Surgical instruments for preparing a patient's tibia to receive an implant

An orthopaedic surgical instrument system for use during a surgical procedure to implant an orthopaedic knee prosthesis, comprising:

• a tibial base trial component including (i) a superior surface, (ii) an inferior surface positioned opposite the superior surface that is adapted to be positioned on a surgically-prepared proximal end of a patient's tibia, (iii) an opening being defined by an inner wall extending inwardly from the superior surface to a shelf surface positioned between the superior surface and the inferior surface and surrounding a passageway extending through the tibial base trial component, and (iv) a number of fixation pinholes extending through a posterior section of the shelf surface and the inferior surface of the tibial base trial component,
• an insert component shaped to be received in the opening defined in the tibial base trial component, the insert component comprising a base plate, and a generally Y-shaped posterior buttress extending upwardly from a superior surface of the base plate, and
• a tibial bearing trial component having an inner sidewall that defines an opening therein,
• wherein the generally Y-shaped posterior buttress of the insert component is configured to be received in the opening of the tibial bearing trial component to prevent rotation of the tibial bearing trial component relative to the tibial base trial component.