Coaxially Lockable Poly-Axial Bone Fastener Assembly
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Solution Overview
Problem
Conventional spinal stabilization systems require large incisions and cause significant trauma to soft tissue, leading to prolonged recovery times and nerve pressure issues due to destabilization of the spine.
Innovation Solution
A coaxially lockable poly-axial bone fastener assembly that allows for minimally invasive procedures by converting into a mono-axial configuration, using a coaxial locking mechanism to prevent poly-axial movements while enabling coaxial rotation, thereby minimizing tissue damage and facilitating efficient vertebral alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional spinal stabilization systems are used, then spinal stabilization is achieved, but large incisions and significant soft tissue trauma occur
Solution Approach 1:
The invention changes the configuration parameter of the bone fastener from poly-axial (multi-directional movement capability) to mono-axial (single-directional locked position) after insertion. This parameter change allows the system to achieve stable spinal fixation while enabling minimally invasive insertion techniques that reduce soft tissue trauma.
Solution Approach 2:
The bone fastener transitions from a dynamic poly-axial state during insertion to a static mono-axial locked state after positioning. This dynamic-to-static transition allows for flexible insertion followed by rigid stabilization, resolving the contradiction between minimally invasive access and reliable fixation.
2Reliability
If conventional spinal stabilization procedures are performed, then spinal stability is restored, but recovery time is prolonged
Solution Approach 1:
The ability to change the fastener configuration from poly-axial to mono-axial enables a less invasive surgical approach, which directly reduces patient trauma and accelerates recovery time while maintaining the ultimate spinal stability outcome.
3Ease of operation
If poly-axial movement is allowed in the bone fastener, then insertion flexibility is improved, but rigid fixation is compromised
Solution Approach 1:
The system is dynamic during insertion (poly-axial freedom) and becomes static after locking (mono-axial fixed position). This temporal separation of flexibility and rigidity resolves the contradiction between ease of insertion and strength of fixation.
Solution Approach 2:
The poly-axial flexibility is only needed temporarily during the insertion phase. Once the fastener is positioned, the system transitions to a locked mono-axial state, providing rigid fixation for the long-term stabilization phase.
4Strength
If mono-axial configuration is used, then rigid fixation is achieved, but insertion flexibility is reduced
Solution Approach 1:
Instead of using a rigid mono-axial fastener from the beginning, the invention inverts the approach by starting with a flexible poly-axial configuration during insertion and then locking it into a rigid mono-axial position afterward. This reversal resolves the contradiction by providing flexibility when needed and rigidity when needed.
Data Source
AI summary
A poly-axial bone fastener assembly having a collar and a bone fastener can be coaxially locked to prevent poly-axial movements of the collar relative to the bone fastener while permitting the collar to rotate about an axis of the bone fastener, thereby combining the functions and advantages of a poly-axial bone screw and a fixed angle bone screw. Some embodiments of a coaxial locking mechanism may include a c-clip with a locking pin, a c-clip with hooks, a split ring with square corners, a pin that spins inside the collar, pins that travel about a neck of the bone fastener, a coaxially locking top that screws into the collar over a head of the bone fastener, and a top nut that threads onto the head of the bone fastener inside the collar to trap a flange of the collar between a shoulder of the bone fastener and the top nut.