A surgical instrument for use in implanting a stemless humeral component to replace the humeral head of a patient's humerus comprises an implant insertion tool (540) having a body (542) with an elongated bore (544) extending through it. A locking rod (548) is captured in the bore so as to rotate freely relative to the body, the locking rod having a set of locking threads (556) formed in a distal end thereof. An alignment collar (560) has a number of alignment keys (562) extending downwardly from a lower surface thereof. A distal end of the elongated bore opens into the lower surface of the alignment collar, and the locking threads extend through the distal end of the elongated bore and are positioned between the alignment keys of the alignment collar.
