Suture anchor failure strength--an in vivo study.

Suture anchors are increasingly used to secure tendons or ligaments to bone. These devices are applicable for arthroscopic shoulder stabilization and rotator cuff repair. This study reports the in vivo characteristics of four anchors, including one absorbable anchor composed of poly-L-lactic acid. Failure strength and method of failure were recorded for these anchors as a function of time. Samples of four anchors [Mitek G2, Zimmer Statak, Acufex TAG wedge, and the absorbable Arthrex expanding suture plug (ESP)] were implanted into ram femurs and harvested at intervals. Each bone-anchor-suture system was stressed to failure. The failure force and failure method was recorded. Mitek G2 and Statak suture anchors failed consistently at 30 pounds by suture breakage. They had no implantation difficulties. The TAG wedge exhibited suture pull-out and implant flipping at insertion. The TAG wedge failed by suture cut-out, anchor pull-out, and suture breakage. Its average failure strength was initially 16 pounds, but increased to 28 pounds at 2 weeks and reached the 30-pound level by 4 weeks. The ESP poly-L-lactic acid anchors experienced implantation breakage in 20% because of their greater length and composition. At pull-out testing, the ESP failed by suture cut-out, anchor pull-out, and suture breakage. Failure strength was initially 27 pounds, was 17 pounds at 2 weeks, and increased to 30 pounds by 6 weeks. The absorbable ESP does not have initial pull-out strength comparable with the Mitek and Statak suture anchors but does achieve this strength by 6 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)