Abstract

Instrumentation has become an integral part in traumatic, infected, neoplastic and degenerative spinal conditions. Misplacement of implants may result in immediate catastrophic events, or may lead to inferior mechanical properties of the construct and may lead to late sequel such as adjacent level degeneration. Many efforts have been made to increase the safety of instrumentation. Factors affecting misplacement include: surgical experience, the area of the spine operated on, factors affecting anatomy (deformity, severe degeneration, previous surgery, etc.). Fluoroscopy guided implantation increases the accuracy, however, lumbar pedicle screw misplacement may reach 30%, thoracic misplacement may reach 50% and cervical screws misplacement may reach 70%. The rate of clinical consequences, although much lower, harbors medical, legal and financial issues. The need for navigated systems in the aid of spinal instrumentation is quite intuitive, however until efficacy and cost-effectiveness are proven their routine use is not expected. Computer assisted navigation systems have been introduced in the 1990's, however none gained enough popularity, and most are sitting in the corridors of the operating theaters serving as "white elephants". The reasons for failure may include high cost, cumbersome procedures, the need for extra-staff and the need for a direct line of sight. Miniature robotic spine surgery is a new concept for aiming instrumentation in various spinal procedures. The basic steps in its use include: 1. A high resolution CT scan 2. Pre-operative planning based on 3-plane 2-D reconstructions of the CT imported to the software 3. Connection of one of the three robotic platforms to the patient 4. Acquisition of 2-plane fluoroscopy images with a target connected to the robotic platform 5. Connection of the robot to the platform and execution of the surgical plan. Studies performed on cadavers have demonstrated its accuracy and reliability, together with a short learning curve and a significant reduction in the need for image control and the exposure of the OR staff to irradiation. Robotic guidance has been used in several centers around the world in the introduction of pedicle screws, trans- laminar screws, vertebral augmentation needles and biopsy needles. It was also used in deformity surgery and to locate and excise small lesion such as osteoid osteoma. Between 9/2006 and 1/2009 robotic guidance was used in 65 patients in our institution. Mean patient's age was 61.7 (14-84), 39 were fames and 29 were males. In 51 patients pedicle screws were inserted with robotic guidance, while 11 patients underwent vertebral body augmentation with cement or core needle biopsy and 1 patient underwent excision of an osteoid osteoma. Mean surgical time was 196 minutes (47-435), off which 34 minutes (14-95) were needed for robotic guidance. 245 trajectories were planned (1 to 8, mean 3.8 per case). Misplaced entry points and trajectories were recorded in slightly over 4% (10 trajectories), however, these were detected before the vertebra was instrumented and therefore no harm was done to the patient. Two critical steps prevent better results at the moment – errors of planning and technical errors causing an unstable connection between the robot's platform and the patient's body. Omitting all cases were technical errors were encountered (Malfunction of the system or mounting the platform in an unstable manner) – the system was found to have an accuracy of 97%