Pop-On Spinal Cap Assembly With Anti-Splay Revision Release
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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 pop-on cap implants that resist receiver-arm splay by angled surfaces and can be easily removed by intentionally splaying receiver arms, utilizing setscrews and specialized instruments for revision procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional pop-on-cap assemblies are used with standard outer diameter, then the device is simpler and easier to manufacture, but the assembly is prone to splay under compression loading which compromises spinal stability
Solution Approach 1:
The cap is designed with non-uniform thickness distribution, featuring thicker walls at specific locations (e.g., at the ends and at intervals along the length) to provide localized reinforcement exactly where splay forces are greatest, while maintaining thinner walls in other areas to preserve overall simplicity and ease of manufacture
Solution Approach 2:
The cap structure is divided into multiple segments or zones with different thickness characteristics, allowing each segment to be optimized for its specific functional requirement while maintaining overall structural integrity and simplicity
2Stability of the object's composition
If the cap outer diameter is increased to prevent splay, then spinal stability is improved, but the profile becomes larger and more invasive
Solution Approach 1:
Instead of uniformly increasing the cap outer diameter, the invention applies selective wall thickness variations that provide enhanced splay resistance only at critical locations, maintaining a compact overall profile while achieving the necessary stability where required
3Strength
If wall thickness is increased throughout the cap, then splay resistance is improved, but the cap requires more material and becomes harder to manufacture
Solution Approach 1:
The cap features variable wall thickness with concentrated reinforcement only at locations experiencing highest splay forces, while other areas maintain standard thickness, thereby achieving high splay resistance without the need to increase wall thickness throughout the entire structure
Solution Approach 2:
Rather than uniformly thickening the entire cap wall, the invention applies excessive thickness (reinforcement) only partially at critical locations where it is most needed, optimizing material usage and manufacturing ease while achieving sufficient strength
Data Source
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AI summary
A spinal-surgery system having a receiver for receiving a rod and/or a receiver cap. The cap has a generally cylindrical body and a set of opposing splay-resisting flanges extending radially from the body. The receiver has arms each having an inner proximal protrusion at or adjacent the proximal end, and an inner sloped splaying surface distal of the proximal protrusion. Each cap flange has a proximal-facing cap splay-prevent 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-prevent surface. The receiver pop-on surfaces are spaced so each cap pop-on surface contacts a respective receiver pop-on surface in operation. Each splaying revision surface extends distally and radially inward toward the longitudinal axis and into a cylindrical plane defined by an inner diameter of the cap. The cap inner diameter is greater than a rod width.