This invention relates to a method of making an inflatable bone plug for plugging the open end of an intramedullary bone canal which is capable of restricting the flow of bone cement, particularly, during the insertion of bone cement, particularly during the pressurized injection of such a cement, during an operative procedure involving the fixation of the stem of an artificial joint prosthesis such as a femoral hip joint prosthesis to the end of a bone such as a femur. The bone plug is designed to be pressurized with a biocompatible fluid and to thereafter deflate in a controlled manner after the cement hardens. Preferably, the bone plug is made by forming a hollow expandable container of a silicone elastomer permeable to carbon dioxide gas which has a valve stem attached to one end of the container and an opening at the opposite end of the container. A shrinkable elastomeric band is placed over the valve stem in which a channel has been made to receive a further cooperating injection means such as a needle. The elastomeric band shrinks over the valve stem to form a resealable valve assembly. The valve assembly is located in the hollow interior of the bone plug and the opening opposite the valve stem is sealed to complete construction of the bone plug. When such a plug is inflated with a biocompatible fluid such as carbon dioxide, the plug remains pressurized for a sufficient amount of time to allow the cement to harden, but the pressure drops to a minimum within about 24 hours after inflation.