Ratchet Retracting Handle for Automatic Stylet Retraction

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Solution Overview

Problem

Existing stylets for bone anchor insertion in spinal surgery face challenges with ease of manipulation and interference during screw insertion, limiting efficient and precise placement.

Innovation Solution

A ratchet retracting handle system that includes a cap assembly, retractor assembly, lead screw, and ratchet mechanism to automatically retract the stylet during bone anchor insertion, allowing for controlled advancement and retraction of the stylet relative to the bone anchor.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a stylet is used to extend beyond the distal tip of the bone anchor, then insertion accuracy and trajectory planning are improved, but ease of manipulation and retraction by the surgeon deteriorates

Engineering Contradiction:

Improveinsertion accuracyVSAvoidease of manipulation

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The device is divided into distinct functional segments: the bone anchor, the stylet, and the ratchet retracting handle. This segmentation allows each component to perform its specific function independently - the stylet provides trajectory guidance while the ratchet handle provides controlled retraction, resolving the contradiction between maintaining insertion accuracy and improving ease of manipulation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The ratchet retracting handle acts as an intermediary device between the surgeon and the stylet-bone anchor assembly. It provides a mechanical advantage system that enables easy retraction of the stylet without requiring the surgeon to directly manipulate the stylet itself, thus improving ease of operation while preserving insertion accuracy

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If a stylet extends beyond the distal tip of the bone anchor, then trajectory planning is improved, but interference with screw insertion occurs

Engineering Contradiction:

Improvetrajectory planningVSAvoidinterference with screw insertion

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The stylet is used to perform preliminary actions - establishing the insertion trajectory and guiding the bone anchor placement - before it needs to be retracted. The ratchet retracting handle enables this preliminary trajectory-planning function while automatically removing the stylet's interference potential once its guiding purpose is fulfilled

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The stylet is extracted or removed from the system after it has fulfilled its trajectory-planning function. The ratchet retracting handle facilitates this extraction by providing a simple one-handed retraction mechanism, eliminating the harmful interference effect while preserving the beneficial trajectory planning function

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of operation

If manual retraction of the stylet is required, then control over retraction timing is improved, but surgical efficiency and productivity deteriorates

Engineering Contradiction:

Improvecontrol over retraction timingVSAvoidsurgical efficiency

Core Design Contradiction:

Ease of operationVSProductivity

Solution Approach 1:

The ratchet retracting handle provides a self-service retraction mechanism where the surgeon's simple rotational input automatically produces the stylet retraction motion. The ratchet mechanism converts rotational motion into linear retraction motion, allowing the system to perform the retraction action itself rather than requiring complex manual manipulation, thus improving surgical efficiency while maintaining control

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The ratchet retracting handle introduces dynamic motion conversion - transforming the surgeon's rotational input motion into linear retraction motion of the stylet. This dynamic mechanism enables efficient retraction with minimal surgical effort, improving productivity while preserving control over retraction timing through the surgeon's directional input

Inventive Principle:

Principle #15Dynamics

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 efficient insertion of bone anchors by enabling one-handed operation, confirming trajectory, and ensuring the stylet is automatically retracted after insertion, reducing interference and improving surgical efficiency.

Implementation Method 1

a lead screw rotatably coupled with the retractor assembly; a ratchet assembly comprising a ratchet knob and a ratchet body, the ratchet body being coupled to a distal end of the lead screw

Methodology Applied

Scientific EffectScrew mechanism: Screw

Implementation Method 2

Due to the ratcheting relationship between ratchet body and ratchet knob, rotation of the cover in a first direction is configured to advance the stylet and the bone anchor distally, while rotation of the cover in a second direction, opposite the first direction, is configured to retract the retractor assembly and the stylet proximally

Methodology Applied

Scientific EffectRatchet mechanism: Ratchet

Data Source

PatentUS20260026850A1Ratchet retracting handles and methods of using the same

Publication Date: 2026.01.29 NUVASIVE INC

AI summary

Disclosed herein are ratchet retracting handles and related methods for automatically retracting a stylet during insertion of a bone anchor.