Biomechanical comparisons of all--suture suspensory button vs. interference screw for inlay subpectoral bicep tenodesis.

Background: All-suture buttons (ASBs) and interference screw (IS) are commonly utilized in the inlay subpectoral biceps tendon tenodesis. However, the biomechanical characteristics of these two methods have not been compared directly. The aim of present study was to compare the biomechanical properties of ASB vs. IS for inlay subpectoral biceps tendon tenodesis in a human cadaveric model.

Methods: Sixteen fresh-frozen human cadaveric shoulders were randomly divided into two experimental inlay biceps tenodesis groups: ASB or IS. After tenodesis, every specimen was preloaded at 5 N for 2 minutes, followed with a cyclic loading test from 5 to 70 N for 500 load cycles. Then the load-to-failure test was performed. Afterward, the humerus was placed in a cylinder tube and secured with anchoring cement. Lastly, a two-point bending test was performed to determine the strength of the humerus. Destructive axial force was applied, and the failure strength and displacement were recorded.

Results: No difference in stiffness was observed between the two groups (ASB = 27.4 ± 3.5 N/mm vs. IS = 29.7 ± 3.0 N/mm; P = .270). Cyclic displacement was significantly greater in the ASB group (6.8 ± 2.6 mm) than the IS group (3.8 ± 1.1 mm; P = .021). In terms of failure load, there were no statistical differences among the two groups (P = .234). The ASB group was able to withstand significantly greater displacement (11.9 ± 1.6 mm) before failure than the IS group (7.8 ± 1.5 mm; P = .001). During the humeral bending test, the ASB group exhibited significantly greater maximal load (2354.8 ± 285.1 N vs. 2086.4 ± 296.1 N; P = .046) and larger displacement (17.8 ± 2.8 mm vs. 14.1 ± 2.8 mm; P = .027) before fracture.

Conclusions: In inlay subpectoral bicep tenodesis, ASB fixation appears to offer comparable stiffness and failure load to that of IS fixation. Additionally, the ASB group exhibited greater resistance to load and displacement before humeral fracture. However, the ASB group did demonstrate increased cyclic displacement compared to IS group.