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Imaging of the Microstructural Failure Mechanism in the Human Hip
Published on: September 29, 2023
Differences in external and internal cortical strain with prosthesis in the femur
Olav Reikeras1, Gudrun T Aarnes, Harald Steen
1Oslo University Hospital, University of Oslo, Rikshospitalet, NO-0027 Oslo, Norway.
The Open Orthopaedics Journal
|January 12, 2012
Summary
Strain patterns differ significantly between the internal and external femur cortex after hip stem prosthesis implantation. Internal strain cannot be predicted from external measurements, crucial for understanding implant fixation and loosening risks.
Area of Science:
- Orthopedic biomechanics
- Biomaterials science
- Surgical implant analysis
Background:
- Femoral stem prosthesis loosening is a critical concern linked to interface stress.
- Current understanding of strain patterns at the bone-implant interface is limited.
- Investigating internal cortical strain is essential for predicting implant stability.
Purpose of the Study:
- To investigate and compare internal and external cortical strain in the proximal femur post-femoral stem prosthesis insertion.
- To determine if external strain measurements accurately reflect internal strain at the bone-implant interface.
Main Methods:
- Utilized a human cadaveric femur for strain gauge measurements on the external cortex.
- Employed optical fibers embedded in the endosteal cortex to measure internal deformations.
- Applied loading to the femur before and after prosthesis implantation.
Main Results:
- External strain showed significant changes, particularly medial compression reduction proximally after implantation.
- External principal strain patterns remained largely consistent longitudinally.
- Greatly divergent strain values and patterns were observed between internal and external cortices, with some transcortical differences showing compression and distraction simultaneously.
Conclusions:
- Significant discrepancies exist between internal and external cortical strain in the proximal femur with a stem prosthesis.
- External strain measurements do not accurately represent or predict internal cortical strain.
- These findings highlight the need for direct internal strain assessment to understand bone-implant interactions and prevent loosening.
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