Bendable Orthopedic Fastener Structure for Torque and Flexure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional bendable fasteners for orthopedic applications face a tradeoff between flexibility and strength, where increased flexibility leads to a higher likelihood of breakage during driving, while increased strength reduces flexibility.
Innovation Solution
A flexible fastener design featuring a shaft with a helically wound land surface and interior pockets containing torque drivers, allowing for flexure and torque transmission, with a unique geometry that balances torsional strength and bending flexibility through a combination of torque bridges and a shaft core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the fastener is made more flexible to allow bending during insertion, then the ability to navigate curved bone paths is improved, but the likelihood of breakage during driving increases
Solution Approach 1:
The shaft is divided into multiple lands separated by flexure openings, creating a segmented structure that allows controlled bending while maintaining overall integrity. Each land acts as a discrete structural element that can flex independently, enabling the shaft to navigate curved paths without breaking.
Solution Approach 2:
The fastener employs a composite structure combining solid shaft material with strategically placed flexure openings. This composite design creates regions of high strength (solid lands) and controlled flexibility (opening regions), allowing the fastener to simultaneously resist breakage and accommodate bending during insertion.
2Strength
If the shaft material is made stronger to resist breakage during driving, then the reliability improves, but the flexibility to bend off-axis decreases
Solution Approach 1:
Different regions of the shaft have different structural qualities - the lands maintain full material strength for breakage resistance, while the flexure opening regions provide controlled flexibility. This local differentiation allows the shaft to be strong where needed and flexible where needed without compromising either property globally.
Solution Approach 2:
The shaft transitions from a static, uniformly rigid structure to a dynamic structure with variable flexibility. The flexure openings enable the shaft to adapt its rigidity during insertion - bending flexibly during navigation then maintaining strength during driving - making the structural properties dynamic rather than fixed.
3Adaptability or versatility
If flexure openings are added to enable bending, then the adaptability improves, but the torsional strength decreases
Solution Approach 1:
The multiple lands create continuous torque transmission paths around the shaft circumference. Even with flexure openings present, the remaining land material maintains uninterrupted stress flow paths that allow effective torque transmission during driving while preserving flexure capability during insertion.
Solution Approach 2:
The structure combines flexure openings (providing adaptability) with sufficient land material (providing torque strength) in a composite arrangement. The optimized distribution and sizing of lands versus openings creates a balance where both flexure and torque transmission functions are satisfied simultaneously.
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 design enhances the strength and flexibility of the fastener, enabling it to withstand greater twisting forces without yielding, while maintaining the ability to bend up to 45° off-axis, suitable for various orthopedic applications.
Implementation Method 1
A flexure opening extends through the shaft in the radial direction from the land surface to an inward facing surface of the interior pocket. The flexure opening extends helically about the longitudinal axis to provide for flexure of the shaft, of the land surface, and of the external thread.
Implementation Method 2
A torque driver is seated in the interior pocket, the torque driver having a torque face configured to abut a torque face of the interior pocket to develop torque along the shaft when a driving torque is applied to the proximal end of the shaft.
Data Source
AI summary
In accordance with at least one aspect of this disclosure, a flexible fastener includes, a shaft having a proximal end and a distal end spaced apart along a longitudinal axis and a land surface winding helically around the shaft. An interior pocket extends in an axial direction inside the shaft, radially inward from the land surface. A flexure opening extends through the shaft in the radial direction from the land surface to an inward facing surface of the interior pocket. The flexure opening extends helically about the longitudinal axis to provide for flexure of the shaft, of the land surface, and of the external thread. A torque driver is seated in the interior pocket, the toque driver having a torque face configured to abut a torque face of the interior pocket to develop toque along the shaft when a driving torque is applied to the proximal end of the shaft.