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Motor unit potential morphology differences in individuals with non-specific arm pain and lateral epicondylitis.

Calder KM, Stashuk DW, McLean L - J Neuroeng Rehabil (2008)

Bottom Line: Significant group differences were found for all MUP variables and for MU firing rate (p < 0.006).SMUP duration was significantly shorter in the NSAP group compared to the control group (p < 0.006).A prospective study is needed to confirm any causal relationship between smaller MUPs and SMUPs and NSAP as found in this work.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Rehabilitation Therapy, Louise D, Acton Building, 31 George Street, Queen's University, Kingston, Ontario, Canada. calderkristina@hotmail.com

ABSTRACT

Background: The pathophysiology of non-specific arm pain (NSAP) is unclear and the diagnosis is made by excluding other specific upper limb pathologies, such as lateral epicondylitis or cervical radiculopathy. The purpose of this study was to determine: (i) if the quantitative parameters related to motor unit potential morphology and/or motor unit firing patterns derived from electromyographic (EMG) signals detected from an affected muscle of patients with NSAP are different from those detected in the same muscle of individuals with lateral epicondylitis (LE) and/or control subjects and (ii) if the quantitative EMG parameters suggest that the underlying pathophysiology in NSAP is either myopathic or neuropathic in nature.

Methods: Sixteen subjects with NSAP, 11 subjects with LE, eight subjects deemed to be at-risk for developing a repetitive strain injury, and 37 control subjects participated. A quantitative electromyography evaluation was completed using decomposition-based quantitative electromyography (DQEMG). Needle- and surface-detected EMG signals were collected during low-level isometric contractions of the extensor carpi radialis brevis (ECRB) muscle. DQEMG was used to extract needle-detected motor unit potential trains (MUPTs), and needle-detected motor unit potential (MUP) and surface detected motor unit potential (SMUP) morphology and motor unit (MU) firing rates were compared among the four groups using one-way analysis of variance (ANOVA). Post hoc analyses were performed using Tukey's pairwise comparisons.

Results: Significant group differences were found for all MUP variables and for MU firing rate (p < 0.006). The post-hoc analyses revealed that patients with NSAP had smaller MUP amplitude and SMUP amplitude and area compared to the control and LE groups (p < 0.006). MUP duration and AAR values were significantly larger in the NSAP, LE and at-risk groups compared to the control group (p < 0.006); while MUP amplitude, duration and AAR values were smaller in the NSAP compared to the LE group. SMUP duration was significantly shorter in the NSAP group compared to the control group (p < 0.006). NSAP, LE and at-risk subjects had lower mean MU firing rates than the control subjects (p < 0.006).

Conclusion: The size-related parameters suggest that the NSAP group had significantly smaller MUPs and SMUPs than the control and LE subjects. Smaller MUPs and SMUPs may be indicative of muscle fiber atrophy and/or loss. A prospective study is needed to confirm any causal relationship between smaller MUPs and SMUPs and NSAP as found in this work.

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Related in: MedlinePlus

Experimental set-up and electrode position. The active electrode (A) was placed over the motor point of the ECRB muscle. The passive electrode was placed over the radial styloid process (B). The common reference electrode was placed on the dorsum of the hand (C). A concentric needle electrode (D) was inserted in a distal to proximal direction parallel to the muscle fibers so that the tip of the needle was underneath the active electrode (A).
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Figure 1: Experimental set-up and electrode position. The active electrode (A) was placed over the motor point of the ECRB muscle. The passive electrode was placed over the radial styloid process (B). The common reference electrode was placed on the dorsum of the hand (C). A concentric needle electrode (D) was inserted in a distal to proximal direction parallel to the muscle fibers so that the tip of the needle was underneath the active electrode (A).

Mentions: All subjects underwent an electrophysiologic evaluation of the ECRB muscle. The affected limb or the more seriously affected limb (as determined by subjective complaint) was used for electrophysiologic evaluation in the LE and NSAP subjects. The dominant arm was selected in control subjects; for at-risk subjects, the limb selected (dominant/non-dominant) was matched to an LE or NSAP subject of the same age and sex. For this evaluation, subjects were seated in a straight-backed chair with the elbow of the tested arm flexed to 90° and the forearm pronated and resting on a custom-built table (Figure 1). Adjustable straps attached to the bottom of the testing table were passed through an opening and secured around the dorsum of the hand to provide resistance during the isometric extension contractions.


