Evaluation of a curved intramedullary button vs. traditional flat button for proximal biceps tenodesis: a biomechanical study

Background: Although variations in fixation techniques for proximal biceps tenodesis have been evaluated by different biomechanical studies, the optimal fixation technique remains unclear. To further advance the biceps tenodesis technique using unicortical button, a novel curved button was developed. This study aimed to compare the time-zero biomechanical performance of a curved intramedullary button with that of a standard flat button in proximal biceps tenodesis.

Methods: A total of 16 cadaveric fresh-frozen shoulders were randomly allocated to undergo proximal biceps tenodesis using either a standard flat button or the new curved button (developed by Materialise, Leuven, Belgium). Following the tenodesis, the biceps tendon was subjected to a cyclic load, ranging from 5 to 100N, at a frequency of 2.5 Hz for a total of 1000 cycles. After this, the tendon was loaded to failure. During testing, displacement after cyclic loading, ultimate failure load, stiffness, and modes of failure were evaluated.

Results: All 16 specimens were included in the data analysis. No failure occurred during cyclic testing. After cyclic testing, the median displacement was 10.4 mm (6.1-16.1) for curved button and 11.9 mm (6.0-43.9) for flat button (P = .534). The mean ultimate load to failure for the curved button was 239.4 ± 35.1 N, and 227.0 ± 42.0 N for the flat button (P = .721). The mean stiffness was 70.0 ± 10.3 N/mm for the curved button and 61.3 ± 17.3 N/mm for the flat button (P = .242).

Conclusions: In this time-zero in-vitro study, the curved and flat buttons exhibited similar biomechanical properties in terms of displacement, load to failure, and stiffness. Considering these results and the theoretical advantages of the curved button, this technique could be a new alternative for the treatment of proximal long-head biceps tendon pathology.