Interbody Spacer Screw Receiver Anti-Backout Mechanism
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Solution Overview
Problem
Current intervertebral spacers face issues with screw stability due to anatomical forces and degeneration of vertebral bone, leading to screw loosening and instability, which can result in increased pain for patients.
Innovation Solution
An interbody spacer design featuring a screw receiver with a threaded lumen and a cover plate that secures bone screws, preventing them from backing out, along with a cage structure that mimics the spinal disc and includes radiographic markers for precise placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bone screws are used to secure the interbody spacer to the spine, then the implant can be anchored between vertebral bodies, but the screws may vibrate, toggle, loosen, or back out due to anatomical forces and bone degeneration
Solution Approach 1:
The cover plate is pre-positioned over the bone screw heads before final tightening, creating a preliminary constraint that prevents screw movement during the implantation process and under subsequent anatomical forces. This preliminary action ensures screws cannot toggle or vibrate out of position during critical loading phases.
Solution Approach 2:
The cover plate acts as an intermediary component between the bone screws and the external environment, providing a protective barrier that prevents screw backs-out while maintaining the functional connection to the vertebral bodies. This intermediary structure resolves the contradiction by adding a stabilization layer without interfering with the primary anchoring function.
2Reliability
If the interbody spacer is designed with a cover plate and screw receiver mechanism, then screw backing out is prevented, but the device complexity increases
Solution Approach 1:
The cover plate and screw receiver are merged into a single integrated component rather than separate parts, reducing the number of assembly steps and simplifying the overall device structure. This merging maintains the screw retention function while minimizing the increase in device complexity.
Solution Approach 2:
The cover plate serves multiple functions simultaneously: it protects bone screw heads, prevents screw backs-out, provides structural support, and facilitates radiographic monitoring when combined with markers. This multi-functionality justifies the added complexity by delivering multiple benefits from a single component addition.
3Strength
If bone screws are inserted at upward and downward angles into vertebral bodies, then the interbody spacer can be secured to adjacent vertebrae, but the screws are susceptible to loosening due to extreme anatomical forces
Solution Approach 1:
The cover plate is positioned over the bone screw heads before final tightening and loading, creating a preliminary lock that prevents screw movement during the critical period when anatomical forces are applied. This preliminary action ensures that even at angled insertions, screws cannot loosen or back out under extreme loads.
Solution Approach 2:
The cover plate structure provides beforehand cushioning by distributing anatomical forces across a broader area and preventing concentrated stress on the screw-bone interface. This prior cushioning effect protects the angled screw fixations from loosening under extreme physiological loads.
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
Enhances screw stability and prevents loosening, ensuring the interbody spacer remains securely anchored between vertebral components, reducing the risk of pain and instability.
Implementation Method 1
The screw receiver has a threaded lumen extending between a proximal end and a distal end along the longitudinal axis of the screw receiver. The plate screw is sized and configured to be threadingly and removably received inside the threaded lumen of the screw receiver.
Implementation Method 2
Over time, the interface between the screws and the bone may present some problems of stability. Due to the anatomical structure of the spine and the extreme anatomical forces that are brought to bear on the skeleton and transmitted to the vertebral bodies, the screws securing the interbody spacer to the spine may vibrate or toggle out of position.
Implementation Method 3
Each bone screw has a head at a proximal end and a threaded shank extending toward a distal end for anchoring into bone.
Data Source
AI summary
An interbody spacer for the spine is provided. The interbody spacer includes a polymer cage and a plurality of bone screws configured to anchor the cage between two vertebrae of the spine. The cage includes a screw receiver configured to receive a metallic plate screw for attaching a plate to cover the proximal ends of the bone screws to prevent them from backing out over time with respect to the cage. The screw receiver has deflectable extensions that snap into cage to retain the screw receiver to the cage. The screw receiver also includes a transverse flanges that provide anti-rotation and alignment to the screw receiver relative to the cage and; furthermore, the screw receiver further includes a self-locking feature that increases purchase on the plate screw providing a secured cover plate for anti-backout protection for the bone screws.