BACKGROUND & OBJECTIVE
Axonal reaction to nerve strain isn’t well understood. Epineurial strain correlates with increased compliance near joints. When dealing with clinical neurodynamics, it is important to know what design features withstand deformation, and how strain is directed to specific regions within the nerve. Axon undulations differ regionally depending on nerve geometry and required elongation. Connective tissue regulates epineurial strain and nerve compliance. Mesoneurial structures, attaching epineurium to the interface, create deformation on neural tissue. The degree to which epineurial strain is transmitted intraneurally is not clear. The authors propose that axon undulations are increased in regions of high epineurial strain.
Epineurial strain of median and ulnar nerves in mice were measured proximal and distal to the elbow joint from an imaginary line connecting the medial and lateral epicondyles while under a tensioned state. Strains were also measured after circumferential decompression of the mesoneurium. Images of the nerves in two joint configurations were taken using microscopy.
Excised nerves were placed in a tissue stretching device and imaged using a confocal microscope. Software was used to measure up to 3 different visible axon lengths and their corresponding nerve lengths. Tortuosity was verified and quantified.
Higher epineurial strain occurs in joint regions compared with non-joint regions. Mesoneurial decompression noticeably reduced the strain disparity between regions, with strains in joint regions particularly reduced.