Bone Screw With Segmented Insertion Post for Torque Control

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Solution Overview

Problem

Existing screws, particularly bone screws, risk damaging surrounding tissue and becoming impossible to remove due to excessive torque during tightening, often requiring specialized and expensive tools for removal.

Innovation Solution

A screw design featuring a recess with a predetermined breaking point for the insertion post, allowing torque transmission after breaking, preventing excessive torque and enabling easy removal without damaging tissue or requiring specialized tools.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a predetermined breaking point is formed in the attachment region between the head and shank (as in WO 97/27812), then the screw can be screwed in tightly without damaging bone or screw, but the breaking point is rough and may irritate or damage surrounding tissue, and a special tool is required for removal

Engineering Contradiction:

Improvescrew fixation reliabilityVSAvoidtissue irritation and damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The insertion post is segmented into two parts: a removable shank portion that breaks off at the predetermined breaking point, and a retained tip portion that remains in the recess. This segmentation allows the harmful shank to be separated from the beneficial tip, resolving the contradiction between reliable fixation and tissue protection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The harmful portion (insertion post shank) is extracted from the system by designing it to break off and be removed. Only the beneficial portion (insertion post tip with mating contour) remains in the screw head, eliminating tissue irritation while maintaining torque transmission capability.

Inventive Principle:

Principle #2Taking out (Extraction)

2Reliability

If a predetermined breaking point is formed in the attachment region between the head and shank, then the screw can be screwed in tightly without damaging bone or screw, but a special tool is required for removal which is expensive and not always available

Engineering Contradiction:

Improvescrew fixation reliabilityVSAvoidscrew removal ease

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The recess with its contour serves multiple functions: it receives the insertion post during assembly, transmits torque during screwing-in, and accepts standard unscrewing tools for removal. This multi-functionality eliminates the need for special removal tools, resolving the contradiction between reliable fixation and ease of removal.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The recess with its contour acts as an intermediary element that mediates between the insertion post and standard unscrewing tools. It provides a universal interface that allows both the insertion mechanism and removal tools to interact with the screw head without requiring specialized equipment.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Object-affected harmful factors

If the insertion post breaks off at the predetermined breaking point, then tissue damage is prevented, but the breaking point must be rough which could irritate surrounding tissue

Engineering Contradiction:

Improvetissue damage preventionVSAvoidbreaking point contour smoothness

Core Design Contradiction:

Object-affected harmful factorsVSShape

Solution Approach 1:

The rough breaking point is extracted from the final product by designing the insertion post to break off. The harmful rough surface is separated and removed, while only the smooth, precisely formed tip portion with mating contour remains in contact with surrounding tissue.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The breaking process, which could create harmful rough surfaces, is converted into a beneficial separation mechanism. The controlled break at the predetermined point allows the rough surface to form on the removed portion while the retained portion maintains a smooth, precise contour suitable for tissue contact.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 screw design prevents tissue damage and ensures easy release by controlling torque, allowing for reliable fixation and subsequent removal without specialized tools, reducing costs and improving clinical accessibility.

Implementation Method 1

During the screwing-in, the torque acting on the predetermined breaking point increases. When the screwing-in depth has been reached, the torque is so great that the screw body breaks off from the shank at the predetermined breaking point.

Methodology Applied

Scientific EffectTorque: Torque

Data Source

PatentUS10582959B2Screw with insertion post

Publication Date: 2020.03.10 MEDARTIS HOLDING AG

AI summary

A screw (1), in particular a bone screw, comprising a head (16), a shaft (2) and a point (15). The screw (1) has a recess (4) with a contour (5) on a head side (3), The screw (1) is provided with an insertion post (8) in the recess (4), which insertion post is connected to the screw (1) via a predetermined breaking point (7). After breaking the predetermined breaking point and separation of the insertion post (6) from the screw (12), a counter-contour (13) of a tool (12) can be brought into operative connection with the contour (5) of the recess (4). The predetermined breaking point (7) is arranged within the recess (4) such that, after removal of the insertion post (6), a transmission of torque is possible between the tool (12) and the screw (1) via the contour (5) and the counter-contour (13).