Modular Bone Screw Fixation With Polyaxial Locking Feedback
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Solution Overview
Problem
Existing orthopaedic fixation systems, particularly spinal stabilization systems, lack flexibility and usability, making it difficult for surgeons to ensure proper component alignment and secure locking during assembly, especially in situations requiring variable angular orientations.
Innovation Solution
A fixation assembly featuring a tulip housing with a cap that includes resiliently deflectable wings and spring elements, allowing for poly-axial movement and secure locking of a spinal rod to a bone engaging fastener, with tactile and audible feedback for proper assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a set screw is used to lock the bone screw head and rod within the yoke, then the fixation strength is improved, but the surgeon's ability to visualize and ensure proper orientation of components is limited
Solution Approach 1:
The patent incorporates visual feedback mechanisms through colored indicators and alignment features that allow the surgeon to verify proper component orientation before final tightening. The system provides tactile and visual cues during assembly to confirm correct positioning of the bone screw head within the yoke and proper alignment with the rod, thereby resolving the visualization limitation while maintaining fixation strength.
2Ease of operation
If the components are assembled in situ with limited visualization, then the surgical procedure is simplified, but the assurance of proper component sitation is reduced
Solution Approach 1:
The fixation system incorporates self-aligning features and visual indicators that automatically guide proper component positioning during assembly. The design includes keyed interfaces, colored alignment markers, and tactile feedback mechanisms that enable the components to self-verify their correct orientation without requiring complex external measurement tools or extensive surgeon visualization, thereby maintaining both ease of operation and reliability.
3Adaptability or versatility
If a poly-axial bone fastener is used to accommodate various angular orientations, then the adaptability is improved, but the device complexity increases
Solution Approach 1:
The patent employs a dynamic locking mechanism that allows the bone screw head to rotate and orient itself at various angles relative to the rod before being secured in the desired position. The system transitions from a mobile, adjustable state during assembly to a fixed, locked state after installation, providing poly-axial adaptability through controlled movement and rotation capabilities within the yoke structure.
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
Enhances flexibility and usability for surgeons by providing tactile and audible feedback, ensuring secure locking of components while allowing poly-axial movement for precise angular adjustments.
Implementation Method 1
a pair of resiliently deflectable wings extend from the cap
Implementation Method 2
spring elements, allowing for poly-axial movement and secure locking
Data Source
AI summary
A fixation system includes a rod, a fastener with a spherical head, a tulip housing and a cap within the tulip housing. The housing includes a pair of arms that define a rod channel, and each arm defines an upper locking opening and a lower locking opening, all of which open to the interior of the housing. The cap includes a main body defining a spherical cavity for receiving the spherical head of the fastener, and a plurality of legs that can flex to receive the spherical head and to clamp the spherical head within ta conical bore of the tulip housing. The cap includes a pair of wings with locking tabs, each locking tab configured to engage a corresponding upper and lower locking opening. When the tabs are engaged in the upper locking openings, the cap is in an unlocked state in which the spherical head of the fastener can be introduced into the spherical cavity of the cap from the bottom of the tulip housing. The cap is then moved downward within the housing until the tabs engage the lower locking openings, so that the cap is in its locking state, with the head of the fastener locked within the housing. The cap includes spring elements between the main body and the plurality of legs that allows the main body to be moved axially toward the legs when the rod is tightened within the housing.