Thermographic assessment of heat-induced cellular damage during orthopedic surgery

The heat generated during orthopedic surgery can cause thermal damage to bone cells, leading to cell necrosis, death, and bone resorption. In this study, the drill-exit surface in cortical bone drilling was firstly investigated by infrared thermography to understand the thermal characteristics of bone cutting. In order to mimic the short-term thermal condition of high temperature during surgical cutting, the osteoblasts were exposed to heat shock for short periods of time to investigate the effect of cutting heat on the bone. Necrosis and apoptosis were investigated immediately after heat shock for 2 s, 5 s, and 15 s at 50 °C, 60 °C, 70 °C, and 80 °C, respectively. The cells were then incubated for 4 days at 37 °C and analyzed by fluorescein annexin V-FITC/PI double staining. The temperature and heat-duration were precisely controlled by a novel heating approach. In comparison to the control group (37 °C), immediate necrotic and apoptotic response to heat shock was found in cells exposed to 50 °C for 5 s (11.8%, p<0.05); however, the response was negligible in cells exposed to 50 °C for 2 s. In addition, recovery was found in the group exposed to 50 °C and 60 °C for 2 s (p ≤ 0.05) after incubation for 4 days. Cell damage depends on the magnitude and duration of heat exposure. These findings provide fundamental knowledge for future developments of surgical tool design and cutting methods.