Bone Rod Coupling Assembly With Undercut Collet Locking

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Solution Overview

Problem

Existing bone implant systems face challenges in securely coupling the implant, tulip, and rod, particularly in maintaining the stability and preventing the collet from loosening under axial forces during rod manipulation.

Innovation Solution

The system incorporates a bone implant with a radially recessed collet receiving region angled at less than ninety degrees relative to the longitudinal axis, featuring an undercut design that reduces the likelihood of collet expansion and loosening, and a tulip assembly with a modular interface allowing for rotational freedom and secure attachment to the rod.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a collet is used to couple the implant and tulip, then the assembly allows for rotational freedom and ease of assembly, but the collet may expand and loosen under axial forces during rod manipulation

Engineering Contradiction:

Improveease of assemblyVSAvoidstability under axial forces

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The recessed collet receiving region with its angled radially extending surface is designed to preemptively counteract the expansive force that causes collet loosening. When axial forces are applied during rod manipulation, the angled surface converts the outward radial expansion into downward engagement with the recess, preventing the collet from loosening before the problem can occur.

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The invention changes the geometric parameters of the collet interface by introducing a recessed region with a specific angle (less than 90 degrees) relative to the longitudinal axis. This parameter change transforms how axial forces are transmitted to the collet, converting potentially harmful radial expansion into stable engagement within the recessed region.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the collet is secured tightly to prevent loosening, then stability under axial forces is improved, but assembly and disassembly become more difficult

Engineering Contradiction:

Improvestability under axial forcesVSAvoidease of assembly and disassembly

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The system exhibits dynamic behavior where the collet can move freely during assembly until it reaches the recessed region, at which point it transitions to a locked state. The angled surface allows the collet to slide in easily during assembly, then automatically engages at the recess to prevent loosening during use, and can be released by reversing the assembly motion.

Inventive Principle:

Principle #15Dynamics

3Reliability

If the collet receiving region is designed with an angled surface, then the likelihood of collet expansion and loosening is reduced, but the structural complexity of the implant increases

Engineering Contradiction:

Improveprevention of collet looseningVSAvoidstructural complexity of implant

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Rather than complicating the entire implant structure, the invention applies a localized geometric feature - the recessed collet receiving region with its angled surface - only where needed at the collet interface. This local modification provides the necessary reliability improvement without significantly increasing overall structural complexity.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS20260083481A1Rod coupling assemblies for bone stabilization constructs

Publication Date: 2026.03.26 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.