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Updated: Jul 27, 2026
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Potentiodynamic Corrosion Testing
Published on: September 4, 2016
Acid attack and cathepsin K in bone resorption around total hip replacement prosthesis
Y T Konttinen1, M Takagi, J Mandelin
1Institute of Biomedicine, Department of Anatomy, University of Helsinki, Finland.
Summary
Pathological bone destruction may be driven by macrophages, not osteoclasts. This study found acidic conditions and cathepsin K activity in interface tissue, suggesting a new mechanism for bone resorption around implants.
Area of Science:
- Biochemistry
- Orthopedic Surgery
- Cell Biology
Background:
- Bone resorption is typically attributed to osteoclasts, which create acidic microenvironments for matrix degradation.
- Understanding pathological bone loss mechanisms is crucial for treating conditions like implant loosening.
Purpose of the Study:
- To investigate the role of acidic conditions and cathepsin K in bone resorption around loosened total hip replacement prostheses.
- To explore an alternative mechanism of pathological bone resorption mediated by macrophages.
Main Methods:
- Utilized a sting pH electrode to measure acidity at the interface membrane of loosened hip replacements.
- Employed confocal laser scanning to visualize bone demineralization.
- Detected cathepsin K, its messenger RNA (mRNA), and protein in interface tissue and pseudosynovial fluid.
Main Results:
- The interface membrane around loosened prostheses was found to be acidic.
- Irregular demineralization of the bone surface was observed in contact with the acidic interface.
- Cathepsin K was identified in interface tissue macrophages/giant cells and pseudosynovial fluid, with high mRNA and protein levels detected.
Conclusions:
- These findings suggest an acid- and cathepsin K-driven pathological bone resorption mechanism.
- This process appears to be mediated by uncontrolled macrophage activity in the extracellular space, rather than by osteoclasts.
