Wear debris. An environmental issue in total joint replacement

Area of Science:

• Orthopedic Surgery
• Biomaterials Science
• Biomedical Engineering

Background:

• Osteolytic lesions near total hip implants are a growing concern.
• Potential causes include changes in implant materials or design.
• Particulate debris from hip replacement components is a suspected factor.

Purpose of the Study:

• To investigate if modern hip replacement bearings and modular connections are a source of particulate debris.
• To assess the role of component design and manufacturing tolerances in debris generation.

Main Methods:

• Measurements of surface finish and sphericity for contemporary metal and polyethylene hip components.
• Hip simulator testing of assembled polyethylene inserts and metal shells.
• Bending and torsional tests on metal/metal modular connections to assess debris release.

Main Results:

• Significant mismatches in surface finish and sphericity were found between mating metal and polyethylene components.
• Polyethylene inserts showed worse sphericity than femoral heads, further degraded by shell placement.
• Hip simulator tests revealed greater polyethylene wear in metal-backed shells compared to inserts alone.
• Modular connections released substantial debris particles under dynamic loading.

Conclusions:

• Implant component mismatches and manufacturing tolerances contribute to particulate debris generation.
• Modular connections in total hip replacements are an unappreciated source of debris.
• Reevaluation of the design, manufacture, and tolerances of modular connections is necessary to address osteolysis.