Acute Effects of Acupuncture in the Response of the Median Neurodynamic Test: a Preliminary, Randomised, Double-blind, Non-inferiority Trial

Abstract

Background and purpose: Musculoskeletal pain syndromes may show signs of neural involvement, such as increased mechanossensitivity to pressure and tension of the peripheral nerves, causing an exacerbation of painful symptoms. Acupuncture has shown positive effects in people suffering from peripheral nerve dysfunction (e.g., reduction in pain intensity and disability); however, whether these benefits are related to reduced mechanossensitivity when tension is applied to the peripheral neural tissues (neurodynamics) is unknown. The purpose of this preliminary study was to assess the acute effects of acupuncture in the response of a neurodynamic test applied to the median nerve (MNT1).
Methods: Thirty-one (n = 31) asymptomatic subjects with normal posture and mobility of the upper body quadrant joints volunteered to participate. After signing the informed consent, subjects, who were blinded to the real study purpose, were randomly assigned to one of 2 groups: one group (n = 14; ♂ = 3; age = 34.6 ± 11.1 years old; mass = 62.5 ± 14.1 Kg; height = 167.1 ± 9.1 cm) was submitted to acupuncture (leopard spot needling technique) on one classical acupoint believed to be beneficial in people with symptoms of median nerve dysfunction (Pc 5 or Jiānshǐ); the other group (n = 17; ♂ = 6; age = 33.6 ± 12.6 years old; mass = 60.5 ± 8.5 Kg; height = 167.1 ± 10.1 cm) was submitted to the same technique on a new acupoint (5 cm below P 5 or Chǐzé) selected upon the clinical experience of one of the authors (H. J. G.). One assessor, blinded to group allocation and measurement results, performed the MNT1 on the dominant arm, before and after acupuncture. On both occasions, subjects were asked to report the onset of symptoms (e.g., stretching, tingling) as the elbow was being passively moved from 90º of elbow flexion to extension, with the arm at 90º of shoulder abduction. The test ended when the maximum range of motion (ROM) tolerated was reached (Fig. 1). Elbow extension ROM (in degrees) was assessed using a smartphone (iPhone 4, iOS 7.1.2, app Compass, Apple Inc., Cupertino CA, USA). Two 2-way repeated measures analysis of variance (ANOVA) with interaction (pre-post x group) were performed to assess the effects of acupuncture on elbow extension ROM at the onset of symptoms and maximum tolerated point. Analyses were conducted using SPSS v22.0 (IBM Corp., Armonk, NY, USA) and significance level was set at p < 0.05. Effect size (η2p) was calculated to complement inferential statistics.
Results: Acupuncture had a small (up to 6º) but significant effect on elbow extension ROM at both the onset of the symptoms (p = 0.029, η2p = 0.154) and maximum tolerated point (p = 0.002, η2p = 0.277). No significant differences were found between groups at either the onset of the symptoms (p = 0.901, η2p = 0.001) or the maximum tolerated point (p = 0.585, η2p = 0.010) (Fig. 2).
Conclusion: Acupuncture increased the elbow extension ROM during the MNT1 in asymptomatic subjects, possibly due to reduced mechanossensitivity of the median nerve or altered pain perception. No acupoint proved to be better at improving the onset of symptoms and the maximum tolerated elbow extension ROM. Further studies are necessary to understand the clinical significance of these findings.

Full text

Title: Acute Effects of Acupuncture in the Response of the Median
Neurodynamic Test: a Preliminary, Randomised, Double-blind, Non-inferiority
Trial
Authors: Nuno Morais1, Maria João Santos3, Henry Johannes Greten2,3
1 Polytechnic Institute of Leiria; School of Health Sciences (ESSLei-IPL),
Leiria, Portugal
2 Heidelberg School of Chinese Medicine (HSCM), Heidelberg, Germany
3 University of Porto, Instituto de Ciências Biomédicas Abel Salazar (ICBAS-
UP), Porto, Portugal
Background and purpose: Musculoskeletal pain syndromes may show signs
of neural involvement, such as increased mechanossensitivity to pressure and
tension of the peripheral nerves, causing an exacerbation of painful
symptoms. Acupuncture has shown positive effects in people suffering from
peripheral nerve dysfunction (e.g., reduction in pain intensity and disability);
however, whether these benefits are related to reduced mechanossensitivity
when tension is applied to the peripheral neural tissues (neurodynamics) is
unknown. The purpose of this preliminary study was to assess the acute
effects of acupuncture in the response of a neurodynamic test applied to the
median nerve (MNT1).
Methods: Thirty-one (n = 31) asymptomatic subjects with normal posture and
mobility of the upper body quadrant joints volunteered to participate. After
signing the informed consent, subjects, who were blinded to the real study
purpose, were randomly assigned to one of 2 groups: one group (n = 14; ♂ =
3; age = 34.6 ± 11.1 years old; mass = 62.5 ± 14.1 Kg; height = 167.1 ± 9.1
cm) was submitted to acupuncture (leopard spot needling technique) on one
classical acupoint believed to be beneficial in people with symptoms of
median nerve dysfunction (Pc 5 or Jiānshǐ); the other group (n = 17; ♂ = 6;
age = 33.6 ± 12.6 years old; mass = 60.5 ± 8.5 Kg; height = 167.1 ± 10.1 cm)
was submitted to the same technique on a new acupoint (5 cm below P 5 or
Chǐzé) selected upon the clinical experience of one of the authors (H. J. G.).
One assessor, blinded to group allocation and measurement results,

performed the MNT1 on the dominant arm, before and after acupuncture. On
both occasions, subjects were asked to report the onset of symptoms (e.g.,
stretching, tingling) as the elbow was being passively moved from 90º of
elbow flexion to extension, with the arm at 90º of shoulder abduction. The test
ended when the maximum range of motion (ROM) tolerated was reached
(Fig. 1). Elbow extension ROM (in degrees) was assessed using a
smartphone (iPhone 4, iOS 7.1.2, app Compass, Apple Inc., Cupertino CA,
USA). Two 2-way repeated measures analysis of variance (ANOVA) with
interaction (pre-post x group) were performed to assess the effects of
acupuncture on elbow extension ROM at the onset of symptoms and
maximum tolerated point. Analyses were conducted using SPSS v22.0 (IBM
Corp., Armonk, NY, USA) and significance level was set at p < 0.05. Effect
size (η2p) was calculated to complement inferential statistics.
Results: Acupuncture had a small (up to 6º) but significant effect on elbow
extension ROM at both the onset of the symptoms (p = 0.029, η2p = 0.154)
and maximum tolerated point (p = 0.002, η2p = 0.277). No significant
differences were found between groups at either the onset of the symptoms (p
= 0.901, η2p = 0.001) or the maximum tolerated point (p = 0.585, η2p = 0.010)
(Fig. 2).
Conclusion: Acupuncture increased the elbow extension ROM during the
MNT1 in asymptomatic subjects, possibly due to reduced mechanossensitivity
of the median nerve or altered pain perception. No acupoint proved to be
better at improving the onset of symptoms and the maximum tolerated elbow
extension ROM. Further studies are necessary to understand the clinical
significance of these findings.
Fig. 1 – Example of the MNT1 with measurement of elbow extension range of
motion by means of a smartphone. Initial position (left frame), onset of

symptoms (centre), and maximum tolerated elbow extension range of motion
(right frame).
Fig. 2 – Effects of acupuncture on elbow extension range of motion during the
MNT1. Left frame, onset of symptoms, and right frame, maximum tolerated
range of motion (see text for details)