Postoperative infection is a well-known risk of surgery that can potentially develop into a serious complication for the patient. Orthopedic postoperative infections can be implant, extremity, and/or life-threatening. Diagnosis of postoperative infections in orthopedic surgery is challenging despite the availability of advanced equipment to assist and specify the diagnostic process. A tool for monitoring surgical sites for inflammation and infection with rapid and specific responses would be preferred.

The overall objective was to investigate thermography as a potential monitoring tool for orthopedic patients treated with external ring fixation to detect early signs of infection at pin sites.

Study I was a systematic literature review aiming to map and summarize the existing literature where thermography has been used to assess signs of inflammation in humans and animals with surgical or traumatic wounds. The results show a pattern of the current state of knowledge for the role of thermography in the assessment of wounds. Study II was a methodological study examining reproducibility. We investigated whether we could reproduce temperature measurements around pin sites by repeating infrared images in a test-retest setup. Furthermore, we investigated the intra- and inter-rater reliability of extracting the temperature values from the infrared images using two different methods. The results show that the methods used for temperature measurement at a pin site have excellent reliability. Study III was a clinical cross-sectional study of patients from two centers in Denmark and the USA of 2000 pin sites. We investigated whether there was a temperature difference between clean and inflamed pin sites. The study reveal a significant temperature difference of 0.9°C between clean and inflamed pin sites categorized by clinical visual signs. 34.1°C (MaxTp) was established as empirically optimal threshold value to discriminate clean and inflamed pin sites.

This thesis provides an evidence-based foundation for future innovative work in the development of a pin site surveillance tool for point-of-care.