Pedicle Screw Tab Extenders for MIS Rod Placement
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Solution Overview
Problem
Minimally-invasive surgery (MIS) procedures for spinal stabilization face challenges in accurately and securely placing and locking rods relative to pedicle screws due to limited access and visualization, necessitating innovative solutions for precise rod placement and securement.
Innovation Solution
A MIS pedicle screw and rod assembly with tab extenders and an inserter tool that allows the rod to be translated and pivoted using a partial spherical bearing mechanism, enabling secure locking with an externally-threaded set screw, and an inserter tool with a squeeze grip or button actuation mechanism for precise rod alignment and locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If MIS procedure is used to minimize incision size and tissue damage, then recovery time is shortened and pain is minimized, but access and visualization are limited making rod placement and securement difficult
Solution Approach 1:
The patent extends the head body of the pedicle screw outward from the bone surface by creating a tab extender structure that projects in a direction substantially perpendicular to the longitudinal axis of the screw. This dimensional extension brings the rod coupling interface to the skin surface, allowing rod placement and securement to be performed externally through the minimally invasive incision, thereby resolving the contradiction between minimal tissue damage and ease of rod placement operation
Solution Approach 2:
The tab extender acts as an intermediary structure between the implanted pedicle screw and the external rod. It provides a coupling interface that allows the rod to be securely attached while extending the interaction point to the skin surface, enabling external manipulation and securement without requiring deep internal access, thus facilitating rod placement while maintaining minimal invasiveness
2Stability of the object's composition
If set screws are used to lock the rod into the head body, then the construct provides rigidity, but the procedure requires accurate and secure engagement which is challenging with limited access and visualization
Solution Approach 1:
The tab extender structure extends the head body to the skin surface, bringing the rod coupling interface and set screw engagement area to an externally accessible location. This allows the surgeon to accurately engage and lock the set screws with proper visualization and dexterity, ensuring accurate and secure engagement while maintaining the rigidity of the construct, thereby resolving the contradiction between construct stability and ease of set screw engagement
3Ease of operation
If the head body is extended to the skin surface, then rod placement and securement are facilitated, but the device complexity increases
Solution Approach 1:
The head body is segmented into two functional portions: the internal portion that couples to the pedicle screw and the tab extender portion that extends to the skin surface. This segmentation allows the structure to perform dual functions - maintaining structural integrity for screw coupling while providing external accessibility for rod placement, thereby facilitating ease of operation without excessive complexity
Solution Approach 2:
The tab extender structure serves multiple functions: it extends the head body to the skin surface for accessibility, provides a coupling interface for the rod, and maintains the structural connection to the pedicle screw. This multi-functionality allows a single structural element to address multiple requirements, facilitating rod placement while controlling overall device complexity
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
Facilitates accurate and secure rod placement and locking within the spinal stabilization construct, enhancing the rigidity and stability of the spinal stabilization system while minimizing tissue damage and recovery time.
Implementation Method 1
The rod incorporates an enlarged portion that forms a partial spherical bearing that is selectively mated with a partial spherical bearing that runs along the length of the interior of the tab extenders. Thus, the rod can be inserted into, aligned with, and translated along the length of the tab extenders, and then selectively pivoted about the enlarged partial spherical bearing into a configuration that is substantially perpendicular to the tab extenders and the head body
Implementation Method 2
an externally-threaded set screw or the like is driven into the head body, which may be internally threaded or the like, thereby driving the enlarged partial spherical bearing of the rod either directly into the screw head or into a locking collar that is then press fit into the head body about the screw head, thereby locking the rod and the head body to the screw head and providing a rigid construct
Implementation Method 3
driving the enlarged partial spherical bearing of the rod either directly into the screw head or into a locking collar that is then press fit into the head body about the screw head
Data Source
AI summary
The present invention provides a minimally-invasive surgery pedicle screw and rod assembly, inserter tool, and insertion method for use in spinal stabilization procedures and the like. The screw and rod assembly utilizes a screw head body that has a pair of tab extenders that extend longitudinally from the head body to a point well outside of the skin and musculature of the patient. A rod is coupled to and translated along these tab extenders, ultimately into proximity with the head body. The rod is inserted into, aligned with, and translated along the length of the tab extenders, and then selectively pivoted about an enlarged partial spherical bearing into a configuration that is substantially perpendicular to the tab extenders and the head body. The present invention also provides an inserter tool that is used to dispose the rod concentrically within the tab extenders, translate the rod along the length of the tab extenders, and then pivot the rod with respect to the tab extenders and the head body.