Modular Pedicle Screw with Interchangeable Inserts
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Solution Overview
Problem
Current pedicle screw systems face challenges such as the need for multiple inventory components due to varying surgical approaches, issues with set screw cross-threading and head splay, and the inability to create a uniplanar pedicle screw configuration that can pivot in only one plane, complicating spinal fixation surgeries.
Innovation Solution
A modular pedicle screw assembly with interchangeable inserts and a rod adapter that allows for multiple rod sizes, enabling the same rod holding element to perform various functions, reducing inventory needs and preventing cross-threading and head splay through a secure locking mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple pedicle screw designs (monoaxial and polyaxial) with different rod holder sizes are manufactured to accommodate varying surgical approaches and rod diameters, then the system becomes more versatile and adaptable to different patient needs, but the device complexity and inventory requirements increase significantly
Solution Approach 1:
The rod holding element is designed with a universal interface that can accommodate multiple rod diameters (5.5mm and 6.0mm) and support both monoaxial and polyaxial screw configurations through interchangeable inserts. This multi-functional design eliminates the need to maintain separate inventories for different screw types and sizes, reducing complexity while preserving versatility across various surgical approaches
Solution Approach 2:
The screw system is divided into modular components: a universal rod holding element, interchangeable inserts (monoaxial and polyaxial), and size-specific rod adapters. This segmentation allows surgeons to assemble the required configuration by combining standard components in different arrangements, simplifying inventory management while maintaining adaptability to different surgical needs
2Stability of the object's composition
If set screws are tightened to secure the rod into the rod holder, then the rod stability is improved, but cross-threading and head splay occur which compromise the assembly reliability
Solution Approach 1:
A recessed cavity is introduced as an intermediary structure between the set screw and the rod holder body. The set screw engages with this recessed cavity rather than directly with the rod holder threads, which prevents the set screw from cross-threading the rod holder and eliminates head splay by providing a controlled engagement path that maintains assembly reliability while ensuring rod stability
3Manufacturing precision
If extensive rod bending and test fitting are performed to align the rod with the pedicle screw, then the alignment precision is improved, but the surgical procedure time increases
Solution Approach 1:
The polyaxial insert enables dynamic adjustment of the rod holder angle relative to the screw shaft during assembly. This dynamic capability allows the rod holder to pivot and orient itself to match the rod's trajectory without requiring extensive pre-bending or test fitting, achieving precise alignment more efficiently and reducing surgical procedure time
Data Source
AI summary
There is provided a modular polyaxial pedicle screw assembly that includes various components which 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, a polyaxial insert, a rod, and a set screw. The pedicle screw includes a threaded shaft and a cap. The rod holding element includes a screw hole, an insert bearing area, a chamber, chamber walls, a saddle area, and a threading area. The insert is disposed within the chamber, and the insert defines a bearing surface, an upper surface, side walls and a receiving area. The insert is positioned within the chamber such that the insert bearing surface contacts the rod holding element insert bearing area; additionally the side walls of the insert can bear against the chamber walls. The pedicle screw is positioned so that the screw shaft passes through the screw hole of the rod holding element and the screw cap rests within the receiving area of the insert. The rod is disposed so as to rest on the upper surface of the insert; and the set screw, joined to the threading area of the rod holding element, secures the rod to the upper surface of the insert.