Modular Polyaxial Bone Screw with Segmented Tulip Assembly
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Solution Overview
Problem
Current pedicle screw designs require the tulip assembly to be coupled with the threaded screw during placement, leading to unnecessary complexity and potential sacrifices in surgical accuracy and time due to the need for precise alignment and rod contouring.
Innovation Solution
A modular polyaxial bone screw design that allows the threaded screw to be placed in bone separately before the tulip assembly is engaged, utilizing a locking collar with spring members that transition from an expanded to a compressed configuration to secure the tulip assembly in the desired orientation, enabling independent placement and subsequent locking with a locking cap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the tulip assembly is coupled with the threaded screw during placement, then the screw provides structural support, but the alignment complexity and surgical time increase
Solution Approach 1:
The bone screw system is divided into two independent components: a threaded screw and a tulip assembly. The threaded screw can be placed in the vertebra first and secured, then the tulip assembly is attached separately to the screw head. This segmentation allows each component to be optimized independently and eliminates the need for complex alignment during single-step installation, reducing surgical time while maintaining structural support.
Solution Approach 2:
The threaded screw is installed and secured in the vertebra before the tulip assembly is attached. This preliminary placement allows the screw to be positioned accurately without the constraint of needing to align with the rod holder during insertion. The tulip assembly is then coupled to the already-positioned screw head, eliminating time-consuming alignment procedures.
2Reliability
If the tulip assembly is coupled with the threaded screw during placement, then the components work together, but the alignment precision decreases
Solution Approach 1:
By separating the threaded screw and tulip assembly into independent components, each can be manufactured and positioned with optimal precision. The screw head provides a precise mounting surface, and the tulip assembly can be accurately attached afterward using a simple coupling mechanism, achieving higher alignment precision than attempting to align both components during a single insertion step.
3Ease of operation
If the threaded screw and tulip assembly are placed separately, then the placement process is simplified, but additional components are required
Solution Approach 1:
The threaded screw and tulip assembly are designed to combine into a single functional unit through a simple coupling mechanism at the screw head. While placed separately for ease of installation, they merge to form the complete bone screw system, providing both operational simplicity and structural integrity without requiring excessive additional components.
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
This design simplifies the placement process, improves surgical accuracy, and reduces the complexity of tooling, allowing for easier alignment and secure fixation of the rod to the screw, while maintaining the benefits of polyaxial screw systems.
Implementation Method 1
the plurality of spring members transition from an expanded configuration in which the tulip assembly is allowed to pivot with respect to the threaded screw to a compressed configuration in which the tulip assembly is prevented from pivoting with respect to the threaded screw
Data Source
AI summary
A modular polyaxial bone screw that incorporates a threaded screw including a head portion and a tulip assembly that selectively “snaps” and locks onto the head portion of the threaded screw in a desired orientation. Thus, the threaded screw may be placed in bone before the tulip assembly is engaged onto the head portion of the threaded screw and a rod is disposed and secured there through using a locking cap, thereby locking the tulip assembly onto the head portion of the threaded screw in the desired orientation.