Osteosynthesis Screw Head Transitioning Mobile to Fixed State
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Solution Overview
Problem
Conventional osteosynthesis systems face difficulties in installing connecting rods due to varying inclinations and directions of bone anchoring elements, making straightening of the vertebral column challenging, especially in severe deformations, and multiaxial-head anchoring elements lack the lever functionality for complete immobilization.
Innovation Solution
An anchoring screw design featuring a screw head with a receiving cavity of varying cross-sections, allowing the screw head to transition from a mobile to a fixed state by aligning the bone anchoring element with the screw head axis, facilitating easier rod placement and straightening through a combination of truncated cone-shaped areas and a cradle for optimal alignment and retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fixed-head anchoring elements are used, then straightening of the vertebrae is facilitated through lever functionality, but installation of connecting rods becomes difficult due to varying inclinations and directions of the anchoring elements
Solution Approach 1:
The anchoring element incorporates a dynamic head portion that can rotate relative to the threaded rod, transitioning between a mobile state during installation and a fixed state during straightening. This dynamic capability allows the head to adapt to various inclinations and directions during rod installation, then lock into a fixed configuration to provide lever functionality for vertebrae straightening.
Solution Approach 2:
The anchoring element is divided into distinct functional segments: a threaded rod for bone anchoring, a head portion for connecting rod reception, and a rotation joint connecting these segments. This segmentation allows each part to perform its specific function independently - the threaded rod provides anchoring, the head receives the connecting rod, and the rotation joint enables adaptive positioning followed by fixed straightening.
2Ease of operation
If multiaxial-head anchoring elements are used, then installation of connecting rods is facilitated through multi-directional reception, but straightening of the vertebrae becomes difficult due to lack of complete immobilization
Solution Approach 1:
The rotation joint provides dynamic adaptability during installation, allowing the head to be positioned at various angles to receive the connecting rod. Once installed, the system transitions to a static fixed state where the head is completely immobilized on the threaded rod, providing stable lever functionality for straightening operations.
Solution Approach 2:
The design allows preliminary positioning and installation of the connecting rod on the anchoring element head before the final tightening operation. The rotation joint enables this preliminary action by allowing movement during installation, and subsequent tightening locks the position to provide stable straightening functionality.
3Adaptability or versatility
If the screw head is completely immobilized on the threaded rod during installation, then straightening lever functionality is maintained, but adaptation to varying inclinations and directions becomes difficult
Solution Approach 1:
The rotation joint creates a dynamic connection between the head and threaded rod, allowing the head to rotate and adapt to various inclinations and directions during installation. After installation, the system transitions to a fixed state where the head is immobilized on the threaded rod, providing stable lever functionality for straightening operations.
Solution Approach 2:
The system changes its mechanical parameters from a mobile state with rotational freedom during installation to a fixed state with complete immobilization during straightening. This parameter change is achieved through the rotation joint that allows movement initially, then locks into a fixed position to provide stable straightening functionality.
Data Source
AI summary
An osteosynthesis system comprising anchoring screws, wherein at least one of the anchoring screws comprises a bone anchoring element with a longitudinal axis AA, comprising a threaded anchoring rod prolonged at the end by a coupling head and a screw head for coupling a connecting element to the bone anchoring element, wherein the screw, comprises a body with a longitudinal axis BB traversed longitudinally by a channel featuring in the lower portion a receiving cavity for receiving the coupling head of the anchoring element, at least one connecting element designed to interconnect the anchoring screws, means of tightening the connecting element on each anchoring screw, a means of straightening the bone anchoring element in relation to the screw head during tightening, wherein the means of straightening are arranged to straighten the threaded rod of the bone anchoring element and place the former in the longitudinal axis BB.