Dr Jian-Sheng Wang

Jian-Sheng Wang, MD PhD,
Biomaterials and Biomechanics Laboratory,
Department of Orthopedics,
Lund University Hospital. Lund, Sweden

Pressurization / Optimizing micro-interlock
Pressurization has been shown to afford greater penetration into cancellous bone, reduce bone cement porosity, improve the interlock of bone cement interface and enhance cement strength.

No laminations of blood and debris in the cement
For good intrusion of the bone cement into the trabeculae, cement viscosity is critical. If viscosity is too low, blood pressure may force the cement out of the bone cavity and cause blood laminations in the cement. Ideal viscosity is high enough to prevent the cement from mixing with blood or fat/bony material yet low enough to penetrate the bone adequately.

Reduced risk for revision with retrograde filling of femur
Cement mixing in a bowl followed by finger packing does not provide adequate fill, especially in the femoral canal. The Swedish Hip Registry in addition to other sources has shown that retrograde cement filling in the femur reduces risk of revision. This technique prevents air entrapment during cement application, reducing porosity. Lamination is also reduced, making it possible to achieve a completely cement-filled cavity.

Improved interlock of the bone cement interface
Pressurizers are available for acetabular, femoral and knee pressurization. They should be used to maintain pressure on the bone cement until it is doughy enough to resist the force of blood pressure. In order to achieve good filling and pressurization in hip and knee arthroplasties, a small piece of bone or a cement restrictor may be used to plug the shaft. Pressurization and lavage of the cancellous bone significantly improves cement penetration.

Even cement mantle for optimal stress distribution
The bone cavity should be shaped to provide an even cement mantle between the bone and prosthesis. Thickness of the cement mantle should be approximately 2-3 mm. Normally 40g cement is used for acetabulum and 60g-80g for femur. A stem centralizer can help guide the femoral prosthesis to a neutral position in the cement. An even cement mantle means better stress distribution and reduced risk of cement mantle failure.