Patient-Specific Cement Removal Guide for Hip Revision Surgery
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Solution Overview
Problem
Removal of well-fixed prosthetic implants in cemented total hip arthroplasty is challenging due to limited information about bone cement location, leading to complications like femur perforation and fracture, and prolonged surgery with increased blood loss and rehabilitation time.
Innovation Solution
A method using a cutting tool with an elongated stem and laterally extending protrusions, guided by a custom-made guide member with profiled grooves, to precisely remove prosthetic cement along the cement/bone interface without damaging the adjacent bone, utilizing a small electrical chainsaw for efficient cement removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If extended trochanteric osteotomy is performed to improve access to implant/cement interface, then surgical access is improved, but surgery time is prolonged and blood loss increases
Solution Approach 1:
The patient-specific guide is manufactured before surgery based on preoperative imaging, allowing the cutting tool to be precisely guided during the procedure without requiring extensive osteotomy for exposure. The guide is inserted into the prosthetic cavity and directs the cutting element along the cement/bone interface, eliminating the need for prolonged surgical access preparation
2Device complexity
If conventional cement removal methods are used without precise guidance, then surgical procedure is simpler, but bone damage such as perforation and fracture occurs
Solution Approach 1:
The patient-specific guide acts as an intermediary device between the surgeon and the bone-cement interface. It features grooves that guide the cutting element precisely along the cement/bone interface, preventing direct contact with bone and eliminating the need for complex surgical techniques to avoid perforation or fracture
Solution Approach 2:
Preoperative imaging data is used to create a customized guide that maps the exact location of the cement/bone interface. This preliminary preparation ensures that during surgery, the cutting tool follows the pre-determined safe path without requiring complex real-time judgment or sophisticated surgical techniques
3Manufacturing precision
If ROBODOC robotic milling system is used for cement removal, then cement removal precision is improved, but surgical time and cost increase significantly
Solution Approach 1:
The complex robotic control system and preoperative pin implantation steps of the ROBODOC system are extracted and replaced with a simpler patient-specific guide that provides mechanical guidance. The guide contains grooves that physically direct the cutting element, eliminating the need for time-consuming robotic milling while maintaining precision through the customized guide geometry
Solution Approach 2:
The patient-specific guide is a disposable, relatively simple device that can be manufactured quickly from preoperative images. It replaces the expensive, time-consuming robotic system with a low-cost guide that achieves similar precision through mechanical guidance rather than complex automation
4Productivity
If high speed milling is used for cement removal, then cement removal efficiency is improved, but heat injury risk increases
Solution Approach 1:
The cutting element moves along the grooves of the guide in a controlled, periodic manner rather than continuous high-speed milling. This allows for intermittent cutting action that generates less heat, while the guide ensures precise following of the cement/bone interface profile
Solution Approach 2:
The patient-specific guide serves as a mediator that controls the cutting element's path and speed. The grooves in the guide physically constrain the cutting tool to follow the exact interface profile, preventing excessive heat generation through uncontrolled high-speed milling while maintaining efficient cement removal
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 method significantly reduces surgical time, morbidity, blood loss, and complications such as fractures and reoperations, while ensuring precise cement removal and early postoperative weight bearing.
Implementation Method 1
providing a cutting tool for forming a running cut substantially completely through the prosthetic cement along the line of intersection
Data Source
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.