System and Methods for Determining Nerve Direction to a Surgical Instrument

Abstract

System (20) and related methods for performing surgical procedures and assessments, including the use of neurophysiology-based monitoring to determine nerve proximity and nerve direction to surgical instruments (30) employed in accessing a surgical target site.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS[0001]This application is a continuation of U.S. patent application Ser. No. 11 / 182,545, filed on Jul. 15, 2005 (now issued as U.S. Pat. No. 8,147,421), which is a continuation of PCT Application Serial No. PCT / US03 / 02056, filed Jan. 15, 2003 (published as PCT Pub. No. WO / 04 / 06434), which claims priority to U.S. Provisional Patent application Ser. No. 60 / 382,318, filed on May 21, 2002, the entire contents of which are hereby expressly incorporated by reference as if set forth fully herein.BACKGROUND[0002]I. Field[0003]The present application relates to a system and methods generally aimed at surgery. More particularly, the present application relates to a system and related methods for determining the direction of a surgical instrument to a nerve during surgical access procedures.[0004]II. Description of Related Art[0005]A variety of surgeries involve establishing a working channel to gain access to a surgical target site. Oftentimes, based on...

AI Technical Summary

Benefits of technology

[0008]The present application may be directed to at least reduce the effects of the above-described problems with the prior art. The present application includes a system and related methods for determining the direction of a surgical instrument to a nerve during surgical procedures. According to one aspect of the system, this involves the use of neurophysiology-based monitoring to determine nerve direction to surgical instruments employed in accessing a surgical target site. The system may do so in an automated, easy to use, and easy to interpret fashion so as to provide a surgeon-driven system.

[0010]A general method according to the present application may include: (a) providing multiple (e.g., four orthogonally-disposed) electrodes around the periphery of the surgical access instrument; (b) stimulating the electrodes to identify the current threshold (IThresh) necessary to innervate the muscle myotome coupled to the nerve near the surgical access instrument; (c) determining the direction of the nerve relative to the surgical access instrument via successive approximation; and (d) communicating this successive approximation direction information to the surgeon in an easy-to-interpret fashion.

[0013]The act of communicating this successive approximation information to the surgeon in an easy-to-interpret fashion may be accomplished in any number of suitable fashions, including but not limited to the use of visual indicia (such as alpha-numeric characters, light-emitting elements, and / or graphics) and audio communications (such as a speaker element). By way of example only, this may include providing an arc or other graphical representation that indicates the general direction to the nerve. The direction indicator may quickly start off relatively wide, become successively more narrow (based on improved accuracy over time), and may conclude with a single arrow designating the relative direction to the nerve.

[0014]Communicating this successive approximation information may be an important feature. By providing such direction information, a user will be kept informed as to whether a nerve is too close to a given surgical accessory element during and / or after the operative corridor is established to the surgical target site. This is particularly advantageous during the process of accessing the surgical target site in that it allows the user to actively avoid nerves and redirect the surgical access components to successfully create the operative corridor without impinging or otherwise compromising the nerves.

[0015]Based on this nerve direction feature, an instrument is capable of passing through virtually any tissue with minimal (if any) risk of impinging or otherwise damaging associated neural structures within the tissue, thereby making the system suitable for a wide variety of surgical applications.

[0016]A direction-finding algorithm that finds a stimulation threshold current one electrode at a time for a plurality of electrodes (e.g., four electrodes) may require 40 to 80 stimulations in order to conclude with a direction vector. At a stimulation rate of 10 Hz, this method may take four to eight seconds before any direction information is available to a surgeon. A surgeon may grow impatient with the system. An “arc” method described herein may improve the direction-finding algorithm and provide nerve direction information to the surgeon sooner. The system may display direction to the nerve during a sequence of stimulations as an “arc” (or wedge), which represents a zone containing the nerve. Computation of the direction arc (wedge) may be based on stimulation current threshold ranges, instead of precise, finally-calculated stimulation current threshold levels. Display of the direction arc (wedge) is possible at any time that the stimulation current thresholds are known to fall within a range of values.

Problems solved by technology

Oftentimes, based on the anatomical location of the surgical target site (as well as the approach thereto), the instruments required to form or create or maintain the working channel may have to pass near or close to nerve structures which, if contacted or disturbed, may be problematic to the patient.

This may be difficult depending on the competing tasks of the user.

In addition, when general anesthesia is used during a procedure, muscular response may be suppressed, limiting the ability of a user to detect the response.

While generally effective (although crude) in determining nerve proximity, such existing systems are incapable of determining the direction of the nerve to the needle or instrument passing through tissue or passing by the nerves.

While the surgeon may appreciate that a nerve is in the general proximity of the instrument, the inability to determine the direction of the nerve relative to the instrument can lead to guess work by the surgeon in advancing the instrument, which raises the specter of inadvertent contact with, and possible damage to, the nerve.

A surgeon may grow impatient with the system.

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