Calder Kristina M, Stashuk Daniel W, McLean Linda
School of Rehabilitation Therapy, Louise D, Acton Building, 31 George Street, Queen's University, Kingston, Ontario, Canada.
J Neuroeng Rehabil. 2008 Dec 16;5:34. doi: 10.1186/1743-0003-5-34.
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.
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.
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).
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.
非特异性手臂疼痛（NSAP）的病理生理学尚不清楚，其诊断是通过排除其他特定的上肢疾病，如外侧上髁炎或神经根病。本研究的目的是确定：（i）从NSAP患者患侧肌肉检测到的肌电图（EMG）信号中得出的与运动单位电位形态和/或运动单位放电模式相关的定量参数，是否与外侧上髁炎（LE）患者同一肌肉以及对照组中检测到的参数不同；（ii）定量EMG参数是否表明NSAP的潜在病理生理学本质上是肌病性或神经病性的。
16名NSAP患者、11名LE患者、8名被认为有发展为重复性劳损损伤风险的受试者以及37名对照受试者参与了研究。使用基于分解的定量肌电图（DQEMG）完成定量肌电图评估。在桡侧腕短伸肌（ECRB）进行低水平等长收缩期间收集针电极和表面电极检测到的EMG信号。DQEMG用于提取针电极检测到的运动单位电位序列（MUPTs）。使用单因素方差分析（ANOVA）比较四组之间针电极检测到的运动单位电位（MUP）、表面检测到的运动单位电位（SMUP）形态以及运动单位（MU）放电率。使用Tukey成对比较进行事后分析。
所有MUP变量和MU放电率均存在显著的组间差异（p < 0.006）。事后分析显示，与对照组和LE组相比，NSAP患者的MUP波幅、SMUP波幅和面积更小（p < 0.006）。与对照组相比，NSAP组、LE组和有风险组的MUP持续时间和AAR值显著更大（p < 0.006）；而与LE组相比，NSAP组的MUP波幅、持续时间和AAR值更小。与对照组相比，NSAP组的SMUP持续时间显著更短（p < 0.006）。NSAP组、LE组和有风险受试者的平均MU放电率低于对照组（p < 0.006）。
与大小相关的参数表明，NSAP组的MUP和SMUP明显小于对照组和LE组受试者。较小的MUP和SMUP可能表明肌纤维萎缩和/或丢失。需要进行前瞻性研究来证实本研究中发现的较小的MUP和SMUP与NSAP之间的任何因果关系。
