Importance

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Abstract

Pedicle screws are inserted in spinal vertebrae in a manner to reduce the likelihood of nerve damage caused by improper screw placement. A screw opening is started in part of a skeletal region, e.g., a pedicle of a lumbar vertebra and an electric potential of a certain magnitude is applied to the inner surface of the opening while the patient is observed for nervous reactions such as leg twitching. The opening continues to be formed while the electric potential is applied until a desired hole depth is obtained in the absence of nervous reaction to the potential. The direction in which the screw opening is being formed is changed to a direction other than the last direction, after observing patient reactions to the electric potential when the screw opening was being formed in the last direction. A tool for carrying out the procedure includes a handle and a probe tip extending from the handle for forming an opening in bone tissue. Stimulator circuitry arranged inside the handle produces an electric potential of a predetermined level, and the potential is applied to the probe tip while the tool handle is manipulated to urge the probe tip into the bone tissue.

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First Claim