Spinal Rod Reduction Tool with Side-Loading Guide and Spring Tabs
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Solution Overview
Problem
Conventional spinal surgery tools are often bulky and invasive, causing trauma to patients when used to implant spinal rods, as they require significant mechanical advantage to force rods into bone screws, which can lead to additional damage and insufficient clearance.
Innovation Solution
A low-profile guide tool assembly with a handle and implant engaging structure, featuring a translation nut and sleeve, allows for side loading and non-rotational axial translation, enabling the secure attachment and positioning of spinal rods with minimal invasion by using spring tabs to engage with bone screws and facilitate rod insertion and closure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If traditional bulky implantation tools are used to force rods into bone screws, then adequate mechanical advantage is provided, but surgical trauma and patient damage increase
Solution Approach 1:
The tool assembly is divided into separate functional components: a guide member with spring tabs for engagement, a rod pushing member with translation nut for axial translation, and a handle for operation. This segmentation allows each component to be optimized for its specific function while maintaining a compact overall profile that reduces surgical trauma.
Solution Approach 2:
The guide member acts as an intermediary between the rod pushing member and the bone screw. The spring tabs on the guide member engage with the bone screw head, providing a stable base while the rod pushing member applies force through the guide member's channel, distributing the mechanical advantage without requiring a bulky structure.
2Object-affected harmful factors
If a low-profile tool structure is used to reduce surgical trauma, then patient damage is minimized, but sufficient mechanical advantage for rod insertion is insufficient
Solution Approach 1:
The translation nut converts rotational motion in one dimension into axial linear translation in another dimension. This allows the tool to generate sufficient axial force for rod insertion through a compact structure, as the mechanical advantage is achieved through the screw mechanism rather than requiring a bulky lever arm.
Solution Approach 2:
The traditional mechanical lever system is replaced with a screw-threaded translation mechanism. The helical thread on the translation nut engages with the guide member, converting rotational input into controlled axial output force. This substitution provides high mechanical advantage in a compact, low-profile configuration that minimizes surgical trauma.
3Volume of moving object
If a compact guide structure is used to minimize invasion, then clearance is improved, but rod forcing capability is reduced
Solution Approach 1:
The guide member serves multiple functions: it provides a low-profile structure to minimize trauma, defines a channel for rod passage, engages with the bone screw via spring tabs, and transmits force from the rod pushing member. This multi-functionality allows the compact structure to maintain adequate rod forcing capability without requiring additional components.
4Reliability
If spring tabs are used to engage bone screws, then attachment reliability is improved, but device complexity increases
Solution Approach 1:
The spring tabs are integrated directly into the guide member as a single piece, combining the engagement function with the guide structure. This merging approach provides reliable attachment through the spring tabs while avoiding the complexity of separate engagement mechanisms, as the guide member and spring tabs form a unified component.
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 tool assembly reduces surgical trauma by providing a compact, low-profile mechanism for securing spinal rods with minimal invasion, allowing for precise alignment and attachment with reduced mechanical stress on the patient, while enabling easy attachment and detachment from bone screws.
Implementation Method 1
The translation nut is configured for rotatable attachment to the guide member... rotation of the translation nut when the first and second guide and advancement structures are mated causes non-rotating axial translation of the sleeve along the guide member
Implementation Method 2
the handle has a spring-loaded pin configured to project into an aperture disposed on an upper portion of the guide member when the handle is received on the guide member
Implementation Method 3
the guide member has an outer surface with a first guide and advancement structure thereon, such as a helically wound thread, and the translation nut has an inner surface having a second guide and advancement structure thereon, mateable with the first guide and advancement structure
Data Source
AI summary
A tool for implantation of a rod into a bone screw implanted in a human spine includes a guide member having a laterally opening channel disposed along an entire length thereof for side loading and receiving an implant fastener. A rod pushing member and a handle with a laterally opening channel are coaxial with the guide member, with the rod pushing member being rotatingly mateable to the guide member and the handle having a spring attachment mechanism for attaching the handle to the guide member. The guide member includes spring tabs for attachment to a bone screw, the tabs biased away from the bone screw. The rod pushing member includes a sleeve that extends substantially about the guide member, pressing the spring tabs toward the bone screw and into apertures on the bone screw arms. The rod pushing member sleeve also operatively functions as a rod pusher that abuts a rod as the sleeve is translated along the guide member and toward the bone screw. The handle lateral opening receives and supports a manipulation tool for inserting and installing an implant fastener for attaching the rod to the bone screw.