Oval Sheath Pedicle Screw for Reduced Vertebral Stress

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Solution Overview

Problem

Existing pedicle screw fixation systems face issues with loosening due to excessive coupling forces, leading to instability and potential need for reoperation, especially in spinal surgeries.

Innovation Solution

A spinal fixation device featuring a spinal fixation pedicle screw with a cup head and a screw body, combined with an outer oval sheath locked via multiple threads, enhancing the contact surface area and structural strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If a circular pedicle screw is used, then initial stabilization is achieved, but stress concentration occurs at the screw-vertebra interface leading to loosening

Engineering Contradiction:

Improveinitial stabilizationVSAvoidscrew loosening resistance

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The patent applies asymmetry by changing the screw cross-section from circular to elliptical or rectangular. This asymmetric geometry creates non-uniform stress distribution that reduces stress concentration at the screw-vertebra interface, thereby preventing loosening while maintaining initial stabilization capability

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes the geometric parameters of the screw cross-section from circular to elliptical or rectangular shapes. This parameter change increases the contact surface area between the screw and vertebra, distributing coupling forces more evenly and reducing the risk of bone loss and screw loosening

Inventive Principle:

Principle #35Parameter changes

2Stress or pressure

If the contact surface area between screw and vertebral arch is increased, then stress on vertebral arch is reduced, but screw complexity increases

Engineering Contradiction:

Improvevertebral arch stressVSAvoidscrew geometric configuration

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The asymmetric elliptical or rectangular cross-section naturally provides increased contact surface area with the vertebral arch without requiring additional complex components. The shape modification alone achieves both stress reduction and maintains manufacturing simplicity

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by optimizing the screw cross-sectional shape specifically at the interface with the vertebral arch. The elliptical or rectangular configuration provides enhanced contact area where needed (at the vertebral interface) while keeping the overall screw structure relatively simple and manufacturable

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12396759B2Minimally invasive and endoscopic spinal fixation device

Publication Date: 2025.08.26 CHANPIN MEDTAK CO LTD

AI summary

The present disclosure provides a spinal fixation device, including a spinal fixation pedicle screw and an outer oval sheath. The spinal fixation device is provided with at least one locking structure and the outer oval sheath is locked to the spinal fixation pedicle screw through the at least one locking structure. The spinal fixation device can strengthen the stability of the spinal fixation pedicle screw for fixation after implantation in vertebrae during the spinal surgery.