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Structural properties of a new fixation strategy in double bundle ACL reconstruction: the MiniShim
S Lenschow1, B Schliemann, K Dressler
1Department of Trauma-, Hand- and Reconstructive Surgery, Wilhelms University Muenster, Muenster, Germany, simon.lenschow@ukmuenster.de.
Archives of Orthopaedic and Trauma Surgery
|June 14, 2011
Summary
Hybrid fixation using the MiniShim implant offers sufficient biomechanical strength for anterior cruciate ligament (ACL) reconstruction, comparable to interference screws. MiniShim alone is insufficient, but hybrid fixation provides a viable alternative for graft stability.
Area of Science:
- Orthopedic Surgery
- Biomedical Engineering
- Sports Medicine
Background:
- Double-bundle anterior cruciate ligament (ACL) reconstruction is a key area of research.
- Graft fixation techniques, including extracortical fixation and aperture fixation with interference screws, are debated.
- The biomechanical properties of novel fixation devices require thorough investigation.
Purpose of the Study:
- To evaluate the biomechanical performance of the MiniShim, a new wedge-shaped implant for soft tissue graft fixation in double-bundle ACL reconstruction.
- To compare the MiniShim's fixation strength against traditional interference screws and extracortical fixation methods.
Main Methods:
- Porcine knees and flexor tendons were used to simulate ACL reconstruction.
- Tunnels of 5 and 6 mm were created for graft fixation.
- Fixation strategies tested included MiniShim (4 and 5 mm), interference screws (6 mm), and hybrid fixation (FlippTack with MiniShim or interference screw).
- Biomechanical properties (maximum load, yield load, stiffness) were measured using a material testing machine.
Main Results:
- Extracortical fixation demonstrated the highest load to failure, followed by interference screws, and then MiniShim alone.
- Hybrid fixation using MiniShim and FlippTack showed significantly higher fixation strength compared to MiniShim or interference screw alone.
- Stiffness was significantly higher with interference screw fixation compared to MiniShim or extracortical fixation.
- Failure modes varied, including tendon slippage, implant pullout, linkage rupture, and tendon rupture at the fixation site.
Conclusions:
- MiniShim fixation alone is insufficient for double-bundle ACL reconstruction.
- Hybrid fixation combining MiniShim with cortical fixation (FlippTack) offers biomechanical strength comparable to interference screws.
- Hybrid fixation presents a viable alternative to aperture fixation with interference screws for achieving primary graft stability.
