Functional and morphological effects of indirect gradual elongation of peripheral nerve: electrophysiological and morphological changes at different elongation rates.

We investigated the neuropathy induced by leg lengthening histological evaluation using teased nerve fiber specimens and electrophysiological evaluation. Indirect elongation of the sciatic nerve associated with leg lengthening was performed at 1 and 3 mm/day over 30 mm in rats. Electrophysiological evaluation was performed immediately and 60 days after the end of elongation, teased nerve fiber specimens were prepared, and the mean axonal diameter was calculated. The electrophysiological results were more wrong, and the recovery was poorer, in the 3-mm than in the 1-mm group. In the 1-mm group, the nerve conduction velocity (NCV) and the duration of the compound nerve action potential (C-NAP) recovered to a level close to the intact side, but the decrease in the amplitude of the C-NAP persisted. In the teased fiber study, while paranodal demyelination was observed in both groups immediately after elongation, demyelination was decreased in the 1-mm group indicationg recovery compared to the 3-mm group. Paranodal demyelination caused by indirect nerve elongation is considered to have induced electrophysiological disorders. Electrophysiological and morphological damages appeared to be more severe according to elongation speed. The nerve disorder were remained even at 1 mm per day in 60 days.