Split Locking Ring for Pedicle Screw Assembly
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current modular head polyaxial pedicle screw assemblies lack a secure method for attaching the tulip to the pedicle screw without clear visibility, leading to potential loosening and weakened screw-bone interface during surgical procedures.
Innovation Solution
A modular head polyaxial pedicle screw assembly featuring a split locking ring with positioning tabs and flexure portions that securely engage the screw head, allowing for axial movement and frictional maintenance of the tulip's orientation, ensuring the screw is firmly anchored within the tulip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tulip is pushed onto the pedicle screw head without clear visibility, then the assembly can be completed, but the screw-bone interface may be weakened due to improper securing
Solution Approach 1:
The split locking ring provides tactile feedback to the surgeon during assembly, allowing detection of proper engagement between the tulip and screw head through resistance changes and positioning tab alignment, eliminating the need for visual confirmation and preventing improper securing
Solution Approach 2:
The split locking ring acts as an intermediary component between the tulip and screw head, providing a mechanical interface with positioning tabs that ensure proper alignment and secure engagement, mediating the connection to prevent loosening while allowing blind assembly
2Reliability
If the pedicle screw is held in the tulip prior to fixing into bone, then the assembly is secure, but the surgeon loses the ability to test and verify the security of the assembly
Solution Approach 1:
The connection system is segmented into three distinct components: the screw head, the split locking ring, and the tulip. This segmentation allows the screw to be independently secured to the bone first, then separately connected to the tulip through the locking ring, enabling both secure assembly and verification capability
3Strength
If a rigid locking mechanism is used to secure the tulip to the screw, then the connection is strong, but the assembly becomes difficult to install without clear visibility
Solution Approach 1:
The split locking ring transitions from a flexible insertion state to a rigid locked state. During assembly, the split design allows the ring to flex and compress for easy insertion without visibility. Once positioned, the positioning tabs engage with the screw head and the ring becomes rigid, providing strong connection strength while maintaining ease of installation
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 split locking ring effectively secures the pedicle screw, preventing dislodging and facilitating easier assembly by providing tactile feedback and increased gripping force, thus enhancing the stability of the screw-bone interface.
Implementation Method 1
The split locking ring is compressed to fit through the distal opening and then expands within the recess to secure the screw head
Implementation Method 2
The one or more positioning tabs are configured to frictionally maintain the angular orientation of the tulip with respect to the pedicle screw
Data Source
AI summary
A modular head polyaxial pedicle screw assembly has a pedicle bone screw, a tulip, a split locking ring and a saddle. The screw has a head and a threaded shank. The split locking ring has a split ring body with one or more positioning tabs extending from a first surface of the split ring body. The split ring locking ring is configured to be placed internal of the tulip positioned in a recess, groove or undercut of an inner surface of the tulip. Upon assembly of the pedicle screw into the tulip, at least a maximum diameter of the head is positioned above the recess, groove or undercut allowing the split locking ring to be inserted into the recess or groove thereby securing the pedicle screw inside the tulip wherein the head of the pedicle screw abuts the one or more positioning tabs.