Motor unit potential morphology differences in individuals with non-specific arm pain and lateral epicondylitis.

Calder KM, Stashuk DW, McLean L - J Neuroeng Rehabil (2008)

Experimental set-up and electrode position. The active electrode (A) was placed over the motor point of the ECRB muscle. The passive electrode was placed over the radial styloid process (B). The common reference electrode was placed on the dorsum of the hand (C). A concentric needle electrode (D) was inserted in a distal to proximal direction parallel to the muscle fibers so that the tip of the needle was underneath the active electrode (A).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2654455&req=5

Figure 1: Experimental set-up and electrode position. The active electrode (A) was placed over the motor point of the ECRB muscle. The passive electrode was placed over the radial styloid process (B). The common reference electrode was placed on the dorsum of the hand (C). A concentric needle electrode (D) was inserted in a distal to proximal direction parallel to the muscle fibers so that the tip of the needle was underneath the active electrode (A).
Mentions: All subjects underwent an electrophysiologic evaluation of the ECRB muscle. The affected limb or the more seriously affected limb (as determined by subjective complaint) was used for electrophysiologic evaluation in the LE and NSAP subjects. The dominant arm was selected in control subjects; for at-risk subjects, the limb selected (dominant/non-dominant) was matched to an LE or NSAP subject of the same age and sex. For this evaluation, subjects were seated in a straight-backed chair with the elbow of the tested arm flexed to 90° and the forearm pronated and resting on a custom-built table (Figure 1). Adjustable straps attached to the bottom of the testing table were passed through an opening and secured around the dorsum of the hand to provide resistance during the isometric extension contractions.

Bottom Line: Significant group differences were found for all MUP variables and for MU firing rate (p < 0.006).SMUP duration was significantly shorter in the NSAP group compared to the control group (p < 0.006).A prospective study is needed to confirm any causal relationship between smaller MUPs and SMUPs and NSAP as found in this work.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Rehabilitation Therapy, Louise D, Acton Building, 31 George Street, Queen's University, Kingston, Ontario, Canada. calderkristina@hotmail.com

ABSTRACT

Background: The pathophysiology of non-specific arm pain (NSAP) is unclear and the diagnosis is made by excluding other specific upper limb pathologies, such as lateral epicondylitis or cervical radiculopathy. The purpose of this study was to determine: (i) if the quantitative parameters related to motor unit potential morphology and/or motor unit firing patterns derived from electromyographic (EMG) signals detected from an affected muscle of patients with NSAP are different from those detected in the same muscle of individuals with lateral epicondylitis (LE) and/or control subjects and (ii) if the quantitative EMG parameters suggest that the underlying pathophysiology in NSAP is either myopathic or neuropathic in nature.

Methods: Sixteen subjects with NSAP, 11 subjects with LE, eight subjects deemed to be at-risk for developing a repetitive strain injury, and 37 control subjects participated. A quantitative electromyography evaluation was completed using decomposition-based quantitative electromyography (DQEMG). Needle- and surface-detected EMG signals were collected during low-level isometric contractions of the extensor carpi radialis brevis (ECRB) muscle. DQEMG was used to extract needle-detected motor unit potential trains (MUPTs), and needle-detected motor unit potential (MUP) and surface detected motor unit potential (SMUP) morphology and motor unit (MU) firing rates were compared among the four groups using one-way analysis of variance (ANOVA). Post hoc analyses were performed using Tukey's pairwise comparisons.

Results: Significant group differences were found for all MUP variables and for MU firing rate (p < 0.006). The post-hoc analyses revealed that patients with NSAP had smaller MUP amplitude and SMUP amplitude and area compared to the control and LE groups (p < 0.006). MUP duration and AAR values were significantly larger in the NSAP, LE and at-risk groups compared to the control group (p < 0.006); while MUP amplitude, duration and AAR values were smaller in the NSAP compared to the LE group. SMUP duration was significantly shorter in the NSAP group compared to the control group (p < 0.006). NSAP, LE and at-risk subjects had lower mean MU firing rates than the control subjects (p < 0.006).

Conclusion: The size-related parameters suggest that the NSAP group had significantly smaller MUPs and SMUPs than the control and LE subjects. Smaller MUPs and SMUPs may be indicative of muscle fiber atrophy and/or loss. A prospective study is needed to confirm any causal relationship between smaller MUPs and SMUPs and NSAP as found in this work.

Show MeSH
Related in: MedlinePlus