The Intra-rater reliability and validity of ultrasonography in the evaluation of hypertrophic scars caused by burns

Abstract

Purpose: Hypertrophic scars that occur after burns are less flexible and less elastic than normal skin. Objective measurement tools are required to assess hypertrophic scars after thermal injury. Cutometer® MPA 580 has been widely used for evaluating the properties of hypertrophic scars. Ultrasonography can evaluate elasticity, stiffness, and structure of tissues simultaneously using elastography and B-mode. This study aimed to investigate the intra-rater reliability and validity of elastography to visualize hypertrophic scars.

Methods: Sixteen participants with a total of 96 scars were evaluated. The measurement sequence was elastography, Cutometer®, and elastography every 10 min. We then analyzed the intra-rater reliability using intraclass correlation coefficients (ICC). The results measured using elastography on the hypertrophic scars and surrounding normal skin were compared. The relationships between the elastographic and Cutometer® measurements using the 2-and 8-mm probes were compared.

Results: The intra-rater reliability of elastographic measurements was acceptable for clinical use in terms of strain ratio (SR), shear-wave elastography (SWE), shear-wave speed (SWS), and SWE ratio ( ICC = 0.913, ICC=0.933, ICC = 0.842, and ICC = 0.921). The average SWS and SWE in hypertrophic scars were significantly greater than that for normal skin ( p < 0.001 and p < 0.001). SWE showed correlations with the R0 (r = -0.32, p = 0.002) and R8 (r = -0.30, p = 0.003) measured with the 8-mm probe. The SWE ratio was correlated with the R7 (r = -0.34, p = 0.001) measured with the 2-mm probe. The thickness of hypertrophic scars showed correlations with the R5 (r = 0.33, p < 0.001), R6 (r = 0.44, p < 0.001) and R8 (r = -0.35, p < 0.001) measured with the 8-mm probe. R0-R9 measured with 2-mm Cutometer® probes were not correlated with scar thickness ( r < 0.30, P > 0.05). The total scores of mVSS showed correlations with the R0 (r = 0.35, p < 0.001), R1(r = 0.32., p = 0.001), R3 (r = 0.38, p < 0.001), R4 (r = 0.38, p < 0.001), R8 (r = 0.34, p = 0.001), and R9 (r = 0.34, p = 0.001) measured with the 2-mm probe. R0-R9 measured with 8-mm Cutometer® probes were not correlated with mVSS ( r < 0.30, P > 0.05). The thickness of hypertrophic scars showed correlations with the SWE (r = 0.38, p < 0.001) and SWE ratio (r = 0.35, p < 0.001). Elastographic findings were not correlated with mVSS ( r < 0.30, P > 0.05).

Conclusion: In this study, together with the Cutometer®, ultrasound was confirmed as an evaluation tool that can objectively compare and analyze the difference between normal skin and hypertrophic scars.

Keywords: Burn; Cutometer; Elastography; Hypertrophic scar; Objective measurements.