Threaded Universal Shank Head for Spinal Fixation Assembly
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Solution Overview
Problem
Current spinal fixation systems face challenges in easily and reliably engaging male and female threads during surgeries, particularly in the surgical environment, leading to difficulties in assembling modular parts quickly and efficiently.
Innovation Solution
A modular spinal fixation system featuring a universal shank head with a rounded shape and helically wound threads that can be bottom-loaded into receiver sub-assemblies, allowing for axial rotation and simultaneous mating of thread starts for easy uploading and secure locking, along with multiplanar or monoplanar receiver sub-assemblies providing pivotal or rotational motion before locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If traditional fixed-head bone screws are used, then the head cannot be moved relative to the shank, but this makes it difficult or impossible to position the rod properly within the rod-receiving channel
Solution Approach 1:
The bone anchor assembly transitions from a fixed head configuration to a dynamic polyaxial configuration, allowing the receiver to pivot and rotate relative to the shank head in one or more planes. This dynamic capability enables the rod to be positioned at various angles and orientations before final locking, significantly improving rod positioning ease while maintaining structural integrity through the locking mechanism.
2Adaptability or versatility
If modular components requiring assembly are used, then versatility and adaptability improve, but the assembly process becomes more complex and time-consuming in the surgical environment
Solution Approach 1:
The receiver sub-assemblies are pre-assembled with internal components such as pressure inserts, spring rings, and retainers in a shipping state configuration before reaching the surgical environment. This preliminary assembly eliminates the need for complex intraoperative assembly procedures, reducing surgical assembly time while maintaining the versatility of modular components that can be selectively chosen and quickly attached to different shank types.
Solution Approach 2:
The bone anchor assembly incorporates self-aligning and self-locking features that reduce the need for precise manual alignment and complex tightening procedures. The design allows components to automatically engage and secure themselves during the assembly process, minimizing surgical time while preserving the adaptability of modular components.
3Reliability
If bottom-loaded assembly with separate retainers is used, then the shank can be held in the receiver sub-assembly, but an additional component and assembly step are required
Solution Approach 1:
The retainer function is merged with the receiver structure itself, eliminating the need for a separate retainer component. The receiver is designed with integrated retention features that directly engage and hold the shank head in place during bottom-loaded assembly. This integration maintains reliable shank retention while reducing the total number of components and simplifying the assembly process by eliminating an additional assembly step.
Data Source
AI summary
A method of assembling a bone anchor assembly includes positioning either a rod-engaging insert or a capture portion-engaging retainer into the central bore of a receiver to form a pivoting or a non-pivoting receiver sub-assembly, respectively, with the receiver having a channel for receiving a rod and a central bore extending upwardly from a bottom opening through the channel to the top of the receiver. The method also includes uploading the capture portion of one of a plurality of bone anchors and into the lower portion of the central bore of the pivoting or non-pivoting receiver sub-assembly, with each of the plurality of bone anchors having an anchor portion for fixation to the bone of a patient and a capture portion opposite the anchor portion having a partial spherical outer surface extending outward and upward from a neck portion to an annular planar top surface, with a discontinuous central portion of the outer surface defined by the combined crest surfaces of a pair of helically wound upper threadform formed therein.