Set Screw Retention Mechanism for Implantable Medical Devices
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Solution Overview
Problem
Implantable medical devices face issues with set screws disengaging and potentially falling out of blocks, leading to costly replacements, time-consuming re-engagement efforts, and potential health risks if the set screw is lost within the patient.
Innovation Solution
A set screw apparatus is designed with a set screw body featuring radial threads and an abutment, where the abutment is sized to inhibit movement past the block threads, allowing the set screw to be retained within the block even when completely backed out, enabling secure rotation and engagement without risk of dislodgment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the set screw is completely backed out of the block, then the set screw can be removed or disengaged, but the set screw may fall out of the block and potentially into the patient
Solution Approach 1:
A retention feature acts as an intermediary element between the set screw and block. This feature includes a retention opening in the block and a corresponding retention protrusion on the set screw that extends through the opening, preventing the set screw from falling out while still allowing it to be backed out and removed when needed.
2Reliability
If the set screw is re-engaged within the block, then the set screw is retained, but this process costs valuable time and effort
Solution Approach 1:
The retention protrusion is pre-formed on the set screw and the retention opening is pre-formed in the block. This preliminary configuration ensures that when the set screw is backed out and re-inserted, the retention features automatically align and engage, eliminating the need for time-consuming manual re-engagement procedures.
3Reliability
If the set screw is unable to be re-engaged, then the device must be replaced, but this costs considerable money and time
Solution Approach 1:
The retention feature provides a safety mechanism that prevents the set screw from being completely lost. By having the retention protrusion and opening configured in advance, the system cushions against the worst-case scenario of set screw loss, ensuring the set screw remains recoverable and the device remains reusable.
4Object-affected harmful factors
If the set screw falls out into the patient, then health issues may arise, but preventing this requires additional retention features
Solution Approach 1:
The retention feature is segmented into two distinct parts: a retention opening in the block and a retention protrusion on the set screw. This segmentation allows the retention function to be added without significantly complicating either component, as each part has a simple, dedicated geometry that is easy to manufacture and assemble.
Data Source
AI summary
In various examples, a set screw apparatus includes a set screw including a set screw body. An abutment extends radially outwardly from the set screw body and longitudinally separated from a threaded set screw area of a first length by an unthreaded set screw area of a second length of the set screw body. A block includes a bore. A threaded block area includes a third length, wherein the abutment inhibits movement of the set screw past the threaded block area and removal of the set screw from the bore. The third length is shorter than the second length so that an entirety of the threaded block area can be disposed within the unthreaded set screw area, such that the set screw is freely rotatable within the bore, but retained within the bore, if turned in a first direction with respect to the block.