a bone cavity sealing gasket which can be fitted over the resected end of a bone to be provided with bone cement in its axial cavity , includes a sealing plate which has a quantity of a resiliently deformable material on its lower face to enable a seal to be created between the plate and the upper edge of the bone , and an opening extending through it . a plug can be received in the opening in the sealing plate . the plug has an injection port extending through it aligned with the opening in the sealing plate in which the injection nozzle of bone cement delivery apparatus can be received .