Liquefiable Anchoring Fastener for Bone Graft Fixation

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Solution Overview

Problem

Current soft tissue fixation methods in orthopedic surgery, such as for ACL replacement, often result in graft damage, tissue slippage, and poor long-term stability due to mechanical stress and thread-related issues with interference screws, and may not adequately integrate with weakened bone tissue.

Innovation Solution

A method and fastener system that uses a press-fit mechanism combined with an anchoring element capable of liquefaction, allowing for a positive-fit connection within the bone tissue, reducing mechanical stress on the graft and enhancing integration with the bone, while minimizing damage to the tissue and bone.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If interference screws are used for soft tissue fixation, then the graft can be secured in the bone opening, but the threads cause mechanical stress and damage to the graft and tissue slippage occurs

Engineering Contradiction:

Improvefixation stabilityVSAvoidgraft damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the threaded mechanical fixation system with a smooth press-fit cylindrical fastener that relies on friction and compression forces. The fastener has a smooth surface without threads, eliminating thread-related graft damage while maintaining fixation stability through radial compression against the bone opening wall and friction between the fastener and graft

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the geometric parameters of the fastener, using a cylindrical shape with constant or slightly varying diameter rather than a threaded form. The fastener diameter is selected to create appropriate compression force against the bone opening wall, and the length is optimized to provide sufficient anchoring while minimizing graft compression

Inventive Principle:

Principle #35Parameter changes

2Reliability

If press-fit fasteners are used for fixation, then integration with bone tissue is improved, but mechanical stress on the graft increases

Engineering Contradiction:

Improvelong-term stabilityVSAvoidmechanical stress on graft

Core Design Contradiction:

ReliabilityVSForce

Solution Approach 1:

The patent applies local quality by creating a smooth surface zone in contact with the graft to minimize stress concentration, while the ends of the fastener may have different characteristics for bone integration. The cylindrical geometry provides uniform stress distribution along the graft-contacting surface, avoiding localized stress peaks that would occur with threaded structures

Inventive Principle:

Principle #3Local quality

3Reliability

If the fastener diameter is increased to provide wider fixation footprint, then natural ACL fixation is better accommodated, but the opening size in bone must be larger

Engineering Contradiction:

Improvefixation footprintVSAvoidopening diameter

Core Design Contradiction:

ReliabilityVSLength of stationary object

Solution Approach 1:

The patent employs dynamic design by providing a fastener that can be inserted in a compressed state through a relatively small opening, then expanded or maintained at full diameter to provide a wide fixation footprint. The fastener may be slightly flexible or elastic, allowing it to navigate through the bone opening and then achieve its full stabilizing diameter within the opening

Inventive Principle:

Principle #15Dynamics

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

This approach improves primary stability, reduces graft damage, and allows for wider fixation footprints, better accommodating natural ACL fixation, with enhanced long-term stability and integration, even in osteoporotic bone, and is suitable for various tissue types and surgical techniques.

Implementation Method 1

an anchoring element (6) comprised of a material capable of being liquefied by application of energy, by liquefying the material in situ such that the liquefied material is capable to penetrate preferably the trabecular structure of the bone tissue of the wall of the opening, where on re-solidification it constitutes an anchorage

Methodology Applied

Scientific EffectPhase change (liquefaction): Phase Change

Data Source

PatentUS20230210569A1Method of fastening a tissue or a corresponding prosthetic element in an opening provided in a human or animal bone and fastener suitable for the method

Publication Date: 2023.07.06 SPORTWELDING

AI summary

A graft or prosthetic element suitable, e.g., for replacing a tendon or ligament is fastened in a bone tunnel or blind opening with the aid of a fastener. In a first step, the graft or prosthetic element is press-fitted in the tunnel or opening by forcing the fastener into the opening or by positioning the fastener in the opening and then expanding it, wherein the fastener is in contact with the graft or prosthetic element and with the bone wall of the tunnel or blind opening. In a second step, the fastener is anchored in the bone wall of the tunnel or blind opening with the aid of a liquefiable material which is liquefied in the vicinity of the bone wall where it is in contact with the fastener and by making the liquefied material penetrate into the bone wall.