Regenerating axons emerge far proximal to the coaptation site in end-to-side nerve coaptation without a perineurial window using a T-shaped chamber.
BACKGROUND
Considerable controversy exists concerning the mechanism of axonal regeneration in end-to-side neurorrhaphy. The authors studied the mode of axonal regeneration in end-to-side neurorrhaphy without a perineurial window using a rat sciatic nerve model.


METHODS
Twenty-seven rats were used. A 10-mm segment of peroneal nerve was harvested and coapted to the ipsilateral tibial nerve in end-to-side fashion using a T-shaped silicone chamber to minimize the tibial nerve damaged by surgery. To explain the role of nerve damage on axonal regeneration in end-to-side neurorrhaphy, we also used an isogenic nerve transplantation model in which the peroneal nerve remained intact. The mode of axonal regeneration was studied with electron microscopy, morphometric analysis, immunofluorescence, and immunohistochemistry.


RESULTS
Both morphometric analysis and immunolabeling of neurofilaments demonstrated that regenerating axons emerge at sites far proximal to the coaptation site, travel within the tibial nerve, traverse the perineurium circumferentially around the coaptation site, and then invade into the peroneal nerve. Electron microscopy and a double-labeled immunofluorescence study with antibodies against neurofilament and tenascin-C confirmed large-scale axonal penetration into the perineurium around the coaptation site. Immunofluorescence with antibody against NG2, a marker of axonal regeneration, prevented the possibility of collateral sprouting at the coaptation site. In addition, an end-to-side neurorrhaphy model with an isogenic peroneal nerve clearly demonstrated that nerve damage is a prerequisite for axonal regeneration through end-to-side neurorrhaphy.


CONCLUSIONS
The authors could not locate the site of axonal sprouting in end-to-side neurorrhaphy without a perineurial window; however, this study cast doubts on current hypothesis on the mode of axonal regeneration in end-to-side neurorrhaphy.
Department of Orthopedic Surgery, Mie University Faculty of Medicine, Tsu City, Japan.
Koji
K
Akeda
Hitoshi
H
Hirata
Mamoru
M
Matsumoto
Aki
A
Fukuda
Masaya
M
Tsujii
Takeshi
T
Nagakura
Satoru
S
Ogawa
Toshimichi
T
Yoshida
Atsumasa
A
Uchida
D000818:Animals; D001369:Axons / Q000502:physiology*; D005109:Extracellular Matrix / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D007150:Immunohistochemistry; D008297:Male; D009416:Nerve Regeneration; D019635:Neurosurgical Procedures; D010525:Peripheral Nerves / Q000601:surgery*; D051381:Rats; D011917:Rats, Inbred Lew; D013536:Suture Techniques; D013979:Tibial Nerve / Q000502:physiology