Telescopic Dilator with Rotatable Window for Nerve Direction Detection
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Solution Overview
Problem
Current methods for lateral access spinal surgery face challenges in accurately determining nerve location and direction due to increased nerve density in the psoas muscle, leading to potential nerve damage during instrument insertion.
Innovation Solution
An apparatus comprising a first dilator with a tubular body and electrodes, and a second dilator with a discrete window, allowing for telescopic alignment and rotational adjustment to focus current flow and monitor neural activity, enabling precise determination of nerve proximity and direction for safe passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a monopolar probe with electrical stimulus is used to monitor neural activity, then nerve proximity can be detected through muscle action potential activation, but the ability to determine nerve direction and location precision is insufficient
Solution Approach 1:
The circumferential electrode is divided into multiple discrete electrodes spaced around the dilator circumference. Each electrode can be independently stimulated and monitored, allowing the system to segment the 360-degree field of view into multiple directional sectors. This segmentation enables determination of both nerve proximity (through action potential detection) and nerve direction (through identification of which specific electrode elicits the response), thereby resolving the technical contradiction between measurement precision and information loss.
2Ease of operation
If larger instruments are introduced for lateral access spinal surgery, then surgical access is improved, but the potential for harmful engagement with nerves increases
Solution Approach 1:
The system performs preliminary neural monitoring and directional identification before the surgical instrument is advanced further into the psoas muscle. By first determining the precise location and direction of nerves using the monopolar probe with circumferential electrodes, the surgeon can plan the instrument trajectory to avoid nerve engagement. This preliminary action allows larger instruments to be introduced with improved surgical access while minimizing nerve damage risk through informed trajectory selection.
Solution Approach 2:
The system provides real-time feedback about nerve proximity and direction during instrument insertion. As the dilator advances, the monopolar probe continuously monitors muscle action potentials and identifies which circumferential electrode responds to stimulation, indicating nerve location and direction. This feedback loop allows the surgeon to adjust the instrument trajectory dynamically, maintaining surgical access while avoiding harmful engagement with nerves through continuous neural activity monitoring.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates more efficient re-positioning of surgical instruments to avoid nerves, reducing the risk of damage and improving the accuracy of nerve location and direction detection during spinal surgery.
Implementation Method 1
Current is applied to the tip with a ground electrode attached to the skin. Current is introduced through the probe and the activity of surrounding nerves is monitored using electrodes placed on muscles innervated by the nearby nerves (knows as myotomes). Activation of a muscle action potential by the electrical stimulus threshold value indicates proximity to a nerve.
Data Source
AI summary
An apparatus is provided herein for dilating bodily tissue and for monitoring neural activity in the distracted bodily tissue. In one aspect of the invention, the apparatus includes a first dilator having a tubular body with a distal end, a proximal end, and at least one electrode mounted about a circumference thereof; and, a second dilator having a tubular body of electrically-insulative material, the tubular body having a distal end, a proximal end, and a lumen extending therebetween sized to permit the second dilator to subsequently telescopically slide over the first dilator and come into overlapping coaxial alignment with the first dilator. A discrete window is formed through the tubular body, at or near the distal end, in communication with the lumen. With the second dilator being in overlapping coaxial alignment with the first dilator, the window is located to come into registration with at least one electrode such that, upon rotation of the second dilator relative to the first dilator, the window is positionally adjustable about the circumference of the first dilator. Advantageously, in addition to detecting the proximity of a nerve to the first dilator, the apparatus permits determination of the direction of the nerve from the first dilator. This facilitates more efficient re-positioning of the apparatus for avoidance of nerves, if a new path is necessary.