Evaluation of smartphone-assisted infrared thermal imaging efficiency in carpal tunnel syndrome

Background: Thermography is an industrial method for surface temperature measurements, and although it is medically safe and non-invasive, its place in daily practice has been limited. With the development of technology, thermal cameras have become more accessible and practical via adaptation to mobile phones. Among patients evaluated with bilateral nerve conduction studies (NCS) for suspected carpal tunnel syndrome (CTS), those with electrophysiological findings consistent with mild-to-moderate unilateral CTS were accepted for this prospective study. The hands with positive NCS findings were the study group, and the unaffected hands were the control group. The images were evaluated with the thermal analysis software (FLIR Tools ver. 6.4, Windows 10) and compared with NCS for statistical significance. In addition, thermal images were examined by three orthopaedic surgeons, and interobserver correlation was analyzed. Our study aims to evaluate the mobile phone-assisted thermal camera (FLIR One Pro, FLIR Systems, Wilsonville, OR, USA) as a suitable tool to diagnose CTS. Results: 48 patients, 35 women and 13 men were included in the study. Bilaterally, a total of 96 hands were evaluated. 18 patients had mild, and 30 patients had moderate NCS stages unilaterally. The mean temperature difference at the region of interest in the palm, first and third fingers were statistically significant between the study and control groups (p < 0.05). NCS values and stages were correlated with the temperature difference in the third finger (p = 0.002). The inter-observer reliability was high (ICC = 0.858) while detecting temperature differences. Conclusions: Since smartphone-assisted thermal cameras are easy and convenient to use, we think they are helpful in the daily practice of diagnosing mild-to-moderate carpal tunnel syndrome.