An orthopaedic surgical instrument (12) includes an anchor (92) configured to be coupled to a prosthetic tibial component, a shaft (94) coupled to the anchor, and a separator (96) coupled to the shaft. The separator is configured to move along the shaft between a first position in which the separator is spaced apart from the prosthetic tibial component and a second position in which the separator is positioned between the tibial tray and the sleeve of the prosthetic tibial component.