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 system for carrying out the procedure includes a tool handle and a probe member extending from the handle with a tip for working an opening in bone tissue. An electrical stimulator in the form of a self-contained nerve stimulator unit, or circuitry provided inside the tool handle, produces an electric potential at a selected level. The potential is applied to the tip of the probe member while the tool handle is manipulated and the tip is directed toward the bone tissue.

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First Claim