Spinal Rod Receiver Cap Assembly to Resist Arm Splay and Rotation
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Solution Overview
Problem
Existing spinal surgery implants face challenges with receiver arm splay during locking and difficulty in revising previously implanted constructs, particularly in removing set-screws for adjustments or removals.
Innovation Solution
A system featuring caps that can be popped onto receivers with opposing flanges and wings to resist splay, allowing easy installation and later removal by intentionally splaying receiver arms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If receiver arms are designed to allow rod insertion, then rod installation is facilitated, but receiver arms splay away from each other during locking
Solution Approach 1:
The cap includes opposing flanges that contact the receiver arms during installation to prevent splay, and opposing rotation-preventing wings that engage with the receiver arms to maintain alignment. These features apply counter-action in advance to offset the harmful splaying effect that occurs during rod insertion and locking.
2Reliability
If set-screws are used to secure the rod, then fixation is achieved, but removal and adjustment become difficult
Solution Approach 1:
The cap is designed to be installed first onto the receiver, creating a pre-secured state that facilitates subsequent rod insertion and locking. This preliminary action simplifies the overall assembly process and enables easier revision procedures by establishing a stable base configuration before final fixation.
3Stability of the object's composition
If caps are designed to prevent rotation, then rotational stability is achieved, but intentional rotation for removal becomes difficult
Solution Approach 1:
The rotation-preventing wings are designed with specific geometric characteristics that allow them to engage firmly with the receiver arms during normal operation to prevent rotation, while also enabling controlled rotation when intentional rotation is needed for cap removal. The dynamic engagement between the wings and receiver arms adapts to different operational requirements.
Data Source
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AI summary
A spinal-surgery system having a rod receiver and/or a cap for use insertion and removal from the receiver. The cap has a generally cylindrical body, a set of opposing splay-resisting flanges, and set of opposing rotation-preventing wings, the flanges extending radially from the body along a first radial line of the body, and the wings extending radially away from the body along a second radial line of the body generally orthogonal to the first radial line. Each cap flange has a proximal-facing cap splay-resisting surface, and a distal-facing cap pop-on surface. Each receiver proximal protrusion has a proximal-facing sloped receiver pop-on surface, and a distal-facing sloped receiver splay-resisting surface. The receiver pop-on surfaces are spaced such that each cap pop-on surface contacts a respective receiver pop-on surface when the cap is centered, with the cap wings aligned between receiver arms, and moved distally to contact the receiver.