A medical device delivery system includes a joining element with a bumper having a distal end portion configured to engage a proximal portion of a medical device and a proximal end portion adjacent a distal end portion of an elongated tubular member. The proximal end portion defines a slot having a length along a first direction. The joining element further includes an aperture extending through the bumper and having a first, greater, cross-sectional dimension along a second direction and a second, smaller, cross-sectional dimension along a third direction. The system can include an elongated shaft having a distal region and a flattened region proximal of the distal region, the flattened region having a greatest cross-sectional dimension that is smaller than the first cross-sectional dimension but larger than the second cross-sectional dimension The flattened region can be received within the slot.