Orthopedic Locking Screw Shoulder Design for Bone Movement
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Solution Overview
Problem
Existing locking screws and plates used in orthopedic surgery often experience back-out, where screws loosen over time, leading to instability and pain, as they either fail to secure properly to the bone or allow excessive rotation relative to the plate, preventing a tight fit and lagging with bone movement.
Innovation Solution
A screw and plate system where the screw has a shoulder with a larger diameter than the neck and shaft, allowing it to snap fit through an aperture, with a locking bushing that expands radially to prevent rotation and a two-torque mechanism for secure engagement and disengagement, enabling the screw to lock axially while allowing rotation and pivoting for better bone alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the screw is designed with a locking mechanism to prevent rotation relative to the plate, then rotational stability is improved, but the ability to accommodate bone movement and pivoting is reduced
Solution Approach 1:
The screw is segmented into distinct functional zones: a smooth shaft for insertion, a threaded shaft for axial locking into bone, and a smooth shoulder for plate engagement. This segmentation allows each zone to perform its specific function independently, enabling the screw to lock axially while allowing controlled pivoting motion.
Solution Approach 2:
The screw design transitions from a static locking mechanism to a dynamic system that allows controlled motion. The smooth shoulder portion enables the screw to pivot and lag relative to the plate while maintaining axial stability, accommodating bone movement during healing while preventing excessive rotation.
2Stability of the object's composition
If the screw head is designed to prevent rotation relative to the plate, then rotational stability is improved, but the ability to lag with bone movement is reduced
Solution Approach 1:
The screw is segmented into distinct functional zones: a smooth shaft for insertion, a threaded shaft for axial locking into bone, and a smooth shoulder for plate engagement. This segmentation allows each zone to perform its specific function independently, enabling the screw to lock axially while allowing controlled pivoting motion.
Solution Approach 2:
The screw design transitions from a static locking mechanism to a dynamic system that allows controlled motion. The smooth shoulder portion enables the screw to pivot and lag relative to the plate while maintaining axial stability, accommodating bone movement during healing while preventing excessive rotation.
3Stability of the object's composition
If the screw is designed to lock securely to the plate, then stability is improved, but the risk of back-out increases if rotation is completely prevented
Solution Approach 1:
The screw is segmented into distinct functional zones: a smooth shaft for insertion, a threaded shaft for axial locking into bone, and a smooth shoulder for plate engagement. This segmentation allows each zone to perform its specific function independently, enabling the screw to lock axially while allowing controlled pivoting motion.
Solution Approach 2:
The screw design transitions from a static locking mechanism to a dynamic system that allows controlled motion. The smooth shoulder portion enables the screw to pivot and lag relative to the plate while maintaining axial stability, accommodating bone movement during healing while preventing excessive rotation.
Data Source
Figure 1~2B
Figure 3A~3C
Figure 4A~4C
AI summary
A screw is configured to be inserted into an aperture of a plate. The screw comprises a head, a neck that extends distally from the head and having a diameter, a shoulder that extends distally from the neck and has a diameter, and a shaft that extends distally from the shoulder and has a thread, a major diameter and a minor diameter. The diameter of shoulder is larger than the diameter of the neck and larger than the minor diameter of the shaft.