Effect of implant design on the cyclic loading properties of mini suture anchors in carpal bones.

Mini suture anchors are commonly used in hand surgery involving attachment of soft tissue to bone. There are few data on the biomechanical behavior of these implants under physiologic conditions. Commercially available mini anchors were inserted into the carpal bones of fresh-frozen cadaver wrists. Anchors were divided into threaded and pronged types according to design. The anchors were cyclically loaded. Pronged anchors (1.3 and 2.1 mm) failed at a range of 199 to 5,155 cycles. Threaded anchors (2.5 and 2.8 mm) consistently completed 40,000 cycles without failure. Before failure pronged anchors displaced on average 5.1 mm and threaded anchors displaced on average 0.01 mm. The pronged implants failed because of either prong fatigue or fracture; the threaded anchors remained structurally intact. The larger threaded suture anchors seem to have superior biomechanical properties than smaller pronged anchors.