Extensive porosity at the cement-femoral prosthesis interface: a preliminary study

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Materials Engineering

Background:

• Total hip replacements (THRs) utilize cemented femoral components, relying on the cement mantle for fixation.
• The interface between the cement and the femoral prosthesis is critical for long-term implant stability.
• Understanding factors affecting cement mantle integrity is crucial for improving THR outcomes.

Purpose of the Study:

• To describe and characterize the extensive porosity observed at the cement-prosthesis interface in cemented femoral components.
• To investigate the potential impact of this interfacial porosity on the mechanical strength of the cement mantle.
• To identify factors influencing the formation of interfacial porosity.

Main Methods:

• Examination of cement-metal interfaces from numerous in vivo and in vitro THR specimens.
• Utilized both optical and scanning electron microscopy for detailed analysis.
• Included diverse stem designs, alloys (Co-Cr, Ti), surface finishes, and cement types (centrifuged/uncentrifuged).

Main Results:

• Marked porosity was consistently observed at the cement-metal interface across all examined samples (in vivo and in vitro).
• Interfacial porosity significantly exceeded the general porosity found within the bulk cement.
• Porosity was independent of stem design, alloy type, surface finish, and cement centrifuging.

Conclusions:

• The cement-prosthesis interface in cemented femoral components exhibits significant, preferential porosity.
• This interfacial porosity poses a risk to the mechanical integrity of the cement mantle and overall implant fixation.
• The rheological characteristics of the bone cement are suggested as a potential cause for this observed porosity.