Spinal cord mechanism involving the remote effects of dry needling on the irritability of myofascial trigger spots in rabbit skeletal muscle

Abstract

Objective: To elucidate the neural mechanisms underlying the remote effects produced by dry needling rabbit skeletal muscle myofascial trigger spots (MTrSs) via analyses of their endplate noise (EPN) recordings.

Design: Experimental animal controlled trial.

Setting: An animal laboratory of a university.

Animals: Male New Zealand rabbits (N=96) (body weight, 2.5-3.0kg; age, 16-20wk).

Intervention: Animals received no intervention for neural interruption in group I, transection of the tibial nerve in group II, transection of L5 and L6 spinal cord in group III, and transection of the T1 and T2 spinal cord in group IV. Each group was further divided into 4 subgroups: animals received ipsilateral dry needling, contralateral dry needling, ipsilateral sham needling, or contralateral sham needling of gastrocnemius MTrSs.

Main outcome measures: EPN amplitudes of biceps femoris (BF) MTrSs.

Results: BF MTrS mean EPN amplitudes significantly increased (P<.05) initially after gastrocnemius verum needling but reduced to a level significantly lower (P<.05) than the preneedling level in groups I and IV with ipsilateral dry needling or contralateral dry needling, and in group II with contralateral dry needling (but not ipsilateral dry needling). No significant EPN amplitude changes were observed in BF MTrS in group III or in the control animals receiving superficial needling (sham).

Conclusion: This remote effect of dry needling depends on an intact afferent pathway from the stimulating site to the spinal cord and a normal spinal cord function at the levels corresponding to the innervation of the proximally affected muscle.