Modular Spinal Fixation Receivers for Curved-Spine Rod Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing spinal fixation systems face challenges in aligning elongate rods with bone screws due to the immovable yoke-shaped heads, making it difficult to secure them in highly curved spines, and require complex assembly processes that increase costs and operational complexity.
Innovation Solution
A modular spinal fixation system with a bi-spherical universal shank head that allows for connection with various receiver sub-assemblies, providing multiplanar, monoplanar, and monoaxial movements, and includes a pre-lock friction fit mechanism for easy assembly without additional tooling, enabling versatile and efficient attachment of elongate rods to the spine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fixed yoke-shaped heads are used on bone screws, then the structure is simple and manufacturing is easy, but the rods cannot be aligned properly in highly curved spines
Solution Approach 1:
The bone screw is divided into separate components: a fixed shank and a movable receiver sub-assembly. The receiver can pivot and rotate independently relative to the shank, allowing the rod alignment capability to be decoupled from the manufacturing simplicity of the shank portion.
Solution Approach 2:
The receiver sub-assembly is made dynamic with respect to the shank through polyaxial pivoting capability. The receiver can pivot within a spherical head during surgery to accommodate curved spine geometries, then be locked in position. This transforms the static fixed head into a dynamic adjustable connection.
2Adaptability or versatility
If polyaxial pivotal bone screws with separate receivers are used, then rod alignment in curved spines is improved, but the assembly process becomes more complex and costly
Solution Approach 1:
Multiple functional components are merged into a single pre-assembled receiver sub-assembly unit that includes the spherical head, pivoting mechanism, and locking features. This integration reduces the number of separate parts the surgeon must handle and assemble during surgery.
Solution Approach 2:
The receiver sub-assembly is pre-assembled and pre-configured with all necessary components for polyaxial adjustment and locking before surgery. This preliminary preparation eliminates the need for complex intraoperative assembly procedures, reducing surgical time and complexity.
3Device complexity
If traditional bone screws with fixed heads are used, then the number of components is minimized, but additional tooling and complex assembly procedures are required
Solution Approach 1:
The receiver sub-assembly incorporates self-aligning and self-locking features that eliminate the need for additional alignment tools or complex assembly procedures. The spherical head geometry provides inherent alignment guidance, and the integrated locking mechanism secures the receiver to the shank without requiring separate fastening tools.
4Ease of operation
If modular receiver sub-assemblies with pre-lock friction fit are used, then assembly without additional tooling is enabled, but the structural complexity of the connection mechanism increases
Solution Approach 1:
A friction fit interface acts as an intermediary mechanism between the receiver and shank. This intermediate connection provides temporary holding without requiring additional fastening tools, allowing the components to be assembled by simple insertion while maintaining structural integrity through controlled friction.
Data Source
AI summary
A spinal fixation system includes a plurality of bone anchors, each having an anchor portion and a shank head with an upper spherical surface having a first diameter extending downward to an inner edge of an annular shelf spaced below a hemisphere plane, and a lower spherical surface having a second diameter greater than the first diameter extending downward from an outer edge of the annular shelf toward a neck extending between the shank head and anchor portion. The system also includes both pivoting and non-pivoting receiver sub-assemblies, with each receiver sub-assembly including a receiver having a central bore with a seating surface adjacent a bottom opening and a channel for receiving a rod. Each receiver sub-assembly also includes one of a multiplanar retaining structure, a monoplanar retaining structure, or a monoaxial retaining structure positioned therein and slidably engageable with the seating surface after capturing the shank head upon its uploading through the bottom opening.