Dual-Thread Bone Fixation Implant for Cortical and Epiphyseal Purchase
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Solution Overview
Problem
Current bone fixation methods for medial malleolar fractures, such as those using partially threaded cancellous screws, fail to account for varying bone densities in the tibia, leading to nonunion and screw backout issues, particularly in elderly patients with osteoporotic bone.
Innovation Solution
A threaded implant with specialized thread geometries and configurations designed to capture both cortical and epiphyseal bone densities, featuring varying diameters, lengths, and pitches, ensuring maximum bone purchase and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If fixation screws are made long to obtain secure bone purchase in the distal metaphysis, then bone purchase in cortical bone is improved, but secure bone purchase in cancellous bone of the metaphysis is not achieved
Solution Approach 1:
The implant is divided into two distinct thread zones: a first set of threads for cortical bone engagement and a second set of threads for cancellous bone engagement. This segmentation allows each thread type to be optimized for its specific bone density, resolving the contradiction between cortical and cancellous bone purchase.
Solution Approach 2:
Different thread geometries are applied to different regions of the implant shaft. The first thread zone has characteristics optimized for dense cortical bone, while the second thread zone has characteristics optimized for less dense cancellous bone. This local differentiation enables the implant to achieve secure purchase in both bone types simultaneously.
2Ease of operation
If standard partially threaded cancellous screws are used for medial malleolar fractures, then fixation is provided, but nonunion and screw backout occur due to inability to account for varying bone densities
Solution Approach 1:
The implant separates thread functions into two distinct zones, allowing the first thread zone to engage cortical bone for stable anchorage while the second thread zone engages cancellous bone for fracture compression, thereby preventing screw backout and promoting union.
Solution Approach 2:
The implant varies thread parameters (geometry, pitch, depth) along its length to match the varying bone density profile from cortical to cancellous bone. This parameter optimization ensures reliable fixation across different bone densities, reducing nonunion rates.
3Device complexity
If a single thread design is used for all bone densities in the distal tibia, then device simplicity is maintained, but maximum fixation cannot be achieved across varying bone densities
Solution Approach 1:
The thread design is segmented into two functional zones with distinct characteristics, allowing optimization for both cortical and cancellous bone while maintaining a relatively simple overall implant structure.
Solution Approach 2:
The dual-thread implant serves multiple functions: cortical bone anchorage, cancellous bone engagement, fracture compression, and prevention of screw backout. This multi-functionality achieves maximum fixation across varying bone densities without requiring multiple different implant types.
Data Source
AI summary
A threaded implant for bone fixation is provided. The implant includes a head. The implant includes a shaft extending distally from the head. The shaft includes a distal tip. The shaft includes a first set of threads extending a first predetermined length from the distal tip. The first set of threads are configured to capture cortical bone in one of a foot and/or ankle bone of a patient. The shaft includes a second set of threads extending a second predetermined length from the first set of threads. The second set of threads configured to capture epiphyseal bone in the one of the foot and/or ankle bone. Related methods are also provided.