Variable Angle Bone Screw With Curved Head And Self-Cutting Thread

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing bone locking systems are inefficient due to the complex machining required for unused bores on bone plates, leading to increased production costs and unnecessary damage to screws during locking, as they often feature threads on both the plate and screw head, which complicates manufacturing and usage.

Innovation Solution

A novel screw design with a screw head featuring curved surfaces and a star-shaped socket, where the screw body has a self-cutting thread, allowing for variable locking angles without threads on the screw head, enabling simpler manufacturing and adaptable use with standard or non-standard threads, shifting machining complexity to the screw rather than the plate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the plate is made with specifically machined bores for variable angle locking, then the locking capability is improved, but the manufacturing complexity and cost increase significantly

Engineering Contradiction:

Improvelocking capabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Instead of machining complex variable-angle bores in the plate, the invention inverts the approach by providing variable-angle curved surfaces on the screw head that can lock into simple cylindrical bores in the plate. This transfers the complexity from the plate to the screw, allowing the plate to be manufactured with simple standard bores while maintaining variable-angle locking capability.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention applies local quality by providing the complex variable-angle geometry only where needed (on the screw head contact surfaces) while keeping the plate bores simple and cylindrical. This localized complexity approach reduces overall manufacturing complexity compared to machining variable-angle bores throughout the plate.

Inventive Principle:

Principle #3Local quality

2Strength

If threads are machined on both the plate bores and screw head, then the locking strength is improved, but the manufacturing cost and complexity increase

Engineering Contradiction:

Improvelocking strengthVSAvoidmanufacturing cost

Core Design Contradiction:

StrengthVSEase of manufacture

Solution Approach 1:

The invention extracts the thread feature from the screw head, eliminating the need to machine threads on the screw head while maintaining locking strength through the self-cutting thread in the bone and friction-based locking on the curved surfaces. This reduces manufacturing complexity and cost.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The screw design utilizes the bone itself to provide the threading function through self-cutting threads, eliminating the need for separate threads on both the plate and screw head. The system serves itself by using the bone structure to provide the threading mechanism.

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If unused bores remain on the plate, then the plate geometry flexibility is improved, but the production cost increases due to unnecessary complex machining

Engineering Contradiction:

Improveplate geometry flexibilityVSAvoidproduction cost

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The invention inverts the complexity allocation by making the screw head geometry adaptable rather than the plate bore geometry. This allows all plate bores to be manufactured simply, and the screw head's variable-angle curved surfaces provide the adaptability needed for different configurations, reducing production costs.

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11786281B2Screw with a variable locking angle and a corresponding locking system

Publication Date: 2023.10.17 ORTHOLOCK D O O

AI summary

A locking system can comprise a screw head without threads and a thread created only inside a bore of a bone plate. The machining of thread geometry can thus pertain to the screw body, while the screw head can be formed by curved surfaces and contact surfaces by simple machining process. A plurality of screws can be implemented, and each bone plate can have a larger number of bores for accepting the screws than the number of screws. The said locking screw can be used with other bone plates having continuous or partial threads created inside their bores.