Proximal Biceps Tenodesis - Biomechanical Analysis in Sheep: Comparison between Metallic Anchor, Onlay Bioabsorbable Knotless Anchor, and Interference Screw.

Objective  To biomechanically evaluate different fixation devices for the proximal biceps in the humerus of sheep, comparing their fixation strength to failure, tendon displacement, and failure site in each technique. Methods  A total of 27 humerus tests were performed on sheep, separating them into 3 groups: group A with tenodesis with metallic anchors ( n  = 11), group B with biocomposite knotless devices ( n  = 8) and group C with metallic interference screws ( n  = 8), performing tenodesis with the sheep's own biceps, maintaining its native distal insertion. The three methods were submitted to a universal tensile testing machine. Results  There was no statistically significant difference in the strength of fixation until failure and displacement between the tendons fixed by the different techniques. Regarding the pattern of ruptures, it was observed that most ruptures of the metallic anchors occurred at the level of the myotendinous junction, most of the bioabsorbable knotless anchors failed due to slippage of the wire-screw interface, and all interference screws failed via tendon slip. Conclusion  The three techniques with metal anchor, onlay bioabsorbable knotless anchors, and interference screws are largely resistant to tensile loads for long head of the biceps tenodesis in sheep. There was no statistical difference between the three groups. Cyclic load resistance studies can provide more valuable data for comparing groups.