Reliability of measurement of elastomer samples by soft tissue stiffness meter

Purpose: We assessed the TK-03C soft tissue stiffness meter (STSM) (Tokushukeisoku Corporation, Japan) for inter/intra-rater reliability. This device measures load and displacement simultaneously. Subjects: Ten students from the Physical Therapy Department were the subjects. Methods: The 10 subjects measured the surface stiffness of three elastomer samples with known mechanical properties: a polyurethane test piece and two sorbos test pieces. They each took 7 consecutive readings using the STMS at the same site on each test piece. We calculated the displacement for a load of 10 N. Result: The overall rating reliability for all sites was high: site1, coefficient of variation (CV) (range)=5.3 (2.6-10.0); site2, CV=3.9 (2.3-6.1); site3, CV=5.0 (2.2-9.2). The intra-rater reliability of the 10 subjects was high showing an intra-class correlation coefficient (ICC) (1•1) ≥0.97. The inter-rater reliability was also high; ICC(2•1)=0.96. In addition, the hardness of the three test pieces were significantly different (p<0.01). Conclusion: It seems that this STSM is a reliable and useful device for objective quantitative evaluation of soft tissue stiffness.