Physical properties and functional alignment of soft-embalmed Thiel human cadaver when used as a simulator for ultrasound-guided regional anaesthesia

Background We evaluated the physical properties and functional alignment of the soft-embalmed Thiel cadaver as follows: by assessing tissue visibility; by measuring its acoustic, mechanical and elastic properties; by evaluating its durability in response to repeated injection; and by aligning images with humans. 

Methods In four soft-embalmed Thiel cadavers, we conducted three independent studies. We assessed the following factors: (i) soft tissue visibility in a single cadaver for 28 weeks after embalming; (ii) the displacement of tissues in response to 1 and 5 ml interscalene and femoral nerve blocks in a single cadaver; and (iii) the stiffness of nerves and perineural tissue in two cadavers. We aligned our findings with ultrasound images from three patients and one volunteer. Durability was qualified by assessing B-mode images from repetitive injections during supervised training. 

Results There was no difference in visibility of nerves between 2 and 28 weeks after embalming {geometric mean ratio 1.13 [95% confidence interval (CI): 0.75-1.68], P=1.0}. Mean tissue displacement was similar for cadaver femoral and interscalene blocks [geometric mean ratio 1.02 (95% CI: 0.59-1.78), P=0.86], and for 1 and 5 ml injection volumes [geometric mean ratio 0.84 (95% CI: 0.70-1.01), P=0.19]. Cadavers had higher intraneural than extraneural stiffness [Young's modulus; geometric mean ratio 3.05 (95% CI: 2.98-3.12), P