Combined Fatigue and Wear Testing of Anchored Sutures

Introduction: Abrasion of the suture at the anchor/bone interface is detrimental to the clinical function of anchored sutures. The relative movement of the suture at the anchor point causes windshield wiper effect and leads to early failure. Testing the cyclic wear and fatigue of anchored sutures was performed with a specially developed test frame.

Materials and Methods: The test evaluates the effect of combining a cyclic perpendicular pull, at 1000 cycles/minute, on the suture while the angular position of the anchor varies from –15 to +15 degrees. In each cycle, the load varies from −40 to +40 N about the average. Two anchor systems have been tested at average loads of 80, 130, 180 and 230 N: a 5.5 mm PEEK SwiveLock anchor (Arthrex) with 2 mm FiberTape (Arthrex), and a 4.5 mm Ruby Ti6Al7Nb anchor with a 16 mm Dyneema Purity loop (Kyon). Failure mode and time to failure were recorded.

Results: All sutures failed at the anchorage point. Depending on the load level, the number of cycles to failure for the Ruby system was 500 to 1000 times higher than for the SwiveLock/FiberTape system.

Discussion/Conclusion: The Kyon system with the ruby eyelet at the anchor exit provides a low abrasion contact for the suture. The bone edge at the suture exit with interference screws creates a highly abrasive interface leading to early failure.

Acknowledgement: Funding has been provided by Kyon AG.