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Reliability and responsiveness of a tissue hardness meter and algometer for measuring tissue hardness and pressure
Soukmisai Somphithak1, Uraiwan Chatchawan1,2, Atipong Pimdee1,2
1School of Physical Therapy, Faculty of Associated Medical Sciences (AMS), Khon Kaen University (KKU), Khon Kaen, Thailand.
Background:
Tissue hardness meter and algometer (THA) are used to assess tissue hardness (TH) and pressure pain threshold (PPT), particularly in the evaluation of myofascial trigger points (MTrPs). This study introduces a side-lying protocol designed to comprehensively measure all portions of the upper trapezius (UT) muscle.
Purpose:
The objective was to determine the reliability and responsiveness of THA to measure TH and PPT in patients with MTrPs in the UT muscle.
Methods:
Reliability of TH and PPT measurements was assessed in a sample of 24 participants. Intra-rater and inter-rater reliability were evaluated using the intra-class correlation coefficient (ICC3,1), while absolute reliability was established via Bland-Altman analysis, including the calculation of 95% limits of agreement (95% LoA). To assess responsiveness, 36 additional participants were recruited. Both distribution-based methods (mean difference, effect size (ES), standardized response mean (SRM), standard error of measurement (SEM), and minimal detectable change at 95% confidence (MDC95)) and anchor-based methods (minimal clinically important difference (MCID) and area under the curve (AUC)) were utilized in the analysis.
Results:
Intra-rater reliability was excellent for both TH and PPT (ICC3,1: 0.95-0.97), while inter-rater reliability was moderate (ICC3,1: 0.60). Evidence of both fixed and proportional bias was identified for both TH and PPT. For TH, the SEM and MDC95 were 2.66% and 7.37%, respectively, while for PPT, they were 0.12 kg/cm2 and 0.34 kg/cm2, respectively. Following six physical therapy sessions, significant reductions in TH (mean: -7.86%; MCID: -7.43%; AUC: 0.97) and significant increases in PPT (mean: 0.20 kg/cm2; MCID: 0.21 kg/cm2; AUC: 0.86) were observed. Additionally, changes in PPT showed a negative correlation with improvements in the Neck Disability Index (NDI) (r = -0.35, p < 0.05).
Conclusion:
The side-lying protocol demonstrated reliable and clinically relevant TH and PPT measurements, supporting its use for monitoring treatment outcomes in patients with MTrPs in the UT muscle.
