Polyaxial Pelvic Screw Tulip for Multi-Direction Rod Fixation
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Solution Overview
Problem
Existing medical screws are limited in their ability to accommodate stabilizing rods extending in both cranial-to-caudal and medial-to-lateral directions, requiring separate screw types for pelvic and sacroiliac screw fixation, which increases manufacturing costs.
Innovation Solution
A medical screw design with a chamfer or multiple recesses on the tulip end face, allowing the tulip to pivot relative to the threaded shaft at specific angles, enabling connection to both cranial-to-caudal and medial-to-lateral stabilizing rods, using a single screw for both pelvic and sacroiliac screw fixation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate screw types are used for pelvic and sacroiliac screw fixation, then the screws can be optimized for specific rod directions, but manufacturing costs increase and device complexity increases
Solution Approach 1:
The patent applies universality by designing a single medical screw that can accommodate both cranial-to-caudal rods (sacroiliac fixation) and medial-to-lateral rods (pelvic fixation). The tulip-shaped socket with its specific geometry and pivot capability allows the same screw to function in both fixation types, eliminating the need for separate screw designs and reducing device complexity while maintaining fixation reliability
Solution Approach 2:
The patent applies dynamics through the tulip-shaped socket's pivot capability relative to the threaded shaft. The socket can pivot within a defined angle range to adapt to different rod orientations, allowing the screw to dynamically adjust to either cranial-to-caudal or medial-to-lateral rod directions. This dynamic adjustment mechanism enables a single screw design to handle multiple fixation scenarios
2Device complexity
If a single screw design is used for both pelvic and sacroiliac fixation, then manufacturing costs decrease and device complexity decreases, but the ability to accommodate specific rod directions may be compromised
Solution Approach 1:
The patent achieves universality by designing the tulip-shaped socket with specific geometric features including a pivot axis oriented at a defined angle to the threaded shaft axis. This geometry enables the same screw to accommodate both cranial-to-caudal rods (when pivoted to one angle) and medial-to-lateral rods (when pivoted to another angle), maintaining full adaptability while using a single screw type
Solution Approach 2:
The patent applies parameter changes by allowing the tulip-shaped socket to change its orientation parameter (pivot angle) relative to the threaded shaft. This parameter change enables the socket to adapt to different rod directions without changing the screw's fundamental design, thus maintaining versatility while simplifying the overall device
Data Source
Figure 1a~1b
Figure 1c~2b
Figure 3a~3b
AI summary
The present disclosure relates to a medical screw (1), designed and intended for selective screwing into the sacrum (2) and the ilium (3) of a patient, comprising a threaded shaft (4) whose proximal end section (4.pE) is formed into a ball head (5), a sleeve-shaped tulip (6) which is pivotably and rotatably held on the ball head (5) at its distal axial end section (6.dE) with respect to the threaded shaft (4), and which has a transverse recess (7) open at the proximal end face (6.pS) of the tulip (6) which is provided for transversely receiving a stabilizing rod (8), wherein the transverse recess (7) is located in the proximal axial end section (6.pE) of the tulip (6) is formed with an internal thread (9) and a setscrew (10) which is screwed or can be screwed into the internal thread (9) and is designed to press a stabilizing rod (8) inserted into the transverse recess (7) directly or indirectly against the ball head (5) and to fix the tulip (6) on the ball head (5) in a selectable relative orientation, characterized by a chamfer (11) formed on or from the distal end face (6.dS) of the tulip (6) which increases the swivel angle (α) of the tulip (6) with respect to the threaded shaft (4), the radial central axis (11.r) of which, viewed in the circumferential direction (u), is aligned in a tulip radial direction between a transverse recess axis (7.A) and a tulip transverse axis (6.A) rotated by 90° thereto. Furthermore, the present disclosure relates to a medical screw device (13), characterized by at least two such medical screws (1).