Shrinkage of centrifuged cement.

Two postulated mechanisms for the failure of prosthetic implants secured with bone cement are: failure of the cement itself, and loosening at the bone/cement interface. Failure rate with cement can be reduced by increasing the strength of the cement, and loosening can be reduced by minimizing cement shrinkage during polymerization. This paper shows that centrifuging cement to reduce porosity (and presumably increase strength) results in a substantial increase in cement shrinkage over uncentrifuged cement. A second set of experiments demonstrated that pressurization of cement to four atmospheres during polymerization resulted in tensile strengths comparable with those reported for centrifuged cement. Thus, the use of uncentrifuged bone cement, pressurized during polymerization, should minimize implant failure rates.