It is necessary to provide radiographic localization of the correct surgical level and the proper placement of the surgical instruments. The MIS technique relies heavily on intraoperative
navigation, and traditional technique usually uses fluoroscopy. Using fluoroscopy exposes the patient, the surgeon, and the other staff to radiation. However, nowadays tracking of surgical spinal instruments is done by using CT scan or machines such as the O-arm that shows direct images allowing for real-time navigation of the spinal anatomy. As the navigation system configures the patient’s spine in 3-D, registration of the patient’s spinal anatomy is the primary element to image-guided spinal navigation surgery. Initial techniques of spinal registration for navigated open procedures included point and surface matching that involved meticulous dissection of the spinal bone anatomy. After the bone anatomy had been exposed, the surgeon had to match points on the dissected anatomy to points chosen on a preoperative 3-D reconstructed CT scan or by using fluoroscopy-based intraoperative navigation. Utilizing MIS procedure, this step was replaced by acquiring images (CT or 3-D spins). The images are reconstructed in the machine and by using semi-automated registration. No more calibration is required as the images are downloaded directly to the system. This is considered a major advancement that minimizes the time required for such procedures.