Segmented Acetabular Guide for Precise Screw Trajectory
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Solution Overview
Problem
Traditional patient-specific guides for hip replacement surgeries are inefficient in accurately determining the position, path, diameter, and length of screws for the pelvic joint acetabulum due to their design limitations, which fail to cover the entire bone surface and cannot account for varying bone qualities and thicknesses, leading to potential surgical failures.
Innovation Solution
A patient-specific guide consisting of two parts, one for the pubic and one for the ischial part of the pelvic joint's cotyloid cavity, designed using the finite element method and computer-assisted surgery, with an internal surface topology matching the acetabular bone anatomy, allowing precise fixation and specification of screw positions, paths, diameters, and lengths based on individual patient anatomy, including complicated cases like bone corrosion and fractures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional three-cylinder fixation guides are used, then the guide structure is simple and easy to manufacture, but the guide cannot accurately cover the entire pelvic bone surface and determine precise screw positions, paths, diameters and lengths
Solution Approach 1:
The guide is divided into two separate parts: a first guide for the pubic part and a second guide for the ischial part of the pelvic joint. Each guide has its own fixation openings and internal guide surfaces that match specific anatomical regions. This segmentation allows each guide to be optimized for its specific location while collectively covering the entire acetabular bone surface, thereby improving measurement precision without requiring a single overly complex monolithic structure.
Solution Approach 2:
The internal guide surfaces of both guides are designed as imprints or copies of the actual pelvic bone anatomy. The first guide's internal surface matches the pubic part anatomy, while the second guide's internal surface matches the ischial part anatomy. These copied surfaces ensure accurate positioning and fixation on the patient-specific bone geometry, enabling precise determination of screw parameters while maintaining reasonable structural complexity through additive manufacturing.
2Adaptability or versatility
If standard traditional tools are used, then the tools are universally applicable and easy to manufacture, but they cannot account for varying bone qualities and thicknesses in different patients
Solution Approach 1:
Before surgery, patient-specific CT scans are performed to obtain three-dimensional images of the pelvic bone. Computer-assisted surgery software processes these images to determine the optimal screw positions, paths, diameters, and lengths based on the patient's specific bone quality and thickness. The guides are then manufactured with pre-determined openings and internal surfaces that incorporate this pre-calculated information, allowing the guides to adapt to individual patient anatomy without requiring complex intraoperative adjustments.
Solution Approach 2:
The guides are created as patient-specific copies based on individual CT scan data. Each guide's internal surface is an imprint of the patient's actual bone anatomy, ensuring perfect adaptation to that patient's unique bone structure, quality, and thickness. This copying approach enables full adaptability to varying patient conditions while simplifying manufacture through modern additive manufacturing technologies that can easily produce complex custom geometries from digital models.
3Area of stationary object
If three fixation cylinders with small surface areas are used, then the guide structure is simple, but the guide does not completely cover the bone surface and cannot accurately determine screw paths
Solution Approach 1:
Instead of using a single guide or three small cylinders, the solution segments the coverage area into two distinct guides, each responsible for a specific anatomical region (pubic and ischial parts). This segmentation allows each guide to have a larger, more effective surface area for its designated region, achieving complete coverage of the acetabular bone surface. The segmented approach manages structural complexity by dividing the overall system into two manageable components rather than one overwhelming structure.
Solution Approach 2:
The guides transition from the traditional three-dimensional cylinder format to two-dimensional planar templates with extensive surface areas. This dimensional change allows the guides to flatten out and cover larger portions of the bone surface, providing comprehensive coverage and accurate reference surfaces for determining screw paths. The 2D format enables better surface contact and more precise anatomical matching while maintaining reasonable structural complexity.
Data Source
AI summary
A patient specific guide for hip replacement for patients undergoing hip replacement surgery. The guide works for correction of the acetabulum defects based on a finite element model, which detect the bone quality and guide the surgeons for the optimum screws trajectories. The guide surface reflects the acetabular morphology which provide a correct posting of the cup, especially for the complex case as bone loss, severe fractures and tumors. CT-scan images are used to construct the 3D model of the acetabulum bone, therefore a finite element and virtual surgery planning methods are applied to create the electronic file of the patient specific guide. In final step, the 3D printers are used to produce the patient specific guide.