Polyaxial Screw Locking Cap Threaded Geometry
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Solution Overview
Problem
Current spinal stabilization techniques using screws, hooks, and clamps for treating spinal irregularities often fail to provide adequate rigidity and ease of installation, leading to suboptimal transfer of corrective forces and increased risk of motion restriction.
Innovation Solution
A clamp assembly featuring a tulip with a threaded inner surface and a threaded locking cap with various geometries, including square, buttress, and angled threads, along with drive features for efficient engagement with driving instruments, to securely lock pedicle screws and spinal rods, allowing for axial derotation, parallel compression, and reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional screws, hooks, and clamps are used for spinal stabilization, then the treatment can be implemented, but the rigidity and ease of installation are insufficient, leading to suboptimal transfer of corrective forces
Solution Approach 1:
The locking cap is designed to transition the construct from a dynamic state during installation to a rigid locked state upon tightening. The polyaxial screw allows dynamic adjustment during insertion, then the locking cap secures the position to create rigidity when needed.
Solution Approach 2:
The system is divided into separate components (screw, rod, locking cap) that can be independently installed and then assembled. This segmentation allows for easier installation of each component separately while achieving rigid fixation when combined.
2Reliability
If traditional clamps are used to secure spinal rods, then the components can be attached, but the grip on the spinal rod is insufficient and motion restriction is increased
Solution Approach 1:
The traditional complex mechanical clamp system is replaced with a threaded locking cap that uses simple rotational threading to secure the spinal rod. The threaded engagement provides reliable grip through friction and mechanical interlocking without complex moving parts.
Solution Approach 2:
The locking cap is designed to fit over the spinal rod and engage with the polyaxial screw, creating a nested arrangement where components fit within each other. This nested design provides secure grip while maintaining a compact structure.
Data Source
AI summary
Systems, methods, and devices for securing a spinal rod are provided. A clamp assembly comprises a tulip comprising an opening comprising an inner surface, wherein the inner surface is threaded; and a threaded locking cap disposed in the opening, wherein threads of the locking cap and the inner surface include various geometries.