Squeaky Ceramic Hip Prosthesis
A study on the squeaking ceramic hip prosthesis that was conducted in the Materials and Structural Testing Core led to an award-winning paper and added to the understanding of this peculiar phenomenon.
The core designed and implemented an in vitro bench test to simulate and identify potential biomechanical causes for hip squeaking with alumina ceramic-on-ceramic-bearing surfaces. All bearings were third-generation alumina ceramic with a 32-millimeter head coupled with a 56-millimeter acetabular component and a 32-millimeter ceramic insert.
Conditions for testing were normal gait, high load, stripe wear, stripe wear in extreme load, material (metal) transfer, edge wear with extreme load and microfracture.
Each condition was tested two times in dry conditions and two times in a lubricated condition with 25 percent bovine serum. Squeaking was reproduced in all dry conditions. It occurred quickly with high load, stripe wear or metal transfer. Once squeaking occurred, it did not stop. Squeaking disappeared for all conditions when a small amount of lubricant was introduced. In lubricated conditions, squeaking was only reproduced for the material transfer condition.
These observations suggest that squeaking is a problem of ceramic-ceramic lubrication and that this noise occurs when the film fluid between two surfaces is disrupted. Material transfer was the only condition that led to squeaking in a lubricated situation.
For more information, see: The 2009 Frank Stinchfield Award: "Hip Squeaking": A Biomechanical Study of Ceramic-on-ceramic Bearing Surfaces.