Establishment of an animal model of extra vertebral foramen cervical nerve entrapment by local electrical stimulation with different stimulation parameters*,*,*,☆

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Abstract

BACKGROUND:

Previous studies demonstrated that electric stimulation provocate local muscle spasm, which can press the peripheral nerves, this process is correspondence with the actual conditions of patients.

OBJECTIVE:

To observe the effect of different parameters on rat's local muscle and to discuss the possibility of establishing animal model of extra vertebral foramen cervical nerve entrapment syndrome by local electrical stimulation.

DESIGN, TIME AND SETTING:

The randomized controlled experiment was completed in the Department of Orthopaedics and Central Laboratory, the Sixth People's Hospital of Shanghai, Shanghai Jiao Tong University.

MATERIALS:

Sixty-eight healthy, adult, Sprague Dawley rats. Eight of them were randomly selected as a means of stimulating parameters, and the remaining 60 rats were divided into an experimental (n=40), sham operation (n=10), and implantation of wire (n=10) groups, the right side of rats were served as the experimental sides, while their contralateral side as the control sides.

METHODS:

Exposed cutaneous branches rooted in rami posterior nervi spinalis and dominated muscles by exciding the median skin at the back of the rat's neck, given electric stimulation to the muscles by Low-frequency pulse transmitter. The output range was Voltage 0-40 V, frequency 1-111 Hz and pulse width 0-1 000 ms. The appropriate stimulation parameters of establishment of animal model of extra vertebral foramen cervical nerve entrapment were confirmed by observing the response of local and systemic to various stimulation and recording the change of local EMG. We exposed the area of the right side at the back of the rat's neck, lateral muscle and dominated by rami posteriores nervorum cervicalium. The bare wire of two electrodes was fixed to muscle and sewed electrodes into muscle. In the experimental group, appropriate parameters of electric stimulator was implanted into rat abdomen and joined the electrode wire to the neck though the channel under the skin of the rat's back. There was no stimulator implanted in the sham-operation group. The electrode wire enwrapped silicone tube was implanted into rats of the implantation of wire group.

MAIN OUTCOME MEASURES:

The nerve electrophysiological and histological changes were observed at weeks 2, 3, 4, 5 after implantation.

RESULTS:

The intensity of the local and systemic responses to electrical stimulation increased as pulse width increasing. The change of frequency was unconspicuous when the pulse width fixed. The amplitude of EMG had not increased with the frequency increased, when the pulse width fixed. Between the amplitude of EMG and the contraction intensity had obvious positive correlation due to the contraction intensity and the EMG result. Following parameters: 50 Hz, 200 μs, interval (1/3 s), 20 V was suitable to buildanimal model. Denervation potentials were found though neural electrophysiology test after 2 weeks of electric stimulation, and the extent aggravated gradually. Gistological detection showed that the local neutral cells aggregation, telangiectasia, endothelial cell proliferation, muscle cell atrophy, gap increase and granulation tissue regeneration, especially the transect of muscle fibers gradually reduced and atrophied due to chronic electrical stimulation.

CONCLUSION:

Different stimulation parameters can affect the muscle contraction and strength. The muscle can be induced to shrink effectively in a fixed stimulation parameters.

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