Strain, stress and stretch of peripheral nerve Rabbit experiments in vitro and in vivo

Abstract

Mechanical stretching is known to cause morphologic and functional changes in peripheral nerve. The points at which these changes occur, however, are not clearly defined and reported data are conflicting. The studies presented in this paper provide a basic understanding of the biomechanical properties, stretch-injury patterns, and changes of conduction properties of peripheral nerves due to stretching. Our studies showed that peripheral nerves exhibited non-linear stress-strain characteristics when placed under tension. Initially, under tension, the nerve had a low modulus that increased gradually with increasing strain until reaching a maximal value. When the nerve failed under tension, the perineurium inside the nerve ruptured, but the exterior of the nerve remained intact. Our results also show that a peripheral nerve in situ was under significant strain, but minimal in situ stress (less than 0.05 MPa). The in situ strain might vary with limb position, but did not appear to exceed the limit beyond which substantial tension or stress would be developed in the nerve. The time-dependent viscoelastic behavior of peripheral nerves were also characterized. The maintenance of small in situ stresses suggests that sustained increases in tension could be adversely affecting the electrophysiologic properties of the nerve. Indeed, marked alteration of conduction properties resulted from even a small stretch of 6 percent beyond the in situ length of the nerve, or stress less than 10 percent of the ultimate strength of the nerve.

Mechanics dictate where and how freshwater planarians fission

“…We found that the nerve cords break last during fission (Fig.S7). Because their diameter is only 50µm (Fig.S7), this implies stresses in the MPa range, similar to what has been reported as the tensile strength limit for nerve tissues in other organisms (25,31).…”

“…The rupture stresses we found are in the kPa range, which is orders of magnitude lower than stresses previously reported for rupture of tissues in other animals (25,26). It is possible that biological processes proceeding or accompanying waist formation weaken the waist and lower the required rupture stresses.…”

Outcomes differ between subgroups of patients with low back and leg pain following neural manual therapy: a prospective cohort study

“…Denervation may result from compromise of nerve microcirculation. A minimal stretch of perturbed nerve tissue may add further hypoxia and concomitant nerve damage [23]. It seems therefore reasonable to propose that if a nerve root were compressed, hypoxic and oedematous, using a mobilisation technique implying further tensile stress would have a detrimental effect.…”

Multimodal Treatment Program Comparing 2 Different Traction Approaches for Patients With Discogenic Cervical Radiculopathy: A Randomized Controlled Trial

“…20 Based on the literature, this tension may adversely affect the central nervous system and nerve root function due to the absence of the perineurium, which is the primary load carrying structure. 21 The work of Harrison et al was pioneering in regard to the association between the extension position and the normal biomechanics of the nervous system. [22][23][24] Although, the extension traction has become more popular, 25,26 the extension position is still questioned in treating CR.…”