Polyaxial Bone Anchoring System Frustoconical Split Ring
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Solution Overview
Problem
Conventional polyaxial bone anchoring systems with bottom loading mechanisms are complex, requiring multiple elements such as springs, retaining rings, and ramps for screw insertion and retention, which complicates the assembly process.
Innovation Solution
A polyaxial bone anchoring system featuring a tubular shaft with a frustoconical housing and a conical split ring made of deformable material, allowing for simple assembly through a joint movement of the split ring and hemispherical head, with a radial groove for expansion and a cradle body for locking, facilitating secure attachment without the need for additional components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional bottom-loading bone anchoring systems use multiple elements (springs, retaining rings, ramps) for screw insertion and retention, then the retention reliability is improved, but the device complexity increases
Solution Approach 1:
The patent combines multiple retention elements (retaining ring, spring, and locking mechanism) into a single integrated cradle body. The cradle body includes an upper surface for receiving the connecting rod, a lower surface for receiving the hemispherical head, and internal features that provide both retention and locking functions, eliminating the need for separate components while maintaining reliability
Solution Approach 2:
The cradle body is designed as a multi-functional component that simultaneously provides retention of the hemispherical head, support for the connecting rod, and locking capability through axial movement. This single component performs multiple functions that previously required separate elements, reducing overall device complexity while maintaining all necessary retention and locking capabilities
2Reliability
If conventional systems use multiple components for assembly, then the retention security is improved, but the ease of operation deteriorates
Solution Approach 1:
By merging the retaining ring, spring, and locking mechanism into the integrated cradle body, the assembly process is simplified to a single operation. The cradle body is inserted axially into the tubular shaft in one motion, eliminating the need to separately assemble multiple components while maintaining secure retention through the integrated design
3Ease of manufacture
If the tubular shaft has a frustoconical housing with specific dimensions, then the ease of manufacture is improved, but the volume of the component increases
Solution Approach 1:
The frustoconical housing provides a curved, tapered geometry that facilitates the insertion and expansion of the cradle body during assembly. The conical shape allows for smooth radial expansion of the cradle body as it is inserted axially, enabling easy manufacture through standard machining processes while the tapered geometry efficiently contains the component within a compact volume
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 system enables rapid and secure loading of the bone anchoring element into the connector, reducing complexity and ensuring reliable retention, while allowing for axial movement and rotational locking, thus simplifying the assembly process and enhancing stability.
Implementation Method 1
said ring being made of a deformable material between an expanded position allowing passage of the hemispherical head through the ring, and a constricted position to a section smaller than the minimum section at rest for its insertion into the tapered housing
Data Source
Figure 1~2
Figure 3a~3e
Figure 4
AI summary
The invention concerns a polyaxial bone anchoring system (1) comprising a bone anchoring member provided with a hemispherical head (21) and a tubular barrel (3) comprising a base (33) traversed by an axial channel of which the cross section is greater than the cross section of the hemispherical head (21), said channel having, in the lower part, a frustoconical housing (9) that widens in the direction opposite the hemispherical head (21) and, upstream from the frustoconical housing (9), a transverse shoulder (11) of which the internal cross-section is substantially equal to the cross-section of the hemispherical head (21), the system further comprising a conical split ring (4) of which the outer surface matches the inner surface of the frustoconical housing (9) and of which the minimum cross-section when idle is smaller than the nominal cross-section of the hemispherical head (21), said ring being made from a deformable material.