Image Guidance in Spine Surgery

Abstract

Present-day computer-assisted image guidance enables surgeons to intraoperatively visualize the spine far beyond traditional exposure and to position implants with a higher accuracy than is possible with conventional techniques. Moreover, this accuracy may be maintained even in complex cases such as scoliosis or percutaneous procedures. Image guidance in spine surgery is based on merging the images of the patient obtained earlier to the patient’s anatomical position and orientation in the operating room. This can be performed with a preoperative computed tomography (CT) scan using intraoperative manual registration, with an intraoperative fluoroscopic C-arm or CT imaging and automated registration, or with a preoperative CT scan coupled with intraoperative fluoroscopic images. Placement precision is within the millimeter range, and >95 % of pedicle screws are placed accurately. Nevertheless, image guidance does not replace a profound knowledge of spinal anatomy. For instance, unnoticed displacement of a reference array after registration can be misleading, and it is the surgeon’s responsibility to judge whether the multiplanar reconstruction of the location of the instruments concurs with what the surgeon expects to see. Analysis of radiation exposures suggests that image guidance results in reduced dose to the patient and the surgical staff. This is of particular importance for minimal access surgeries, where anatomical orientation can only be obtained and maintained with real-time imaging. Experienced surgeons may initially find that using image guidance results in longer procedures, although after a short learning curve operation times are likely to compare favorably with those for conventional techniques and may even become shorter, particularly for minimal access surgeries. Image guidance in spine surgery is associated with a considerable investment, and availability is limited to hospitals and societies with the necessary resources for both acquisition and maintenance. Nevertheless, surgeons and patients alike may embrace the high level of precision and safety that image guidance can persistently ensure for the practice of spine surgery.