Polyaxial Pedicle Screw With Spherical Head Insertion

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Solution Overview

Problem

Conventional polyaxial pedicle screws are limited by the major diameter of the screw due to the need to fit through a tulip, restricting the size of interchangeable screw bodies that can be used.

Innovation Solution

A polyaxial pedicle screw system comprising a screw body, screw insert, and head assembly, where the screw insert has a spherical head with a larger head diameter than the narrowest part of the axial bore, and a bushing frictionally engages to maintain the spherical head's seat, allowing for a larger major diameter screw body than the tulip's bore diameter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the screw body is designed to pass through the tulip bore for seating, then the screw can be mounted to the tulip, but the major diameter of the screw is limited to the bore diameter

Engineering Contradiction:

Improvescrew body interchangeabilityVSAvoidmajor diameter of screw

Core Design Contradiction:

Adaptability or versatilityVSLength of moving object

Solution Approach 1:

The screw system is divided into separate components: the screw body with threads, the spherical head, and the tulip with axial bore. This segmentation allows the screw body to have a larger major diameter than the tulip bore by using a spherical head interface instead of requiring the entire screw to pass through the bore.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mounting interface transitions from a linear through-bore arrangement to a spherical head arrangement where the spherical head seats against the interior surface at the narrowest part of the bore. This dimensional change allows the screw body major diameter to exceed the bore diameter while still achieving secure mounting.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Length of moving object

If the spherical head diameter is larger than the narrowest part of the bore diameter, then the screw body can have a larger major diameter, but the spherical head cannot pass through the narrowest part of the bore

Engineering Contradiction:

Improvemajor diameter of screw bodyVSAvoidinsertion of spherical head

Core Design Contradiction:

Length of moving objectVSEase of operation

Solution Approach 1:

The spherical head is inserted into the axial bore of the tulip before final seating occurs. The spherical head initially passes through the larger opening and is guided into position, then seats against the interior surface at the narrowest part of the bore diameter, achieving both large diameter capability and proper insertion.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The axial bore of the tulip serves as an intermediary pathway that guides the spherical head into its final seated position. The bore's geometry allows the spherical head to be inserted and then retained at the narrowest part, facilitating both insertion and secure mounting.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the bushing frictionally engages the spherical head, then the spherical head is maintained in its seat, but the assembly requires additional components

Engineering Contradiction:

Improvemaintenance of spherical head seatVSAvoidnumber of components

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The bushing acts as an intermediary component inserted into the axial bore that frictionally engages both the spherical head and the tulip interior surface. This intermediary element provides reliable retention of the spherical head while maintaining a relatively simple overall structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The mechanical retention system replaces complex locking mechanisms with simple frictional engagement. The bushing's frictional contact with the spherical head and tulip interior surface provides sufficient retention without requiring additional locking components or complex assembly procedures.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

Enables the use of interchangeable screw bodies with larger diameters than conventional top-loading screws, enhancing the versatility and applicability of the polyaxial pedicle screw system.

Implementation Method 1

The insertion of the bushing in an assembled mode of the polyaxial pedicle screw system may cause the bushing to frictionally engage between the interior surface of the head component and the spherical head to maintain the seat of the spherical head against the interior surface at the narrowest part of the bore diameter of the axial bore.

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS11490932B2Polyaxial pedicle screw system

Publication Date: 2022.11.08 NEXT ORTHOSURGICAL INC

AI summary

This disclosure presents a polyaxial pedicle screw system. The system may comprise one or more of a screw body, a screw insert, a head component, a bushing, and/or other components. The screw body may have a major diameter. The screw insert may comprise a spherical head having a head diameter. The head component may have an axial bore forming an interior surface which defines a bore diameter of the axial bore. The interior surface may define a narrowest part of the bore diameter of the axial bore at a first end of the head component. The head diameter of the spherical head of the screw insert and/or the major diameter of the screw body may be larger than the narrowest part of bore diameter of the axial bore.