Sustained Decrease in Oxygen Saturation in Human Fibular Fractures Monitored with Laser-Doppler and White-Light Spectroscopy: A Longitudinal Observational Pilot Study

Noninvasive light-based measurements have recently been suggested for monitoring fracture healing and for the development of smart implants. The aim of this study was to collect the first exploratory longitudinal in vivo data from human distal fibular fractures. In this prospective observational pilot study, blood flow, oxygen saturation, and relative hemoglobin were noninvasively measured by using combined laser Doppler and white-light spectroscopy at depths of 3 mm and 10 mm. In patients with fibular fractures, measurements were performed at 1–3 days, 2 weeks, 6 weeks, 3 months and 6 months after surgery. Patients with fibular nonunion and healthy control participants underwent a single measurement. Fourteen longitudinal fracture patients, a nonunion patient, and 42 controls were included. In the longitudinal fracture group, oxygen saturation at a depth of 10 mm significantly decreased from baseline to 2 weeks (p < 0.001) and remained at a low plateau significantly below healthy control levels throughout the 6-month period. Blood flow and relative hemoglobin levels did not longitudinally change but remained significantly elevated compared with controls (p < 0.001). A single nonunion case demonstrated a markedly low oxygen saturation value (8.3%) combined with increased blood flow. Fibular fractures treated with plate fixation exhibit a prolonged low-oxygen saturation plateau, in contrast to the rapid recovery observed in tibial shaft fractures, possibly due to differences in anatomy or healing mechanisms. The low oxygen saturation observed in the nonunion requires further investigation, as it may have prognostic potential.