Modular Vertebral Fixation Screw With Bottom-Loaded Piston Retention
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Solution Overview
Problem
Existing vertebral fixation systems with top-loaded screws require complex tool engagement with the housing, increasing the size of the surgical site and complexity of minimally invasive procedures.
Innovation Solution
A modular screw design with a fastener that is bottom-loaded into a housing, utilizing biasing members and a piston to engage a ring, preventing removal of the fastener from the housing, and allowing for a smaller tool and reduced surgical site.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If top-loaded screw configuration is used, then the fastener can be inserted into the housing, but the tool complexity and surgical site size increase
Solution Approach 1:
The patent inverts the traditional top-loaded configuration by implementing a bottom-loaded screw design where the fastener is inserted into the housing from the distal end rather than from the proximal end. This inversion eliminates the need for complex tool engagement with the housing and reduces surgical site size, as the tool no longer needs to interface with the housing or pass through it to turn the fastener.
2Device complexity
If bottom-loaded screw configuration is used, then the tool size and complexity are reduced, but the fastener must be inserted after housing placement
Solution Approach 1:
The patent segments the screw assembly into separate components (housing and fastener) that can be independently prepared and then assembled in a simplified sequence. The housing is placed first, followed by insertion of the pre-prepared fastener from the distal end, eliminating the need for complex integrated tool-housing-fastener interactions.
3Ease of operation
If the head is bottom-loaded into the housing, then the alignment complexity is reduced, but the locking mechanism must prevent removal
Solution Approach 1:
The patent incorporates a pre-designed locking mechanism within the housing that automatically engages with the fastener head upon insertion. This preliminary preparation of the locking structure ensures that once the fastener is bottom-loaded into the housing, it is automatically secured and prevented from removal, maintaining reliability without adding alignment 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
The design reduces the complexity of tool interaction and minimizes the surgical site, facilitating easier insertion and reducing the impact on the patient, especially in minimally invasive procedures.
Implementation Method 1
one or more biasing members that bias the piston toward the ring and into the head cavity
Data Source
AI summary
A modular screw for a vertebral fixation system includes a fastener with a head and shank, and a housing assembly including a housing and a piston. The head is insertable via bottom-loading into a distal end of the housing. The housing assembly may include a ring and one or more biasing members, where the piston is downward biased by the one or more biasing members and holds the ring in a first position. The head engages the piston and causes the piston to release the ring, which transitions to a second position and engages the head and prevents removal of the head from the housing. The one or more biasing members include a spring that is optionally integrally formed with the piston. In addition, the piston is optionally a multi-piece component. Further, the head is optionally a multi-piece component, with a portion installed within the housing via a shear pin.