Broach Holder Tool Coplanar Strike Plate Reduces Rasp Moments

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Solution Overview

Problem

Existing broach holder tools for total hip replacement surgery introduce non-axial forces during rasp insertion and removal, leading to increased risk of femur fractures due to moments applied to the intramedullary canal, which can result in intraoperative and postoperative complications.

Innovation Solution

A broach holder tool with an angled strike plate and withdrawal plate, designed to minimize rasp moments by aligning the strike and withdrawal forces perpendicular to the rasp, reducing the vertical offset angle and allowing for a more horizontal insertion force, thereby minimizing hoop stresses in the femur.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If a traditional broach holder tool with offset strike plate is used, then the rasp can be inserted at an angle to access the intramedullary canal, but non-axial forces create moments that increase the risk of femur fractures

Engineering Contradiction:

Improveangled insertion capabilityVSAvoidfracture risk

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The strike plate is repositioned from an offset location to be coplanar with the rasp, inverting the traditional design. This reversal eliminates the moment arm that causes non-axial forces, allowing angled insertion while maintaining axial force application to prevent fractures

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The vertical offset distance between the strike plate and rasp is changed from a non-zero value to zero (coplanar positioning). This parameter change eliminates the moment creation while preserving the ability to insert the rasp at the required angle for anterior approach surgery

Inventive Principle:

Principle #35Parameter changes

2Force

If the strike plate is offset from the rasp centerline, then insertion force can be applied, but a moment is created that propagates non-axial forces through the rasp

Engineering Contradiction:

Improveinsertion force applicationVSAvoidnon-axial forces

Core Design Contradiction:

ForceVSObject-generated harmful factors

Solution Approach 1:

Instead of offsetting the strike plate to apply force, the design inverts this approach by placing the strike plate coplanar with the rasp. This allows force application without creating a moment arm, eliminating the generation of harmful non-axial forces while maintaining effective insertion capability

Inventive Principle:

Principle #13The other way round (Inversion)

3Productivity

If an angled broach holder tool is used for anterior approach, then adequate rasping of the canal can be attained, but microfractures may occur due to over-stressed bone at the rasp entry site

Engineering Contradiction:

Improvecanal rasping effectivenessVSAvoidmicrofractures

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The design inverts the traditional offset approach by positioning the strike plate coplanar with the rasp. This allows the rasp to be inserted at the necessary angle for adequate canal access while ensuring forces remain axial, preventing the bone over-stressing and microfractures that occur with non-axial loading

Inventive Principle:

Principle #13The other way round (Inversion)

Data Source

PatentUS11246624B2Broach holder tool with reduced rasp moment

Publication Date: 2022.02.15 JOINT DEVELOPMENT INC

AI summary

The broach or rasp holder tool with reduced rasp moment includes an angled strike plate with an optional curved or spheroidal surface and/or an angled withdrawal plate having a contact surface for receiving a generally perpendicular strike force that generally aligns with a point along a rasp for substantially eliminating a moment applied thereto while broaching the intramedullary canal in preparation for implanting a prosthetic stem during joint replacement surgery.