Biomechanical Analysis of All-Suture Suture Anchor Fixation Compared With Conventional Suture Anchors and Interference Screws for Biceps Tenodesis

Abstract

To compare the biomechanical properties of all-suture suture anchors (ASSAs) with conventional interference screws (CISs) and conventional suture anchors (CSAs) for long head of the biceps tendon fixation during proximal biceps tenodesis (BT). We randomized 21 fresh-frozen human cadaveric shoulders into 3 subpectoral BT treatment groups: ASSA, CSA, and CIS. Each construct was cyclically loaded from 5 to 70N for 500 cycles (1Hz). All specimens that survived cyclic loading were then pulled to failure (1mm/s). Elongation, maximum load, energy, and failure mode were recorded. The humerus was stripped of tissue and then subjected to torsional displacement at a rate of 1°/s until fracture occurred. Maximum load, displacement, stiffness, and energy were recorded. During tendon testing, 3 specimens (43%) in the CIS group failed early during cyclic testing by the tendon tearing at the screw-tendon interface. All other specimens in the CIS group, as well as all specimens in the ASSA and CSA groups, survived cyclic testing and failed during pull-to-failure testing. Failure occurred at the tendon-anchor or -screw interface in all specimens (100%), with no anchor or screw pullout. The CIS group had significantly decreased elongation (8.9 ± 2.23mm) at maximum load compared with the ASSA (19.2 ± 5.2mm) and CSA (18.9 ± 2.23mm) groups (P= .001). During torsional testing, the ASSA group was able to withstand significantly greater torsional displacement (9.22° ± 0.86°) before failure and had greater energy to failure (497.3 ± 45 Nmm-degrees) than the CIS group (6.13° ± 1.24° and 256.6 ± 70.3 Nmm-degrees, respectively; P= .005). This study shows that the biomechanical properties of ASSA, CSA, and CIS constructs are similar. The interference screw group had lower tendon elongation at maximum load but had several early failures compared with the suture anchor groups. The use of suture anchors results in maximum tendon and torsional bone loads similar to interference screws for the long head of the biceps tendon. Torsional testing of the CIS resulted in spiral fractures traversing the screw tunnel in 100% of the specimens, which was not found in the suture anchor groups. The ASSA is a viable fixation method for BT in comparison with the CSA and CIS.