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Biotribological Testing and Analysis of Articular Cartilage Sliding against Metal for Implants
Published on: May 14, 2020
Metal-on-metal hip joint tribology
1School of Mechanical Engineering, The University of Leeds, Leeds, UK. DDryedale@aol.com
Summary
Metal-on-metal hip implants require large head diameters and small clearances for optimal elastohydrodynamic lubrication, unlike metal-on-polymer designs. Proper tribological engineering ensures significantly reduced wear rates in these advanced joints.
Area of Science:
- Biomedical Engineering
- Tribology
- Materials Science
Background:
- Metal-on-polymer hip replacements necessitate smaller femoral head diameters to minimize wear and friction.
- Metal-on-metal (MoM) hip implants represent a resurgence of hard-on-hard bearing surfaces.
Purpose of the Study:
- To review the tribological principles governing metal-on-metal total hip replacements.
- To contrast design considerations for MoM joints with those for metal-on-polymer (MoP) joints.
- To elucidate the engineering science behind MoM joint lubrication and wear.
Main Methods:
- Review of tribological features and lubrication regimes.
- Analysis of design parameters influencing elastohydrodynamic film formation.
- Explanation of film thickness calculation and the lambda ratio.
Main Results:
- MoM implants can achieve a mild mixed lubrication regime with effective elastohydrodynamic films.
- Optimal MoM design requires large head diameters and minimal clearances.
- Laboratory tests confirm the potential for very low steady-state wear rates in MoM joints.
Conclusions:
- Effective elastohydrodynamic film generation is crucial for minimizing wear in MoM hip replacements.
- Design guidance for MoM joints is opposite to that for MoP joints, emphasizing larger heads and tighter clearances.
- Understanding tribology is key to the successful engineering of modern hard-on-hard hip implants.
