The mechanical properties of fresh versus fresh/frozen and preserved (Thiel and Formalin) long head of biceps tendons : a cadaveric investigation

Abstract

Human cadaveric specimens commonly serve as mechanical models and as biological tissue donors in basic biomechanical research. Although these models are used to explain both in vitro and in vivo behavior, the question still remains whether the specimens employed reflect the normal in vivo situation. The mechanical properties of fresh-frozen or preserved cadavers may differ, and whether they can be used to reliably investigate pathology could be debated. The purpose of this study was to therefore examine the mechanical properties of cadaveric long biceps tendons, comparing fresh (n = 7) with fresh-frozen (n = 8), formalin embalmed (n = 15), and Thiel-preserved (n = 6) specimens using a Universal Testing Machine. The modulus of elasticity and the ultimate tensile strength to failure was recorded. Tensile failure occurred at an average of 12 N/mm2 in the fresh group, increasing to 40.1 N/mm2 in the fresh-frozen group, 50.3 N/mm2 in the formalin group, and 52 N/mm2 in the Thiel group. The modulus of elasticity/stiffness of the tendon increased from fresh (25.6 MPa), to fresh-frozen (55.3 MPa), to Thiel (82.5 MPa), with the stiffest being formalin (510.6 MPa). Thiel-preserved and formalin-embalmed long head of biceps tendons and fresh-frozen tendons have a similar load to failure. Either the Thiel or formalin preserved tendon could therefore be considered as alternatives for load to failure studies. However, the Young’s modulus of embalmed tendons were significantly stiffer than fresh or fresh frozen specimens, and these methods might be less suitable alternatives when viscoelastic properties are being investigated.