Intra-rater reliability of an experienced physiotherapist in locating myofascial trigger points in upper trapezius muscle

Abstract

Objectives: Myofascial trigger points (MTrPs) are considered the principal clinical feature of myofascial pain syndrome (MPS). An MTrP consists of spot tenderness within a taut band of muscle fibers and its stimulation can produce both local and referred pain. The clinical diagnosis of MPS depends on correct history taking and a physical examination aimed at identifying the presence of MTrP. The purpose of this study was to investigate the intra-rater reliability of a palpation protocol used for locating an MTrP in the upper trapezius muscle.

Methods: Twenty-four subjects with MTrP in the upper trapezius muscle were examined by an experienced physiotherapist. During each of eight experimental sessions, subjects were examined twice in randomized order using a palpation protocol. An anatomical landmark system was defined and the MTrP location established using X and Y values.

Results: The intraclass correlation coefficient ICC(1,1) values were 0.62 (95% CI: 0.30-0.81) for X and 0.81 (95% CI: 0.61-0.91) for Y. The Bland-Altman plots for X and Y showed a mean of difference of 0.04 and -0.2 mm, respectively. Limits of agreement for X ranged from -26.3 to 26.2 mm and for Y from -27 to 26.4 mm.

Discussion: The ICC(1,1) for the observed values revealed a moderate to high correlation and the Bland-Altman analysis showed means of difference very close to zero with narrow limits of agreement. An experienced physiotherapist can reliably identify MTrP locations in upper trapezius muscle using a palpation protocol.

Keywords: Intra-rater reliability; Myofascial pain syndromes; Myofascial trigger points; Palpation; Upper trapezius muscle.

Figures

Figure 1

A graphical representation of the anatomical landmark system and the two variables, X and Y, used to define the MTrP location on the upper trapezius. AA indicates the acromial angle of the scapula and C7 the spinal process of the seventh cervical vertebra. ALS_d is the distance between C7 and AA. MTrP, myofascial trigger point; AA, acriomial angle; C7, spinous process of the seventh vertebrae; ALS_d, distance between AA and C7.

Figure 2

Bland Altman plots showing the intra-rater reliability of the palpation protocol in locating MTrPs in the upper trapezius muscle. X and Y are variable used to define the MTrP location according to the ALS. The difference of values is plotted against the mean values of for each subject. The middle dotted line shows the mean of difference. The two lines above and below the mean of difference represent the 95% upper and lower limits (two standard deviations). X1, X value measured during the first palpatory examination; X2, X value measured during the second palpatory examination; Y1, Y value measured during the first palpatory examination; Y2, Y value measured during the second palpatory examination.

Figure 3

Locations of MTrP_1 and MTrP_2 for each subject according to the ALS. X and Y values are normalized with respect to ALS_d. Coloured circles are used to distinguish subjects in left and right ALS. The dotted line joining MTrP_1 and MTrP_2 represent the normalized MTrP_d. MTrPs are located in well-defined area medially to the ALS midpoint and right MTrPs are located in more caudal area (P<0.001). ALS, anatomical landmark system; MTrP_1, myofascial trigger point detected during the first palpatory examination; MTrP_2, myofascial trigger point detected during the second palpatory examination; AA, acriomial angle; C7, spinous process of the seventh vertebrae.