Low Profile Bone Screw Coupling Assembly with Nested Housing
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Solution Overview
Problem
Conventional coupling assemblies for bone screws in spinal surgery often protrude significantly from the vertebrae, occupying excessive space and not allowing the coupling element to seat closely to the bone screw, which can impede proper spinal alignment and fusion.
Innovation Solution
A coupling assembly with a coupling element that engages both the head of a bone screw and an elongate rod, featuring an outer housing that biases the coupling element to seat closer to the vertebrae, minimizing protrusion and utilizing a deformable material like Titanium alloy for enhanced engagement and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional coupling assemblies are used to connect bone screws and rods, then the coupling element can engage both components, but the assembly protrudes significantly from the vertebrae occupying excessive space
Solution Approach 1:
The coupling element is nested within the outer housing, with the coupling element positioned inside the housing cavity. The outer housing contains the coupling element while allowing it to engage the bone screw head and rod, creating a compact integrated assembly that minimizes protrusion from the vertebrae while maintaining full engagement functionality.
Solution Approach 2:
The outer housing is configured to be movable relative to the coupling element, allowing dynamic adjustment during installation. The housing can be positioned at different locations along the coupling element's longitudinal axis to achieve optimal engagement while minimizing protrusion, and the biasing mechanism provides dynamic force to maintain proper engagement.
2Reliability
If the coupling element is designed to engage the bone screw head and rod, then connection stability is improved, but the space between vertebrae and coupling element increases
Solution Approach 1:
The outer housing and coupling element are merged into a single integrated assembly where the housing contains the coupling element. This merging creates a compact structure that maintains stable engagement of the bone screw and rod while minimizing the overall space occupied between vertebrae, as the housing and coupling element work together as one unit rather than separate components.
Solution Approach 2:
The outer housing acts as an intermediary structure between the coupling element and the surrounding bone structure. It provides a compact enclosing structure that allows the coupling element to engage the bone screw and rod stably while the housing itself minimizes the protrusion distance, effectively mediating between engagement requirements and space constraints.
3Reliability
If the coupling assembly uses a deformable material like Titanium alloy, then engagement and stability are enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent specifies Titanium alloy as the material for the outer housing, changing the material parameter to achieve optimal balance between strength, deformability for engagement, and biocompatibility. This material selection enhances engagement stability while Titanium alloy's properties allow for manufacturing through established aerospace and medical implant processes, managing the complexity through material property optimization.
Data Source
AI summary
A coupling assembly is presented. The coupling assembly is used to selectively couple a bone screw having an elongate shaft and a head to an elongate rod. The coupling assembly has a coupling element configured to engage the head of a bone screw, as well as the elongate rod. When the elongate rod is engaged by the portion of the top of the coupling element, the coupling element does not extend above a top most portion of elongate rod.