Bendable Orthopedic Fasteners With Helical Flexure and Torque Drivers
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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 use, while increased strength results in reduced 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 without integral attachment, with a clearance gap and cul-de-sac cross-sections to prevent rotation beyond abutment, enhancing both flexibility and strength.
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 reach difficult surgical sites is improved, but the likelihood of breakage during driving increases
Solution Approach 1:
The fastener is divided into multiple segments or sections with varying degrees of flexibility. The shaft includes a first portion with higher flexibility for bending during insertion, and a second portion with greater strength for torque transmission during driving. This segmentation allows each portion to be optimized for its specific function, resolving the contradiction between flexibility and breakage resistance.
Solution Approach 2:
Different portions of the fastener have different structural properties tailored to their specific functions. The proximal portion has a configuration optimized for flexibility and bending, while the distal portion has a configuration optimized for strength and torque transmission. This local differentiation of quality allows the fastener to simultaneously achieve both flexibility and breakage resistance in different locations.
2Strength
If the fastener is made stronger to transmit torque and avoid breakage, then the reliability during driving is improved, but the flexibility for bending is reduced
Solution Approach 1:
The fastener structure is segmented into a proximal portion and a distal portion, each with optimized structural characteristics. The proximal portion has features that enhance flexibility for bending during insertion, while the distal portion has features that maximize strength for torque transmission during driving. This segmentation resolves the contradiction by allocating different functional requirements to different segments.
Solution Approach 2:
The fastener exhibits local quality variations along its length, with the proximal portion having material or structural properties optimized for flexibility, and the distal portion having properties optimized for strength. This localized optimization allows the fastener to simultaneously satisfy both flexibility and strength requirements in different locations without compromise.
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 provides improved strength and flexibility, enabling bendable fasteners to withstand torque without breaking, 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.