Mechanical properties of the bicipital aponeurosis

This study reports the first biaxial mechanical characterization of the human bicipital aponeurosis (BA). Square specimens (~7×7 mm) harvested from proximal, mid, and distal BA regions (n=8, elderly cadaveric donors) were tested along longitudinal (collagen-aligned) and transverse axes. The BA exhibited strong directional dependence: longitudinal stiffness and elastic modulus were significantly greater than transverse, and hysteresis was higher in the longitudinal direction, indicating substantial energy dissipation and non-elastic behavior. No significant regional differences in stiffness, modulus, or hysteresis were detected along the BA length. The authors conclude that the BA likely functions as a compliant, load-dissipating ‘sling’ that can divert load from the distal biceps tendon and influence supination mechanics, supporting its potential importance in distal biceps injury/repair modeling.