The prosthesis has a valve at one end formed of a fixed base and a coiler body which is able to rotate on the base. A flexible elastic body defining a hollow chamber extends from the coiler body and is able to receive filling medium via the valve. A compact strand extends from the free end of the elastic body. An instrument is provided for implanting the prosthesis between two vertebrae along with a drive belt for rotating the coiler body about the fixed base and, thus the elastic body about the coiler body. Filling of the elastic body takes place after coiling.