Comparison of diametral shrinkage of centrifuged and uncentrifuged Simplex P bone cement.

Reducing the porosity of bone cement substantially strengthens the cement in fatigue. However, concern has been raised that reducing the porosity of the cement would increase the shrinkage of the cement and thus compromise the cement-bone interface. We measured diametral shrinkage of cement mantles prepared with and without centrifugation of the cement. Four cement preparations (centrifuged and uncentrifuged mixed with monomer at either room temperature or 0 degrees C) were used to form cement mantles of four different thicknesses (2, 4, 6, and 8 mm) around a stainless steel rod. We conclude that porosity reduction dramatically increases the fatigue strength of bone cement without substantially changing the diametral dimensions of the polymerized cement when studied in the shape and volume of a cement mantle that would be used for total hip replacement.