Bone Screw With Variable Thread Pitch For Bone Fragment Compression

Solution Overview

Problem

Existing bone screws for osteosynthesis do not provide complete satisfaction in terms of stability and compression of bone fragments, especially in cases where cancellated or subchondral bones are of poor quality.

Innovation Solution

A bone screw design featuring a threaded proximal portion with constant diameter and pitch, a conical median portion with increasing diameter and decreasing pitch, and a distal portion with constant diameter and larger pitch, along with optional transverse holes for immobilization, allowing for secure positioning and compression of bone fragments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a bone screw with constant diameter and constant pitch is used throughout, then the manufacturing is simple, but the compression and stability of bone fragments is insufficient

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidstability of bone fragments

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The screw applies local quality by varying the thread pitch along its length: a first pitch in the proximal portion for cortical bone engagement, and a second, smaller pitch in the distal portion for cancellous bone engagement. This allows each section to be optimized for its specific function, improving overall reliability while maintaining manufacturing feasibility through a systematic gradient design.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the geometric parameter of thread pitch along the screw length, transitioning from a larger pitch at the proximal end to a smaller pitch at the distal end. This parameter variation enables the screw to provide both compression and stability functions simultaneously, resolving the contradiction between manufacturing simplicity and clinical effectiveness.

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If a bone screw with larger pitch is used, then the insertion is easier, but the compression effect on bone fragments is reduced

Engineering Contradiction:

Improveinsertion easeVSAvoidcompression force on bone fragments

Core Design Contradiction:

Ease of operationVSForce

Solution Approach 1:

The screw applies local quality by varying the thread pitch along its length: a first pitch in the proximal portion for cortical bone engagement, and a second, smaller pitch in the distal portion for cancellous bone engagement. This allows each section to be optimized for its specific function, improving overall reliability while maintaining manufacturing feasibility through a systematic gradient design.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the geometric parameter of thread pitch along the screw length, transitioning from a larger pitch at the proximal end to a smaller pitch at the distal end. This parameter variation enables the screw to provide both compression and stability functions simultaneously, resolving the contradiction between manufacturing simplicity and clinical effectiveness.

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If a bone screw with constant thread diameter is used, then the manufacturing is simple, but the adaptability to different bone qualities is poor

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidadaptability to different bone qualities

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The screw applies local quality by varying the thread pitch along its length: a first pitch in the proximal portion for cortical bone engagement, and a second, smaller pitch in the distal portion for cancellous bone engagement. This allows each section to be optimized for its specific function, improving overall reliability while maintaining manufacturing feasibility through a systematic gradient design.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The screw achieves multi-functionality by combining two different pitch configurations in a single device, enabling it to effectively engage both cortical and cancellous bone. This universal design allows the same screw to adapt to different bone qualities and anatomical locations, resolving the contradiction between manufacturing simplicity and adaptability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS8668726B2Bone screw, in particular for osteosynthesis

Publication Date: 2014.03.11 STRYKER EUROPEAN OPERATIONS HOLDINGS LLC

AI summary

A bone screw having a threaded proximal portion, a threaded median portion, and a threaded distal portion. The threaded proximal portion has a proximal thread with a constant diameter and a proximal pitch. The threaded median portion has a median thread with a constant diameter smaller than the diameter of the proximal thread and a median pitch that becomes increasingly smaller from a distal end of the threaded median portion towards a proximal end of the threaded median portion. The threaded distal portion has a distal thread having a constant diameter that is smaller than the diameter of the median thread and a distal pitch that is larger than the median pitch at the distal end of the threaded median portion.