embodiments, a stem extends longitudinally between a proximal end and a distal end, and the stem can include at least one enlargement positioned between the proximal end and the distal end. In some embodiments, a catheter can be positioned over the at least one enlargement and over a region of the stem that is proximal to the at least one enlargement. In further embodiments, a collar can be mated to the stem.