NEED AND PERSPECTIVE IN SPINE NAVIGATION

Abstract

Following orthopaedic reconstruction and cranial neurosurgery, spine surgery is now entering its low invasive period. When, in 90’s, computer went routinely available in the surgical field, the main goal was to help surgeons operate on with more accuracy some difficult but standard procedures. The surgery was “computer aided”. The displayed tools on 2D or 3D images allowed surgeons to avoid permanent intra operative landmarks. Once patient personal anatomy was capture into the machine and the tools calibrated, the surgeon was able to plan and optimised ideal trajectories without direct vision to check tools position. “Navigation” starts to be more obvious to describe this intra operative control. Anyway, we still needed large exposure to get the full bone surface in order to build a 3D surface based model. This model optically localised was matched using rigid or elastic algorithm with preoperative CT scan model or bone morphing^®. Ultrasound recognition of the soft tissue/bone interface let think about trans cutaneous palpation. However, automatic segmentation of the bone surface never lead to commercially available soft. Only X-ray is commonly use during surgery to help surgeon to see tools and bone without surgical exposure. Fluoroscopy allows percutaneous trajectory as iliosacral screwing, vertebroplasty, fracture nailing et caetera. Radiation exposition could therefore be an issue for patient but also for surgeon. Fluoronavigation is a good response to percutaneous surgery. In spine no transversal view could be available. Surgeons should make mental reconstruction of the volume to perform the right trajectory. Industrial proposed intra operative tomography on C-arm with 3D reconstruction. It works well for limbs, but in thoracic and lumbar spine the large amount of surrounding soft tissues leads to low quality images. Flat panel X-ray receptor are a path to get more accurate images. Other perspectives are circular intra CT scan. The cost and the volume of machines stops the spread of such device.

Robots are used by knee surgeons but abandoned by hip surgeons. In spine tool holder robot are available in order to place a pedicular drill guide. Matching with bone is based on fluoroscopy.

Spine navigation could be useful to e-leaning and simulators too. The training of percutaneous surgery is long, because of mental matching between fluoroscopic 2D projections and the vertebra volume. We need a simulator allowing 3D virtual trajectory checked on AP and lateral view to short the learning curve.