Minimally Invasive Vertebral Tracking System for CAS

DESCRIPTION (provided by applicant): The goal of this Phase II SBIR proposal is to develop a novel electromagnetically tracked bone screw and comprehensive demonstration software for minimally invasive spinal procedures. The prototype bone screws were developed in the Phase I work and the feasibility of using these screws for non-line-ofsight localization of a vertebral body was demonstrated. Percutaneous lumbar instrumentation and fusion techniques can result in substantially less trauma to the patient, but these methods are technically difficult and traditional image-guided systems require substantial exposure of the spine. The bone screws will be further refined into a form resembling tracked k-wires. The image-guided system we propose will utilize C-arm fluoroscopy, which is readily available in spinal surgery suites. The successful completion of this work will: 1) validate the concept of percutaneously placed bone screws for image guidance in the spine; and 2) result in a prototype image-guided system based on electromagnetic tracking for percutaneous spinal procedures. The bone screws will then become part of Traxtal's product line and the prototype system can be licensed to commercial vendors. The specific aims of the proposal are: 1. Bone screw enhancements. The bone screws successfully prototyped and validated in Phase I will be further developed to decrease their size and form factor. 2. Develop fiducial-based registration system. As an intermediate step, an image-guided system incorporating pre-operative insertion of the bone screws and CT will be developed. A method for registration using two 5 degree of freedom bone screws will be implemented. 3. Develop 2D/3D anatomy-based registration system. The image-guided system developed in Aim 2 will be extended to include anatomy-based registration. This registration does not require pre-operative insertion of the bone screws. The C-arm will be calibrated and electromagnetically tracked. The bone screws will be used intraoperatively to track vertebral motion only. 4. System validation. The system developed in Aims 2 and 3 will be validated through a series of phantom and cadaver studies.