Segmented Bone Screw with U-Shaped Fork Head for Polyaxial Fixation
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Solution Overview
Problem
Existing bone screws with movable screw heads face challenges in achieving a secure hold in bones due to limitations in reducing screw body size while maintaining a stable fixation, especially when the screw head is small.
Innovation Solution
A bone screw design featuring a screw body with a coupling element and a U-shaped fork head, allowing for detachable connection of two screw body parts, enabling a larger screw body diameter without increasing the screw head size, and incorporating a spherical coupling element for polyaxial adjustability and secure anchoring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the screw body diameter is increased to ensure a secure hold in the bone, then the fixation strength is improved, but the screw head size must also be increased which protrudes more from the bone
Solution Approach 1:
The screw body is divided into two detachable parts: a first screw body part with a coupling element and a second screw body part with an external thread. This segmentation allows the screw body to achieve a large diameter for secure bone fixation while the screw head can be designed independently with smaller dimensions, resolving the contradiction between fixation strength and screw head size.
2Shape
If the screw head is made small to reduce protrusion from the bone, then the aesthetic appearance is improved, but the screw body cannot be securely connected
Solution Approach 1:
By segmenting the screw body into two detachable parts with specific coupling elements, the screw head can be minimized in size while maintaining reliable connection through the coupling mechanism between the screw body parts and the screw head.
Solution Approach 2:
The coupling element acts as an intermediary component that enables reliable connection between the screw head and the threaded screw body part, allowing the screw head to be small while ensuring secure attachment through the intermediate coupling mechanism.
3Ease of manufacture
If the screw body is made as a single piece for simplicity, then the manufacturing is easier, but the ability to adjust screw head alignment is limited
Solution Approach 1:
The screw body is segmented into two detachable parts that can be assembled in different configurations, enabling polyaxial adjustment of the screw head alignment while maintaining manufacturing simplicity through modular construction with standardized coupling elements.
Solution Approach 2:
The detachable design allows the screw head to be dynamically adjustable relative to the screw body, providing polyaxial alignment capabilities while keeping each individual component simple to manufacture.
4Ease of operation
If the coupling opening diameter is made large to facilitate assembly, then the assembly is easier, but the screw body diameter is limited in its ability to provide secure hold
Solution Approach 1:
The screw body is divided into two parts where the first part with the coupling element can be assembled separately from the second threaded part. This allows the coupling opening to be designed with appropriate dimensions for assembly while the threaded screw body part maintains a large diameter for secure bone fixation.
Data Source
AI summary
In order, even in the case of bone screws with a particularly small head, to ensure a secure hold of the bone screw in a bone, a bone screw is proposed, having a screw body, which defines a longitudinal axis and is provided with a screw body external thread and has a proximal and a distal end, having a coupling element disposed on the proximal end for detachably connecting the screw body to a screw head designed substantially in the form of a U-shaped fork head with a coupling opening, wherein an edge of the coupling opening forms an axial stop for the coupling element for limiting a movement of the coupling element relative to the screw head in distal direction, wherein a maximum outside diameter of the screw body is larger than an inside diameter of the coupling opening, wherein the screw body comprises at least a first and a second screw body part. An osteosynthesis device having such a bone screw and a method of manufacturing such a bone screw are further proposed.