Cervical Plate Screw Retention Clip Design
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Solution Overview
Problem
Conventional spinal osteosynthesis implants face challenges in achieving desired screw positioning and retention, as well as preventing screw backout while allowing for easy removal.
Innovation Solution
An osteosynthesis implant system featuring a plate with lateral fastener apertures and a horseshoe-shaped clip member that uses a flat-edged receiver and curved lobes to securely retain screws, preventing backout while allowing for tool-assisted removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional spinal osteosynthesis plates use screws to secure the plate adjacent the vertebrae, then the plate can be positioned and fixed relative to the spine, but the screws may back out or become loose over time
Solution Approach 1:
A retention clip is introduced as an intermediary component between the screw head and the plate aperture. The clip engages with the screw head and extends into the aperture to prevent backout, while allowing intentional removal with appropriate tools. This mediator resolves the contradiction by providing reliable retention without preventing controlled removal.
Solution Approach 2:
The retention function is segmented from the screw itself and implemented through a separate clip component. The clip has distinct functional segments: a base that engages the screw head, lobes that extend into the aperture for retention, and a portion that allows tool access for removal. This segmentation allows each element to be optimized for its specific function.
2Ease of manufacture
If the plate structure is simplified for ease of manufacture, then production costs decrease, but the screw retention and positioning capabilities are compromised
Solution Approach 1:
The retention functionality is segmented into a separate clip component rather than being integrated into the plate structure. This allows the plate to remain simple and easy to manufacture, while the clip provides the specialized retention features needed for reliable screw fixation.
Solution Approach 2:
The clip acts as an intermediary that provides complex retention functionality without requiring the plate itself to be complex. The plate maintains its simple, manufacturable design while the clip delivers the advanced retention capabilities through its multi-part structure with lobes, base, and engagement features.
3Reliability
If the retention structure is made more secure to prevent screw backout, then screw retention improves, but the ability to remove screws when needed becomes difficult
Solution Approach 1:
The retention clip is designed with dynamic characteristics that allow it to provide strong retention under normal conditions but become removable with appropriate force and tools. The clip can be intentionally disengaged from the screw head using a removal tool, providing the needed flexibility for repair and adjustment while maintaining reliable retention during normal use.
Data Source
AI summary
An implant system includes a pair of fasteners, a plate, and a horseshoe-shaped clip member. The clip member is located within a recess of the plate and is shaped so as to cooperate with the recess so that lobes of the clip block installed fasteners from backing out, yet, the lobes may be purposefully be deflected to enable removal of fasteners if desired.