Bone Stabilization Rod Coupling With Anti-Loosening Collet Geometry

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Solution Overview

Problem

Existing bone implant systems face challenges in securely coupling the implant, tulip, and rod, particularly in resisting axial forces that can cause the collet to loosen or expand, compromising the stability of the fixation.

Innovation Solution

The bone implant features a radially recessed collet receiving region with a radially extending surface angled less than ninety degrees relative to the longitudinal axis, combined with a chamfered proximal end and optional modular tulip assembly, to enhance the stability and resistance to axial forces during rod fixation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a collet is used to couple the implant and tulip, then the assembly can be easily assembled and disassembled, but the collet may expand or loosen under axial forces, compromising stability

Engineering Contradiction:

Improveease of assemblyVSAvoidstability under axial forces

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The radially extending surface is angled at less than 90 degrees relative to the longitudinal axis, creating a geometric configuration that converts axial compressive forces into radial compressive forces on the collet. This parameter change in surface orientation transforms the mechanical advantage to prevent collet expansion while maintaining ease of assembly.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The asymmetric angular orientation of the radially extending surface creates unequal force distribution that actively compresses the collet against the recessed region during axial loading. This asymmetric geometry ensures the collet remains tightly secured under physiological axial forces while allowing straightforward assembly procedures.

Inventive Principle:

Principle #4Asymmetry

2Device complexity

If the radially extending surface is orthogonal to the longitudinal axis, then the structure is simpler, but the collet is more likely to expand and loosen under axial forces

Engineering Contradiction:

Improvestructural simplicityVSAvoidresistance to collet loosening

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

By changing the angular parameter of the radially extending surface from 90 degrees (orthogonal) to less than 90 degrees, the design achieves improved collet security. This parameter modification creates a mechanical advantage where axial forces naturally compress the collet, providing enhanced reliability with minimal additional structural complexity.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If the collet receiving region is recessed radially, then the collet is better retained, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvecollet retentionVSAvoidprecision of recessed region

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The angular orientation parameter of the radially extending surface (less than 90 degrees) provides inherent mechanical advantage that compensates for normal manufacturing tolerances. This geometric parameter choice ensures reliable collet retention through self-compression under axial loading, making the system robust against typical manufacturing variations without requiring excessive precision.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12419668B2Rod coupling assemblies for bone stabilization constructs

Publication Date: 2025.09.23 SI BONE INC

AI summary

Bone implants and stabilizing rod coupling assemblies to secure a stabilizing rod relative to the bone implant. Bone implants may include a radially recessed collet receiving region that includes a proximal end with an undercut ledge configuration that is sized and configured to interface with and couple to a collet of a tulip assembly.