Healing of surgical site after total hip and knee replacements show similar telethermographic patterns

Background: Isolated reports indicate the efficacy of infrared thermography for monitoring wound healing and septic complications, but no long-term analysis has ever been performed on this, and there are no data on the telethermographic patterns of surgical site healing after uncomplicated total hip prosthesis and after knee prosthesis. Materials and methods: In this prospective, observational, nonrandomized cohort study, two groups with forty consecutive patients each, who were operated on respectively for total hip and for total knee replacements, underwent telethermographic examination of the operated and contralateral joints prior to and at fixed intervals for up to 1 year after uncomplicated surgery. A digital, portable telethermocamera and dedicated software were used for data acquisition and processing. Results: No thermographic difference was observed preoperatively between the affected side and the contralateral side in both groups. After the intervention, a steep increase in the temperature of the operated joint was recorded after total hip replacement and after knee replacement, with a peak mean differential temperature measured three days postoperatively between the operated and unoperated joint of 3.1 ± 0.8°C after total hip replacement, and 3.4 ± 0.7°C after total knee replacement. Thereafter, the mean differential temperature declined slowly to 0.7 ± 1.1°C and to 0.5 ± 1.3°C at 60 days, and to 0.0 ± 1.0°C and -0.1 ± 1.1°C 90 days post-operatively, respectively. No further changes were observed for up to 1 year after surgery. Results were similar when comparing the average telethermographic values of an elliptical area where the main axis corresponded to the surgical wound. Conclusions: The surgical sites after uncomplicated total hip or total knee replacement show similar telethermographic patterns for up to 1 year from surgery, and can easily be monitored using a portable, digital, telethermocamera.