Biomet Cement and Cementing Systems

Pressurization

In the 1980´s techniques for pressurization of bone cement were introduced. Proper pressurization is important. The pressure on the cement has to be larger than the blood pressure no to be pushed out of the bone. Pressure should be applied until the viscosity of the bone cement has increased so it is high enough to resist blood pressure.

Many studies state that pressurization results in greater penetration of the bone cement into the bone.

This results in the following:

Reduction of porosity in bone cement
Micro-interlock, improved bone-cement interface
Increased fatigue strength of the cement
Improved mechanical anchorage

Pressurization has been shown to afford greater penetration into cancellous bone, reduce bone cement porosity, improve bone cement interface and increase cement strength. It is recommended to use a cement delivery gun, special pressurizers and centralizers.

For good intrusion of the bone cement into the trabeculae, the cement's viscosity is the most important factor. The bone cement should not be in a too low viscosity stage during delivery and pressurization. If viscosity is too low, it is possible that blood pressure might push the cement out of the bone cavity and cause laminations of blood in the cement. Ideal viscosity will be high enough to avoid any cement mixing with blood or fat/bony material from the implantation region yet low enough to penetrate the bone adequately.

Pressurizers should be used to maintain pressure on the bone cement until it is sufficiently doughy to resist the force of blood pressure. This consistency will prevent bleeding from the bone surfaces and lamination of blood into the cement. Required pressurization time varies according to type of cement used and OR temperature. When pressurizing the cement in the femur, a positive sign of pressurization is marrow extrusion in the greater trochanter (the so-called sweating trochanter sign).