Rotational Quick Closure for Spinal Bone Screws
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Solution Overview
Problem
Existing quick closure devices for spinal implants face challenges in securely fastening connecting elements to bone screws without applying excessive stress to the bone bed, particularly in cases of porotic bones and limited space, where they often require high moments or torque, risk collisions, and have issues with end stops and load transfer.
Innovation Solution
A rotatively attachable and lockable quick closure system that engages with screw head protrusions and recesses, allowing two-directional torque absorption and direct force transmission, using hooks and a filler to secure the clamping element without additional stress on the bone bed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If slidingly insertable quick closures are used, then assembly is simplified, but high moments must be applied to long instruments creating uncontrolled situations at the screw location
Solution Approach 1:
The quick closure device transitions from linear sliding insertion to rotational insertion, changing the dimension of the insertion motion. This rotational approach allows the device to be inserted by turning the instrument rather than pushing it linearly, reducing the moments applied to long instruments while maintaining ease of assembly.
Solution Approach 2:
Instead of sliding the quick closure linearly onto the screw, the invention inverts the approach by rotating the quick closure device onto the screw head. This reversal of the insertion method from linear to rotational motion reduces the harmful moments on long instruments while achieving secure attachment.
2Ease of operation
If rotatively insertable quick closures are used, then torque application is simplified, but collisions with transverse processes or facet joints may occur in limited space
Solution Approach 1:
The quick closure device incorporates asymmetric features including a non-circular insertion path and asymmetric engagement surfaces. This asymmetry allows the device to be rotated into place while following a controlled trajectory that avoids collisions with surrounding anatomical structures like transverse processes and facet joints, while still enabling simplified torque application.
3Device complexity
If quick closures without end stops are used, then device complexity is reduced, but screws cannot be tightened without additional instruments that have difficult access to the screw
Solution Approach 1:
The quick closure device incorporates an integrated end stop feature that is part of the device itself rather than requiring a separate instrument. This self-service approach allows the surgeon to tighten the screw directly using the same instrument used for insertion, eliminating the need for additional instruments with difficult access while maintaining relatively simple device complexity.
4Reliability
If quick closures are used in porotic bones, then anchoring ability is improved, but excessive stress on the bone bed must be avoided
Solution Approach 1:
The quick closure device replaces traditional linear threading mechanisms with a rotational engagement system. This mechanical substitution allows the device to achieve secure anchoring in porotic bones through rotational locking rather than linear threading, reducing excessive stress on the bone bed while maintaining reliable anchoring ability.
Data Source
Figure 1
Figure 2a~2b
Figure 3a~3b
AI summary
Spinal implant comprising a quick closure (4) for securing a connecting element (2) in a bone screw (1) where the quick closure (4) is rotatively attachable in the clockwise or counterclockwise direction and lockable such as to be able to take up torques applied to the bone screw (1) while preserving the bone anchorage from manipulative stress.