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Fatigue testing of suture anchors
Stefan Rupp1, Thomas Georg, Christian Gauss
1Department of Orthopaedic Surgery, University of Saarland, Homburg/Saar, Germany.
The American Journal of Sports Medicine
|March 26, 2002
Summary
Suture anchors are critical for bone fixation. Fatigue testing reveals suture-anchor interface weakness, especially with smaller sutures. Using larger sutures or anchors improves fatigue strength, highlighting the importance of material selection for robust fixation.
Area of Science:
- Orthopedic biomechanics
- Biomaterials science
- Surgical device engineering
Background:
- Suture anchors are widely used in orthopedic surgery for bone fixation.
- The mechanical integrity of anchor-suture constructs is crucial for successful surgical outcomes.
- Previous evaluations often focused on static pullout strength, potentially underestimating in-vivo performance.
Purpose of the Study:
- To evaluate the fatigue strength of commonly used suture anchor-suture combinations in a porcine tibia model.
- To identify the primary failure modes and weakest links within these constructs under cyclic loading.
- To determine how variations in anchor size and suture diameter affect mechanical performance.
Main Methods:
- A fatigue-testing protocol was applied to various anchor-suture combinations using a porcine tibia model.
- Constructs were subjected to cyclic loading to simulate physiological conditions.
- Failure modes were analyzed, focusing on the suture, anchor, and their interface.
Main Results:
- The Ethibond No. 2 suture was identified as the weakest link in single-pull tests.
- Cyclic loading reduced fixation strength compared to single-pull tests.
- The suture/anchor interface was the weakest point in several tested combinations (Mitek GII/No. 2, Zimmer Statak 3.5/No. 2), with suture wear at the eyelet.
- Using a larger suture (No. 5) with the GII anchor or larger anchors with No. 2 sutures increased fatigue strength.
- Biodegradable anchors primarily failed at the suture knot when inserted into cortical bone.
- The Super Anchor/No. 5 combination in cortical bone exhibited the highest fatigue strength.
Conclusions:
- Fatigue testing is essential for comprehensive suture anchor evaluation, complementing single-pull tests.
- Mechanical performance depends on anchor pullout strength, suture tensile strength, and the suture-anchor interface.
- Optimizing anchor-suture combinations, particularly by considering suture size and anchor-suture interaction, is vital for enhancing fixation strength and durability.