Cervical Plate Locking Mechanism Prevents Screw Backout
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Solution Overview
Problem
Conventional cervical plates lack an effective locking mechanism to prevent bone screws from reverse threading or backing out over time, leading to instability in spinal fixation and graft placement.
Innovation Solution
A cervical plate locking mechanism featuring holes with a locking lip structure and locking screws with a head portion having outwardly biased petal structures, where the lead-in torque is less than the lead-out torque, utilizing a c-ring to maintain secure engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional cervical plates with standard screw holes are used, then the plate structure is simple and manufacturing is easy, but the bone screws can reverse thread or back out over time causing instability
Solution Approach 1:
The locking lip is formed by curving the inner surface of the plate at each hole, creating a curved recess that receives the petal structures. This curvature generates differential torque during screw insertion and locking, preventing reverse threading while maintaining structural simplicity.
Solution Approach 2:
The petal structures are designed to be outwardly biased, allowing them to dynamically expand during insertion and then lock against the locking lip. This dynamic behavior enables the screws to transition from a loose state to a locked state, preventing backout while keeping the mechanism simple.
2Reliability
If polymeric bushings or securing caps are used as locking mechanisms, then reverse threading is prevented, but the device becomes overly complicated and cumbersome to implement
Solution Approach 1:
The locking function is merged into the plate structure itself through the locking lip, eliminating the need for separate polymeric bushings or securing caps. The petal structures on the screw head work integrally with the plate's curved surface to achieve locking, simplifying the overall device.
Solution Approach 2:
The complex polymeric bushings and securing caps are extracted from the system, replacing them with a simpler metal-on-metal locking interface between the petal structures and the locking lip, while maintaining the same reliability function.
3Reliability
If conventional screw holes with uniform diameter are used, then manufacturing is simple, but the screws lack a reliable locking mechanism to prevent disengagement
Solution Approach 1:
The plate holes have non-uniform diameter with a smaller diameter at the entry point and a larger diameter at the interior portion, creating a localized locking lip. This local variation in geometry provides the locking function without requiring complex manufacturing processes throughout the entire hole structure.
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
Prevents reverse threading or backing out of bone screws, ensuring stable fixation and fusion of vertebrae, while being robust, simple, and cost-effective.
Implementation Method 1
The plurality of petal structures disposed about the central driver bore are outwardly biased. Each of the one or more locking screws also includes a c-ring selectively disposed within the inner groove disposed adjacent to the central driver bore, the c-ring configured to outwardly bias the plurality of petal structures disposed about the central driver bore.
Implementation Method 2
the lead-in torque of each of the locking screws is less than the lead-out torque of each of the locking screws. Thus, reverse threading or backing out is prevented.
Data Source
AI summary
The cervical plate locking mechanism of the present invention is elegant in its design and effective in its performance, and utilizes a plate with holes that each incorporate a locking lip structure and locking screws that each incorporate a head portion having petal structures that are outwardly biased prior to insertion via an internally-disposed c-ring or the like. Advantageously, the lead-in torque of each of the locking screws is less than the lead-out torque of each of the locking screws. Thus, reverse threading or backing out is prevented.