Surgical Coupling Assembly With Interference Fit to Prevent Cross-Threading
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Solution Overview
Problem
Conventional surgical and pedicle screw coupling systems are bulky, causing tissue damage, complicate surgical maneuvers, and lack flexibility in rod stiffness adjustment, making them difficult to install and prone to cross-threading and torque-related issues.
Innovation Solution
A coupling assembly with male and female members that utilize an interference fit and engagement features, allowing for adjustable coupling through a sliding cinch band and engagement teeth, enabling precise adjustments and secure attachment without simultaneous locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional coupling assemblies are used to connect surgical screws, then bone stabilization is achieved, but tissue damage increases due to the bulky size of the devices
Solution Approach 1:
The coupling system is divided into separate modular components: a coupling device with a body and a separate rod. This segmentation allows each component to be optimized independently, reducing the overall bulk while maintaining structural integrity and stabilization function.
Solution Approach 2:
The rod is designed to be received within the coupling device body, creating a nested configuration. This nesting approach minimizes the external profile and tissue displacement while maintaining the mechanical coupling function between screws.
2Strength
If conventional coupling systems are used, then surgical screws can be connected, but surgical maneuvers are complicated and installation becomes difficult
Solution Approach 1:
The rod is pre-formed with specific geometric features (hexagonal cross-section, flattened portions) that enable straightforward engagement with the coupling device. This preliminary preparation eliminates the need for complex intraoperative adjustments or bending maneuvers.
Solution Approach 2:
The coupling device body acts as an intermediary component that simplifies the connection process. The rod engages with the body through a simplified interface, and the set screw provides a single-point locking mechanism, reducing the complexity of surgical maneuvers compared to traditional multi-component systems.
3Strength
If traditional coupling systems are used, then rod connection is achieved, but flexibility in adjusting rod stiffness along multi-segmented constructs is lost
Solution Approach 1:
The system uses individual coupling devices at each screw location, allowing independent selection and configuration of rods with varying stiffness properties for different spinal segments. Each coupling-rod-screw assembly can be optimized for local mechanical requirements.
Solution Approach 2:
The coupling device incorporates a set screw mechanism that allows for adjustable locking, enabling dynamic control over the rod-coupling interface stiffness. This provides flexibility in tuning the mechanical properties of each construct segment.
4Stability of the object's composition
If conventional coupling systems are used, then screws can be fixed in position, but the ability to easily extend fusion in revision procedures is lost
Solution Approach 1:
The modular design with separable coupling devices and rods allows for easy extension of the construct. Additional coupling devices and rod segments can be added to extend the fusion to adjacent levels without removing the entire existing construct.
Solution Approach 2:
The coupling device is designed with a body and rod interface that facilitates future extensions. The rod can be cut and extended, and new coupling devices can be attached to existing rod ends, making revision procedures simpler.
5Strength
If prior art coupling systems are used, then rod and screw assembly is achieved, but cross-threading of set screws and torque-related issues occur
Solution Approach 1:
The rod features an asymmetric hexagonal cross-section with flattened portions that prevent rotational misalignment. This asymmetric geometry ensures the rod can only be inserted in the correct orientation, eliminating cross-threading risks.
Solution Approach 2:
The coupling device body serves as an intermediary that guides and aligns the rod before final engagement. This alignment interface ensures proper orientation and distributes torque evenly, preventing torque-related issues during tightening.
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 tissue damage, simplifies surgical procedures, allows for varying rod stiffness, and prevents cross-threading, providing a robust and durable connection that can be easily assembled and disassembled.
Implementation Method 1
The first and second bodies can be coupleable to one another by an interference fit when the raised portion of the male member is positioned within the area of decreased diameter associated with the internal bore of the female member
Implementation Method 2
The engagement features can be operable to provide a gripping interface between the male member and the female member to couple the male member and the female member one to another
Data Source
AI summary
A coupling assembly for use in surgical constructs includes a first body and a second body. One of the first body and the second body includes a male member and another of the first body and the second body includes a female member. The male member is sized and shaped to be received within the female member and the female member has an internal bore sized and shaped to receive the male member therein. One of the male member or the female member includes one or more engagement features formed therewith or attached thereto. The engagement features are operable to provide a gripping interface between the male member and the female member to couple the male member and the female member one to another.