Comparison of Two Methods, the Sponge Method and Young's Modulus, for Evaluating Stiffness of Skin or Subcutaneous Tissues in the Extremities of Patients with Lymphedema: A Pilot Study.

The purpose of this study was to compare two methods, the sponge method and SOFTMEASURE, to evaluate the stiffness in lymphedema extremities. We investigated 12 lower extremities of six patients with lymphedema using the methods and compared the results with International Society of Lymphedema classification and lymphoscintigraphic staging. The average age was 53.8 years (43-70 years). We prepared three sponges with different hardness, each of them was numbered as 2, 4, or 6, for the sponge method. We compared the stiffness of the lymphedema extremities and recorded the number of the sponge that was most comparable in stiffness. SOFTMEASURE is a portable device used to measure Young's modulus of an object. Measurement was performed thrice for each extremity. We excluded the most extreme value and the average of the other two values was used for evaluation. The correlation coefficient between SOFTMEASURE and the International Society of Lymphology (ISL) stage was 0.79, and between SOFTMEASURE and the lymphoscintigraphic stage was 0.85 (indentation force of 0.5 N). The correlation coefficient between the sponge method and the ISL stage was 0.57, and between the sponge method and the lymphoscintigraphic stage was 0.54, which indicated an intermediate correlation. In conclusion, evaluation of the stiffness of the skin or subcutaneous tissue in the lymphedema extremities using SOFTMEASURE or the sponge method to assess lymphedema severity was easy and minimally invasive. Sponge method seemed to be more useful than SOFTMEASURE because it had higher correlation with the ISL staging and lymphoscintigraphic staging. Recognizing the change in stiffness is important for determining the therapeutic strategy of lymphedema.