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Medical image-based design of an individualized surgical guide for pedicle screw insertion

To reduce the complication risk of pedicle screw insertions it may be unavoidable to introduce a certain degree of automation of the critical surgical actions. The approach presented here proposes a mechanical drill guide that can be placed on the posterior surface of the vertebra and indicates-by means of holes-the correct direction of the pedicle screw. The CAD/CAM system Unigraphics enables a pre-operative planning based on CT-images of the patient's spine. The CT-images also yield surface information of the vertebra which along with the pre-operative planning is translated into a drill guide design. The drill guide concept has been optimized using non-linear finite element software Marc K6.2. The guide is produced by stereolithography as rapid prototyping technique using a Zeneca experimental resin which is sterilizable and USP Class VI. Two prototypes have been developed and evaluated.