Spring-Loaded Extension Device for Bone Anchor Detachment
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Solution Overview
Problem
Existing extension devices for bone anchors in minimally invasive spinal surgery lack a reliable mechanism to prevent unintentional detachment from the bone anchor head, while maintaining accessibility for surgical instruments and implantation tools.
Innovation Solution
The extension device comprises separate shell parts with a radial projection and a deformable spring element that forms a captively holding connection with the bone anchor head, allowing for secure attachment without requiring direct force, and can be released using a specialized instrument to prevent unintentional detachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the extension device uses a simple attachment mechanism to the bone anchor head, then the ease of operation is improved, but the reliability of preventing unintentional detachment deteriorates
Solution Approach 1:
The extension device employs a dynamic spring element that can be actively deflected between engaged and disengaged states. The spring element includes a support region that engages with the bone anchor head to prevent unintentional detachment, while also allowing controlled release through radial deflection using a specialized instrument. This dynamic mechanism resolves the contradiction by providing both ease of attachment and reliable prevention of unintentional detachment.
2Stability of the object's composition
If the extension device uses a rigid connection to the bone anchor head, then the stability during surgical procedures is improved, but the ease of detachment for instrument access deteriorates
Solution Approach 1:
The connection mechanism transitions from a purely rigid structure to a dynamically controllable system. The spring element maintains rigid engagement during surgical procedures through its support region contacting the bone anchor head, ensuring stability. For detachment, a specialized instrument applies radial force to deflect the spring element, releasing the engagement. This dynamic design resolves the contradiction between stability and ease of detachment.
3Reliability
If the extension device uses a complex locking mechanism to prevent detachment, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The spring element serves multiple functions simultaneously: it provides the locking mechanism to prevent unintentional detachment, maintains rigid engagement during surgery, and enables controlled release through instrument actuation. This self-service approach, where a single element performs multiple critical functions, resolves the contradiction between reliability and device complexity by avoiding the need for separate complex locking and release mechanisms.
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 solution provides a secure, detachable, and non-rotatable attachment of the extension device to the bone anchor, ensuring stability during surgical procedures and preventing unintentional detachment, while maintaining access for surgical instruments through a working channel.
Implementation Method 1
the spring element being deflectable radially outwardly so as to detach the extension device, such that the support region of said spring element is freed from the head of the bone anchor
Data Source
AI summary
The invention relates to an extension device for a bone anchor, in particular for a bone screw, in particular for a pedicle screw, in particular in minimally invasive spinal surgery, the device having an axial longitudinal direction, a peripheral direction concentric therewith, and a radial direction, wherein the extension device extends in the axial longitudinal direction and engages, by means of a radial projection, an engageable region on the head of the bone anchor in the longitudinal direction and also in the radial direction and can be supported against the head of the bone anchor in the opposite direction so that the extension device can thereby be fixed to the head of the bone anchor so as to be detachable, yet also rigid in the longitudinal direction and non-rotatable.