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Reduced compression time is not sufficient for stability in patellar buttons
Leandra Bauer1, Johannes Gramzow1, Matthias Brensing1
1Experimental Orthopaedics, University Hospital Jena, Campus Eisenberg, Waldkliniken Eisenberg, Friedrich-Schiller-Universität Jena, Jena, Germany.
Summary
Reducing patellar button compression time in knee replacement surgery did not alter cement shape but increased micromotion, suggesting potential early instability. Longer compression may be needed for optimal fixation.
Area of Science:
- Orthopedic surgery
- Biomaterials science
- Biomechanical engineering
Background:
- Patellar resurfacing in total knee arthroplasty (TKA) relies on stable cement fixation.
- Current methods require prolonged manual compression of the patellar button until cement cures.
Purpose of the Study:
- To investigate the impact of reduced manual compression time on cement morphology, micromotion, and load-to-shear failure of cemented patellar buttons.
- To determine if shorter compression times are sufficient for primary fixation in TKA.
Main Methods:
- Twelve human patellae were implanted with cemented all-polyethylene buttons.
- Groups were assigned to either 30-second or 600-second compression.
- Micro-computed tomography (µCT) analyzed cement morphology; biomechanical testing assessed micromotion and shear failure load.
Main Results:
- Cement morphology (volume, penetration, expansion, height) was comparable between groups.
- Micromotion was significantly higher in the 30-second group (0.015 ± 0.009 mm) versus the 600-second group (0.006 ± 0.003 mm).
- Maximum shear force did not significantly differ between the 30-second and 600-second compression groups.
Conclusions:
- Reduced compression time did not affect cement morphology or ultimate shear strength.
- Shortened compression significantly increased micromotion, indicating reduced early interface stability.
- Micromotion may be a more sensitive indicator of early stability than shear force for patellar button cementing.