A method for the fixation of an implantable spinal cord NIRS sensor

Introduction: We previously developed an implantable near-infrared spectroscopy (NIRS) sensor to provide real-time monitoring of spinal cord oxygenation and hemodynamics in a porcine model of acute SCI. Here, we present a method to fix an improved design of the sensor to the spinal cord for up to 14-days post-injury which will be important for its clinical application. Methods: Two Yucatan mini-pigs received a T2 contusion-compression injury. A multi-wavelength NIRS system with a custom-made miniaturized sensor was laid over the dura. The NIRS sensor consisted of a five wavelength LED and photodetector from the previous design. The placement of the LED and photodetector was reconfigured to create a sensor with a slimmer shape. The sensor was mounted on a flexible printed circuit board (PCB) and enclosed by an implantable soft silicone with thin flaps on its side. This allowed the sensor to sit flush on the dura and secured with a fibrin sealant material (TISSEEL), eliminating the need for additional spinal fixation devices. The surgical incision was sutured closed, and the sensor was fixed on the spinal cord while the animal recovered for 14-days post-injury. A fluoroscopy was performed on the surgery day, 7- and 14-days post-injury to assess the positioning of the sensor. Results/Conclusion: The implantable NIRS sensor appeared to remain fixed on the spinal cord after 14-days post-injury upon analysis of fluoroscopy images and examining the re-exposed surgical wound. Securing the NIRS sensor to the spinal cord with a fibrin sealant may provide a method for fixation for up to 14-days post-injury.