The mechanical properties measurement could be affected by forceps: a technical note on sampling human annulus fibrosus

Purpose To compare the mechanical properties of human annulus fibrosus obtained by forceps versus bistoury and observe whether the measurement could be affected by forceps sampling method. Methods In this study, the mechanical properties of the the extracellular matrix (ECM) of human annulus fibrosus, including elastic modulus and stiffness, were investigated using atomic force microscope (AFM). Tissue was obtained from patients during operation using a bistoury or nucleus pulposus forceps. Tissues obtained with the nucleus pulposus forceps were considered as the forceps group and those obtained with a bistoury were considered as the bistoury group. Results There was no significant difference observed between the forceps and bistoury group according to histological staining. The elastic modulus of the forceps group was 0.41 +/- 0.08 MPa, and that of bistoury group was 0.53 +/- 0.13 MPa, and the difference between the two groups was statistically significant (p < 0.05). The stiffness of the forceps group was 0.024 +/- 0.003 N/m, and that of the bistoury group was 0.037 +/- 0.003 N/m, and the difference between the two groups was statistically significant (p < 0.05). Conclusion The results indicate that the forceps sampling method has a substantial negative effect on the micromechanical properties of the ECM of the annulus fibrosus. Bistoury sampling method is recommended as the experimental subject for exploring the micromechanics mechanisms of cervical degenerative disease.