Relationship between skin temperature and soft tissue hardness in diabetic patients: an exploratory study

Abstract

Objective: The role of skin temperature and soft tissue hardness in the development of plantar ulcers is still in debate. However, the relationship between skin temperature and soft tissue hardness has not been explored. This study intends to analyse an eventual association between skin temperature and soft tissue hardness in the foot of diabetic patients Approach: Twenty diabetic patients enrolled for this study. The analysis was done at the foot level, therefore, skin temperature and soft tissue hardness data of the plantar surface of 40 feet were obtained in eight regions of the foot, two in the heel, two in the midfoot, three in the forefoot and one in the hallux. Information regarding glycaemic control (HbA1c levels) was retrieved from the clinical records of the patients. Main results: After averaging skin temperature and soft tissue hardness in the calcaneum (medial and lateral), in the midfoot (medial and lateral) and in the metatarsal head (1st, 2nd–3rd and 4th–5th), a negative, moderate and significant association was found between skin temperature and soft tissue hardness in the metatarsal head (rho = −0.553; p < 0.001), a positive, low and significant association was found in the midfoot (rho = 0.333; p = 0.036), but no association was found in the heel. The multiple linear regression models with skin temperature as dependent variable and soft tissue hardness as predictor were statistically significant in the metatarsal heads and midfoot, and explained 28.8% (R2 = 0.288, F(1,38) = 15.37, p < 0.001) and 11.9% (R2 = 0.119, F(1,38) = 5.151, p = 0.029) of the variance in skin temperature, respectively. Significance: Skin temperature is negatively associated with soft tissue hardness in the metatarsal head region and positively associated with soft tissue hardness in the midfoot. These findings imply that soft tissue hardness should be considered in the assessment of diabetic foot patients and that this variable should be controlled in studies assessing the determinants of foot skin temperature.