Abstract: A method and apparatus for use in reducing the volatilization of the monomer component of bone cement is used after a prosthesis is implanted and throughout the polymerization of bone cement. The apparatus includes a generally annular inflatable sealing member having a centrally located opening therein for fitting over the exposed end of the prosthesis. The sealing member has an outer diameter covering the exposed surface of the bone cement. The sealing member has a deformable surface disposed in a substantially co-planar relationship with the exposed surface of the bone cement. The sealing member is resiliently expandable by inflation and extends beyond the edges of the bone defining the cavity, to seal the bone cavity upon the deformation of the deformable surface thereon. A pump is provided for inflating the sealing member and causing the deformable surface to apply pressure to the exposed surface of the bone cement.