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Biomechanical Comparison of Torque to Humeral Fracture Between Two Biceps Tenodesis Locations

      Introduction

      Tenodesis of the long head of the biceps is the preferred surgical treatment for pathology of the tendon. Several case reports have shown fracture of the humerus following subpectoral biceps tenodesis; the location of the tenodesis was implicated as a stress riser for fracture. The purpose of our study is to compare the likelihood of spiral fracture of the humerus following biceps tenodesis at the position of arthroscopic suprapectoral tenodesis versus the subpectoral meta-diaphyseal location.

      Methods

      16 fresh-frozen humeri (8 matched pairs) were dissected and intraosseous tenodesis was performed. Unicortical tenodesis holes were drilled at the bottom of the bicipital groove (Group 1, suprapectoral), or just below the pectoralis major tendon insertion (Group 2, subpectoral) in the humeral diaphysis. The tenodesis was performed in a bone tunnel with a validated technique using suture fixation. Each humerus was mounted to a load frame and rotation torque was applied distally until fracture occurred, with torque measured (N-m).

      Results

      Fracture occurred at the subpectoral cortical drill hole in 8 of 8 specimens (Group 2). Only two fractures occurred through the tenodesis hole in Group 1, with spiral fracture resulting in the diaphysis of the humerus in 6 of 8 specimens (Group 1). Average torque to failure for Group 1 was 31.35 N-m. Average torque to failure for Group 2 was 25.10 N-m. The difference is statistically significant (p = 0.0001).

      Conclusion

      Subpectoral drill holes were shown to be a stress riser for humeral fracture. Suprapectoral drill holes were shown to be significantly less of a stress riser. The torque required to fracture the humerus through the subpectoral drill holes was less than was required to fracture the shaft of the humerus with a suprapectoral drill hole. Clinically, the risk for fracture potential should be considered when selecting tenodesis location and technique.