Rotatable Base Multi-Axial Screw Assembly Design
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Solution Overview
Problem
Existing orthopedic implant systems face challenges in securely fixing multi-axial screws during surgery due to the complexity of multi-angle positioning between fastening and receiving portions, which can complicate the precise placement required for effective stabilization of bones.
Innovation Solution
A multi-axial screw assembly comprising a bone anchoring member, a receiver member, a base member, and a crown, where the base member is compressibly inserted into the receiver member's aperture and engages with an internal groove, allowing axial restraint while enabling relative rotation, and the crown is used to lock the assembly in place, facilitating easier rod placement and stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If multi-angle positioning between fastening portion and receiving portion is allowed, then ease of rod placement is improved, but difficulty in fixing screws in place during surgery increases
Solution Approach 1:
The base member is designed with a deflectable ring that can dynamically change its diameter. During insertion, the ring is compressed to a smaller diameter to pass through the aperture, then springs back to its original larger diameter to engage with the groove and lock the base member in place. This dynamic transformation allows the device to transition from a flexible insertion state to a rigid locked state, resolving the contradiction between ease of placement and stability during surgery.
Solution Approach 2:
The deflectable ring's diameter is changed as a key parameter during the assembly process. The ring is designed to have two distinct diameter states: a compressed state for insertion through the aperture, and an expanded state for engagement with the groove. This parameter change enables the base member to be easily inserted while maintaining stability once in place, addressing both requirements of the contradiction.
2Ease of operation
If base member is compressed to less than aperture diameter for insertion, then ease of insertion is improved, but structural stability during insertion decreases
Solution Approach 1:
The deflectable ring provides dynamic structural support by being compressed only during the insertion phase, then expanding to provide rigidity. The slot in the base member allows controlled deflection of the ring during compression, maintaining structural integrity even in the compressed state. Once inserted, the ring expands to engage the groove, providing the necessary structural stability for the surgical procedure.
Solution Approach 2:
The base member is segmented with a slot that divides the deflectable ring structure, allowing it to compress uniformly while maintaining structural coherence. This segmentation enables the ring to be compressed to less than the aperture diameter for easy insertion, while the divided structure prevents collapse and maintains strength during the insertion process.
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
This design enhances the ease of screw placement and stabilization by allowing for relative rotation between components, reducing the complexity of positioning and improving the stability of the implant system during surgery.
Implementation Method 1
The base member has a deflectable ring configured to mate with the internal groove of the receiver member and a slot configured to allow the deflectable ring to compress to a diameter less than the diameter of the aperture
Data Source
AI summary
A multi-axial screw assembly comprises a receiver member, a base member, a crown and a bone anchoring member. The receiver member has an aperture configured to receive the base member and an internal groove. The base has a deflectable ring configured to mate with the internal groove of the receiver member and a slot configured to allow the deflectable ring to compress to a diameter less than the diameter of the aperture such that the base member may be compressed and axially received within the receiver member. The base member is axially restrained within the base member relative to the receiver member while allowed to rotate relative to the receiver member. The crown is received within the receiver member along the central axis of the receiver member. The crown maintains the diameter of the deflectable ring greater than the diameter of the aperture.