Bone Screw With Tapered Sidewall For Joint Fusion

Solution Overview

Problem

Current bone screw systems for immobilizing the sacroiliac joint often fail to effectively promote bony growth and fusion across the joint, leading to temporary pain relief and instability.

Innovation Solution

A bone screw system with a shaft having distinct sections, including a threaded first section, a threadless second section with a tapered sidewall for directing autologous bone radially outward, and a threaded third section with helical depressions to collect and distribute bone pieces within the joint, enhancing surface area contact between the ilium and sacrum for fusion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional bone screw is used to immobilize the sacroiliac joint, then the joint is stabilized, but bone growth and fusion across the joint are not effectively promoted

Engineering Contradiction:

Improvejoint stabilityVSAvoidbone fusion duration

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The screw shaft is divided into three distinct sections: a first threaded section for cortical bone engagement, a second threadless tapered section for directing bone pieces radially outward, and a third threaded section with helical depressions for collecting and distributing bone pieces. This segmentation allows each section to perform its specific function, thereby promoting both joint stability and bone fusion simultaneously

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the screw shaft have different local properties: the first section has aggressive threads for cortical bone grip, the second section has a tapered smooth surface for radial bone distribution, and the third section has helical depressions for bone piece collection. These localized quality variations enable the screw to address multiple requirements (stability and fusion) in different regions

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If bone pieces are collected within the bone screw, then bone growth is encouraged, but the surface area contact between ilium and sacrum is reduced

Engineering Contradiction:

Improvebone pieces collectedVSAvoidbone contact surface area

Core Design Contradiction:

Quantity of substanceVSArea of stationary object

Solution Approach 1:

The screw shaft is divided into three distinct sections: a first threaded section for cortical bone engagement, a second threadless tapered section for directing bone pieces radially outward, and a third threaded section with helical depressions for collecting and distributing bone pieces. This segmentation allows each section to perform its specific function, thereby promoting both joint stability and bone fusion simultaneously

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second shaft wall section tapers inwardly towards the longitudinal axis, directing bone pieces radially outward from the screw shaft in a three-dimensional distribution pattern. This dimensional approach maximizes the surface area contact between ilium and sacrum by spreading bone pieces across a wider area rather than confining them to a single location

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS11974791B1Bone screw system and method

Publication Date: 2024.05.07 ROBBINS JOSEPH T

AI summary

The present disclosure generally pertains to methods and systems for fusing a joint. The disclosure includes mechanically immobilizing the joint by insertion of a bone screw, the bone screw including a screw shaft operatively coupled to a screw head, the screw shaft including a longitudinal axis, a channel extending along the longitudinal axis, a first shaft wall section, a second shaft wall section and a third shaft wall section. Fusing of the joint includes inserting the screw into a first bone, a second bone and a joint formed between the first bone and the second bone. Insertion further includes cutting bone pieces away from the first bone using the third shaft wall section of the bone screw and directing the first bone pieces into a helical depression formed in the third shaft wall section.