Continuous-flow cryocompression therapy penetrates to bone level in hip fracture patients in a numerical simulation

Abstract

Background The aim of this study was to define deep tissue temperature during cryotherapy in postoperative hip fracture patients, by using measured skin temperature as input parameter for a simple numerical model. Second, an association was investigated between pain and tissue temperature distribution, to assess cryotherapy-induced analgesia of soft tissue-derived pain. Methods Data from 35 participants in an ongoing trial was used. In three subjects who consented on optional measurements, skin temperature was measured in 3 days during and after cryotherapy. A simple numerical model was developed to calculate tissue temperature distribution during cryotherapy. Results Inter and intrasubject skin temperature displayed high variation: trochanter 11–27 °C, mid-femur 11–24 °C, distal femur 10–16 °C. Predicted temperatures decreased to 20 °C at 1 cm, 26 °C at 2 cm, and 30 °C at 3 cm tissue depth. Smallest soft tissue layer was measured at the trochanter; 42% had less than 30 mm and 21% had less than 20 mm. Numeric rating scale pain varied (mean = 2.14; SD = 1.92), and no association was found between pain and decrease in temperature ( r = 0.064; p = 0.204). Conclusions Cryotherapy was predicted to reduce temperature up to 3 cm; in cachectic patients, this reaches the bone, where it might have implications for bone tissue healing when treated for a prolonged period of time. Cryotherapy-induced analgesia is likely to originate from skin analgesia rather than analgesia of muscle or bone-derived pain.