A surgical instrument (130) for use in an orthopaedic arthroplasty procedure includes a shaft (140) having a first end (144) and a second end (142) and an impactor head (150) disposed at the second end of the shaft. The impactor head includes first (174) and second (200) spaced ends, two spaced impaction surfaces (208) disposed at the second end, and a cavity (210) disposed between the impaction surfaces. The cavity is adapted to accommodate posterior-stabilizing spines of at least a first tibial implant component and a second tibial implant component having a size which is different from that of the first tibial implant component. Each of the impaction surfaces includes a first section with a contour that conforms to a contour of a bearing surface of the first tibial implant component and a second section with a contour that conforms to a contour of a bearing surface of the second tibial implant component.
