Adaptation Sphere Saddle Sagittal Alignment Spinal Rod
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Solution Overview
Problem
Existing polyaxial screws lack surgical flexibility and ease of use, particularly in sagittal direction manipulation, which complicates spinal deformity corrections due to fixed angle limitations during spinal surgeries.
Innovation Solution
A tulip-shaped pedicle screw assembly with a rod locker and set screws that allow for sagittal alignment and transition between locked and unlocked configurations, enabling independent adjustment of screw components for enhanced intraoperative flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If fixed angle surgical screws are used, then manufacturing precision is improved, but adaptability deteriorates
Solution Approach 1:
The screw head is designed with dynamic articulation capability, allowing it to pivot and rotate relative to the screw shaft during insertion, then lock into a fixed position once the rod is inserted. This enables the screw to adapt to varying anatomical angles intraoperatively while maintaining precise fixed-angle configuration for final load-bearing function.
Solution Approach 2:
The screw mechanism allows change in angular parameters during the surgical procedure. The head portion can be positioned at different angles relative to the shaft during insertion, then locked into a predetermined angle configuration for the final fixed-angle state, thus transitioning between variable and fixed angle states.
2Adaptability or versatility
If polyaxial screws with variable angle configuration are used, then adaptability is improved, but device complexity increases
Solution Approach 1:
The screw is divided into functionally independent segments: the shaft for bone insertion, the articulating head portion for angle adjustment, and the locking mechanism for fixation. This segmentation allows each component to perform its specific function independently, simplifying the overall design while maintaining variable angle capability.
Solution Approach 2:
A rod receptacle or locking mechanism serves as an intermediary between the variable angle head and the fixed rod. This intermediary component enables the transition from variable angle configuration during insertion to fixed angle configuration for final stabilization, reducing the complexity of the articulation mechanism itself.
3Stability of the object's composition
If rigid screws with immobilized head portion are used, then stability is improved, but ease of operation deteriorates
Solution Approach 1:
The head portion transitions from a dynamic, articulating state during insertion to a static, immobilized state after rod insertion. This dynamic-to-static transition allows the screw to be easy to operate during surgery while providing stable fixed-angle support in the final configuration.
Solution Approach 2:
The articulation capability is provided preliminarily during the insertion phase, allowing the surgeon to adjust the angle as needed. Once the rod is inserted, the locking mechanism is activated to immobilize the head, ensuring stability for the remainder of the procedure and post-operative healing.
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
Facilitates precise and secure alignment and immobilization of spinal rods, improving surgical flexibility and ease of use by distributing forces through a concave surface, reducing stress points and enhancing the ability to correct spinal deformities.
Implementation Method 1
the force distributor is structured to distribute this force along the contact surface with the rod... When the inner set screw is tightened, the force distributor immobilizes the rod within the saddle via frictional forces between the mated surface of the saddle and the rod
Data Source
AI summary
An improvement of a polyaxial screw head disclosed in the U.S. Pat. No. 8,277,490. A saddle resides within a tulip. The saddle is configured to mate with a rod. An outer set screw engages an inner surface of the tulip. An inner set screw is disposed within a lumen of an outer set screw. A force distributor has a concave surface configured to mate with the rod. The force distributor has a bore configured to accept a conical end of the inner set screw. The force distributor is configured to distribute the force applied onto the bore by the inner set screw along the contact area with rod. The force distributor allows the rod to pivot and have sagittal motion when the inner set screw is untightened. The force distributor immobilizes the rod within the saddle when the inner set screw is tightened.