Reliability of different methodologies of infrared image analysis of myofascial trigger points in the upper trapezius muscle

BACKGROUND Infrared thermography is recognized as a viable method for evaluation of subjects with myofascial pain. OBJECTIVE The aim of the present study was to assess the intra- and inter-rater reliability of infrared image analysis of myofascial trigger points in the upper trapezius muscle. METHOD A reliability study was conducted with 24 volunteers of both genders (23 females) between 18 and 30 years of age (22.12 ± 2.54), all having cervical pain and presence of active myofascial trigger point in the upper trapezius muscle. Two trained examiners performed analysis of point, line, and area of the infrared images at two different periods with a 1-week interval. The intra-class correlation coefficient (ICC(2,1)) was used to assess the intra- and inter-rater reliability. RESULTS With regard to the intra-rater reliability, ICC values were between 0.591 and 0.993, with temperatures between 0.13 and 1.57 °C for values of standard error of measurement (SEM) and between 0.36 and 4.35 °C for the minimal detectable change (MDC). For the inter-rater reliability, ICC ranged from 0.615 to 0.918, with temperatures between 0.43 and 1.22 °C for the SEM and between 1.19 and 3.38 °C for the MDC. CONCLUSION The methods of infrared image analyses of myofascial trigger points in the upper trapezius muscle employed in the present study are suitable for clinical and research practices.