Orthopedic Plate Variable Angle Locking via Radial Expansion

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Solution Overview

Problem

Existing orthopedic plate systems with locking fasteners fail to provide adequate holding power for variable angle fasteners, leading to potential backout and irritation to surrounding soft tissue, and require multiple types of fasteners for different angles.

Innovation Solution

An orthopedic plate system with both fixed and variable angle locking fasteners, featuring internally threaded holes for fixed angle fasteners and concavely rounded holes with locking inserts that expand radially or have internal threads for variable angle fasteners, allowing for secure locking at selected angles without the need for multiple fastener types.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If variable angle fasteners are used in non-threaded holes, then angular versatility is improved, but holding power deteriorates

Engineering Contradiction:

Improveangular versatilityVSAvoidholding power

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

A locking insert is introduced as an intermediary component between the non-threaded hole and the variable angle fastener. The insert includes a cam raceway that engages with a camming member on the fastener head, converting rotational motion into radial expansion that locks the fastener securely at any angle while maintaining strong holding power.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The locking insert is designed to dynamically expand radially when the camming member rotates within the cam raceway. This dynamic expansion mechanism allows the insert to adapt to any insertion angle while providing progressive locking force that secures the fastener with high holding power.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If multiple types of fasteners are used for different angles, then angular versatility is improved, but device complexity deteriorates

Engineering Contradiction:

Improveangular versatilityVSAvoidnumber of fastener types

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The locking insert mechanism provides universal compatibility with a single fastener type across all angular positions. The cam raceway design allows the same fastener to be locked at any angle, eliminating the need for multiple specialized fasteners for different angles and simplifying the overall device configuration.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Stability of the object's composition

If locking fasteners are used, then fastener stability is improved, but soft tissue irritation worsens

Engineering Contradiction:

Improvefastener stabilityVSAvoidsoft tissue irritation

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The locking mechanism changes the engagement parameter from threaded (fixed angle) to cam-based (variable angle with expansion locking). This parameter change allows the fastener to be securely locked at the optimal angle for each bone fragment while minimizing protrusion and potential soft tissue irritation.

Inventive Principle:

Principle #35Parameter changes

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 provides enhanced holding power and reduced risk of fastener backout, accommodating various bone angles while minimizing the number of fastener types required, thus improving surgical efficiency and reducing tissue irritation.

Implementation Method 1

the locking insert may include one or more expansion slots that allow the locking insert to be expanded in the opening in the plate so as to secure it in the plate

Methodology Applied

Scientific EffectRadial expansion:

Implementation Method 2

the locking insert may also include a cam raceway that accepts a camming member on the head of the fastener that causes the locking insert to expand radially

Methodology Applied

Scientific EffectMechanical expansion:

Implementation Method 3

the locking insert may include internal threads that mate with external threads of the fastener

Methodology Applied

Scientific EffectThreaded engagement: Screw

Data Source

PatentUS9687282B2Orthopedic plate having threaded holes for locking screws or pegs and non-threaded holes for a variable axis locking mechanism

Publication Date: 2017.06.27 STRYKER CORP

AI summary

An orthopedic plate system comprises a plurality of fasteners such as pegs or screws and a plate having two sets of holes for the fasteners. The first set of at least one hole includes internal threads that receive a fastener having a head which includes external threads that mate with the internal threads of the hole to lock the fastener at a fixed angle relative to the plate. The second set of at least one hole is devoid of internal threads and has a concavely rounded internal surface and which receives a convexly rounded external surface of a locking insert, which receives a variable axis fastener. The variable axis fastener causes the locking insert to expand to lock the variable axis fastener at a selected angle relative to the plate.