Locking-Cap Module Reduces Connector Height
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional set screws used to secure a longitudinal rod within a connector increase the height of the construct and may compromise the strength of the connection due to the need for a certain distance of threads for mechanical clamping, which can be detrimental in applications like securing a connector to a patient vertebrae.
Innovation Solution
A locking-cap system with a pre-loaded connection between the locking-cap and set screw, featuring flanges and retaining rails that mate with the connector to secure the rod, allowing the locking-cap to be rotated into a locked position using the set screw, and then further secured by overcoming the pre-loaded connection to advance the set screw and fully retain the rod.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional set screw is used to secure the longitudinal rod within the connector, then the rod is retained in the passageway, but the height of the connector increases and the connection strength is compromised
Solution Approach 1:
The locking mechanism is divided into two separate components: a locking cap that interfaces with the connector body, and a set screw that secures the rod. This segmentation allows the set screw to be contained within the locking cap, eliminating the need for extended threads outside the connector body and reducing overall height while maintaining secure rod retention
Solution Approach 2:
The set screw is nested within the locking cap structure, with the set screw head positioned inside the locking cap's internal cavity. This nesting arrangement allows the clamping mechanism to be contained within the connector's height envelope, preventing the height increase that would occur with conventional external set screw threading
2Strength
If the set screw requires a certain distance of threads for mechanical clamping, then sufficient clamping force is achieved, but the connector height increases
Solution Approach 1:
The threading interface is redirected from a vertical orientation (along the connector height) to a horizontal orientation (within the locking cap's internal cavity). The set screw threads engage with the locking cap in a direction perpendicular to the connector's height axis, allowing sufficient thread engagement distance to be achieved without increasing connector height
Solution Approach 2:
The clamping function is separated from the height-determining connector body and relocated to the locking cap component. This segmentation allows the threading and clamping mechanism to be positioned in a location that does not contribute to connector height, while still providing the necessary mechanical clamping force on the rod
3Length of stationary object
If the locking cap uses flanges that are nested within recesses of the connector, then the top surface is flush with the connector, but the locking mechanism becomes more complex
Solution Approach 1:
The locking cap is designed to perform multiple functions simultaneously: it provides the threading interface for rod clamping, contains the set screw mechanism, interfaces with the connector body through flange-recess engagement, and maintains a flush top surface. This multi-functionality reduces the need for separate components and simplifies the overall assembly despite the sophisticated geometry
Data Source
AI summary
A locking-cap module may include a locking-cap having a first connecting flange and a second connecting flange opposite the first connecting flange extending from a side surface of the locking-cap. The locking-cap may further include a first retaining rail and a second retaining rail opposite the first retaining rail. The locking-cap module may further include a set screw configured to engage with corresponding threads of the locking-cap. In some embodiments, the first connecting flange and second connecting flange are configured to engage with a connector such that the top surface of the locking-cap is generally flush with a top surface of the connector when the locking-cap is in a locked position relative to the connector. In some embodiments, the set screw is initially coupled to the locking-cap by a pre-loaded connection. In some embodiments, an end user may visually verify that the locking-cap module is in the locked position.