Helical Channel Reducer for Capless Spinal Screw Rotation
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Solution Overview
Problem
Current retraction tubes are not compatible with capless spinal screws, which require rotation of the screw body for locking, as they do not allow for rotational movement necessary for rod locking during surgical procedures.
Innovation Solution
A retractor/reducer assembly that includes a tubular member with a helical channel, allowing for the rotation of a polyaxial screw receiver and guiding a rod into a locking channel, enabling rotational screw locking within the retraction tube.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a retraction tube is designed to rigidly attach to the screw body, then tissue retraction is effective, but rotation of the screw body is prevented which is necessary for locking the fixation element
Solution Approach 1:
The retraction tube is divided into two functional segments: an outer tubular member that provides rigid tissue retraction, and an inner rotating member that allows screw body rotation. The inner member can rotate independently within the outer member, enabling both tissue retraction and screw locking operations to be performed simultaneously without interference.
2Ease of operation
If the retraction tube is designed to allow screw body rotation, then capless screw locking is enabled, but the structural rigidity for effective tissue retraction is reduced
Solution Approach 1:
A friction fit interface serves as an intermediary mechanism between the inner rotating member and outer tubular member. This interface allows controlled rotation of the inner member relative to the outer member while maintaining sufficient frictional engagement to provide stable tissue retraction. The friction fit enables the system to accommodate both rotational movement and rigid stabilization as needed.
3Reliability
If a locking cap is used to secure the fixation element, then rod locking is achieved, but the capless screw design requiring rotation is compromised
Solution Approach 1:
The system transitions from a static locking cap design to a dynamic rotation-based locking mechanism. The inner member rotates within the outer member to engage the fixation element, providing a dynamic locking action that is compatible with capless screw designs. This rotational mechanism maintains reliable rod locking while adapting to modern capless screw architectures.
Data Source
AI summary
A retractor system and method for locating and placing a polyaxial screw while substantially simultaneously retracting tissue is shown and described. The retractor has a channel that facilitates introducing a rod into the polyaxial screw. Various embodiments are shown, including one which utilized a reducer for moving the rod in the retractor.