Modular Pedicle Screw With Uniplanar Insert
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Solution Overview
Problem
Current pedicle screw systems face challenges in aligning bone screws and rods due to complex spinal anatomy, requiring extensive bending and inventory of multiple components for varying surgical procedures, and lack a uniplanar configuration that can pivot in only one plane of motion.
Innovation Solution
A modular pedicle screw assembly with interchangeable inserts and a rod adapter that allows use of different rod diameters, enabling various screw functions with a single rod holding element, and a uniplanar insert that moves within a plane of freedom to facilitate precise alignment and stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If traditional monoaxial screw designs are used, then the rod holder is held perpendicular to the bone screw direction providing strong stability, but it requires extensive rod bending and makes it difficult to position the screw and rod properly
Solution Approach 1:
The rod holder is designed with polyaxial capability, allowing it to pivot on the bone screw head within a cone of motion. This dynamic feature enables the rod holder to interface with the rod at various angles without requiring extensive rod bending, while still providing stable fixation when locked in place
2Ease of operation
If polyaxial screw designs are used, then the rod holder can pivot on the bone screw head allowing minimal rod contouring, but it causes lateral forces to pivot the rod holder rather than rotate the vertebral body
Solution Approach 1:
The rod holder is segmented into multiple functional components: a bone screw for vertical anchoring, a rod holder body for lateral rod interface, and a locking mechanism. This segmentation allows the bone screw to resist lateral forces while the rod holder interfaces with the rod, preventing unwanted pivoting
3Adaptability or versatility
If multiple monoaxial and polyaxial screw variants are manufactured for different rod diameters, then specific surgical procedures can be addressed, but inventory requirements increase with many parts that are rarely utilized
Solution Approach 1:
A single polyaxial rod holder design is created that can accommodate multiple rod diameters (5.5mm and 6.0mm) through its conical interface and adjustable locking mechanism. This universal design eliminates the need to manufacture separate monoaxial and polyaxial variants for different rod sizes, reducing inventory requirements while maintaining versatility for different surgical procedures
4Manufacturing precision
If extensive rod bending is performed to align the rod holder with the rod, then proper approximation is achieved, but surgical time and complexity increase
Solution Approach 1:
The polyaxial rod holder allows the rod to be inserted at various angles relative to the bone screw without requiring extensive bending. The rod holder pivots within a cone of motion to accommodate anatomical variations, achieving proper alignment with minimal rod contouring and reduced surgical time
Data Source
AI summary
Provided is a modular pedicle screw assembly which includes various components that may be configured in various manners so as to provide different functionalities to the pedicle screw assembly. This advantageously decreases surgery time, reduces repetitive and tedious surgical steps, and allows for streamlining inventory of expensive medical equipment. In one embodiment, a pedicle screw assembly includes a pedicle screw, a rod holding element, an insert, a rod, and a set screw. The insert may have a uniplanar configuration which allows movement of the insert, prior to final attachment, in a plane of motion. The insert may optionally have a monoaxial configuration which prevents movement of the insert. A method is also provided for securing a rod to a pedicle screw assembly. Also provided is an assembly tool for use in assembling a pedicle screw assembly.