Percutaneous Spinal Screw Extension Assembly
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Solution Overview
Problem
Current spinal fixation systems require invasive procedures with large incisions and significant muscle retraction, and there is a need for simpler, minimally invasive methods that ensure accurate rod introduction and connection to spinal implants.
Innovation Solution
A screw extension assembly that includes an elongate hollow outer sleeve and inner sleeve, movable relative to each other, with a securement member to radially secure the sleeves and maintain engagement with the bone anchor, facilitating percutaneous placement of a connecting rod through a spinal bone anchor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If percutaneous spinal fixation is implemented, then tissue disruption is reduced, but rod introduction and connection accuracy may be compromised
Solution Approach 1:
The patent introduces a securement member as an intermediary component between the inner and outer sleeves. This securement member includes engagement features that positively secure the rod's position during percutaneous introduction, ensuring accurate connection to the spinal implant without requiring large incisions or extensive tissue retraction
2Manufacturing precision
If a securement member is added to ensure rod connection, then rod introduction accuracy is improved, but device complexity increases
Solution Approach 1:
The patent employs a nested structure where the securement member is disposed within the inner sleeve, which itself is disposed within the outer sleeve. This nested arrangement allows the securement member to be integrated into the existing extension assembly without requiring separate components or complex assembly procedures, thereby minimizing the increase in device complexity while still providing enhanced rod connection assurance
Data Source
AI summary
A bone screw extension assembly for use in placing a connecting rod percutaneously into tissue of a patient comprises a multi-axial bone screw and a screw extension releasably coupled to yoke of the bone screw. The screw extension includes coaxially disposed outer sleeve and inner sleeves that are movable axially relative to each other. A screw engaging member projects radially from the distal end of the inner sleeve and is configured to releasably engage an extension coupling surface on the inner surface of opposed upstanding arms of the yoke. A securement member including cooperative surfaces is defined adjacent the distal end of the inner and outer sleeves that is operable upon relative axial movement of the inner and outer sleeves to radially secure the sleeves together for minimization of splaying and to thereby maintain the engagement of the screw engaging member and the bone screw.