An impactor for positioning and holding a surgical or veterinary prostheticimplant whilst it is being driven into position, said impactor including:- (a)an impaction means； (b) an impaction shoe which is configured to receive and supporta prosthetic implant in a predetermined position； (c) connection means whichconnect the impaction means to the impaction shoe and are configured to transmitan impact from the impaction means to the impaction shoe； (d) arms configuredto engage an implant supported upon the impaction shoe； (e) said arms being biasedinto engagement with said implant, but movable against the bias out of engagementwith the implant； (f) said connection means being adjustable between a firstsetting at which the impaction shoe is spring-loaded so as to bias an implant supportedupon the impaction shoe into engagement with said arms but at which the impactionshoe can slide relative to said arms, against said spring bias； and a second settingat which both the impaction shoe and the arms are rigidly engaged with an implantsupported upon the impaction shoe, to hold the implant in a predetermined positionand orientation relative to the impaction means.
