Pedicle Screw Base with Position-Limiting Flange
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Solution Overview
Problem
Existing pedicle screw systems face issues with the positioning compression ring sinking during use due to line contact with the connecting rod, leading to poor fixation, and the existing rotation prevention methods are complex and prone to errors, resulting in a large screw base diameter, thin side walls, and reduced strength, which can cause safety risks during surgery and affect tissue healing.
Innovation Solution
A low-profile screw base with a cylindrical positioning compression ring featuring a position-limiting flange and rotation-preventing lug, where the flange and lug are designed to fit into specific grooves and protrusions, allowing for a small outer diameter, thick side wall, and high strength, along with a simplified assembly process that prevents upward drawing and rotation of the compression ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a U-shaped positioning compression ring is used to improve fixation with the connecting rod, then the fixing effect is improved, but the screw base diameter increases and the side wall becomes thinner
Solution Approach 1:
The positioning compression ring is segmented into a cylindrical ring body and a separate position-limiting flange. The flange is inserted into a groove on the screw base, separating the fixation function (ring body with connecting rod) from the positioning function (flange in groove), allowing the ring body to be smaller while maintaining fixation reliability.
Solution Approach 2:
The position-limiting flange is nested within a groove on the screw base, with the flange's outer diameter being smaller than the groove's inner diameter. This nesting arrangement allows the flange to be constrained laterally by the groove while maintaining a compact overall structure, reducing the screw base diameter and preserving side wall strength.
2Reliability
If a position-limiting flange with slope is used to prevent upward drawing, then the prevention effect is improved, but the assembly complexity increases and manufacturing precision requirements increase
Solution Approach 1:
The anti-upward-drawing function is extracted from the position-limiting flange's slope and transferred to a dedicated limiting protrusion on the screw base. The protrusion fits into a corresponding groove on the flange, creating a simple snap-fit structure that eliminates the need for complex sloped surfaces and reduces manufacturing precision requirements.
Solution Approach 2:
Instead of using a sloped surface to resist upward force passively, the design uses an active mechanical stop where the limiting protrusion physically blocks upward movement. This inversion from passive resistance to active blocking simplifies the structure and improves reliability.
3Reliability
If a side-stamping bump structure is used to prevent rotation, then the rotation prevention is improved, but the screw base side wall strength decreases and the structure becomes more complex
Solution Approach 1:
The anti-rotation mechanism transitions from a two-dimensional side-stamping bump on the side wall to a three-dimensional groove-flange interface. The groove is formed on the screw base and receives a corresponding protrusion on the positioning compression ring, creating anti-rotation constraint through a different spatial arrangement that preserves side wall integrity.
4Object-affected harmful factors
If the screw base diameter is reduced to minimize tissue stimulation, then the tissue healing is improved, but the strength and reliability of the screw base decrease
Solution Approach 1:
The positioning compression ring is segmented into a cylindrical ring body and a separate position-limiting flange. The flange is inserted into a groove on the screw base, separating the fixation function (ring body with connecting rod) from the positioning function (flange in groove), allowing the ring body to be smaller while maintaining fixation reliability.
Solution Approach 2:
The position-limiting flange is nested within a groove on the screw base, with the flange's outer diameter being smaller than the groove's inner diameter. This nesting arrangement allows the flange to be constrained laterally by the groove while maintaining a compact overall structure, reducing the screw base diameter and preserving side wall strength.
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
The solution provides a safer, more reliable, and smaller-profile screw base with improved fixation and reduced tissue stimulation, enhancing surgical safety and postoperative healing, especially for patients with smaller body sizes, while preventing screw disengagement during operation.
Implementation Method 1
punching the positioning compression ring downward, so that the slope on the lower side of the position-limiting flange applies a force on the ring body on both left and right sides of the rod-containing groove, causing the ring body to have an elastic deformation and insert into the lower side of the snapping protrusion
Data Source
AI summary
The low profile screw base comprises a screw base body and a positioning compression ring. An assembly hole penetrates longitudinally through the screw base body. A U-shaped slot for a connecting rod to pass through is provided on an upper portion of the screw base body. The inner wall of the screw base body on the opposite sides of the U-shaped slot is provided with internal threads. Snapping protrusions are formed on the inner wall of the screw base body on the opposite sides of the U-shaped slot below the internal threads. A lower ball socket matched with the round head of the ball screw is arranged in the assembly hole of the lower portion of the screw base body. The positioning compression ring used for compressing the round head is snap fitted above the lower ball socket and below the snapping protrusions (6).