Vertebral Fixation Screw With Pivotable Head And Movable Washer
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Solution Overview
Problem
Conventional screws for fixing vertebrae in pedicle screw insertion surgeries have limited degree of freedom, restricting spinal motion and making it difficult for patients to perform desired movements post-surgery.
Innovation Solution
A screw system comprising a screw body with a spherical head, a movable washer, a fastening nut with sloping apertures, and a clamping bolt, allowing for greater angular movement and flexibility by forming sliding contacts and elongating portions without threads, enabling smoother and wider angle range motion between vertebras.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional screws for fixing vertebrae are used, then the screw structure is simple and easy to manufacture, but the degree of freedom between the screw body and fastening screw is limited, restricting spinal motion
Solution Approach 1:
The screw system is divided into multiple independent components: a screw body with spherical head, a movable washer with head seat portion, and a fastening nut with washer seat portion. This segmentation allows each component to move independently, increasing the degree of freedom for spinal motion while maintaining manageable complexity through modular design
Solution Approach 2:
The screw system transitions from a static fixed connection to a dynamic movable connection. The spherical head portion rotates within the head seat portion, and the movable washer slides within the fastening nut, creating a dynamic joint that accommodates spinal motion. This dynamic mechanism provides multi-directional movement capability while maintaining structural integrity
2Adaptability or versatility
If the screw structure is designed to allow wider angle range motion, then patient comfort and spinal motion are improved, but the profile and size of the screw increase
Solution Approach 1:
The spherical head portion of the screw body rotates within the head seat portion, providing multi-directional motion capability. This spherical geometry naturally accommodates wide angle ranges in all directions without requiring excessive linear dimensions, maintaining a compact profile while enabling extensive rotational freedom
Solution Approach 2:
The movable washer is nested within the fastening nut, with the head seat portion of the washer containing the spherical head. This nested arrangement consolidates multiple moving components into a compact configuration, achieving wide angle range motion without increasing the overall screw profile or volume
3Ease of operation
If conventional fixed connection screws are used, then the structure is stable and reliable, but spinal motion is restricted and patient comfort is reduced
Solution Approach 1:
The screw system employs dynamic connections where the spherical head rotates within the head seat portion and the movable washer slides within the fastening nut. These dynamic joints maintain reliable fixation through continuous contact and mechanical interlocking while permitting natural spinal motion, achieving both stability and mobility
Solution Approach 2:
The spherical head portion provides stable rotational contact within the head seat portion through curved surface engagement. This spherical geometry ensures reliable fixation during motion by maintaining constant contact area and distributing loads evenly, preventing loosening while enabling smooth spinal movement
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
Enhances patient comfort by allowing more natural and varied spinal motion while maintaining a lower profile, reducing constraints on spinal movement post-surgery.
Implementation Method 1
a spherical head portion formed at the top end of the screw portion; a movable washer, which includes a head seat portion formed therein so that the head portion of the screw body is mounted thereon after the screw portion of the screw body is inserted therein, and in which the screw body is pivotally joined therein in sliding contact between the head portion and the head seat portion
Implementation Method 2
a washer seat portion formed below the insertion hole so that the movable washer is pivotally mounted thereon in sliding contact between the movable washer and the washer seat portion
Data Source
AI summary
A screw for fixing vertebra for letting a patient perform spinal motion more smoothly after a pedicle screw insertion surgery is disclosed. A head portion of the screw body is pivotally joined in sliding contact on the head seat portion of a movable washer, which is also pivotally joined in sliding contact on the washer seat portion of a fastening nut. A first aperture and a second aperture are formed in the fastening nut and movable washer respectively, and an elongating portion without a thread is formed between a screw portion and the head portion of the screw body.