What Protects Certain Nerves from Stretch Injury?

Area of Science:

• Neuroscience
• Anatomy
• Histology

Background:

• The tibial nerve is less susceptible to injury during joint arthroplasty compared to the peroneal nerve.
• Anatomical distribution alone may not explain this difference in injury proneness.

Purpose of the Study:

• To investigate the histological differences in size, shape, and connective tissue distribution between the tibial and peroneal nerves.
• To understand how these features contribute to nerve protection against stretch injury.

Main Methods:

• Human cadaver tibial and peroneal nerves were harvested mid-thigh.
• Segments were stretched (20-25%) or maintained at natural length and fixed.
• Paraffin sections were stained for connective tissue and examined via light microscopy.

Main Results:

• Tibial nerves possessed twice the number of fascicles compared to peroneal nerves, with similar axonal content.
• Stretched tibial nerve fascicles became more oval, unlike peroneal nerve fascicles.
• Tibial nerves had a higher proportion of epineurial (extrafascicular) adipose tissue (50-55%) than peroneal nerves (38-42%).

Conclusions:

• Tibial nerves exhibit distinct histological characteristics, including more fascicles and a more substantial epineurium, which likely provide protection against stretch-induced injury.
• The tightly bound perineurium and robust epineurium of the tibial nerve are suggested as key protective factors.
• Further mechanical studies are recommended to elucidate the role of nerve size and shape in neurapraxia and protection.