bonecement.com

Biomet Cement and Cementing Systems


Vacuum Mixing & Delivery

History

Until the 1980s the composition and preparation of bone cement did not stray from the standards introduced by Charnley in 1959. Techniques for improving cement strength were not extensively tried. Since the 1980s, though, new cement mixing systems, aiming to produce homogenous cement of low porosity, have been developed. They serve to enhance cement’s mechanical properties, improve cementing technique and safeguard the operating room environment.


 

 

The evolution of cement mixing systems

Hand mixing
As its name implies, hand mixing means that the cement is hand mixed in a bowl in the operating room and then inserted by hand or injected into the desired location. Because PMMA comes as a powder composed of prepolymerized particles to be mixed with a liquid monomer, a certain amount of porosity in the final material is unavoidable when hand mixing.

Vibration
During the 1980s a vibrating mixing technique was introduced in hopes of improving bone cement properties. The results, however, were not convincing.1

Centrifugation
In this technique, cement was first mixed manually and then subjected to centrifugation to eliminate any air inclusions introduced during mixing. The method varied significantly depending on the type of centrifugation and cement used. The procedure did not  work well with high viscosity cement. The resulting cement, however, was not consistently homogenous.

Vacuum mixing
At about the same time, mixing under vacuum was introduced.3,4,5 After some refining, it produced better results than centrifugation, which was soon thereafter retired in favour of vacuum mixing. Today vacuum mixing is widely accepted as the best method for reducing cement porosity and increasing cement strength.

Wang and others added another important step to the system collection of cement under vacuum.6 Collection under vacuum prevented air from being trapped in the cement during transfer to the cement gun. This step reduced the number of macropores and micropores while increasing bone cement density.

Vacuum mixing and collection in a delivery cartridge gives a reproducible high-quality cement that is delivered directly with a cement delivery gun. This reduces the risk of blood intrusion and contact allergy.