Threaded Implant Plug Start Structure for Lower Closure Force
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Solution Overview
Problem
Existing bone anchor closure mechanisms for spinal surgery require significant force to secure longitudinal connecting members due to difficulties in aligning and rotating closure structures, especially in cases of spinal misalignments and irregularities, making the process cumbersome and challenging.
Innovation Solution
A multi-start closure structure with helically wound guide and advancement features, featuring two or more start surfaces that engage simultaneously with the open implant arms, allowing for easier rotation and axial advancement, reducing the force required to secure the connecting member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-start helical closure structure is used, then the closure mechanism is simpler in design, but significant force is required to rotate and advance the closure due to alignment difficulties
Solution Approach 1:
The single-start helical structure is segmented into multiple starts (two or more). This segmentation allows the closure to engage multiple points on the rod simultaneously, distributing the engagement force and reducing the total force needed for rotation and advancement while maintaining secure fixation.
Solution Approach 2:
The invention transitions from a single-start to a multi-start helical configuration, adding a dimensional aspect to the engagement pattern. This creates multiple engagement zones along the helical path, enabling simultaneous multi-point contact with the rod and reducing rotational resistance.
2Reliability
If significant force is applied to rotate the closure during surgery, then the closure can be secured, but spinal misalignments and irregularities make alignment and rotation difficult and cumbersome
Solution Approach 1:
By segmenting the helical engagement into multiple starts, the closure can engage the rod at multiple points simultaneously. This segmentation reduces the cumulative friction and resistance during rotation, making the closure process easier to operate despite spinal misalignments and irregularities.
Solution Approach 2:
The invention changes the helical parameter from single-start to multi-start configuration. This parameter change modifies the engagement characteristics, reducing the rotational force required and improving ease of operation during surgical procedures with spinal misalignments.
3Force
If a multi-start helical closure structure is used, then the force required to secure the connecting member is reduced, but the device complexity increases
Solution Approach 1:
The segmentation of the helical structure into multiple starts achieves the dual benefit of reducing required force through distributed engagement while maintaining relatively simple manufacturing processes. The multi-start pattern can be produced using standard machining techniques, limiting the increase in device complexity.
Data Source
AI summary
A medical implant assembly includes a receiver including an upper portion and a channel formed in the upper portion configured to receive an elongate member therein. The assembly also includes a plug being threaded and configured to be positioned within the upper portion of the receiver, the plug having an axis of rotation, a bottom surface with an annular outer edge, and a continuously helically wound thread form comprising a start structure having a top edge and a bottom edge extending between a root and a crest of the continuously helically wound thread form, the start structure having a leading face extending between the top edge and the bottom edge of the start structure, the bottom edge of the start structure being spaced apart and above the annular outer edge of the bottom surface of the plug so as to not be connected with the annular outer edge.