Guided Cement-Cutting Tool for Bone-Sparing Hip Revision

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Solution Overview

Problem

The removal of well-fixed prosthetic cement in revision total hip arthroplasty surgeries is challenging due to limited information about cement location and extent, leading to complications like bone loss, fractures, and prolonged recovery, with existing methods being either costly and time-consuming or risking heat injury.

Innovation Solution

A cutting tool with a chainsaw blade and driven cutting chain, guided by a custom-made guide member with longitudinally running grooves, is used to follow the cement/bone interface profile, allowing precise removal of cement without damaging the bone, and a hook tool for removing remaining cement pieces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If extended trochanteric osteotomy is performed to improve access to implant/cement interface, then surgical access is improved, but surgical time is prolonged and blood loss increases

Engineering Contradiction:

Improvesurgical accessVSAvoidsurgical time

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The guide member is pre-formed with grooves that correspond to the cement/bone interface profile obtained from preoperative imaging. This preliminary preparation allows the cutting tool to follow the exact interface path without requiring extensive surgical exposure through osteotomy, thus improving access while avoiding the time loss and blood loss associated with extended trochanteric osteotomy.

Inventive Principle:

Principle #10Preliminary action

2Productivity

If high speed milling is used to remove bone cement, then cement removal is effective, but heat injury risk increases

Engineering Contradiction:

Improvecement removal efficiencyVSAvoidheat injury risk

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the high-speed milling system with a mechanical cutting system using a chainsaw-like cutting tool with a cutting chain. This mechanical cutting approach removes cement effectively while generating minimal heat compared to high-speed friction-based milling, thus maintaining productivity while eliminating the heat injury risk to surrounding bone and soft tissues.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If robotic milling system is used for cement removal, then cement removal is precise, but surgical time and cost increase

Engineering Contradiction:

Improvecement removal precisionVSAvoidmilling time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The guide member is created as a physical copy or replica of the patient's specific anatomy based on preoperative imaging data. The grooves in the guide member replicate the exact cement/bone interface profile, allowing the simple cutting tool to achieve precise cement removal that would otherwise require complex robotic systems. This copying approach maintains precision while dramatically reducing time and cost.

Inventive Principle:

Principle #26Copying

4Device complexity

If conventional cement removal methods are used, then surgical simplicity is maintained, but bone loss and fractures increase

Engineering Contradiction:

Improvesurgical procedure simplicityVSAvoidbone integrity

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The guide member acts as an intermediary device that bridges the simplicity of conventional manual cutting tools with the precision required to protect bone integrity. The grooves in the guide member guide the cutting tool along the exact cement/bone interface, preventing accidental bone contact and fractures. This intermediary guide allows simple manual operation while ensuring reliable bone protection.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 method reduces surgical time, morbidity, blood loss, and complications, enabling early weight-bearing and minimizing fractures and reoperations by ensuring precise cement removal without bone damage.

Implementation Method 1

a driven cutting chain, which is arranged to cut the prosthetic cement at one outer end of the blade

Methodology Applied

Scientific EffectMechanical cutting: Abrasion

Data Source

PatentUS11801080B2Tool system for removing prosthetic cement from a bone of a patient undergoing a joint prosthesis replacement operation

Publication Date: 2023.10.31 UMC UTRECHT HLDG BV

AI summary

A method for providing a tool system for removing prosthetic cement from a bone of a patient undergoing a joint prosthesis replacement operation includes scanning the patient in the area of the joint prosthesis to obtain a profile of a line of intersection of a prosthetic cement/bone interface at its intersection with a longitudinally pre-selected plane; providing a guide member shaped as a stem of the prosthesis in a prosthetic cavity located in said prosthetic cement; and providing a cutting tool for forming a running cut through the prosthetic cement along the line of intersection. A stem of the cutting tool includes two protrusions along the length thereof. A guide member includes two grooves which each engage one of said protrusions. Grooves are profiled so the outer end of the stem is forced to follow a path corresponding to the profile of the line of intersection of the cement/bone interface.