Cement penetration and stiffness of the cement-bone composite in the proximal tibia in a porcine model.

PURPOSE To assess the stiffness of the cement bone composite and the depth and uniformity of cement penetration into the surface of the tibial component during total knee reconstruction in a porcine model. METHODS The effectiveness of 3 protocols were compared: 2 commonly used cementing techniques-finger-packing of cement on the cut surface followed by impaction, and coating of the undersurface of the prosthesis with cement followed by impaction-and a new method using a tibial cement-pressurising device. Cement penetration was measured by computed tomography; stiffness was determined by hydraulic penetration testing. RESULTS Cement penetration at a depth of 1 mm was significantly greater following coating the undersurface of the prosthesis than following finger-packing (p=0.008). There was no significant difference at deeper levels or between the tibial-pressurising device group and either of the 2 other groups at any level (p>0.3 in all cases). Differences in surface stiffness by tibial plateau region were found in tibiae that had been cemented using finger-packing and in those that had had their undersurface coated, but not in tibiae that had been cemented using the tibial-pressurising device. CONCLUSION The tibial cement-pressurising device eliminated regional differences in stiffness seen with other cementing methods. Elimination of these differences by using this device should reduce micromotion and the incidence of aseptic loosening of tibial base plates in total knee arthroplasty.