Skull-Mounted Trajectory Guide with Below-Surface Pivot
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Solution Overview
Problem
Existing trajectory guides face challenges in providing constrained rotate and tilt/sweep movements in a low-profile manner, particularly when the center pivot point of the ball needs to be located below the skull surface, such as within a burr hole or other entry portal.
Innovation Solution
A skull-mounted trajectory guide with a base that includes a low-profile flange secured to the skull, a socket for the ball with a central pivot point below the flange, and a guide stem that allows for adjustable positioning and movement, including Z-direction height adjustment, rotational alignment, and pivot sweep constraints, enabling precise instrument guidance through the skull.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a ball-and-socket trajectory guide is used to provide constrained rotate and tilt/sweep movement, then the guide can enable precise instrument positioning, but the profile height increases and the center pivot point cannot be located below the skull surface
Solution Approach 1:
The trajectory guide is divided into separate functional components: a base portion that interfaces with the skull surface, a stem portion that extends downward to position the pivot point below the skull, and a ball-and-socket assembly that provides the constrained movement. This segmentation allows each component to be optimized independently, enabling the pivot point to be positioned below the skull while maintaining a low overall profile.
Solution Approach 2:
The design transitions from a conventional above-surface pivot configuration to a below-surface pivot configuration by extending the stem downward. This dimensional change allows the pivot point to be located in a different spatial zone (below the skull surface), resolving the contradiction between achieving precise positioning and maintaining a low profile.
2Length of stationary object
If the center pivot point is located below the skull surface within a burr hole, then a low-profile configuration is achieved, but providing constrained rotate and tilt/sweep movement becomes difficult
Solution Approach 1:
The stem acts as an intermediary element that transmits and constrains the ball-and-socket movement. The stem's geometry and connection to both the base and the ball assembly enable it to transfer the constrained rotate and tilt/sweep movements from the ball-and-socket joint to the instrument guide, even when the pivot point is positioned below the skull surface.
Solution Approach 2:
The ball-and-socket joint provides dynamic constrained movement with one degree of freedom for rotation and another for tilt/sweep. This dynamic mechanism allows the instrument to be positioned and oriented precisely while maintaining a low-profile configuration with the pivot point below the skull surface.
Data Source
AI summary
An instrument guiding trajectory guide can include a ball-and-socket motion constrained by an arch. Z-height adjustment of a trajectory guide lumen can be provided, with or without a ball-and-socket, such as to permit target-centered alignment of the trajectory to a target. A polar-offset or x-y stage can be included. Contrast-enhanced imageable fiducial marker concentric rings can be used to help align the trajectory to the target. The concentric rings can be progressively smaller in a direction along the trajectory.