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No effect in primary stability after increasing interference fit in cementless TKA tibial components
Esther Sánchez1, Christoph Schilling2, Thomas M Grupp3
1Radboud University Medical Center, Radboud Institute for Health Sciences, Orthopaedic Research Lab, Nijmegen, the Netherlands.
Journal of the Mechanical Behavior of Biomedical Materials
|March 15, 2021
Summary
Increasing interference fit in cementless total knee arthroplasty (TKA) tibial implants from 350 to 700 μm did not significantly affect initial stability or bone-implant micromotions. Posterior regions showed more gap closing than anterior regions.
Area of Science:
- Orthopedics
- Biomedical Engineering
- Biomechanics
Background:
- Cementless total knee arthroplasty (TKA) relies on interference fit for initial implant stability.
- The optimal interference fit for tibial components remains undetermined.
- Understanding interference fit effects is crucial for improving TKA longevity and patient outcomes.
Purpose of the Study:
- To investigate the impact of varying interference fit levels on the initial stability of cementless tibial TKA implants.
- To quantify micromotions and gap changes at the bone-implant interface under simulated physiological loading.
- To compare the effects of a low (350 μm) versus a high (700 μm) interference fit.
Main Methods:
- Experiments were conducted on human cadaveric tibias using a clinically established cementless porous-coated tibial implant.
- Two interference fit levels (350 μm and 700 μm) were tested.
- Simulated gait and squat loads were applied, and micromotions/gap changes were measured using Digital Image Correlation (DIC) across six regions of interest (ROIs).
- Multilevel linear mixed-effect models analyzed the data.
Main Results:
- No significant differences in micromotions or gap opening/closing were observed between the low (350 μm) and high (700 μm) interference fits during gait or squat simulations.
- Significant differences were found across ROIs, with greater gap closing observed in posterior regions compared to anterior regions.
- This suggests that while regional bone response varies, the overall initial stability is not significantly altered by doubling the interference fit.
Conclusions:
- Increasing the interference fit from 350 μm to 700 μm does not enhance the initial stability of cementless tibial TKA implants.
- Regional variations in bone-implant micromotions and gap changes exist, particularly a greater gap closing in posterior tibial regions.
- These findings suggest that current interference fit ranges may not be a primary determinant of initial stability for this type of TKA implant, highlighting the importance of regional bone characteristics.
