Patient-Specific Instruments for Revision Knee Arthroplasty
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Solution Overview
Problem
Current revision knee arthroplasty procedures face challenges in accurately determining the size and position of revision prostheses due to distortions and artifacts in CT scans from primary implants, and existing patient-specific instruments are not suitable for revision surgeries where cartilage is absent.
Innovation Solution
A method and device for patient-specific instruments in revision knee arthroplasty that uses CT-scan data to create 3D models, corrects scan distortions, and produces customizable cutting guides for both femoral and tibial components, enabling accurate planning and execution of bone cuts for various types of revision implants, including those without cartilage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional instruments are used for revision knee arthroplasty, then the procedure can be performed with standard equipment, but the accuracy in determining prosthesis size and position is insufficient and the procedure becomes time-consuming
Solution Approach 1:
The system performs preoperative planning and creates patient-specific instruments before surgery. CT scans are processed, 3D models are generated, and cutting guides are manufactured in advance, allowing the actual surgery to proceed quickly with pre-determined prosthesis sizing and positioning
Solution Approach 2:
The system creates accurate 3D digital copies of the patient's bone anatomy from CT scan data. These digital models are then used to generate patient-specific cutting guides that perfectly match the patient's unique bone geometry, enabling precise prosthesis placement
2Loss of information
If CT scan is used for imaging in revision knee arthroplasty, then detailed bone structure can be visualized, but distortions and artifacts are produced due to the primary implant
Solution Approach 1:
The system extracts and isolates the bone surface geometry from the CT scan data, separating it from the metallic implant artifacts. By focusing specifically on the bone-cement interface region and using specialized segmentation algorithms, the system recovers accurate bone surface details despite the presence of implants
Solution Approach 2:
The system introduces an intermediate processing step that converts raw CT scan data into corrected 3D bone models. This intermediate representation filters out artifacts while preserving essential bone geometry, serving as a bridge between the problematic raw data and the useful final model
3Adaptability or versatility
If existing patient-specific instruments are used, then they are suitable for primary TKR with cartilage, but they are not applicable for revision TKR where cartilage is absent and articular surface is replaced by implant
Solution Approach 1:
The system creates a universal platform that can handle both primary and revision TKR cases. The patient-specific instrument generation process is adapted to work with different anatomical conditions - using cartilage surfaces for primary TKR and implant-cement-bone interfaces for revision TKR, making the system applicable across multiple surgical scenarios
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 solution provides accurate and precise guidance for surgeons during revision knee arthroplasty, allowing for correct sizing, orientation, and positioning of revision prostheses, and is applicable to both one-stage and two-stage procedures, overcoming the limitations of conventional instruments and existing patient-specific instruments.
Implementation Method 1
The method based on translate the Dicom coming from CT-scan to a 3D model of bone
Implementation Method 2
the virtual templates, which are then converted to physical templates using the 3D printing techniques
Data Source
AI summary
The surgery of revision knee arthroplasty is complex one for both of one and two stages for constraint and hinged implants. The inventor create a method and device to overcome the difficulties of this surgery as determining the size of the revision prosthesis and position of it on the bone after cut and replacement of the failed primary prosthesis. This method enable the surgeons to overcome the abnormalities, distortions and artifacts on bone surface which resulted from the CT scan due to the primary implant. It enables the surgeons to detect the size and position of the implant, also uses land marks on bone surface to design and product the device which use to perform the bone cutting. The device enables the surgeon to determine and guiding the bone cuts below the cement plane in case of cemented implants. Also guiding to the bone cuts below the implant surface in case of cement-less implants.