Polyaxial Screw Driver with Locking Alignment Mechanism

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Solution Overview

Problem

Current surgical instruments are inadequate for efficiently inserting and orienting polyaxial pedicle screws, particularly those with favored angles, due to their movable components, which complicate surgical procedures and require multiple attempts to properly position the screws.

Innovation Solution

A driver device with an engagement mechanism for the screw shaft, an alignment mechanism for the screw head, and a counter-rotation mechanism that allows for precise orientation of the screw head relative to the shaft, ensuring the favored angle is aligned during insertion and removal.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If polyaxial screws with movable components are used to allow alignment freedom, then adaptability is improved, but device complexity increases and ease of operation deteriorates

Engineering Contradiction:

Improvealignment freedomVSAvoidease of insertion

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The driver device incorporates a movable alignment mechanism that can transition between locked and unlocked positions. In the unlocked position, the alignment mechanism allows the screw head to be oriented at various angles relative to the shaft. In the locked position, the alignment mechanism rigidly couples the head to the shaft for stable insertion. This dynamic transformation resolves the contradiction by providing alignment freedom when needed and operational simplicity when required.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If polyaxial screws with movable components are used to allow alignment freedom, then adaptability is improved, but device complexity increases

Engineering Contradiction:

Improvealignment freedomVSAvoiddevice complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The driver device is segmented into distinct functional components: an engagement mechanism for the screw shaft, an alignment mechanism for the screw head, and a counter-rotation mechanism. Each component performs a specific function and can be independently controlled. This segmentation allows the complex polyaxial screw to be manipulated through simpler, modular operations, reducing the perceived complexity while maintaining adaptability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The alignment mechanism dynamically transforms from a movable state during positioning to a locked state during insertion. This dynamic behavior allows the device to provide alignment freedom only when needed, rather than requiring complex mechanisms to be continuously active, thereby reducing overall device complexity while maintaining adaptability.

Inventive Principle:

Principle #15Dynamics

3Adaptability or versatility

If multiple attempts are made to properly position the screw, then adaptability is improved, but loss of time increases

Engineering Contradiction:

Improvepositioning capabilityVSAvoidprocedural time

Core Design Contradiction:

Adaptability or versatilityVSLoss of time

Solution Approach 1:

The alignment mechanism allows the surgeon to preliminarily position and orient the screw head at the desired angle before final insertion. The counter-rotation mechanism enables precise orientation adjustments while the screw is still accessible. This preliminary positioning action prevents the need for multiple insertion attempts, thereby reducing procedural time while maintaining full positioning capability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The alignment mechanism acts as an intermediary between the surgeon's positioning intentions and the final screw insertion. It provides a controlled interface for adjusting the screw orientation without requiring removal and reinsertion. This intermediary mechanism enables precise positioning in a single procedural step, eliminating time loss associated with multiple attempts.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Manufacturing precision

If the screw head orientation is maintained during insertion, then manufacturing precision is improved, but device complexity increases

Engineering Contradiction:

Improvehead position accuracyVSAvoiddevice complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The alignment mechanism dynamically locks the screw head orientation during insertion, maintaining the precisely positioned angle throughout the insertion process. This dynamic locking capability ensures manufacturing precision is preserved without requiring permanently complex mechanisms, as the complexity is only activated when precision is needed.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS8100916B2Instrument for inserting, adjusting and removing a surgical implant

Publication Date: 2012.01.24 DEPUY SPINE INC

AI summary

An instrument for inserting, adjusting and engaging an implant, such as a polyaxial screw of a spinal fixation system, includes at least one retractable tab for engaging a corresponding recess on the implant and a shaft that moves relative to the retractable tab. The movable shaft selectively moves the tab between an expanded position for engaging the recess and a retracted position out of engagement with the recess. The shaft selectively engages a portion of the implant to rigidify the implant after the retractable tab engages the recess. The axially extending shaft may be disposed within an axially extending passageway of a body assembly. A rotatable collar surrounding the body assembly is coupled to the shaft for moving the shaft relative to the retractable tab.