Mechanical comparison of cortical button fixation, interference screw and keyhole techniques in subpectoral biceps tenodesis, including digital image correlation assessment of bone surrounding the drill hole.

Purpose: Subpectoral biceps tenodesis is a widely used surgical technique to relieve pain and restore function in the shoulder by securing the long head of the biceps tendon. This study aimed to evaluate the mechanical performance of three fixation techniques using cortical button, interference screw and keyhole methods by assessing their strength, durability and strain distribution, incorporating the novel application of digital image correlation (DIC). Methods: Thirty fresh porcine bone-tendon specimens were allocated evenly among the fixation techniques. Biomechanical testing involved cyclic axial loading (10-100 N) for 500 cycles, followed by load-to-failure testing using a universal testing machine. DIC analysis assessed strain distribution around the bone drill site. Statistical comparisons of displacement, load-to-failure and strain patterns were performed. Results: Cortical button fixation demonstrated the highest average load-to-failure at 353 ± 45 N, with all specimens completing 500 cycles and showing the least variability. In comparison, interference screw fixation had the lowest average load-to-failure (271 ± 71 N) with two failures occurring before 500 cycles, and the keyhole technique showed intermediate performance at 319 ± 45 N, also with two early failures. Cyclic displacement after 500 cycles was lowest for the interference screw (3.16 ± 0.52 mm), followed by the keyhole (11.51 ± 2.08 mm), and highest for the cortical button (13.84 ± 1.90 mm). Displacement range after 500 cycles was also lowest in the interference screw group (0.62 ± 0.05 mm), compared to the cortical button (0.88 ± 0.07 mm) and keyhole (0.91 ± 0.23 mm). DIC revealed the highest maximum first principal strain around cortical button fixation (0.21%), followed by interference screw (0.16%) and keyhole (0.13%). Conclusion: Cortical button fixation demonstrated the highest load-to-failure and the lowest variability, indicating mechanical reliability. The interference screw and keyhole techniques showed comparable load-to-failure values and cyclic displacement but exhibited greater variability. DIC analysis revealed higher localized strain around the cortical button fixation, whereas the interference screw and keyhole techniques displayed more evenly distributed strain. Level of Evidence: Level V.