Pedicle Screw Tulip Assembly for Reduced Splay and Secure Locking
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Solution Overview
Problem
Existing pedicle screw systems lack improved strength, stability, and versatility to address various spinal pathologies, including increased splay and inadequate instrument connections.
Innovation Solution
The development of bone fastener assemblies with tulip heads, locking caps, and modular components that include polyaxial, uniplanar, and monoaxial screws, along with instruments for open and minimally invasive surgeries, providing enhanced stability and versatility through features like friction rings, retaining clips, and tower removal tools.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional bone fastener systems are used, then the basic fixation function is provided, but the strength and splay resistance are insufficient for increased spinal pathologies
Solution Approach 1:
The bone fastener system is divided into multiple functional components: a polyaxial screw assembly allowing angular adjustment, a tulip head component for rod reception, and a locking cap for securing. This segmentation enables each component to be optimized for specific functions while working together to provide enhanced strength and splay resistance through controlled degrees of freedom and mechanical interlocking.
Solution Approach 2:
The system transitions from a static fixed connection to a dynamic assembly process. The polyaxial screw head allows dynamic angular adjustment during installation, the tulip head provides dynamic rod insertion, and the locking cap enables dynamic locking from unlocked to locked states. This dynamic capability allows optimization of the fixation construct based on surgical needs while maintaining reliability.
2Reliability
If a secure locking mechanism is implemented, then the stabilization is improved, but the device complexity increases
Solution Approach 1:
The locking cap integrates multiple functions into a single component: it receives the spinal rod, engages with the tulip head locking mechanism, and secures the entire assembly. This merging reduces the number of separate parts needed for locking while maintaining security, simplifying the overall device complexity without compromising reliability.
Solution Approach 2:
The tulip head acts as an intermediary component between the polyaxial screw and the spinal rod. It provides a receptacle for the rod and interfaces with the locking cap, mediating the connection between these elements. This intermediary structure simplifies the locking mechanism by providing a dedicated interface point, reducing the complexity of direct screw-to-rod locking.
3Ease of operation
If precise alignment features are added, then the instrument connection is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The tulip head features an asymmetric U-shaped configuration with a specific opening direction and internal geometry that receives the spinal rod. This asymmetric design provides precise alignment cues for instrument insertion and rod placement while being manufacturable as a single molded or machined piece, balancing alignment precision with manufacturing ease.
Data Source
AI summary
Orthopedic fixation devices, assemblies, instruments, and methods relating to the same. The orthopedic fixation device may include a tulip head with one or more internal components configured to secure a bone fastener, such as a saddle, retaining clip, and friction ring. A spinal rod may be secured in the tulip head, for example, with a locking cap, thereby securing the bone fastener. One or more instruments, such as screwdrivers and correction instruments may be used for reduction, derotation, compression and/or distraction.