Biomechanical evaluation of humeral torsional strength following biceps tenodesis: A cadaveric study

Humerus fractures are a known and devastating complication of subpectoral biceps tenodesis. The purpose of this study is to compare the torsional failure strength of the humerus after subpectoral biceps tenodesis using three fixation methods: unicortical button, interference screw, and all-suture anchor.

Thirty matched pairs of cadaveric humeri were randomized into three study arms (ten pairs each): interference screw versus unicortical button, interference screw versus all-suture anchor, and unicortical button versus all-suture anchor. Torsional loads to failure were applied to the cadavers using a MTS Bionix tabletop system. Maximum torque, degree of rotation to failure, and torsional stiffness were compared using paired t-tests.

Unicortical button fixation exhibited significantly higher maximum torque at failure compared to both interference screw (41.86 N.m ± 13.20 N.m to 29.81 N.m ± 9.47 N.m) and suture anchor (39.13 N.m ± 16.65 N.m to 30.90 N.m ± 18.31 N.m) fixation. There was no significant difference in maximum torque between interference screw and suture anchor (31.67 N.m ± 13.43 N.m to 30.39 N.m ± 13.31 N.m). No significant differences were observed in the degree of rotation or stiffness in any of the three study arms.

Unicortical button fixation offers superior resistance to torsional forces and humerus fracture compared to interference screw and all-suture anchor fixation techniques in subpectoral biceps tenodesis. This information could help surgeons make choices for implants to minimize complications and better educate their patients on potential outcomes.