The Assessment of Lymphatic Drainage Using ICG Near-Infrared Imaging and Ultrasound After Fracture

Traumatic fractures are often accompanied by impaired lymphatic drainage function. Reduced lymphatic drainage and lymph node enlargement after fracture indicate ongoing, dynamic processes of the acute inflammatory response and immune cell recruitment. This article describes a method in which 6 µL of 0.2 mg/mL indocyanine green was injected intradermally into the plantar region of mice undergoing sham or tibial fracture surgery. Near-infrared fluorescence imaging quantified plantar ICG signal at 0 h and 24 h to compute the 24 h clearance rate as a readout of murine lymphatic drainage. Ultrasound was used simultaneously to 3D-reconstruct the popliteal lymph nodes (PLNs), compare their volumes, and assess fracture-induced enlargement.  The results demonstrated that after fracture, the lymphatic clearance rate significantly decreased, the fluorescence intensity of ICG in the plantar region was markedly higher, and the volume of the PLNs was significantly enlarged.  Compared with previous methods of measuring the lymphatic system, such as histopathological sections or lymphoscintigraphy, which often fail to achieve in vivo, dynamic, and continuous observation, this method demonstrates high stability and reproducibility. Notably, it enables dynamic in vivo. monitoring of lymphatic drainage function, providing robust technical support for investigating changes in lymphatic reflux in fracture models.