A study of intrusion characteristics of low viscosity cement Simplex-P and Palacos cements in a bovine cancellous bone model

Aseptic loosening is the most common long-term complication of cemented total hip arthroplasties (THA). The functional longevity of these implants depends on the bone-cement interface. The inlfuence of cement injection pressure, type of cement, ambient temperature, chilling of the monomer, and centrifugation of cement-on-cement intrusion depth was investigated in specimens of bovine cancellous bone. In order to validate the bovine model for comparative purposes relative to use in man, a linear relationship between human and bovine cancellous bone was first demonstrated for various porosities and cement intrusion depth. Three cements (Low Viscosity Cement [LVC], Simplex-P, and Palacos) were intruded at three different pressures (20, 40, and 60 PSI) at the same ambient temperature and relative humidity into commercially prepared plugs of bovine cancellous bone. Cement intrusion depth was proportional to injection pressure for all three cements, but was significantly different for each cement at a given pressure. At 20, 40, and 60 PSI, Palacos had a cement intrusion depth of 1.4, 2.4, and 2.8 mm respectively, while the figures for Simplex-P were 2.2, 4.2, and 5.0 mm, and for LVC were 8.0, 12.0, and 14.6 mm. Ambient temperature had an inverse relationship with cement intrusion depth for all three cements given the same experimental conditions. Chilling the monomer increased the intrusion of Simplex-P to 5.8, 8.2, and 12.7 mm at 20, 40 and 60 PSI injection pressure respectively. Simplex-P intrusion depth was not modified by cement centrifugation at any of the three injection pressures tested. Cement intrusion depths obtained with three popular commercial cements were compared with respect to pressures, usually generated in the operating room, and prepared in various conditions in a bovine cancellous bone. In an experimental system, the cement intrusion depth obtained in conditions usually achieved in the operating room (60 PSI pressure, 22° ambient temperature, and 65% relative humidity) is greater than the remaining cancellous bone bed in the prepared human femoral canal. Cement centrifugation does not change cement intrusion depth. Notwithstanding the limitations of the experiment, the information seems clinically relevant.