A locking apparatus for connecting a catheter to a stem. The locking apparatus comprises a collet sleeve, which includes an annular wall defining a center channel and a plurality of resilient prongs protruding inwardly into a portion of the center channel. The locking apparatus also comprises a lockable insert, which includes an annular wall defining a center channel. The center channel of the lockable insert is coaxial with the center channel of the collet sleeve. The lockable insert is configured to be placed at a first locking position in which the annular wall of the lockable insert asserts no or minimal radial compression against the plurality of the resilient prongs of the collet sleeve, and the lockable insert is further configured to be moved to a second locking position in which the annular wall of the lockable insert radially compresses the plurality of the resilient prongs of the collet sleeve.