Press-Fit Pedicle Screw Coupling for Low-Bulk Rigid Fixation
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Solution Overview
Problem
Conventional surgical and pedicle screw coupling systems are bulky, causing tissue damage and irritation, difficult to install, and lack flexibility in rod stiffness, complicating surgical procedures and fusion extensions.
Innovation Solution
A coupling assembly with a pedicle screw and a member that allows for a press fit attachment, enabling full screw insertion against bone while maintaining the ability to apply force for rigid fixation, and a member that can be inserted at various angles, facilitating easier installation and flexibility in rod stiffness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional coupling assemblies are used, then rigid fixation is achieved, but tissue damage and irritation increase due to bulky size
Solution Approach 1:
The coupling assembly is divided into separate components: a pedicle screw with head, a rod, and a coupling device that connects them. This segmentation allows each component to be optimized independently, reducing overall bulk while maintaining fixation strength through precise intercomponent interfaces.
Solution Approach 2:
The coupling device features a receiving bore that receives the screw head, with the rod positioned within or adjacent to this structure. This nested arrangement consolidates multiple functions into overlapping spatial volumes, reducing the overall footprint and tissue displacement compared to conventional distributed components.
2Reliability
If conventional coupling systems are used, then fixation is achieved, but surgical installation becomes difficult and time-consuming
Solution Approach 1:
The coupling device is pre-assembled with the rod positioned in its receiving bore before surgery. This preliminary preparation eliminates complex intraoperative assembly steps, allowing the surgeon to simply attach the pre-assembled unit to the pedicle screw, thereby maintaining fixation reliability while dramatically simplifying the installation process.
Solution Approach 2:
Multiple functions are merged into the coupling device: it serves as both the connection interface between screw and rod, and as a structural element that provides fixation. This consolidation reduces the number of separate components and assembly steps required during surgery.
3Stability of the object's composition
If traditional coupling systems are used, then rod attachment is achieved, but flexibility in rod stiffness cannot be varied along multi-segmented constructs
Solution Approach 1:
The spinal construct is divided into multiple segments, each with its own coupling device and rod portion. This segmentation allows different rod segments to have different stiffness properties while maintaining stable attachment at each coupling interface through the standardized receiving bore design.
Solution Approach 2:
The coupling device is designed as a universal interface that can accommodate various rod types and stiffness characteristics. The standardized receiving bore and attachment mechanism work with different rod configurations, enabling surgeons to mix and match rod segments with varying stiffness properties along the spinal construct.
4Reliability
If conventional systems are used, then screw-rod connection is achieved, but the system is difficult to extend for revision procedures
Solution Approach 1:
The modular design with discrete coupling devices and rod segments allows individual components to be removed or added during revision procedures. The standardized interfaces maintain connection reliability while enabling easy extension of the fusion by simply adding new screw-rod-coupling units to the existing construct.
5Strength
If conventional coupling assemblies are used, then fixation is achieved, but rod bending is required which applies unintended stress to bones
Solution Approach 1:
The coupling device incorporates a receiving bore that allows the rod to be positioned at various angles relative to the pedicle screw axis. This dynamic angular adjustment capability eliminates the need for rod bending, as the rod can be directly inserted at the appropriate angle, thereby avoiding unintended stress application to the bone while maintaining fixation strength.
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 installation, and allows for flexible rod stiffness, improving surgical maneuverability and enabling full screw seating without compromising fixation strength.
Implementation Method 1
The coupling assembly includes a pedicle screw having a threaded shaft and a head portion. The head portion includes a driving feature and a proximally oriented bore having a bore diameter. The member includes a protrusion adapted for insertion into the bore of the pedicle screw, the protrusion having a protrusion diameter that is larger than the bore of the pedicle screw head portion.
Data Source
AI summary
Variations on improved pedicle screw coupling assemblies, along with methods for use of such assemblies provide improved functional characteristics over existing devices. A coupling assembly is capable of providing rigid fixed attachment between a pedicle screw fully seated to underlying bone and a member extending between adjacent pedicle screws. The coupling assembly includes a pedicle screw having a threaded shaft and a head portion. The head portion includes a driving feature and a proximally oriented bore having a bore diameter. In one version, the coupling assembly includes a member adapted to extend between adjacent pedicle screws. The member includes a protrusion adapted for insertion into the bore of the pedicle screw, the protrusion having a protrusion diameter that is larger than the bore of the pedicle screw head portion. In another version, the coupling assembly includes a spherical bore in the screw head. Additional implementations are described.