Bottom-Loaded Pedicle Screw Assembly for Thread Compatibility
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Solution Overview
Problem
Existing pedicle screws face challenges in efficiently securing spinal rods due to complex assembly processes and limited compatibility with varying thread diameters and pitches, leading to increased manufacturing complexity and potential misalignment during surgical procedures.
Innovation Solution
A pedicle screw design featuring a bottom-loading mechanism with a spherical connector, retainer collar, locking ring, and tulip head, allowing for assembly of screw shank, rod seat, and retainer collar components before insertion into the tulip head, enabling compatibility with various thread diameters and pitches, and facilitating secure angular positioning of the spinal rod.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional top-loading pedicle screw design is used, then assembly is straightforward, but manufacturing complexity increases and compatibility with varying thread diameters and pitches is limited
Solution Approach 1:
The patent inverts the traditional loading direction by implementing bottom-loading instead of top-loading. The screw shank is inserted from the bottom end through the tulip head, allowing the threaded portion to engage the bone first. This inversion enables universal compatibility with various thread diameters and pitches while simplifying manufacturing by eliminating the need for complex internal mechanisms in the head portion.
Solution Approach 2:
The tulip head design serves multiple functions: it acts as both the loading interface and the angular positioning mechanism. The head portion can accommodate screw shanks with different thread configurations while providing angular adjustment capabilities. This multi-functionality reduces the need for multiple specialized components, thereby reducing manufacturing complexity.
2Reliability
If complex assembly processes are used to secure spinal rods, then secure positioning is achieved, but surgical efficiency decreases
Solution Approach 1:
The retainer collar and locking ring are pre-assembled onto the screw shank before insertion into the tulip head. This preliminary assembly ensures proper positioning and engagement of components, eliminating the need for complex post-insertion adjustments. The spinal rod can be directly secured against the rod seat through the tulip head's angular positioning mechanism, streamlining the surgical process while maintaining secure positioning.
Solution Approach 2:
The retainer collar fits over the screw shank, and the locking ring engages with both the retainer collar and the tulip head, creating a nested assembly structure. This nesting allows all components to be compactly integrated, reducing the number of separate assembly steps required during surgery while ensuring reliable securement of the spinal rod.
3Adaptability or versatility
If multiple inventory variants are maintained for different thread configurations, then compatibility is ensured, but manufacturing inventory complexity increases
Solution Approach 1:
The tulip head and retainer collar are designed as universal components that can accommodate screw shanks with various thread diameters and pitches. The head portion's angular positioning mechanism and the retainer collar's retention groove work together to secure any standard pedicle screw configuration, eliminating the need to maintain separate inventory variants for different thread types.
Solution Approach 2:
By inverting the loading direction to bottom-loading, the patent allows the threaded portion to engage the bone first, making the thread configuration irrelevant to the head's function. This enables a single universal head design to work with multiple thread configurations, significantly reducing manufacturing inventory requirements.
Data Source
AI summary
A pedicle screw includes a tulip head, a rod seat, a screw shank, and a retainer collar. The tulip head has an upper opening disposed in a top end of the tulip head and a lower opening disposed in a bottom end of the tulip head opposite the upper opening. The upper and lower openings form a single cavity extending through the tulip head from a top end to the bottom end. The rod seat is disposed within the cavity of the tulip head and engages a stop extending inwardly from an interior wall of the cavity. The screw shank has a thread disposed along a length of the screw shank and a connector positioned at an upper end. The retainer collar has a pass through aperture, an expansion slit, and is disposed about the connector of the screw shank. Other embodiments are described and claimed.