Bone Plate Locking Screw Mechanism for Spinal Fusion Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing spinal fusion implants face challenges with bone screws loosening over time, leading to improper fusion and potential tissue damage, as current locking mechanisms are often ineffective, difficult to use, or prone to dislodging within the patient.
Innovation Solution
The implementation of a locking screw mechanism with a partially open shaft and variable diameter, opposite thread direction, and optional snap ring or resilient band to securely fasten bone screws to the implant, preventing backout and facilitating easy installation and removal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If bone screws are used to secure the implant to vertebrae, then the implant is kept properly positioned, but the bone screws can work loose and back out due to patient movement
Solution Approach 1:
The locking screw is inserted through the bone screw, creating a nested configuration where the locking screw passes through the hollow shaft of the bone screw. This nested arrangement allows the locking screw to engage with the bone screw's internal threads and secure it against backout, while the bone screw remains functional for anchoring the implant to the vertebrae.
Solution Approach 2:
The locking mechanism is designed to be installed after the bone screw is initially secured to the implant, but before the implant is fully integrated with the vertebrae. The locking screw is inserted through the bone screw and tightened to prevent backout, establishing a preliminary locking action that secures the bone screw in place during the fusion process.
2Reliability
If locking mechanisms are added to prevent bone screw backout, then bone screw retention is improved, but the device complexity increases
Solution Approach 1:
The locking screw serves multiple functions: it acts as a securing mechanism to prevent bone screw backout, provides a means for adjustment if needed, and can be removed if necessary. The hollow shaft design of the bone screw serves both as the anchoring element and as a guide for the locking screw, eliminating the need for separate locking structures.
Solution Approach 2:
The locking mechanism is segmented into distinct components: the hollow shaft of the bone screw and the separate locking screw. This segmentation allows each component to be optimized independently - the bone screw for anchoring function and the locking screw for retention function - while simplifying the overall assembly process compared to integrated locking structures.
3Reliability
If conventional locking mechanisms are used, then bone screw retention is improved, but they are difficult to use and have high risk of dislodgement
Solution Approach 1:
Instead of having the bone screw lock into a fixed structure, the design inverts the approach by having a locking screw pass through the bone screw and lock it from the opposite direction. This inversion allows for easier installation since the locking screw can be simply inserted through the hollow shaft and tightened, rather than requiring complex locking procedures.
Solution Approach 2:
The locking screw acts as an intermediary element between the bone screw and the implant plate. Rather than directly modifying the bone screw or the plate, the locking screw mediates the connection by passing through the bone screw and engaging with it, providing a simple and effective locking action that reduces dislodgement risk.
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
The described locking mechanism effectively secures bone screws, reducing the risk of implant dislodgement and tissue damage by ensuring stable fixation of vertebrae during fusion, while allowing for easy adjustment and removal as needed.
Implementation Method 1
The locking screw has a thread direction that is opposite the thread direction of the bone screw
Implementation Method 2
resilient band or snap ring to securely fasten bone screws to the implant
Data Source
AI summary
A bone plate that includes apertures for bone screws and locking screws is disclosed. The locking screws can be in an aperture adjacent to the locking screw aperture such that when the locking bone screws and locking screws are in place, the head of the locking screw at least partially covers the head of the bone screw. In another example, the locking screw aperture is threaded, and the locking screw is placed on top of the bone screw.