Myofascial trigger points and innervation zone locations in upper trapezius muscles
Barbero, M. (2016) Myofascial trigger points and innervation zone locations in upper trapezius muscles.
Myofascial pain syndrome is characterized by sensory, motor and autonomic symptoms, and a myofascial trigger point (MTrP) is considered the principal clinical feature. Clinicians recognise myofascial pain syndrome as an important clinical entity but many basic and clinical issues need further research. Electrophysiological studies indicate that abnormal electrical activity is detectable near MTrPs. This phenomenon has been described as endplate noise and it has been purported to be associated MTrP pathophysiology. Authors also suggest that MTrPs are located in the innervation zone (IZ) of muscles. The aim of this thesis was to describe both the location of MTrP and the IZ’ locations in the upper trapezius muscle. The hypothesis was that distance between the IZ and the MTrP in upper trapezius muscle is equal to zero. This thesis includes two preliminary studies. The first one address the reliability of surface electromyography (EMG) in locating the IZ in upper trapezius muscle, and the second one address the reliability of a manual palpation protocol in locating the MTrP in upper trapezius muscle. The intrarater reliability of surface EMG in locating the IZ was almost perfect; with Kappa = 0.90 for operator A and Kappa = 0.92 for operator B. Also the interrater reliability showed an almost perfect agreement, with Kappa = 0.82. Both the operators conducted 900 estimations of IZ’ location through visual analysis of the EMG signals. The reliability of an experienced physiotherapist using a manual palpation protocol in locating the MTrP in the upper trapezius was established. An anatomical landmark system was defined and MTrP’ location established using X and Y values. The ICC values were 0.62 for X and 0.81 for Y. Twenty-four subjects with MTrP in upper trapezius were enrolled for this latter study. MTrP’ and IZ’ locations were described in 48 subjects. MTrPs were located in well-defined areas of the upper trapezius, showing a typical location with a mean distance from the IZ of 10.4 ± 5.8 mm. MTrPs in the upper trapezius are proximally located to the IZ but not overlapped by it (p = 0.6). These results extend the body of knowledge regarding the phenomenon of MTrP iperalgesia.