Suture anchors - Update 1999

New suture anchors continue to become available. Our prior reports on the pullout strength of over 50 different anchors is supplemented by a similar test conducted on 25 additional new anchors. This anchor comparison, using an established protocol in fresh porcine femurs, recorded failure strength, failure mode (anchor pullout, suture eyelet cutout, or wire breakage), eyelet size, minor and major diameters, and drill hole sizes. These new anchors were tested in diaphyseal cortex, metaphyseal cortex, and a cancellous trough. Tensile stress parallel to the axis of insertion was applied at a rate of 12.5 mm/sec by an Instron 1321 until failure and mean anchor failure strengths were calculated. Anchors tested included DePuy 4.5 prototypes D1, D2 Catera 4.5, and D3; DePuy 3.5 prototypes D4- Catera 3.5, D5, and D6; Mainstay 2.7, 3.5, 4.5; ROC EZ 2.8, EZ 3.5, and XS 3.5; Ultrafix RC and Ultrafix MiniMite; 1.3 MicroMitek, Panalok 3.5, and Tacit 2.0; Umbrella Harpoon; PeBA 2.8, 4.0, 6.5; and Stryker 1.9, 2.7, 3.4, and 4.5 prototypes. Screw anchors still tend to have higher values, but for the newer nonscrew designs this distinction is less apparent. The new biodegradable anchors were all composed of poly L-lactic acid suggesting a trend away from other polymers, and these new biodegradable anchors showed load-to-failure strengths comparable to others in their class. All anchors were stronger than the suture for which they are designed to accommodate.