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Strain within the native and reconstructed MPFL during knee flexion.
Patrick C McCulloch1, Aaron Bott1, Prem N Ramkumar2
1Methodist Center for Sports Medicine, Houston Methodist Hospital, Houston, Texas.
The Journal of Knee Surgery
|October 15, 2013
Summary
This study measured medial patellofemofemoral ligament (MPFL) strain during knee motion. Reconstructing the MPFL at 45 degrees of flexion better mimics native knee strain than at 20 degrees.
Area of Science:
- Orthopedic biomechanics
- Knee joint kinematics
- Ligamentous strain analysis
Background:
- Limited data exists on medial patellofemoral ligament (MPFL) and medial retinaculum strain during knee motion.
- Understanding native MPFL strain is crucial for effective surgical reconstruction.
Purpose of the Study:
- To quantify three-dimensional strain in the native MPFL across knee flexion.
- To compare native MPFL strain to strain in an injury model and after reconstruction.
- To evaluate the impact of reconstruction angle on MPFL strain patterns.
Main Methods:
- Controlled laboratory study using eight cadaveric knees.
- Visible-light stereophotogrammetry (VLS) system to measure strain.
- Knees were subjected to simulated activity through a range of motion, including native, injured, and reconstructed states (20° and 45° flexion).
Main Results:
- Native MPFL strain increased with knee flexion, peaking at 120° (87% strain).
- The most significant strain change occurred between 25° and 30° flexion.
- MPFL reconstruction at 45° flexion yielded strain patterns more similar to the native state than reconstruction at 20°.
Conclusions:
- Native MPFL strain increases with knee flexion, with a notable change between 25° and 30°.
- Reconstruction of the MPFL at 45° is biomechanically preferable to 20° for restoring native strain characteristics.
- Accurate MPFL strain knowledge aids in precise reconstruction, potentially reducing patellar maltracking and cartilage overload.
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