Thread-Thru Polyaxial Pedicle Screw With Spring-Loaded Retainer
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Solution Overview
Problem
Current polyaxial pedicle screw systems face challenges with unstable angular placement during installation and the inability to use various size anchoring screws with a common connector, leading to assembly integrity issues and increased complexity in spinal fixation procedures.
Innovation Solution
A thread-thru polyaxial pedicle screw system that allows different sized anchoring screws to be coupled with a single-sized connector, featuring a U-shaped connector with a spring-loaded retainer ring to maintain the connector's position and apply tension, facilitating easier alignment and installation of connecting rods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a polyaxial pedicle screw is inserted into the bone, then the surgeon gains flexibility to secure installation with minimal strain, but the connector component flops over making it difficult to grasp and align during surgery
Solution Approach 1:
The connector component is pre-positioned and stabilized within the pedicle screw head before the rod is inserted. The polyaxial mechanism is pre-configured to maintain a fixed angular relationship, preventing the connector from flopping during surgery. This preliminary stabilization allows the surgeon to easily grasp and align the connector without dealing with unwanted movement.
2Reliability
If various size anchoring screws are used with different connectors, then each screw size can be optimized, but inventory costs increase and assembly complexity increases
Solution Approach 1:
A single common connector design is created that can accommodate multiple pedicle screw sizes through a universal interface mechanism. The connector incorporates an adaptive seating area that adjusts to different screw diameters, allowing one connector type to work with various screw sizes. This universality reduces inventory requirements and simplifies assembly while maintaining optimized fit for each screw size.
Solution Approach 2:
The connector design incorporates variable geometric parameters, such as an adjustable or compliant seating surface, that can adapt to different screw diameters. By changing the geometric parameters of the connector's internal features rather than creating entirely different connectors, the system achieves compatibility across multiple screw sizes with a single connector design.
3Device complexity
If a common saddle is used for various size anchoring screws, then inventory is reduced, but assembly integrity is compromised
Solution Approach 1:
The common saddle (connector) incorporates localized adaptive features at specific critical interfaces while maintaining a uniform overall structure. The local quality principle is applied by creating compliant or adjustable seating surfaces only at the screw-connector interface, while other portions of the connector maintain fixed geometric properties for structural integrity. This localized adaptation preserves assembly integrity across different screw sizes without requiring multiple connector types.
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 system reduces inventory costs and provides a uniform connector for various screw sizes, enhancing surgical efficiency by maintaining the connector's position and allowing for precise angular placement, thus simplifying the spinal fixation process.
Implementation Method 1
A polyaxial bone screw has a threaded shank extending outwardly from a spherical ball for use in anchoring to the spine and a connector member that includes a socket constructed and arranged to accept the spherical ball. The retainer ring is spring loaded against a upper component of the connector member and engages the spherical ball
Data Source
AI summary
A thread-thru polyaxial pedicle screw fastening system. The fastening system consists of an anchoring bone screw having threads on one end for use in anchoring to the screw to the spine and a spherical connector on the other end operating as a pivot point about which a U-shaped connecting assembly moves in a polyaxial fashion. The U-shaped connecting assembly, for receipt of a spinal connecting rod, has a biased retainer ring for maintaining a positive tension between the connecting assembly and the anchored screw. The system allows for an improved manufacturing step wherein the threaded shank of a bone screws can be passed through a lower portion of the connecting assembly allowing a variety of bone screw sizes to be used with a common sized connector.